American Medical Association Family Medical Guide - American Medical Association [809]
joint A point where bone meets bone, such as the hip, knee, or elbow. Most but not all joints are capable of motion, allowing the bones to move in relation to one another.
joint replacement See arthroplasty.
K
keratin A protein that is the main component of the outermost layer of skin, hair, and nails.
kidney stone A small, hard mass of mineral salts that can form in a kidney.
knee replacement See arthroplasty.
L
laceration A torn, jagged wound.
lactase An enzyme needed to break down the milk sugar lactose during digestion.
lactose One of the sugars found in milk.
lactose intolerance The inability to digest lactose due to a deficiency of lactase.
laser A device that produces a highly concentrated, powerful beam of light that can be used as a surgical tool.
LDL cholesterol Low-density lipoprotein cholesterol. A harmful type of cholesterol made by the liver and transported in the blood. Eating foods that are high in saturated fats (such as red meat and whole-milk products) and trans fats (such as stick margarine) increases LDL.
leukocyte A type of infection-fighting white blood cell.
ligament Tough, fibrous tissue that connects bone to bone and provides stability to joints.
light therapy See phototherapy.
lipids Fats that are stored in the body and used for energy.
lipoproteins Substances made of lipids and protein. Most fats, including cholesterol, are carried in the blood in the form of lipoproteins.
living will An advance directive prepared by a competent person that indicates his or her wishes regarding life-sustaining medical treatments. A living will goes into effect only after the person is unable to speak for himself or herself and can be revised or withdrawn by the person at any time.
low-density lipoprotein cholesterol See LDL cholesterol.
lymph A milky fluid that has an important role in the immune system and the absorption of fats from the intestines during digestion.
lymphatic system A network of organs, vessels, nodes, and ducts that drain lymph from the body’s tissues back into the bloodstream. The lymphatic system is an important part of the immune system.
lymph nodes Small glands throughout the body (clustered in the neck, armpits, abdomen, and groin) that are part of the immune system. They supply infection-fighting cells to the bloodstream and act as a barrier to the spread of infection.
lymphocyte A type of infection-fighting white blood cell.
M
macula The part of the retina of the eye that provides sharp sight in the center of the visual field; essential for seeing fine detail.
macular degeneration Age-related damage to the macula, which leads to impaired vision.
magnesium An essential mineral that has several vital roles in the body, including transmission of nerve signals.
malabsorption Inefficient absorption of nutrients through the lining of the small intestine.
malignant Cancerous.
malignant melanoma See melanoma, malignant.
mast cell A type of cell that plays a part in the immune system and in allergic reactions. Mast cells release inflammatory substances in response to allergens.
melanin The pigment that gives skin, hair, and eyes their color.
melanoma, malignant The most serious form of skin cancer, the first sign of which is often a change in an existing mole. Malignant melanoma spreads quickly and can be fatal. The main cause of melanoma is overexposure to sunlight.
meninges Membranes surrounding the brain and spinal cord.
meningitis Inflammation of the meninges, usually as the result of an infection.
menopause The end of menstruation.
metabolism The chemical processes that take place in the body.
metastasis The spread of diseased cells or microorganisms from one part of the body to another part. Metastasis can occur through the lymphatic system or bloodstream or across a body cavity.
metastasize To spread from one part of the body to another. Most cancerous tumors have the capacity to metastasize.
microorganism Any microscopic life form, such as bacteria or viruses.
migraine