Glossary - text only -

• Adipose cell
a fat cell in the body specialising in the storage of globules of fat.

• Allergen
a substance that induces the hypersensitive state of allergy and stimulates the formation of E-antibodies.

• Alveolar macrophages
highly specialised macrophage cells in the lungs that attempt to engulf and digest lung hazards, such as dust and airborne bacteria.

• Amnesia
the severe loss of memory and inability to learn. Amnesia may result from chronic alcoholism, brain tumour and encephalitis as well as brain trauma. There are three types of post-traumatic amnesia: retrograde, where the patient can remember facts after the trauma, but not for a period before; anterograde, where the events before the trauma are remembered, but facts following it are not; and global transitory amnesia, which lasts a short period of time and involves anterograde followed by retrograde amnesia.

• Amniotic fluid
the fluid that surrounds the foetus in the womb, protecting it and the umbilical cord from trauma or compression. Amniotic fluid is also essential for the development of the gastro-intestinal, pulmonary and skeletal systems. It is made up of a variety of substances, including foetal urine and skin and pulmonary secretions. Amniotic fluid is replaced at a rate of once every three hours.

• Amniotic sac
a fluid-filled pouch in the uterus, made of a membrane called the amnion, which encloses the embryo and protects it from trauma. When a pregnant woman's 'waters break', the amniotic sac has ruptured, releasing the fluid within.

• Amygdala
a structure in the centre of the brain, named for its anatomical resemblance to the almond. It plays a large role in processing emotions, as well as in our defensive behaviour.

• Angina
a spasm of pain in the chest, caused by lack of oxygen to the heart as a result of the narrowing of the arteries.

• Antibiotic
a chemical substance produced by a living organism that is detrimental to another organism. The discovery of penicillin in 1928 was the beginning of a revolution in the treatment of bacterial infections.

• Antibody
a protein made by the body to fight foreign substances known as antigens. Each antigen has a specific antibody.

• Antigens
any foreign substance in the body that causes the creation of an antibody.

• Bacteria
a group of microscopic, single-cell organisms that lack a nucleus. Bacteria inhabit almost all environments, including organic matter, soil, water and the bodies of animals. Some are harmful to humans, others are beneficial. Bacteria are the chief cause of infectious diseases in humans.

• B-cells
white blood cells capable of producing antibodies in response to specific antigens.

• Basophils
a type of phagocytic granulocyte.

• Blood platelets
fragments of cell tissue produced in the bone marrow.

• Bone marrow
a collection of soft spongy tissues found in the middle of most bones. Bone marrow produces all blood cells, although some blood cells develop elsewhere.

• Body mass index (BMI)
a mathematical calculation used to determine whether a person is overweight. It is reached by dividing a person's body weight in kilograms by the height in metres squared. The healthy BMI range is between 18.5 and 24.9.

• Botulism
severe food poisoning as a result of infection by the bacteria Clostridium botulinum.

• Brain stem
the stem-like part of the brain located between the cerebrum, the cerebellum, and the spinal cord. The brain stem controls all our involuntary muscles, regulating the heartbeat, breathing, blood circulation and digestion.

• Calorie
a unit of energy, the equivalent of approximately 4.2 joules. Dietitians loosely use the word 'calorie' to mean kilocalorie in measuring the energy value of foods.

• Campylobacter
a type of bacteria that causes food poisoning in humans.

• Capillaries
narrow vessels of the blood circulatory system.

• Carbohydrate
any member of a very abundant and widespread class of natural organic substances that includes the sugars, starch and cellulose.

• Cardiovascular disease
a disease of the heart and the blood vessels — the system that conveys blood to and from all parts of the body, carrying nutrients and oxygen to the tissues and removing wastes and carbon dioxide. Cardiovascular disease is a major cause of death.

• Cataract
a clouding of the eye's lens, which may result in vision problems.

• Cerebral cortex
the outer layer of grey matter in the brain. The cerebral cortex is responsible for a wide range of functions and is made up of a huge range of specialised neurons.

• Cerebral hemispheres
the two interconnected halves of the brain, also known as the cerebrum. In the higher mammals this forms the cerebral cortex and is the largest part of the brain. Each hemisphere receives impulses conveying the senses of touch and vision largely from the opposite side of the body. Auditory input comes from both sides. The cerebral hemispheres are not equal: in every individual, one side of the brain is dominant. The dominant hemisphere controls language, mathematical and analytical functions, as well as determining whether the individual will be left or right-handed. The non-dominant hemisphere is concerned with spatial concepts, recognition of faces and some aspects of music.

• Coma
a complete lack of consciousness, characterised by loss of reaction to external stimuli and the absence of spontaneous nervous activity and usually associated with injury to the cerebrum. Unconsciousness may accompany a number of metabolic disorders or physical injuries to the brain from disease or trauma.

• Cytotoxic T-cells
T-cells capable of killing specific target cells.

• Dendritic lymphocytes
a type of white blood cell with long thread-like protrusions.

• Diabetes
a disorder of the metabolism in which sugar and starch are not properly absorbed from the blood.

• Diarrhoea
a condition of excessively frequent and loose bowel movements, a common symptom of food poisoning.

• E-antibodies
also known as immunoglobin E or IgE-antibodies, E-antibodies are a class of antibody that bind themselves to mast cells found in loose connective tissue. When E-antibodies come into contact with the allergen that first led to their production, they bind together, causing mast cells to release chemicals, including histamine.

• Eczema
itching and inflammation of the skin.

• Embryo
the early developmental stage of an animal, while it is in the egg or uterus of the mother. In humans, the term is applied to unborn children up to the end of the seventh week after conception.

• Eosinophils
a type of white blood cell active in fighting parasites.

• Escheria coli O157
E. coli: a type of bacteria that causes food poisoning in humans.

• Fat
any substance of plant or animal origin that is stable, not soluble in water, and oily or greasy to the touch. Fats in the body are made up of glycerol and fatty acids and, in their basic chemistry, they are identical to the fat we eat in the form of animal and vegetable oils. Fats and oils comprise of the three principal classes of foodstuffs, the others being protein and carbohydrate. Fat contains around twice as much energy as the other two classes of foods.

• Foetus
the unborn young of any mammal. In humans, the unborn child is known as a foetus from the eighth week after conception until birth. It is during the foetal stage that the full development of organ systems takes place.

• Gastro-enteritis
inflammation of the stomach and intestine, causing vomiting and diarrhoea.

• Glucose
also called dextrose, one of a group of carbohydrates known as simple sugars (monosaccharides). Glucose is found in fruits and honey and is the major sugar circulating in the blood of higher animals. It is the source of energy in cell function.

• Gonadotrophins
glycoproteins released by the pituitary gland or the placenta. Gonadotrophins have various effects on the ovaries and testes, including an increase in the weight of the ovaries and the growth of Graafian follicles, which contain the eggs, and, in males, the release of testosterone from the testes.

• Graafian follicle
a small cavity that contains developing ova (eggs) in the ovaries of mammals.

• Granulocytes
a cell containing conspicuous granules.

• Haematoma
the localised collection of blood, usually clotted, in an organ, space or tissue, due to a break in the wall of a blood vessel.

• Helper/inducer T-cells
T-cells that alert other immune system cells to the presence of an antigen.

• Histamine
a hormone/chemical transmitter involved in local immune responses. When released, histamine causes blood vessels to dilate and increase in permeability, allowing fluid and cells of the immune system to leak from the bloodstream. In normal cases, this allows cells to migrate to the site of injury or infection, but in an allergic reaction, too much histamine is released, and it has counter-productive effects.

• Hives
also known as urticaria. This is a skin rash, a symptom that accompanies many allergic disorders. Most individual lesions develop and fade within 24 hours.

• Hypothalamus
the region of the brain lying below the thalamus. The hypothalamus controls water balance, sleep, temperature, appetite and blood pressure. It also co-ordinates patterns of activity and controls emotions.

• Intestine
the part of the alimentary (digestive) canal between the stomach and the anus.

• Interferon
a chemical transmitter emitted by cells which have been invaded by viruses.

• Iris
the pigmented, muscular curtain at the front of the eye, perforated by an opening called the pupil. The muscles of the iris control the size of the pupil, determining how much light reaches the sensory tissue of the retina.

• IQ
intelligence quotient — a way of measuring intelligence. There are various types of IQ tests, most of which rank an IQ of 100 as average. IQ tests have been criticised for being based on a limited concept of intelligence and are widely viewed to be culturally specific.

• Liposuction
the process of surgically removing unwanted fat from specific areas of the body. Also known as lipoplasty. There are various procedures used, but all involve pumping fat out of the body. The process is not considered very risky, although blood clots, allergic reactions and infections can result, and it leaves scars.

• Listeria monocytogenes
a type of bacteria that causes food poisoning in humans.

• Lymph
a clear fluid carried in the lymphatic vessels.

• Lymph nodes
a small mass of tissue containing lymphocytes, where lymph is purified.

• Lymph vessels
the vessels of the lymphatic system, which carry lymph around the body.

• Lymphatic system
a body system consisting of lymph, lymphatic vessels, lymph nodes, the thymus gland and the spleen. It is a circulatory system in which lymph fluid is collected and drained from body tissues, filtered of foreign matter and returned to the bloodstream.

• Lymphocytes
a type of white blood cell that identifies foreign substances and germs (bacteria or viruses) in the body and produces antibodies that specifically target them.

• Lymphokines
soluble chemical messengers secreted by lymphocytes to communicate with other cells.

• Macrophages
a type of 'scavenger' cell, key to the workings of the human immune system. They are produced by stem cells in the bone marrow and circulate through the blood. They settle in many tissues, especially in the spleen and lymph nodes and in the liver, serving as filters to trap microbes and other foreign particles that arrive through the blood.

• Mast cells
white blood cells containing granules of chemicals including histamine, important in inflammatory responses.

• Meconium
a dark green faecal material which accumulates within the foetal intestines and is discharged at or near birth.

• Menarche
the onset of menstruation, signalling the body's coming readiness for childbearing.

• Menstruation
the periodic flow of blood and cells from the lining of the womb, occurring about every 28 days. Menstruation commences and continues, unless interrupted by pregnancy, until the menopause, which occurs around the age of 50.

• Metabolism
the chemical processes by which the body creates energy. The rate at which these processes take place is known as the metabolic rate.

• Microglial macrophages
specialist macrophages in the brain.

• Mitochondria
the sites of cellular respiration, which generate fuel for the cells' activities, converting energy into usable forms.

• Monocytes
circulating white blood cells that can ingest dead or damaged cells and provide immunological defences against many infectious organisms. Monocytes migrate into tissues and develop into macrophages.

• Monokines
chemical messengers secreted by monocytes and macrophages to communicate with other cells.

• Natural killer cells
white blood cells that can destroy a range of antigens on contact.

• Neuron
the basic cell of the nervous system in vertebrates and most invertebrates. Also called 'nerve cell'. A typical neuron has a cell body containing a nucleus and two or more long fibres.

• Neutrophils
a phagocytic granulocyte which engulfs and digests antibodies.

• Obese
anyone with a BMI of more than 30 is considered obese. A BMI of 40 or higher is considered to be 'morbidly obese'.

• Oesophagus
the muscular tube through which food passes to the stomach. The oesophagus can contract and expand to allow for the passage of food.

• Oestrogen
the female sex hormone, synthesised by the reproductive organs and adrenal glands. Oestrogen causes the thickening of the lining of the womb and vagina in the early phase of the menstrual cycle. Oestrogen is also responsible for female secondary sex characteristics, such as breasts.

• Parasites
an organism that lives in or on another and draws nutriment directly from it.

• Persistent vegetative state (PVS)
a state in which the cerebral cortex — the thinking, feeling part of the brain — stops working. People in this condition cannot understand anything that is going on around them and cannot communicate or make voluntary movements. However, the more primitive part of their brain — the brain stem — is largely unaffected.

• Phagocytes
white blood cells of the immune system that engulf and digest antibodies.

• Placenta
the organ that unites the foetus with the mother's uterus. The placenta mediates metabolic exchanges, serving the functions of nutrition, respiration and excretion.

• Protein
any of a group of organic compounds composed of one or more chains of amino acids. Common sources of protein are meat, fish, nuts and pulses.

• Regulatory T-cells
cells involved in controlling immune response.

• Rhinitis
also known as rose fever or hay fever. Rhinitis symptoms include bouts of sneezing, nasal congestion and itching eyes. It is caused by a number of factors, including plant pollen and house mites.

• Salmonella
a rod-shaped bacteria which inhabits the intestines of humans and other animals. Some may exist there without causing disease, others are harmful.

• Sebaceous glands
glands in the skin of mammals that secret an oily substance called sebum. Found on most parts of the body, except on the palms of the hands and soles of the feet.

• Sebum
a mixture of fat and the debris of dead fat-producing cells. Sebum is deposited on hair inside follicles and is brought up to the surface of the skin along the hair shaft. Sebum lubricates and protects the hair and skin, preventing dryness and irritation.

• Spleen
an organ, about the size of a fist, located on the left side of the abdomen, below the diaphragm. It is the primary filtering system for the blood, removing foreign material and initiating immune reactions which result in the production of antibodies. It is also regulates the number of red blood cells in the system, destroying old red blood cells, which have a lifespan of just 120 days.

• SRSVs
small round structured viruses that cause food poisoning in humans.

• Stroke
a sudden impairment of brain function, resulting either from a substantial reduction in blood flow to some part of the brain, or from bleeding within the skull.

• Suppressor T-cells
white blood cells that act to suppress helper/inducer T-cells to control immune response.

• Syntax
the pattern of formation of sentences or phrases in a language.

• T-cells
lymphocytes that develop in the thymus.

• Testosterone
the male sex hormone, secreted by the testes but also synthesised in small quantities in the adrenal glands. Testosterone is necessary in the foetus for the development of male genitalia, and increased levels of testosterone at puberty result in the further growth of genitalia and the development of male secondary sex characteristics such as facial hair.

• Thalamus
one of a pair of large organs that form most of the side walls of the third ventricle of the brain. The thalamus has two important functions: the transmission of neural impulses from various receptors to the cerebral cortex, where they are experienced as touch, pain, and temperature; and the regulation of incoming impulses during resting states.

• Thymus
a lymphatic organ situated in the base of the neck.

• Toxin
a poisonous substance produced by micro-organisms.

• Uterus
a muscular organ of the female reproductive system, situated between the bladder and the rectum. It houses and nourishes the fertilised egg from the time at which the egg is implanted in the uterus a few days after conception, right through to the time at which the child is born nine months later.

• Villi
small, slender vascular projections which increase the surface area of a membrane. They are found within the intestinal tract, where they increase the area for food absorption.

• Virus
an infectious agent of small size and simple composition that can multiply only in the living cells of animals, plants or bacteria. In the strictest sense, viruses should not be considered organisms, because they are not free-living: they cannot reproduce and carry on metabolic processes without a host cell.

• White blood cells
the principal components of the immune system. White blood cells function by destroying foreign substances such as bacteria and viruses. Also known as leukocytes.

• Zygote
the fertilised egg, which travels from the ovary to the uterus.

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