• 24-Hour Urine Sample

    A 24-hour urine sample is simply a collection of all urine passed over a 24-hour period of time.

    Before Starting a urine collection:

    • Read and follow any instructions given to you by your GP or laboratory.
    • Speak to your doctor or laboratory if you have any questions
    • There may be certain foods you need to avoid before and during the collection period for some tests
    • There may be certain medications you need to avoid before and during the collection period, if so, your doctor should have discussed this with you. Don’t stop taking your medication if you have not discussed this with your doctor. Your doctor may prefer to keep you on the medication but interpret the results in light of your medication intake.
    • It is usually best to drink your usual volume of water or other beverages (there is normally no need to drink more or less than usual) - if you know you drink and urinate a lot, you may want to ask for an extra collection container.
    • You may wish to use a clean, disposable tub with a wide lid to urinate into and then transfer this to the collection bottle provided
    • Plan when you do the collection:
      i. It is usually best to start your collection in the morning so you can take the sample to the GP or lab the next day when it is fresh
      ii. you may find it easiest to do this on a day when you can stay at home. However, you may be best to avoid collection on a Friday or Saturday if the GP/ laboratory opening hours mean you cannot take your sample to the lab soon after the collection on Saturday or Sunday
    • Acid
      i. For some tests, there may be a known volume of acid in the bottom of the collection container in order to preserve certain substances in the urine that the laboratory will measure
      ii. Follow any specific instruction given with these collection bottles e.g. do not rinse out or touch the acid
      iii. Follow any instructions given in case of spillage of the acid.

    How to do a 24-hour urine collection

    Note - sometimes, you may be asked to do a shorter or longer collection period, the instructions are just the same as below, only the collection time is changed.

    1. Check that your name and other requested details are filed in on the bottle
    • When your sample gets to the lab, they will need to know who the test results are for
    2. Empty your bladder (go to the toilet and flush away the urine as normal) and record the time e.g. 8 am.
    Imagine your bladder is a bucket, to measure the volume of urine produced over 24 hours you need to start with an empty bucket.
    3. The next time you need to urinate, collect the urine in the collection container supplied (or transfer it from your own tub)
    • This is the first batch of liquid in your bucket and since you recorded the time you emptied your bladder this is the amount of urine produced over that time period
    • If you need a bowel movement, any urine passed with the bowel movement should be collected but try not to include faeces with the urine collection.
    • Store the urine in a cool, dark place, such as the refrigerator, if possible
    4. Continue to collect your urine for the next 24 hours
    • You may want to leave a note (or the container) on top of the toilet, so you don’t miss any collections (i.e. flush your urine away), especially if you get up to urinate at night
    5. 24 hours later (e.g. at 8 am if that is when you first emptied your bladder), empty your bladder and collect your urine for a final time. Again, record the time you finished the collection.
    • This represents the volume of urine produced over that 24-hour period
    • Ensure the lid of the container is on securely
    6. Take your sample to your GP or lab (depending on where you have been asked to take it) as soon as possible

    What happens to the sample when it gets to the laboratory?

    1. The urine volume is measured
    • Usually the laboratory will weigh your collection container with your 24-hour urine collection in it.
    • They will then take a small (e.g. 20 ml) sample for later testing and discard the rest
    • They will then measure the empty container and calculate the difference in weight
    • 1 ml of water weighs 1 gram so the volume can be easily calculated
    2. It depends what the test is for:
    • They may measure the pH of the urine
    • They may measure the creatinine concentration to see how concentrated/dilute the urine sample is (depends on how much you drank over the collection period)
    • They may be able to measure the requested test in the urine quickly (e.g. urine protein)
    • They may have to freeze your sample and measure it at a later date if it is a complex test that needs to be performed in a batch
    • They may need to freeze your sample and transport it to a specialist laboratory for analysis.
    3. Your results will normally be electronically sent to your GP or the doctor who requested the test for you. You can then contact the doctor’s receptionist to request the results or ask to speak to your doctor about the results. Or the doctor may contact you to ask you to make an appointment to discuss the results.


  • Abscess
    An enclosed localised collection of pus formed by the disintegration of tissue within a cavity
  • Acanthosis nigricans
    Darkening and thickening of the skin around the neck, underarms, and skin folds; can be caused by elevated levels of insulin in the blood and is often associated with obesity
  • Acid
    A chemical that has at least one hydrogen atom, tastes sour, turns litmus paper pink or red, and forms a salt when combined with a base. Hydrochloric acid is a part of the digestive juice produced in the normal stomach.
  • Acid-Base Balance
    The body's maintenance of a healthy pH range for blood and tissues that is slightly basic (pH between 7.35 - 7.45). This balance is achieved through the use of systems in the blood (which help to minimize pH changes) and by the lungs and kidneys, which eliminate excess amounts of acids or bases from the body.
  • Acidosis
    Disturbance in the normal acid-base balance of the body in which the blood and body tissues are more acidic than normal. It may result from respiratory causes that lead to retention of carbon dioxide, as in breathing disorders; from metabolic causes such as prolonged or severe diarrhoea, from impaired kidney function, as a complication of diabetes or as a result of several common poisonings (aspirin, antifreeze, methylated spirits).
  • Acromegaly
    a condition in adults resulting from excess growth hormone characterized by enlargement of the hands and feet, change in shoe size, gradual changes in facial features including protrusion of the lower jaw and brow and enlargement of the nasal bone.
  • Acute

    An illness which occurs quickly and doesn't last long.

  • Acute Phase Reactant
    A protein that increases or decreases in concentration with conditions that cause acute tissue inflammation or trauma.
  • Adrenal Gland
    A triangular endocrine, or ductless hormone-secreting gland with one situated above each kidney. There are two functional portions of the adrenal gland.

    The adrenal cortex is the outer part of the gland and manufactures and secretes sex hormones (androgens), glucocorticosteroids (e.g. cortisol) and mineralocorticosteroids (e.g. aldosterone). This portion of the gland is  particularly important for the maintenance of salt and water balance in the body. The inner part and the gland is called the medulla and it manufactures and secretes catecholamines (adrenaline and noradrenaline) which are normally produced under very stressful circumstances.
  • Aerobic
    Living or occurring in an oxygen-rich environment
  • Albumin
    Albumin is the most abundant protein in the blood. It keeps fluid from leaking out of blood vessels; nourishes tissues; and transports hormones, vitamins, drugs, enzymes, and ions like calcium throughout the body. Albumin is made in the liver and is extremely sensitive to liver damage. The concentration of albumin drops when the liver is damaged, when a person is malnourished, or if a person experiences inflammation in the body. Albumin increases when a person is dehydrated.
  • Alkalosis
    Disturbance in the normal acid-base balance of the body in which the blood and body tissues are more alkaline than normal; it may result from overbreathing, vomiting, or other conditions that cause an increase in base ions or a decrease in acid ions.
  • Allele
    Any one of the possible alternative forms in which a specific gene can occur
  • Allergen
    Substance (e.g., grass pollen) that can cause an allergy
  • Ambiguous genitalia

    Sex organs (genitals) that are not distinctly male or female in appearance. It is a condition present at birth (congenital) that results from a disruption in the formation of sex organs during fetal development.

  • Amino Acid
    Amino acids are the building blocks of proteins and DNA.  They are molecules that have an amino group (NH2)
  • Amniotic fluid
    Fluid surrounding and supporting a foetus
  • Amplification
    1) In molecular diagnostics, a process by which multiple copies of genetic material (RNA, DNA) are generated so as to produce adequate levels of the target to be detected or quantitated

    2) The process by which the signal from a detection system is increased so as to improve detection or quantitation of an analyte of interest, such as genes or drugs

    3) When there is more than the normal number of copies of a gene or genes in a cell, as in tumor cells, the gene is said to be amplified.

  • Anaerobic
    Living or occurring in an oxygen-free environment
  • Anaphylaxis

    A life threatening, severe allergic reaction which occurs over a short period of time.  Triggers include bee stings and drugs such as penicillin.  Initial symptoms can include hives, wheezing and low blood pressure which can lead to collapse and even death. Patients at risk may be given self-injectable adrenaline for use in an emergency.  This treatment is only a holding measure and an ambulance should be called.

  • Androgens
    General term for substances that produce masculine characteristics such as a deep voice and facial hair. In males testosterone is the most important androgen. Androgens are also present in females but normally in much small amounts.  Whilst in the womb, androgens produced by the embryo cause the development of the male organs (eg. penis and scrotum).
  • Androstenedione
    A steroid that produces masculine characteristics and is produced by the testis, adrenal cortex and ovaries
  • Anencephaly
    Defect in the development of the brain and skull, resulting in small or missing brain hemispheres.
  • Aneurysm

    Weakened portion of a blood vessel wall that widens or bulges and may eventually rupture; a ruptured aneurysm can bleed heavily and may be fatal.

  • Angioedema
    An allergic reaction involving the skin and deeper (subcutaneous) layers that is characterised by patches of swelling
  • Angioplasty

    Medical procedure used to widen blood vessels that have been narrowed or blocked.  During the procedure, a balloon-tipped catheter is inserted into the body (usually through a small incision in the groin). The catheter is guided to the site of the blockage using X-rays and injected dye. The balloon on the catheter is then gently inflated to flatten the blockage and open the blood vessel.

  • Anorexia Nervosa
    An eating disorder which leads to an intense fear of gaining weight. Mostly affects young women. Sufferers often think that they are overweight despite it being obvious to others that they are underweight. As well as severe mental health problems, the drastic weight loss can lead to missing/stopping periods, and changes in the salts and hormones within the body.
  • Anterior
    At or toward the front
  • Antibody
    Complex molecule (immunoglobulin), produced by lymph tissue in response to the presence of an antigen (such as a protein of bacteria or other infecting organism), that neutralises the effect of the foreign substance.
  • Anticoagulant
    Drugs that delay blood clotting (e.g., coumarin, heparin and warfarin).  Patients will often be given an anticoagulant for 3-6 months after problems with blood clots in the legs (deep vein thrombosis) or lungs (pulmonary embolism).  They are also used in patients who are at risk of developing blood clots, for example in patients with irregular heart beats (atrial fibrillation).
  • Antigen
    Substance (e.g., a toxin) or organism (e.g., an amoeba) that, when entering the body, causes the production of an antibody that reacts specifically with the antigen to neutralize, destroy, or weaken it. The presence of certain antigens is the criterion for typing in the ABO blood group system and is important in tissue cross-matching for transplants (e.g., the HLA antigen in kidney transplants).
  • Antihistamine
    Drug used to treat allergies and hypersensitivity reactions. Antihistamines reduce the effects of histamine, which causes inflammation. (e.g., chlorphenamine maleate, Piriton).
  • Apheresis
    Process of removing a specific component from blood, such as platelets or red blood cells, and returning the remaining components to the donor; allows for more of one particular component to be collected than could be separated from a unit of whole blood
  • Apnoea
    Short pauses in breathing
  • Apoprotein
    General term for a protein without its characteristic prosthetic group, which may be a metal or a small organic compound; for example, the protein apotransferrin combines with iron to form transferrin, and protein apoceruloplasmin combines with copper to form the enzyme ceruloplasmin.
  • Arrhythmia
    Change in the rhythm of heartbeats or in the strength of heart contractions
  • Ascites
    Fluid buildup in the abdomen (peritoneum).  Fluid builds up around the stomach, liver and other abdominal organs and can cause the abdomen to protrude.
  • Aspiration
    1. Action of breathing in, especially inhaling an unwanted substance or foreign object
    2. Use of suction to take liquids or gases from a body cavity or area, as in aspiration biopsy
  • Asymptomatic
    Without symptoms.
  • Atheroma

    Common disease of the arteries in which patches (plaques) consisting mostly of cholesterol and other lipids form on the inner arterial wall. The effect of these deposits is that the vessels become rigid and narrowed, leading to a reduced flow of blood.

    Narrowing of arteries in different parts of the body leads to different problems.  If arteries in the heart (coronary arteries) become narrowed it can lead to a heart attack.  If arteries leading to the brain become narrowed, the result can be a stroke.  Atherosclerosis in the legs can lead to problems with ulcers in the feet and toes.

    Atherosclerosis is associated with high blood pressure, obesity, diabetes, and some inherited metabolic diseases. In some cases, segments of blocked arteries may be surgically bypassed (as in coronary bypass surgery). Preventive measures include cessation of smoking, a low-fat diet, exercise, and avoidance of stress.

  • Atherosclerosis

    Common disorder of the arteries in which deposits consisting mostly of cholesterol and lipids form on the inner arterial wall. As a result, the vessels become nonelastic and narrowed, leading to decreased blood flow. One of the most important examples is coronary artery disease.

  • Autoimmunity
    Production of antibodies against the tissues of one's own body, causing autoimmune disease or hypersensitivity reactions.


  • Bacteraemia
    Presence of bacteria in the blood
  • Bacterium
    Any of a large group of small, single cell microorganisms found in the soil, water, and air, some of which cause disease in humans and other animals. Bacteria are generally classified as rod-shaped (bacillus), spherical (coccus), comma-shaped (vibrio), or spiral (spirochaete).
  • Base
    Substance (chemical) that has a hydroxyl (OH) ion, tastes bitter, turns litmus paper blue and, when combined with an acid, forms a salt.
  • Basophil
    Type of white blood cell (leucocyte), with coarse granules that stain blue when exposed to a basic dye. Basophils normally constitute 1% or less of the total white blood cell count but may increase or decrease in certain diseases.
  • Benign
    Mild, non-cancerous, and/or not spreading (compare Malignant), as of a disease or growth, especially a benign tumour
  • Beta blockers
    A group of drugs that blocks the effect of adrenaline, slows the heart rate, and decreases the strength of the heart's contractions and thereby lowers blood pressure and relieves symptoms of angina and arrythmias.
  • Beta Cells
    Specialised cells in the pancreas that produce and secrete insulin
  • Bile
    Thick, yellow-green-brown fluid made by the liver, stored in the gallbladder, and discharged into the upper part of the digestive tract (duodenum), where it breaks down fats, preparing them for further digestion.
  • Biliary
    To do with bile or the gallbladder and its ducts.
  • Biomarker

    A substance produced by the body, often detectable in body fluids such as blood or urine, that indicates a specific process, condition or disease

  • Biopsy
    Removal of a small amount of tissue and/or fluid from a living body and its examination by microscopic and/or other analytical methods to establish or confirm the presence of a disease, to follow its course, and/or to estimate its outcome. The specimen is usually obtained by suction through a needle, but other methods and instruments, including surgery, are also used.
  • Boil

    A painful, inflamed area of skin with a defined border, collection of pus and a hard central core usually caused by a bacterial infection of a hair follicle and surrounding tissue

  • Bone Marrow
    Specialized soft tissue found within bone. Red bone marrow, widespread in the bones of children and found in some adult bones (e.g., breast bone, ribs), is essential for the formation of mature red blood cells. Fat-laden yellow bone marrow, more common in adults, is found primarily at the ends of long bones.
  • Broad-spectrum Antibiotic Therapy
    A drug that is effective against a wide variety of microorganisms
  • Bronchioles

    The smaller airway passages/branches of the lower respiratory tract

  • Bronchiolitis
    Inflamed bronchioles, the smaller airway passages/branches of the lower respiratory tract
  • Bronchodilator
    A drug that dilates (opens) the bronchi - the tubes that carry air in the lungs
  • Bronchus

    One of the two main branches of the windpipe (trachea) that lead directly to the lungs


  • Calcification
    Hardening of tissue resulting from the formation of calcium salts within it; the abnormal hardening (calcinosis) leads to impaired organ function (e.g., in the kidneys or arteries). The process can result from a disturbance in the normal balance of hormones, vitamin D, and calcium and other minerals in the body. Calcification can also occur at the site of growth of a tumour, and its pattern can help to identify cancer during breast screening.
  • Calibrate
    To adjust the output or reading from a testing device to assure that it gives a correct answer.  The adjustment is based on measurement of one or more known substances called standards (or calibrators).
  • Capillary
    1. Tiny blood vessels approximately 0.008 mm in diameter connecting small arteries (arterioles) and small veins (venules). Through the one cell-layer thick walls of capillaries, oxygen and nutrients are passed from arterioles to body tissues, and carbon dioxide and other wastes are passed from body tissues to venules.
    2. Any other small, hairlike tube for carrying lymph or other material.
  • Carbohydrate
    Any of a group of organic compounds (containing the elements carbon, hydrogen, and oxygen), including starches and sugars, that are the chief sources of for the body. Carbohydrates from foods result in production of glucose, which is then either metabolized to release energy which can be stored as adenosine triphosphate (ATP), or stored as a large carbohydrate molecule, glycogen. Carbohydrates are synthesized by green plants (through the process of photosynthesis), consumed by humans in the forms of cereals, flour products, fruits, and vegetables. After absorption in the intestine they are either used immediately or stored in the form of glycogen or fat.
  • Carbuncle
    A collection of boils caused by an infection of a large area of skin involving several hair follicles and deeper layers of tissue.  The area often has several openings for pus drainage and sloughing dead tissue
  • Carcinoid tumour
    Slow-growing mass that can develop in the mucous membrane of the gastrointestinal (GI) tract and sometimes the lungs
  • Cardiomyopathy

    Cardiomyopathy is a general term for diseases of the heart muscle. It is when the walls of the heart chambers have become stretched, thickened or stiff, affecting the heart's ability to pump blood around the body.

  • Cardiovascular System
    Parts of the body, including the heart and blood vessels, involved in the pumping of blood and transport of nutrients, oxygen, and waste products throughout the body.
  • Carrier
    1. Person, generally in apparent good health, who harbours organisms that can infect and cause disease in others. Probably the most notorious carrier was Typhoid Mary.
    2. Person who has one copy of a recessive disease gene but is not affected themselves.
  • Cartilage

    Cartilage a medical term for gristle.  It is important in lining joints to absorb shock and in producing the shape of body parts such as the ear or nose.

  • Catheter

    1. long, thin, flexible tube inserted into a body cavity or vessel to allow the passage of fluids
    2. thin, flexible tube inserted into a vessel in the body for the purpose of opening (distending) the vessel

  • Central Nervous System
    One of the two main divisions of the human nervous system (the other being the peripheral nervous system), consisting of the brain and the spinal cord. The main coordinating and controlling centre of the body, the central nervous system processes information to and from the peripheral nervous system. The system is made up of grey matter (mostly nerve cells and associated parts) and white matter (mostly nerve fibres) and contains protective cerebrospinal fluid.
  • Centrifugation
    The automated process of separating lighter portions of a solution, mixture, or suspension from the heavier portions, by centrifugal force
  • Cerebrospinal Fluid (CSF)
    Normally clear liquid, produced in the ventricles of the brain, that fills and protects the cavities in the brain and spinal cord. In the adult there is normally about 140 millilitres of cerebrospinal fluid. Samples of the fluid, obtained by lumbar puncture (taking CSF from the bottom of the spine using a special syringe), may be used to diagnose certain diseases.
  • Cervical Adenitis
    Lymph node inflammation in the neck
  • Chain of Custody
    Legal document created when a piece of evidence is obtained that records the movement, location, handling and/or testing of the evidence from the time it is collected until the evidence is used in a legal proceeding and/or until it is no longer needed and is discarded or destroyed
  • Chelation
    Chemical bonding used to remove some substances (e.g., metals) from body tissues. It is used to remove excessive amounts of some metals (e.g., lead, iron), chelation has also been falsely promoted as an effective treatment for atherosclerosis.
  • Chloroquine
    Drug used in the treatment of malaria, rheumatoid arthritis, and systemic lupus erythematosis (SLE)
  • Chromosome
    Threadlike structure in every cell nucleus that carries the inheritance factors (genes) composed of DNA (deoxyribonucleic acid, the gene material) and a protein (usually histone). A human cell normally contains 46 chromosomes, 22 similar pairs and 1 pair of sex chromosomes which are similar in girls but different in boys; one member of each pair of chromosomes is derived from each parent.
  • Chronic

    An illness which occurs over a long time.

  • Clone

    (noun) Cell, group of cells, or organisms that descend from a single cell or organism; clones are genetically identical

    (verb) To replicate or produce identical copies

  • Colonisation
    The presence or growth of bacteria on or in the body; those who are colonised may or may not develop an infection and/or may spread the bacteria to others, in whom they may cause disease.
  • Computed Tomography

    What is it?
    The scanner is a doughnut shaped machine that takes x-rays of your body. This test is not performed in a Pathology laboratory but may well be requested at the same time as laboratory tests.

    How does it work?
    The machine produces a series of narrow beams as it moves through an arc around the body.  The beams are detected after passing through the body.  Beams that pass through dense tissue will be weaker and those that pass through less dense tissue will be stronger.  A detailed picture two dimensional picture can then be produced from these x-rays which is not possible from a simple x-ray.

    There is now a relatively new scanner called spiral CT that is quicker and more accurate for many diseases.  The x-ray beam makes a continuous spiral path with no gaps between images.

    What is it used for?
    Scans can give detailed views of bone, lungs, soft tissue and blood vessels and are commonly used to investigate the head and abdomen.  The brain may be investigated for tumours or bleeding while scans of the abdomen can give information about tumours, tears of organs (following a road accident), or enlarged or inflamed organs.  It is also useful for guiding needles when taking tissue biopsies.

    How is it carried out?
    The patient must remove all metal objects before lying on a motorised couch that passes through the hole of the machine.  A contrast medium may be given, by mouth, injection or enema, to improve the sharpness of the images.  The patient usually lies on their back but may be asked to lie on their side or front.  You will be asked to lie very still but breathe normally.  After each x-ray the couch will be moved forward a small amount.  The scan lasts from a few minutes to about thirty minutes.

    What are the risks?
    CT scans are considered very safe and use low amounts of radiation.  They are quick and accurate and eliminate the need for invasive surgery.

    Pregnant women should not have a CT scan.  Nursing mothers should wait 24 hours after a scan before resuming breast-feeding.

    The contrast media often contain iodine.  Some people are sensitive to iodine and have an allergic reaction.  If you know that you are allergic to iodine or have other allergies you should tell the doctor.  Very rarely the contrast medium can cause kidney damage in patients who already have kidney problems.

  • Congenital
    Present at birth.
  • Conjugated bilirubin

    A water-soluble form of bilirubin formed in the liver by the chemical addition of sugar molecules to unconjugated bilirubin; when present in the blood, some conjugated bilirubin can become chemically bound to albumin, forming delta-bilirubin (also known as biliprotein).

  • Contact isolation

    Form of isolation in which anyone entering the patient's room and having direct contact with the patient wears gloves and a gown.

  • Convalescent
    In the clinical laboratory, pertaining to samples taken at a time when a patient is recovering from a disease or condition
  • Coronial autopsy

    An autopsy ordered by the Coroner, a legal official responsible for assessing the cause of death in an individual

  • Corpus Luteum
    A yellow body in the ovary; it fills the space left by a released egg (ovum) and reduces in size after about 14 days if the egg is not fertilized, but continues to produce a hormone, progesterone, if fertilization occurs.
  • Crohn's disease

    Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract from the mouth to the anus. Symptoms often include abdominal pain, diarrhoea (which may be bloody if inflammation is severe), fever, and weight loss.

  • Cryoprecipitate
    A component in some plasma samples which, after freezing and thawing, produces a precipitate that remains solid. It is rich in fibrinogen and Factor VIII.
  • Cryostat

    A machine for rapidly freezing specimens of tissue

  • Culture
    Deliberate growing of microorganisms in a solid or liquid medium (e.g. agar, gelatin), as of bacteria in a Petri dish.
  • Cyst

    1) a hollow space or fluid-filled cavity surrounded by a distinct lining that develops abnormally in tissue or in an organ in the body, such as "ovarian cyst"

    2) a cellular form of a parasite that has a thick cell wall, which allows for survival of the parasite in the environment and transmission into an uninfected host

  • Cytochrome
    Coloured chemical compounds found in all cells and involved in electron transport.
  • Cytology
    The microscopic assessment of individual cells or groups of cells that are either shed in body fluids, collected by smears and scrapings or by a very fine needle from deeper tissues.
  • Cytoplasm

    The living substance within a cell that is located outside of the nucleus; it is a semi-fluid substance consisting of proteins, fat and other molecules


  • Dehydration
    Extreme loss of water from the body tissues, often accompanied by imbalance of sodium, potassium, chloride, and other electrolytes in the body. Dehydration may occur in prolonged diarrhoea, vomiting, or perspiration and is of particular concern in infants and young children. Symptoms include thirst, dry skin, cracked lips, and dry mouth. Treatment involves restoring the fluid and electrolyte balance either by having the person drink liquids or by the intravenous administration of water and salts.
  • Dementia
    Progressive state of mental decline, especially of memory function and judgment, often accompanied by disorientation, stupor, and disintegration of the personality. It may be caused by certain metabolic diseases, drug intoxication, or injury, in which cases it is often reversible once the underlying cause is treated. If, however, it is caused by a disease such as Alzheimer's disease, by brain injury, or by degeneration brought about by aging (senile dementia), the changes that occur are irreversible.
  • Dermatitis
    Short term (acute) or long term (chronic) inflammation of the skin, which becomes red and itchy and may develop blisters or other eruptions. There are many causes, including allergy, disease (e.g., eczema), and infection. Treatment depends on the cause.
  • Dermatophyte
    Any one of the group of fungi that cause infection of the skin, hair, or nails
  • Diabetes insipidus
    A disorder similar to diabetes mellitus in that it causes symptoms such as increased thirst and increased urine production, but differing in cause, frequency, treatment, and associated complications; diabetes insipidus results from a lack of production of arginine vasopressin (also called antidiuretic hormone or ADH) by the pituitary or a lack of response of the kidneys to ADH, causing an inability of the kidneys to conserve water. It can lead to severe dehydration and high serum sodium if inadequately treated. Diabetes inspididus is a much more rare condition than diabetes mellitus.
  • Diagnostic Test
    A test to identify a disease or other condition.
  • Diuretic
    A drug that increases the production of urine; it is commonly used in the treatment of oedema (too much water in body tissues), high blood pressure, and congestive heart failure. There are several types of diuretics, including thiazides (e.g., chlorothiazide - Saluric and hydrochlorothiazide - Esidrix), loop diuretics (frusemide - Lasix), and others (spironolactone - Aldactone). They work in different ways and can produce side effects chiefly electrolyte (especially sodium and potassium) imbalances.
  • DNA
    Large molecule shaped like a double helix and found primarily in the chromosomes of the cell nucleus, that contains genetic information. This information is coded in the sequence of subunits (nucleotides) making up the DNA molecule.
  • Dominant gene
    One of a pair of genes whose action is expressed even when only one copy is present
  • DRE

    Part of a physical examination performed in order to examine nearby structures (e.g., the prostate in men)

  • Dumping syndrome
    Symptoms such as nausea, cramping, sweating, and weakness that may occur when the stomach contents are emptied rapidly into the small intestine before being digested; may occur in patients who have had gastric resections or bypass surgery
  • Duodenum
    First part of the small intestine that receives digesting material from the stomach
  • DVT

    deep vein thrombosis.  This is a clot that occurs in the veins of the legs.  It can occur at times of poor circulation - for instance on long-haul flights.  If the clot travels from the legs it can get lodged in the lung (pulmonary embolism) which may be life-threatening.

  • Dyslipidaemia
    Unhealthy lipid levels
  • Dystonia
    Continuous muscle contraction that is not intended by the patient that can cause unusual twisting (for example the neck being turned to one side) and repetitive motions.


  • Echocardiography
    Diagnostic procedure using ultrasound waves to study the heart, its structure and motions. It is used to assess disorders of heart muscle function or valve function, or other abnormalities. (Noun: echocardiogram).
  • Eclampsia
    Coma and convulsive seizures that occur at or after 20th week of pregnancy.  Associated with pregnancy-induced hypertension, it can be fatal if untreated.
  • Ectopic Pregnancy
    Abnormal pregnancy, occurring in about 2% of all pregnancies, in which the fertilized egg (conceptus, embryo) implants outside the uterus, most often (90%) in the fallopian tube (tubal pregnancy) but occasionally in the ovary (ovarian pregnancy) or abdominal cavity (abdominal pregnancy). As the embryo develops the tube, ruptures or other complications arise, usually causing haemorrhage and requiring immediate surgery.
  • Eczema

    Inflammation of the outer layers of the skin. There are three main groups of eczema. Atopic eczema is a broad allergic reaction similar to hay fever and asthma. Seborrhoeic eczema is a life-long condition often described as cradle cap in infants or dandruff in adults. Contact dermatitis occurs after irritation (often from chemical substances) or as a specific allergic reaction (often to metals such as nickel).  The most common treatments are moisturisers and steroid creams/ointments.

  • Effusion
    Escape of fluid from blood vessels or lymphatic system into a body cavity or space
  • Electrocardiogram

    Graphic recording, produced by an electrocardiograph, of the electrical activity of the heart. It permits the detection of abnormalities in the transmission of the cardiac impulse through the heart muscle and serves as an important aid in the diagnosis of heart ailments.

  • Embolism & Thromboembolism

    Embolism— a condition in which material (tissue, fat, air, blood clot, etc.—called an embolus) travels through the bloodstream and then becomes lodged in a vein or artery and blocks the flow of blood through that blood vessel.

    Thromboembolism—a blood clot (thrombus) that breaks free in the blood stream and blocks a blood vessel. This can occur in a vein (venous thromboembolism) or in an artery (arterial thromboembolism).

  • Emphysema
    Emphysema Chronic progressive lung disease in which air sacs (alveoli) in the lungs are damaged, resulting in loss of elasticity and function of the lungs. The condition is characterized by shortness of breath and may be accompanied by a cough. It may eventually lead to heart damage.
  • Encephalopathy
    Any disease causing deterioration of the brain
  • Endemic
    Commonly occurring in a particular population or geographic region
  • Endocrine
    Cells or tissue that produce hormones released into the bloodstream. These hormones then have an affect on other cells throughout the body. For example, the thyroid gland produces thyroid hormone that affects metabolism of many cells around the body.
  • Endogenous

    Originating in or produced within an organ, tissue, cell or by the body. The term may be used to distinguish between an internal or external source of a substance, such as insulin or testosterone.

  • Endometriosis
    Condition marked by the presence, growth, and function of the tissue that normally lines the uterus (endometrium) in such sites as within the uterine walls, the fallopian tubes, the ovaries, and other sites within the pelvis or, rarely, out of the pelvic region. Endometriosis is fairly common (est. 15% of women), especially in childless women and women who have children late in life. Symptoms depend on the size and location of the displaced tissue but commonly include painful menstruation, painful coitus, and sometimes painful urination and defaecation and premenstrual bleeding. Endometriosis is a common cause of infertility. Treatment includes analgesics to relieve pain, hormones to decrease the size and number of lesions and, in severe cases, surgery.
  • Enteral nutrition
    Feeding through a tube directly into the gut
  • Enzyme
    Protein produced in cells that acts as a catalyst speeding up the rate of biological reactions without itself being used up. Many enzymes are involved in digestion (e.g., lipase helps to break down fat) and respiration. The names of many enzymes end in -ase.
  • Eosinophil
    White blood cell (leucocyte) with granules that are readily stained with eosin. Eosinophils, normally about 1-3% of the total white blood cell count, are believed to function in allergic responses and in resisting some infections.
  • Erectile dysfunction
    the repeated inability to achieve or sustain an erection
  • Exchange Transfusion
    Removal of a person's blood in small amounts and its replacement with equal amounts of donor blood, especially exchange transfusion of the foetus (intrauterine exchange transfusion) or the newborn to treat erythroblastosis foetalis (or neonatorum) by removing the Rh and ABO antibodies and damaged red blood cells (erythrocytes) and substituting blood with normal oxygen-carrying capacity.
  • Exocrine
    Cells or tissue that produce substances that are released outside of that organ. Examples include saliva production into the mouth, sweat production onto the skin, or enzymes produced from the pancreas into the gut.
  • Exogenous

    External, originating outside of an organ, tissue, cell or the body. It may refer to a substance that is administered to the body, such as exogenous insulin or testosterone.

  • Exudate
    Fluid that has leaked into a body cavity as a result of injury or inflammation; it has a higher than normal protein content and may be cloudy due to increased numbers of white blood cells.


  • False-negative
    Test or procedure result indicating a normal or negative result when, in fact, an abnormal condition is actually present. A test is said to be sensitive when it has a low false-negative rate. An insensitive test has a high false-negative rate and should not be relied upon to exclude abnormality or disease. For example, an electrocardiogram for heart disease is relatively insensitive - many patients with coronary artery disease, including acute heart attacks, have a negative result. Other tests, such as nuclear medicine treadmill scans, are far more sensitive because they have a much lower percentage of false-negative results.
  • False-positive
    Test or procedure result indicating a positive or abnormal result when, in fact, no abnormal condition is actually present. A specific test has a low false-positive rate. A non-specific test has a high false-positive rate and should not be relied upon to suspect or diagnose an abnormality or disease. Some types of urine pregnancy tests are very nonspecific - any type of contaminant (such as dirt, blood, or vaginal secretions) may give a false-positive result when, in reality, the patient is not pregnant. A serum pregnancy test is both sensitive and specific.
  • Feedback System

    The body uses feedback systems to control certain functions. A feedback system uses one of the products of a pathway, usually the end product, to control the activity of the pathway and to regulate the amount of that product. Feedback control may be positive or negative.

    To understand negative feedback, think of how the thermostat in your house controls the temperature. Let’'s say that the thermostat is set at 70 degrees F (the end product concentration). When the temperature falls below 70 degrees F, the feedback system is triggered and the furnace lights and starts to pump warm air into the house. When the air in the house reaches 70 degrees F, the thermostat shuts off the furnace (no more product made; no more hot air generated). A negative feedback system maintains a '“steady state'” or equilibrium and is the one most commonly found in the body.

    Positive feedback systems increase the rate of formation of the product. This tends to cause change in the system rather than maintain a steady state. Think of how when a person works hard and is praised for their efforts (given positive feedback), they work harder still, expecting more praise. There are very few positive feedback systems in the body. One example, however, is lactation. The suckling action of an infant produces prolactin, which leads to milk production; more suckling leads to more prolactin, which in turn leads to more lactation. This is a positive feedback system as the product (milk) produces more suckling and more hormone. When the child is no longer breast feeding, the prolactin drops off and milk production goes down.

  • Fibroid
    A benign tumour containing fibrous tissue (fibroma), especially of the uterus. Fibroid tumours of the uterus are common and in many cases do not require treatment; if, however, they cause discomfort or haemorrhage, surgical removal is necessary.
  • Fluorescence

    The property of some materials to emit light when exposed to radiation or to light of a different colour. The light produced is called fluorescence.

    A fluorescent substance is one possessing the property of fluorescence.

  • Folliculitis
    Infected hair follicles
  • Formalin

    A chemical solution (formaldehyde in water) used to harden and preserve tissues prior to staining and microscopic study. One of a number of fixatives used in pathology laboratories.

  • Functional Testing
    Functional testing is used to determine whether or not a specific substance is properly performing its biological role in the body and to what extent. This testing can determine how well a specific coagulation factor is performing its role in the coagulation cascade; for example, normal amounts of fibrinogen can be present, but if not working properly, abnormal coagulation results. Functional testing can also determine the correct level of activity of other substances such as hormones and enzymes.
  • Fungus
    One of the four major groups of microorganisms (bacteria, viruses, parasites and fungi) that occurs in nature as a yeast (small unicellular structure similar to bacteria) or a mold (large filamentous forms that may be seen with the naked eye)


  • Galactorrhoea
    Breast milk production or nipple discharge when there has been no pregnancy.
  • Ganglioside

    Type of substance found on the surface of cells, particularly in the brain, that is important in cell-to-cell communication

  • Gene
    Basic unit of genetic material; in humans, a segment of DNA on a chromosome that usually codes for the production of a specific protein
  • Genetic Counselling

    Process of determining the risk of a particular genetic disorder occurring within a family and providing information and advice based on that determination; used to help couples in family planning and in the care of children affected or thought to be affected with a particular genetic disorder. An accurate diagnosis is essential and may require special biochemical and cell studies; a careful and complete family medical history is also needed. The subjects of prenatal diagnosis, artificial insemination, sterilization, and termination of pregnancy may be included in the counselling, depending on the particular disease and circumstances involved.

    Related content
    Elsewhere on the web
    NHS: Genetic testing and counselling

  • Gestation
    Period of development of a fetus between the time an egg is fertilized and birth
  • Gigantism
    a condition in children resulting from excess growth hormone characterized by an abnormal growth of the long bones and increased size of feet and hands.
  • Globulin
    Any of a group of simple proteins found in the blood.
  • Glomerulonephritis

    A group of diseases where the glomerulus in the kidney becomes damaged

  • Glomerulus
    Plural: glomeruli; one of a number of specialised structures in the kidney, composed of loops of specialised capillaries that filter blood, allowing small substances to pass through towards the urine but preventing loss of larger proteins and blood cells.
  • Glycogen
    The principal storage form of glucose found primarily in the liver and the muscles.
  • Goitre

    An enlarged thyroid gland

  • Granuloma
    Granulomas are small masses of immune and inflammatory cells and fibrous tissue that create bumps under the skin and throughout the body.
  • Gynecomastia

    Enlargement of breast tissue in the male


  • Haem
    An essential chemical synthesised in the body and found in haemoglobin in blood and cytochromes in other cells.
  • Haemodialysis

    A procedure that removes waste substances from the circulating blood; often performed on patients with kidney disease

  • Haemoglobinopathy
    A group of single gene disorders including structural haemoglobin variants (e.g., sickle cell haemoglobin) and the thalassaemias
  • Haemolysis

    Rupturing of red blood cells.

  • Haemolytic Disease of the Newborn

    A condition in which antibodies in a pregnant woman's blood cross the placenta and destroy her baby's red blood cells; it may develop when the mother and baby have differences in one or more blood group antigens

  • Haemorrhage
    1. bleeding; escape of blood, usually from injured blood vessels
    2. excessive bleeding over a short period of time, either internally or externally; if uncontrolled, can lead to shock and death.
  • Haemosiderosis

    Abnormal deposition of an iron-containing compound (haemosiderin) in tissues, often associated with diseases in which there is extensive destruction of red blood cells (e.g., thalassaemia).

  • Haemostasis

    The stopping of bleeding or the flow of blood

  • Half-life
    The amount of time it takes for the body to inactivate or metabolize half of a substance; a second half-life would decrease the remainder by half again, and so on.
  • Heinz Bodies
    Precipitated haemoglobin that can be seen inside red blood cells under the microscope
  • Heterophile Antibody
    A human antibody that reacts with proteins from another species; may lead to innaccurate results in immunoassay tests; sometimes used to refer to antibodies associated with infectious mononucleosis
  • Heterozygous
    Having two different copies of a particular gene, one of which may be abnormal
  • Hirsutism
    Increased hair in a woman, particularly affecting the face, thighs, chest and abdomen
  • Homozygous
    Having two identical copies of a particular gene, either both normal or both abnormal
  • Hormone
    Chemical produced and secreted by endocrine (ductless) glands that travels through the bloodstream and controls or regulates the activity of another organ or group of cells - its target organ. (For example, growth hormone released by the pituitary gland controls the growth of long bones of the body.) There are two main types of hormones - steroidal (e.g., oestrogen, testosterone, aldosterone, cortisol) and non-steroidal. Secretion of hormones is regulated by feedback mechanisms and neurotransmitters.
  • Human leucocyte antigens
    Group of proteins present on the surface of white blood cells (leucocytes) and other nucleated cells (containing a nucleus). These proteins help the body’s immune system to identify its own cells and to distinguish between “self” and “nonself.” Each person has an inherited combination of HLA antigens and, while not as unique as a fingerprint, the presence or absence of each antigen creates a distinctive HLA combination for each person. HLA antigens are divided into types: Class I (A, B, C) and Class II (DR, DP, DQ).
  • Hydrocephalus
    A condition in which the chambers (ventricles) within the brain become enlarged due to an abnormal accumulation of cerebrospinal fluid
  • Hypercoagulability
  • Hyperglycaemia
    Higher than normal amount of glucose in the blood, most often associated with diabetes mellitus but sometimes occurring in other conditions.
  • Hyperinsulinaemia
    Elevated levels of insulin in the blood
  • Hyperkalaemia
    Higher than normal potassium levels in the blood, with symptoms of nausea, muscle weakness and, if severe, irregular heart beat; occurs in kidney failure and sometimes as an adverse effect following diuretic use.
  • Hyperlipidaemia
    Higher than normal cholesterol and/or triglyceride levels in the blood
  • Hyperlipoproteinaemia
    Any of a large group of disorders of lipoprotein and cholesterol metabolism resulting in higher than normal cholesterol and lipoprotein levels in the blood. Some of the disorders are hereditary (e.g., familial hypercholesterolaemia) whereas others are acquired.
  • Hypernatraemia
    Higher than normal sodium levels in the blood
  • Hyperparathyroidism
    A condition characterised by an overproduction of parathyroid hormone (PTH), a hormone that controls calcium and phosphate levels in blood and calcium in bone; it is made by the parathyroid glands. Primary hyperparathyroidism causes high calcium and low phosphate levels, and can cause kidney stones occasionally. Secondary hyperparathyroidism is caused by low levels of calcium or vitamin D, or high levels of phosphate; it is commonly caused by chronic kidney disease. Either form can cause osteoporosis or bone pain.
  • Hyperplasia
    Excessive growth of cells that form a tissue.
  • Hypochromic
    Paler than normal red blood cells
  • Hypoglycaemia
    Lower than normal level of glucose in the blood, usually resulting from administration of too much insulin in diabetes mellitus, excessive insulin secretion from the pancreas, or poor diet. Symptoms include headache, weakness, anxiety, personality changes, and, if severe and untreated, coma and death. Treatment is by administration of glucose.
  • Hypogonadism
    Defect in the reproductive system which leads to decreased function of the testes or ovaries.  This affects fertility and in hormone production.
  • Hypokalaemia
    Abnormally low level of potassium in the blood, leading to weakness and heart abnormalities; it may result from diuretic intake, adrenal tumour, starvation, or other disorder.
  • Hyponatraemia

    Lower than normal sodium levels in the blood

  • Hypoparathyroidism
    A condition characterised by underactivity of the parathyroid glands and reduced production of parathyroid hormone (PTH), a hormone that controls calcium and phosphate levels in blood and calcium in bone. Symptoms may include tingling in the fingers and toes, muscle aches and spasms, fatigue, dry skin and brittle nails, headaches, anxiety, and depression.
  • Hypopituitarism
    A condition resulting from diminished secretion of pituitary hormones.
  • Hypothalamus
    Area of the brain located just above the brainstem that controls the pituitary gland and regulates many bodily functions, such as body temperature, hunger, thirst, sleep, and mood through the release of hormones
  • Hypoxia
    Lack of oxygen


  • Idiopathic
    A disease or condition that does not have an identifiable cause
  • Immune System

    The body's means of protection against microorganisms and other foreign substances; it is composed of two major parts: the humoral response (B lymphocytes and production of antibodies) and the cell-mediated response (T lymphocytes that attack foreign substances directly).

  • Immunity

    State of being not susceptible to a particular disease. Immunity may be natural or innate, or it may be acquired during life (e.g., as a result of infection or vaccination).

  • Immunocompromised

    Having a reduced ability of the immune system to mount a normal response to infection; can be caused by certain conditions, such as HIV infection, or certain drugs, such as chemotherapy agents; can also be induced deliberately by immune-suppressing drugs, such as those used to help prevent rejection of transplanted organs

  • Immunoglobulin
    Any of the five classes of structurally distinct antibodies produced in lymph tissue in response to a foreign substance. The five kinds are immunoglobulin A, D, E, G and M.
  • Immunoglobulin A
    One of the five classes of immunoglobulins. One of the most common immunoglobulins, it is present in body secretions and is the chief antibody in the mucous membranes of the gastrointestinal and respiratory tract and in saliva and tears.
  • Immunoglobulin D
    One of the five classes of immunoglobulins; it is present in small amounts in serum and is thought to function in certain allergic responses.
  • Immunoglobulin E
    One of the five classes of immunoglobulins; it is present primarily in the skin and mucous membranes and is believed to function in response to environmental antigens and to play a role in allergic reactions characterised by skin eruptions.
  • Immunoglobulin G
    One of the five classes of immunoglobulins; widespread in the body, it is the main antibody defence against most bacterial invasions and other antigens.
  • Immunoglobulin M
    One of the five classes of immunoglobulins; a large molecule, it is found in blood and is involved in combating blood infections and in triggering immunoglobulin G production.
  • Immunosuppressive
    Pertaining to a substance that lowers the body's normal immune response.
  • Impetigo
    Shallow, fluid-filled blisters surrounded by yellow crusts
  • In vitro
    Outside the body; in the clinical lab, in an artificial environment such as a test tube or petri dish
  • In vivo
    Within the body; within a living environment
  • Incubation period

    Time between exposure to an infectious agent, such as a virus, and the onset of symptoms of disease

  • Infarction

    Death of an area of tissue due to lack of blood supply.  It is often used in the term myocardial infarction (MI) which is the medical term for a heart attack. This occurs when a coronary artery (blood vessel supplying part of the heart) becomes blocked.  An infarct (area of dead tissue) can be very small or very large.

  • Infection
    1. Invasion of the body by disease-producing micro-organisms, where they may multiply, causing a disease.
    2. Disease caused by micro-organisms (e.g., certain bacteria).
  • Inflammation

    The response of body tissues to injury such as trauma or infection. Inflammation is a complex process that can be localised or systemic.  When localised, it causes pain, heat, swelling and redness of the affected area; when systemic, it may present as a general feeling or malaise with fatigue and fever.

  • Inhibitor

    1) A substance that stops, blocks, or slows down the action of an enzyme
    2) A substance that stops or impedes a process from taking place in the body

  • Insulinoma
    A tumour of the insulin-producing islet cells in the pancreas, causing low blood glucose levels
  • Intravenous
    Into or within a vein.
  • Intrinsic factor
    Intrinsic factor is a substance (glycoprotein) produced by a group of specific cells in the stomach.  Interference in the production or activity of Intrinsic factor can reduce the absorption of vitamin B12 in the small bowel and result in anaemia.
  • Islet cells
    Specialised cells in the pancreas that produce and secrete one of several hormones that affect certain body functions; some examples include alpha cells that produce glucagon and beta cells that produce insulin.


  • Joint
    Point where two or more bones meet. A joint may be immovable (fibrous), as those of the skull; slightly movable (cartilaginous), as those connecting the vertebrae; or freely movable (synovial), as those of the elbow and knee.


  • Keratin
    A fibrous protein found in the hair, nails, and outer layer of the skin
  • Ketoacidosis
    Acidosis with an accumulation of fat breakdown products called ketone bodies, occurring primarily as a complication of uncontrolled diabetes mellitus. It is characterized by a fruity breath odour, nausea and vomiting, shortness of breath, mental confusion, and, if untreated, coma (diabetic coma). Treatment includes administration of insulin and fluids and the correction of electrolyte imbalance.
  • Klinefelter syndrome

    A rare genetic condition in boys and men caused by an extra X chromosome. (Males normally have one X and one Y chromosome.) The presence of the extra X chromosome may or may not produce obvious signs and symptoms (usually in teens and adults), such as low testosterone, small penis and testicles, enlarged breasts, tall stature and/or behavioral, learning, speech or language disabilities. Most of these individuals are infertile.


  • Latent
    Condition or infectious agent that is present in the body but not causing symptoms and/or actively multiplying; the condition may progress from a latent to active form if the immune system of the patient is no longer able to hold the condition or infection in check.
  • Lipaemic
    Containing high levels of lipids or fats in the blood
  • Lipoprotein

    Protein in the blood whose primary purpose is to transport cholesterol, tryglycerides, and other fats throughout the body

  • Lymphatic system
    Lymphatic system: a collection of tissue and organs with re-circulate lymphocytes as well as fluid and proteins that escaping from blood vessels.  It includes the lymphatic vessels, lymph nodes, spleen, tonsils, thymus and bone marrow and is an important part of the immune system.
  • Lymphocyte
    White blood cell (leucocyte) containing no granules that normally makes up about 25% of the total white blood cell count but increases in the presence of infection. Lymphocytes occur in two forms: B cells, the chief agents of the humoral immune system, which recognize specific antigens and produce antibodies against them; and T cells, the agents of the cell-mediated immune system, which secrete immunologically active compounds and assist B cells in their function.


  • Macrophage
    A large white blood cell (WBC) found in connective tissue, lymph nodes, spleen, bone marrow and other tissues; it is an important part of the body's immune system and helps fight infections by surrounding and ingesting disease-causing microorganisms.
  • Magnetic Resonance Imaging (MRI)

    What is it?
    The MRI scan is relatively new and uses radio and magnetic waves. This means it does not use X-rays or other forms of damaging radiation. This test is not performed in a Pathology laboratory but may well be requested at the same time as laboratory tests.

    How does it work?
    The powerful magnet of the instrument affects the body’s hydrogen atoms contained in body water. The hydrogen atoms line up in the magnetic field. Radio waves are then passed through the body and alter the position of some of the hydrogen atoms. When the radio waves are switched off the hydrogen atoms move back to their original position. When they do this they give out small radio waves of their own that are detected by the instrument.  From these radio waves, the MRI instrument is able to produce a detailed picture of the body.  Parts of the body with little water, like bone, show up dark while areas containing a lot of water, like fat, show up bright.  The machine produces cross sectional pictures along the body and can produce pictures at all angles through the body.  Usually two dimensional pictures are taken but it is possible to take three dimensional pictures.  It can show up soft tissues very clearly.

    What it is used for?
    It is commonly used to look at the brain, spinal cord, pelvis and abdomen, and to investigate injuries to bone, joints and soft tissue.  MRI scans are particularly useful for looking for tumours.

    How is it carried out?
    MRI scans are usually carried out as an outpatient procedure.  The patient lies in a cylindrical chamber open at both ends.  It is important that all metal containing objects are removed, such as watches, jewellery, belts, studs etc.  Also the doctor needs to know if the patient has any surgical clips in the body or if the patient uses any electrical appliances like an internal hearing aid (cochlea implant) or pacemaker as an MRI scan will not be possible in such cases.  It is important that the patient lies perfectly still during the test.  Movement during the test will make images less clear.  Because of this children may be given an anaesthetic.  Some patients may find the chamber claustrophobic and need to tell the doctor, in advance, if they are anxious about this as the doctor may give a mild sedative.  Sometimes an injection is given of a contrast medium, a substance that helps produce clearer images.  You can have a person sit with you during the test but they also must have no metal objects on their person. The test takes from about half an hour to an hour and a half.

    What are the risks?
    There are no known side effects to MRI scans.  The test is not painful and cannot be felt.  The machine makes a banging noise that can be unpleasant but the patient is usually offered headphones to help reduce this unpleasantness.  You can even bring in your own music for the radiographer to play through the headphones.  The test can be repeated as radiation is not used.  The test is not carried out in women less than 12 weeks pregnant.

  • Malignant
    Harmful; tending to cause death; worsening or progressing, especially a cancer that is invasive and is spreading to distant parts of the body (metastatic).
  • Mammogram
    X-ray film of the soft tissue of the breast.
  • Mammography
    Procedure in which the soft tissues of the breast are x-rayed to detect benign or malignant tumours. Periodic mammography is generally recommended for women thought at high risk for breast cancer and in certain other situations. The UK breast screening programme makes use of this technique.
  • Mast cell

    A type of tissue cell found throughout the body but especially in connective tissue such as the skin, lining of the intestine and air passages as well as in the bone marrow. Mast cells contain granules that store chemicals. These chemicals are released as part of the body's normal response to injury but also may be released as part of an allergic response to exposure to an allergen. The chemicals that are released can cause the allergic signs and symptoms.

  • Mastocytosis

    Abnormal accumulation of mast cells within one or more organs. Mast cells are a type of tissue cell found throughout the body that release chemicals as part of the body's normal response to injury but sometimes as part of an allergic response. Cutaneous mastocytosis is a benign disease of the skin, usually affecting children. Systemic mastocytosis affects mostly adults, who may experience signs and symptoms related to the organs affected such as skin rashes or characteristic red, blistering lesions, peptic ulcers, chronic diarrhea, joint pain or enlargement of the liver, spleen, or lymph nodes. Systemic mastocytosis may progress slowly or may be aggressive, causing organ dysfunction and, in rare cases, causing a form of leukaemia.

  • Megakaryocytes

    Large cells in the bone marrow that produce blood platelets

  • Meninges
    Layers of tissue that surround the brain and spinal cord
  • Mesothelioma
    Rare cancer of the membranes that cover the outside of internal organs and line body cavities, including the chest (pleural mesothelioma), abdominal cavity (peritoneal mesothelioma), and the heart (pericardial mesothelioma)
  • Metabolism
    Combined chemical and physical process that takes place in the body, involves the distribution of nutrients, and results in growth, energy production, elimination of wastes, and other body functions. There are two basic phases of metabolism: anabolism, the constructive phase, during which small molecules resulting from the digestive process are built up into complex compounds that form the tissues and organs of the body; and catabolism, the destructive phase, during which larger molecules are broken down into simpler substances with the release of energy.
  • Metabolite
    Product of chemical or biological processes in the body
  • Metastasis
    Spread of a tumour from its site of origin to distant sites, usually through the bloodstream, the lymphatic system, or across a cavity such as that contained by the peritoneum.
  • Microaerophilic
    Living or occurring in a reduced-oxygen environment
  • Microcytic
    Smaller than normal red blood cells.
  • Microorganism
    Organisms (microscopic life-forms) that are not visible to the naked eye such as bacteria, fungi, parasites, and viruses
  • Monoclonal gammopathy

    Abnormal condition in which clones of a single plasma cell or B lymphocyte produce greatly increased amounts of an immunoglobulin molecule; analysis of serum or urine will show a distinct "monoclonal" band, typically in the "gamma" or beta region.

  • Monocyte
    Leucocyte (white blood cell) which ingests bacteria and other foreign particles. Monocytes are usually larger then other peripheral blood leucocytes, have a large central oval or indented nucleus and make up 5-10% of the total white blood cell count.
  • Mutation
    Change in the genetic structure; it may occur spontaneously or be induced (e.g., by radiation or certain mutagenic chemicals).
  • Myelin

    The fatty covering that insulates nerve fibers


  • Narcolepsy
    A chronic condition characterized by sudden uncontrolled sleep spells during the day
  • Nephrotic Syndrome
    Damage to the glomeruli capillaries in the kidneys' filtering units, the nephrons; it leads to the loss of albumin and other proteins into the urine.
  • Neuroendocrine
    That portion of the endocrine system involving hormone produced by or regulated by the nervous system
  • Neutropenia
    Decreased number of neutrophils, a type of white blood cell
  • Neutrophil
    White blood cell (leucocyte) with granules that stain blue. Neutrophils engulf bacteria and cellular debris. An increase in the number of neutrophils occurs in acute infections, certain malignant neoplastic diseases, and some other disorders.
  • Nitrogen
    Non-metallic element that is a component of all protein and many organic compounds. Nitrogen compounds are essential parts of all organisms, present in nucleic acids, proteins, and other biologically important compounds.
  • Non-palpable
    Not perceivable by touch.
  • Normal flora
    Microorganisms that live harmlessly on or in the body and do not cause disease unless the normal protective barriers (skin, mucosa) are compromised
    Abbreviation of ‘Non-Steroidal Anti-Inflammatory Drugs’.  This group of painkillers include drugs such as ibuprofen and aspirin.  They act against fever as well as decreasing pain and inflammation.  They can cause side effects such as stomach ulcers.
  • Nucleus
    The structure in cells that contains the chromosomes, genes, DNA.
  • Nutrient Medium
    Material that provides the proper nutritional environment to promote the growth of microorganisms


  • Oedema
    Formerly know as dropsy

    Abnormal collection of fluid in spaces between cells, especially just under the skin or in a body cavity (e.g., peritoneal cavity) or organ (e.g., the lungs - pulmonary oedema). Causes include injury, heart disease, kidney failure, cirrhosis, and allergy. Treatment depends on the cause but often involves bedrest, diuretics, and restriction of salt.
  • Oligoclonal bands

    Discrete bands observed on an electrophoretic gel as a result of a patient’s sample being analyzed by protein electrophoresis

  • Oncogene
    Gene in a virus that is able to produce a malignant change in an infected cell; several have been identified in human tissue as potential causes of cancer. Researchers are attempting to isolate anti-oncogenes that suppress tumours and may be used in the treatment of cancer. Certain oncogenes may play a role in normal growth and development; if they are damaged or mutated, cancer may result.
  • Opportunistic Infection
    Infection that affects people with suppressed immune systems
  • Organ
    Part of the body which works together to perform one or more roles.  An organ will contain many cells and different types of tissues.  Mostly organs were described by anatomists even before their roles were understood.  Examples include heart, lungs, liver, or even skin.
  • Oxidative Stress
    Damage to cells in the body caused by free radicals; free radicals, groups of atoms containing an oxygen atom and a free electron, can damage and sometimes destroy cells.


  • Pandemic

    An epidemic that occurs over a wide geographic area (across continents)

  • Parasite
    One of the four major groups of microorganisms (bacteria, viruses, fungi, and parasites) that may live freely in nature, live on another organism without harming it, or live at the expense of the host organism
  • Parenteral
    Pertaining to administration of a substance (e.g., a drug), not through the digestive system but, for example, by injection under or through the skin. Also includes intravenous administration of medications.
  • Parietal
    1) Of or pertaining to the cells that line a cavity, such as the chest or abdomen;
    2) A specialized cell in the stomach that makes acid to help in food digestion, as well as intrinsic factor, which is needed to absorb vitamin B12
  • Paroxysmal choreoathetosis
    a condition characterized by involuntary, intermittent and irregular movements of facial muscles and limbs
  • Pathogen
    Organism that causes disease
  • Pathogenic
  • Pathologist
    A physician who has particular knowledge and skills in the use patient’s tissues (fluids such as blood, urine and sputum, and solid tissues from biopsies, surgery and post-mortem) to aid the characterisation, diagnosis and treatment of disease.
    Pathologists work in two broad areas:
    Clinical Pathology /Laboratory Medicine deals with the measurement of chemical constituents of blood and other body fluids (clinical biochemistry), analysis of blood cells (haematology), observation and measurement of proteins related to diseases of the immune system (immunology), identification of microorganisms (microbiology), and the collection, preparation and use of blood for transfusion (transfusion medicine).
    Anatomic Pathology /Cellular Pathology is the examination of the physical appearance and microscopic structure of tissues. Anatomic pathologists look at biopsies and organs removed at surgery (surgical pathology) as well as cells that are collected from brushings or body fluids (cytology). They also perform post-mortems to investigate the cause of death.
    Consultant Pathologists and Clinical Scientists direct the laboratories that perform these tests and provide consultation to other doctors on the significance of test results.
  • Pericardium
    Sac-like membrane that surrounds the heart and the base of the blood vessels that lead into it
  • Peritoneum
    The membrane lining the abdominal cavity that enclose organs such as the stomach and intestines
  • pH
    Measurement of the acidity or alkalinity of a substance. A pH of 7.0 is neutral. A substance with a pH less than 7.0 is an acid, with increasing acidity as the pH decreases toward zero. Likewise, a substance with a pH greater than 7.0 is a base (alkali), with increasing alkalinity as the pH moves toward 14.0.
  • Phaeochromocytoma

    Tumour that causes excess production of epinephrine (adrenaline) and norepinephrine (noradrenaline) and usually occurs in one or both of the adrenal glands but may also occur elsewhere in the abdomen.

  • Phenotype
    The observable physical or biochemical characteristics of a person, as determined by both their genetic makeup and environmental influences
  • Phospholipid
    A substance in the body that contains both lipid (fat) and phosphorus. Phospholipids are found in all cells throughout the body because they are a major component of the cell membrane, the outermost layer of a cell.
  • Pituitary gland
    Pea-sized gland located in the center of the head behind the sinus cavity at the base of the brain; the pituitary consists of two parts that produce different hormones: 1) in the anterior portion, growth hormone (GH), adrenocorticotropin (ACTH), thyroid-stimulating hormone (TSH), lutenizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL) are produced; 2) in the posterior portion, oxytocin and antidiuretic hormone (ADH) (produced in the hypothalamus) are stored for release.
  • Placenta

    The organ that connects a pregnant woman with her developing baby in the uterus; blood from the mother and baby do not mix directly, but a thin membrane within the placenta allows nutrients from the mother to pass to the baby and waste products to pass from the baby to the mother for elimination.

  • Plaque
    1. Flat, raised patch on the skin or mucous membrane
    2. Deposit on the inner arterial walls in atherosclerosis
    3. Deposit of saliva and bacteria on teeth that encourages the development of decay (caries)
  • Plasma
    Straw-coloured fluid part of blood and lymph that contains water, electrolytes (e.g. sodium and potassium), glucose, fats, and proteins, and in which red cells (erythrocytes), white cells (leukocytes) and platelets are suspended. In addition to carrying the cellular elements, plasma helps maintain the fluid-electrolyte and the acid-base balances of the body and helps transport wastes.
  • Plasma cell
    Mature lymphocyte (B cell) that produces and secretes antibodies
  • Pleura
    One of the two membranes that surrounds each lung and lines the chest cavity
  • Polycythaemia
    Abnormal increase in the number of red cells (erythrocytes) in the blood, often associated with lung or heart disease, or exposure to high altitudes for a long period, but in many cases of unknown cause.
  • Polymorphic
    Gene having many different possible forms (alleles)

    See also: Polymorphism
  • Polymorphism
    Inherited person-to-person variation in the genetic code sequence within a specified DNA segment or gene

    See also: Polymorphic
  • Polymyalgia Rheumatica
    A disease that causes pain and weakness in the shoulder, neck, arm and back muscles with morning stiffness that is often severe. It mainly affects women over 50 years of age.
  • Posterior
    At or toward the back
  • Precursor

    1. one that comes before or gives rise to another
    2. in chemistry, one substance that comes before or gives rise to another often more stable substance

  • Preventive Medicine
    That branch of medicine concerned primarily with the prevention of disease; it concerns itself with immunization, eradication of disease carriers (e.g., malaria-carrying mosquitoes), screening programs, and other factors.
  • Primary biliary cholangitis (primary biliary cirrhosis)

    Primary biliary cholangitis (often referred to as primary biliary cirrhosis) is an autoimmune disorder that causes inflammation and scarring of the bile ducts inside the liver, causing continual liver damage and blockage of the bile flow. It is found most frequently in women between the ages of 35 and 60. More than 90% of those affected by primary biliary cirrhosis will have high levels of antimitochondrial antibodies.

  • Prognosis

    1) prediction about the course or outcome of a disease or illness
    2) the likelihood of recovery from a disease or illness

  • Prophylaxis
    (adj. Prophylactic)
    1. Measure taken to prevent or protect against disease
    2. Antibiotic prescribed to prevent infection
  • Prostatitis
    inflammation of the prostate
  • Protein
    Any of a large group of complex compounds, containing carbon, hydrogen, oxygen, nitrogen, and sometimes phosphorus and sulphur, and consisting of chains of amino acids joined by peptide bonds. Proteins form the structural part of most organs, and make up enzymes and hormones that regulate body functions. They are synthesized in the body from their constituent amino acids, obtained in the diet.
  • Purpura fulminans
    Involves severe clotting throughout much of the body, ultimately causing death to the tissues. If not treated immediately, it is a life threatening condition.
  • Pus
    Collection of fluid, white blood cells, microorganisms, and cellular material that indicates the presence of an infected wound or abscess


  • Qualitative Test Results
    Test results expressed in term of the nature or properties of the subject at issue. For instance, your doctor may describe your platelet count as "high" and not give you a definitive number.
  • Quantitative Test Results
    Test results that are expressible in terms of determinate numbers.
  • Quantity Testing
    Quantity testing measures how much of a particular substance or analyte is present. This type of testing can measure amounts of coagulation factors, hormones, enzymes, and many other substances. It does not, however, evaluate how well the substance is working or performing its role in the body.


  • Random Urine Sample
    A small sample (usually less than a cup) of urine, usually collected at the doctor's surgery or the laboratory.
  • Recessive Gene
    Genes are instructions for our body.  Normally genes are inherited in pairs – one from each parent.  A dominant gene needs only one of the pair to cause a change.  A recessive gene will not act on the body unless both of the pair are the same.  For example, the gene for cystic fibrosis is recessive and will not cause disease if a normal gene (which is dominant) is present.  It is therefore only possible to develop cystic fibrosis if both parents pass on a cystic fibrosis gene.
  • Rectal Examination
    This is the most frequently performed test to detect prostate cancer. The patient lies on his side and the doctor inserts a gloved, lubricated finger into the rectum to feel for any growth. The prostate is located next to the rectum and most cancers begin in the area of the gland that can be reached by rectal examination. The test may be uncomfortable, but it is not painful.
  • Retina
    Sensing part of the eye that collects images from the lens and translates them to chemical signals that can be interpreted by the brain
  • Reye's syndrome
    A rare condition that causes degeneration of the brain and is characterised by vomiting, fever, accumulation of fat in the liver, swelling of kidneys and brain, disorientation and coma; often occurs in children and following another illness, such as chicken pox.
  • RNA
    In a cell, a molecule that contains some of the genetic information of the cell involved in cellular processes and activities


  • Sensitivity
    In the clinical laboratory:
    1. a test's ability to correctly identify individuals who have a given disease or disorder;
    2. ability of a test to detect small amounts of a substance or to measure a reaction
  • Septicaemia

    The term septicaemia was historically used to describe sepsis with evidence of bacteraemia, but is no longer considered to accurately describe the processes involved.

  • Serum
    The fluid produced when blood clots.
  • Serum sickness
    An allergic reaction to proteins in a foreign serum, usually in response to an injection; it is characterised by symptoms such as fever, skin rash, pain and swelling in one or more joints, and kidney damage
  • Shwachman-Diamond Syndrome
    A rare congenital disorder characterised by exocrine pancreatic insufficiency, bone marrow dysfunction, and skeletal abnormalities; it is the second most common cause of inherited pancreatic insufficiency after cystic fibrosis.
  • Sign
    Evidence of a disease or condition usually found when a doctor examines a patient.  For instance a patient might complain of a cough (symptom) and when the doctor listens to the chest he might find crackles (sign) which suggest pneumonia.
  • Somatic Cells
    All body cells, except the reproductive cells
  • Specificity
    Specificity measures a test's ability to correctly exclude individuals who do not have the given disease or disorder. The more specific a test is, the fewer false positive results it produces.
  • Speculum

    A metal or plastic device to allow viewing and access to the cervix and vagina

  • Spina bifida
    A birth defect in which the bones of the spine do not close around the spinal cord (the continuation of brain tissue that normally is surrounded by the spinal bones); this opening may be covered by skin (also called spina bifida occulta, which means hidden), in which case there may be no or mild symptoms. In other cases, the skin does not cover the defect, allowing the covering of the brain and spinal cord, the meninges, to protrude out through the skin (meningocele) or, in some cases, to rupture, exposing the spinal cord itself (meningomyelocyle). These latter two examples may cause severe damage to the nerves of the legs and lower abdomen, causing paralysis and bowel and bladder malfunction.
  • Spore
    1. Small, usually single-celled reproductive unit of some microorganisms such as fungi.
    2. Form assumed by some bacteria that is resistant to heat, drying, and chemicals; an example of a disease caused by spore-forming bacteria is anthrax.
  • Sputum

    Sticky thick liquid is which is coughed up from the lungs and bronchi. It may contain substances such as mucous, blood, pus and/or bacteria. It is not the saliva that is produced by the glands in the mouth.

  • Statins
    A group of drugs that reduce the production of cholesterol and promote the clearance of low-density lipoprotein (LDL) from the blood by the liver.
  • Stem cells
    Cells that are able to develop into many (or all) types of cells
  • Steroids

    The term steroid describes a wide variety of chemicals. When discussed as a treatment it most commonly refers to drugs such as prednisolone or dexamethasone which have powerful anti-inflammatory effects.

  • Subcutaneous
    Under the skin
  • Symptom
    Evidence of a disease or condition experienced or perceived by a patient.
  • Systemic
    Affecting the body as a whole, rather than individual parts.


  • Temporal Arteritis
    A chronic inflammation of large arteries in the face and head. Symptoms include headache, tenderness, loss of vision, and facial pain.
  • Thrombocytopaenia

    A decreased number of platelets in the blood.  Platelets help the body to produce clots and therefore thrombocytopenia can lead to bruising and occasionally bleeding (usually from the gums or as a nosebleed).

  • Thromboembolism
    A blood clot (thrombus) that breaks free in the blood stream and blocks a blood vessel.
  • Thrombophilia
    An inherited or acquired tendency to form blood clots within a vein or artery
  • Thrombosis
    The formation of a blood clot in the vascular system.
  • Thrombotic Episode
    The formation of an inappropriate blood clot that blocks a blood vessel.
  • Thymus

    Organ located behind the upper breastbone at the base of the neck that is part of the lymphatic and immune systems; disease-fighting white blood cells called T-cells develop and mature in the thymus before entering circulation. In humans, the thymus is normally active in childhood but becomes less active after puberty, eventually losing most immune activity by adulthood.

  • Thyroiditis
    an inflamed thyroid
  • Timed Urine Sample
    A sample of urine collected over a specified period of time. For a short time (2 hours), you may be asked to do this at the laboratory. For longer collections (e.g. 12 hours), you will do this at home. At the beginning of the time period, empty your bladder and discard that urine. Note the time. Collect all urine passed during the specified period of time. At the end of the time period, empty your bladder and ADD this urine to the container. Note the time. Bring all of the urine collected to the laboratory or doctor's surgery.
  • Tissue
    In medicine the term tissue refers to a collection of cells which all work together to form one particular part of the human body.  For example, if a doctor was to take a sample (biopsy) from an area of inflammation he might say "we are going to send this tissue off to the lab for some tests".
  • Titre
    In the clinical laboratory, titre is a unit of measurement. It is most often thought of as the lowest dilution of a substance in which a reaction takes place. It is usually expressed as a ratio (i.e., 1:20). For example, serum containing an antibody can be diluted with saline in a serial manner producing dilutions 1:5, 1:10, 1:20, 1:40, etc. If the lowest dilution that a reaction can still be detected between the antibody and the antigen it is directed against is 1:20, then that is the result of the antibody titre.
  • Topical
    Applied to the surface of the skin.
  • Toxaemia
    Serious infection in which disease-causing organisms are present in the circulating blood usually resulting from spread of an infection from a specific site. Symptoms include fever, chills, nausea, diarrhoea, headache, and weakness. Treatment is by antibiotics. In the US toxaemia can also mean pre-eclampsia.
  • Toxic megacolon
    A rare but serious, potentially life-threatening condition in which all or part of the colon progressively swells and becomes gangrenous, with tissue death resulting from lack of blood supply.
  • Toxicity
    Extent or degree to which something is poisonous.
  • Tracer
    In radiology, radioactive isotope (e.g., iodine-131) introduced into the body to allow biological structures to be seen as part of diagnostic X-ray techniques.
  • Translocation

    (v. translocate) In genetics, movement of one section of a chromosome to a different position on another chromosome resulting in abnormal chromosome structure

  • Transplantation
    Process of removing cells, tissue, or organ(s) from one body and inserting them into another body, especially using surgery
  • Transudate
    Fluid that has leaked into a body cavity, due to an imbalance between the pressure within blood vessels (which drives fluid out) and the amount of protein in blood (which keeps fluid in); it is a clear fluid with low protein concentration and a limited number of white blood cells.
  • Tubule
    A long, thin hollow tube; in the kidney, a structure that connects to the glomerulus and helps the kidney retain needed small substances (such as water, electrolytes, glucose, calcium) while allowing elimination of waste products. Its contents eventually drain into the collecting system of the kidney as urine.
  • Tumour
    Tissue characterised by uncontrolled cell proliferation. A tumour may be benign or malignant; localised or invasive.
  • Tyrosine kinase
    An enzyme that works by adding phosphate groups to various molecules, changing their function
  • Tyrosine kinase inhibitor

    Drug used to treat certain types of cancer; it inhibits the action of tyrosine kinase, an enzyme involved in cell growth, thus impeding the growth of cancer cells.


  • Ulcerative colitis
    A chronic disease of unknown cause that is characterized by inflammation, ulcers, and fluid collection in the lining of the colon; this condition may cause diarrhoea with blood and/or mucus and stomach cramping and pain.
  • Ultrasound

    Using sound waves to form an image of organs and tissues within the body

  • Unconjugated bilirubin

    A water insoluble but fat-soluble form of bilirubin that is formed during the initial chemical breakdown of haemoglobin and, while being transported in the blood, is almost entirely bound to albumin.

  • Urea

    Main breakdown product of proteins and the form in which nitrogen is excreted from the body in urine.

  • Urethra
    Tube through which urine passes from the bladder to outside of the body; in men, it is also the tube that runs through the penis and through which semen is discharged
  • Uveitis
    Painful swelling and irritation of the uvea, the middle layer of the eye (the layer just beneath the white of the eye), which causes redness without itching; it is a serious condition that can lead to loss of vision.


  • Vaccine
    Preparation of attenuated (weakened) or killed disease-producing viruses or microorganisms (or of substances extracted from them) administered by mouth or by injection to induce active immunity to the specific disease.
  • Venereal
    Pertaining to or caused by sexual intercourse or genital contact, as in a venereal disease.
  • Venesection
    Removal of blood from a vein e.g. in blood donation
  • Venous Thromboembolism
    A comprehensive term for abnormal venous blood clots, including the blocking of a vein by a thrombus (clot), and in some cases, including thrombus fragments then breaking off and lodging in the venous system elsewhere, for instance in the lungs.
  • Vesicle
    A small raised area of the outer layer of the skin filled with a watery liquid
  • Viral load
    Number of copies of viral genetic material
  • Virilization

    Development of masculine physical characteristics in a woman

  • Virus
    Small particle that does not exhibit signs of life, but can reproduce itself within a living cell. A virus particle is called a virion; it consists of a nucleic acid (DNA or RNA) core and a protein coat, called a capsid. A virus reproduces by infecting a host cell and taking over the nucleic acid of that host cell, making more virus nucleic acid and protein. As new virus particles develop, the host cell bursts, releasing the new virus particles. Viruses are responsible for many human diseases.
  • Vitamin
    Any of a group of organic compounds that, in very small amounts, are essential for normal growth, development, and metabolism. They cannot be synthesized in the body (with a few exceptions) and must be supplied by the diet. Lack of sufficient quantities of any of the vitamins produces a specific deficiency disease. Vitamins are generally classified as water-soluble or fat-soluble. The water-soluble vitamins are the vitamin-B complex and vitamin C; the fat-soluble vitamins are vitamins A, D, E, and K.


  • X-linked trait
    A genetic trait found on the X chromosome; women have two copies of this chromosome, while men have only one.