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Medical and Healthy Living Glossary - H

This page of our online glossary of medical and healthy living is for medical and healthy living terms beginning with the letter 'H'.

• Haem Iron - The iron found in meat. It is absorbed more efficiently than non-haem iron, found in cereals, pulses and other plants.
• Haemoglobin - The iron-containing pigment formed of haem and globin that carries oxygen to all parts of the body. It combines with oxygen as blood passes through the lungs. It gives red blood cells their color - the more oxygen haemoglobin is carrying, the brighter blood will be.
• Haemophilia - A disorder which is linked to a recessive gene on the X-chromosome in which the blood clots much more slowly than usual, resulting in extensive bleeding from even minor injuries. The gene is passed by women to their male children. Haemophilia is seen almost exclusively in boys.
• Hemianopia - A state of partial blindness in which someone has only half the usual field of vision in each eye.
• Hepatocytes - Liver cells which synthesise and store substances, and produces bile.
• High-fibre Diet - A diet which contains a large percentage of cereals, nuts, fruit and vegetables.
• High-protein Diet - A diet containing mostly foods which are high in protein and low in carbohydrates and saturated fat, adopted by people who are trying to lose weight.
• Histamine - A chemical, found in most tissues, that forms part of the body's defence mechanism and is also involved in gastric secretion and the contraction of smooth muscle. Histamine is released in large amounts during allergic reactions, causing itching and rashes, sneezing, watering eyes, wheezing and swelling. Histamines dilate blood vessels, constrict the cells of smooth muscles and cause an increase in acid secretions in the stomach.
• Holistic Care - The care and treatment of a whole person rather than just their medical symptoms.
• Hormones - Chemical messengers sent through the bloodstream to control the functioning of the body's organs. Most hormones manufactured by the glands of the endocrine system, which is controlled by the pea-sized pituitary gland, located at the base of the skull. Insulin is a hormone which helps to control the level of glucose in the blood.
• HUS (Hemolytic Uremic Syndrome) - A serious complication of some foodborne illnesses including poisoning by E. coli O157:H7. HUS causes destruction of blood cells and then kidney damage when the shredded blood cells clog the kidneys.