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Medical and Healthy Living Glossary - G

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

Galactose - A sugar which forms part of milk. Galactose is converted into glucose by the liver.
Gallstone - A small stone which forms from insoluble deposits from bile in the gall bladder. Gallstones usually are harmless, but some cause pain and inflammation and a serious condition can develop if a gallstone blocks the bile duct. A sudden pain going from the right side of the stomach towards the back is an indication that a gallstone is passing through the bile duct.
Gamma Radiation - A type of radiation emitted from radioactive isotopes. Gamma radiation is used to irradiate food.
Gastroenteritis - An inflammation of the stomach and intestinal tract caused by a viral infection that usually results in diarrhea and vomiting.
Genes - The fundamental units of genetic material found at a specific location on a chromosome. It is chemically complex and responsible for the transmission of information from older to younger generations. Each gene contributes to a particular trait or characteristic. There are more than 100,000 genes in humans, and gene size varies with the characteristic, e.g. the gene that codes for the hormone insulin is 1,700 base pairs long. There are several types of gene, depending on their function. Genes are either dominant or recessive. A dominant characteristic is one that occurs whenever the gene is present, while the effect of a recessive gene (e.g. a disease) only appears if both parents have contributed the same form of the gene.
Genetic Code - The characteristics of the DNA of a cell which are passed on when the cell divides and therefore are inherited by a child from its parents.
Genetically Modified Food - Food developed by manipulating DNA.
Glia - The connective tissue of the central nervous system, surrounding cell bodies, axons and dendrites.
Glucagon - A hormone, secreted by the pancreas, that increases the level of glucose in the blood by stimulating the breakdown of glycogen.
Glucose - Also called dextrose. Glucose is the most abundant naturally occurring sugar. A simple form of sugar, carried in the bloodstream and used directly by the body as an energy source. Only a few foods, such as grapes, contain pure glucose. Combustion of glucose with oxygen to form carbon dioxide and water is the body’s main source of energy. The concentration of glucose in the blood - the blood sugar level - is regulated by the hormones glucagon and insulin.
Glycogen - A type of starch, converted from glucose by the action of insulin. When the body absorbs more glucose than it needs to meet immediate energy demands, some is stored in the liver and muscles as glycogen which is made up of glucose units linked together. These can be broken down and quickly released back into the bloodstream as required, for example during exercise. Glycogen is often called animal starch.
Gout - A disease in which larger than normal quantities of uric acid are produced and form crystals in the cartilage around joints. Excess intake of alcohol can provoke an attack of gout by interfering with the excretion of uric acid.
Gram (g) - Basic metric unit of weight, equal to 1000 milligrams or one-thousandth of a kilogram. There are 28.4 g to 1 oz.
Grave's Disease - A disorder typified by thyroid gland overactivity, which results in an enlargement of the gland and protruding eyes. It is caused by antibody production and is most likely an auto-immune response. Patients commonly exhibit excess metabolism (because thyroid hormones control the body's metabolism), nervousness, tremor, hyperactivity, rapid heart rate, plus an intolerance of heat and breathlessness. Treatment can follow one of three courses: drugs to control the thyroid's production of hormones; surgery to remove part of the thyroid; or radioactive iodine therapy.
Grey Matter - The part of the brain and spinal cord that contains neuron cell bodies. It is a dark grey color and forms part of the central nervous system.
Gut - The intestines.