L    

Laceration       a torn, jagged wound.-lacerate, v., lacerated, adj.

Lactation       the process of the synthesis and secretion of milk from the breasts for the nourishment of an infant.

Lactogen   /lak'tæjæn/     a drug or other agent that stimulates the production and secretion of milk.-lactogenic, adj.

Lamb       a body part, such as an arm or leg, or a branch of an internal organ.

Lamina  /lam'inæ/     pl. laminae, a thin, flat plate or layer, such as the lamina of the thyroid cartilage that overlays the structure on each side.

Languid , adj. without vigor.

Laryngeal cancer       a malignant tumor arising from the lining of the voicebox (larynx). Laryngeal tumors are almost 20 times more common in men than in women and occur most frequently between 50 and 70 years of age. Chronic alcoholism and heavy use of tobacco increase the risk of developing the cancer. Persistent hoarseness is usually the first sign. Advanced lesions may cause a sore throat, breathing and swallowing difficulties, and swelling of the lymph glands in the neck. Treatment for small lesions is usually radiation. Surgical removal (laryngectomy), often combined with radiation, is indicated for extensive lesions. Following the operation, many persons with laryngectomies learn esophageal speech, some use an electric voicebox, and a few undergo surgical reconstruction. See also 10485laryngectomy.

Larynx  /ler'ingks/     the voicebox that is part of the air passage connecting the throat with the windpipe (trachea) leading toward the lungs. It produces a large bump in the neck called the Adam's apple, which remains the same size in both sexes until puberty, and then becomes larger in men than in women. The larynx, lined with mucous membrane, forms the bottom portion of the front wall of the throat. It is composed of rings of cartilages, all connected together by ligaments and moved by various muscles.-laryngeal, adj.

Lateral       1. on the side. 2. away from the middle of the body or body part or organ.

Lavage  /læväzh'/     the process of washing out an organ, usually the bladder, bowel, sinuses, or stomach for therapeutic purposes, as when a poison has been swallowed. Kinds of lavage are blood lavage, gastric lavage, peritoneal dialysis. See also 10055irrigation.

Lead  /lèd/     an electric connection attached to the body to record electric activity, especially of the heart or brain. See also 6448electrocardiograph, 6459electroencephalograph.

Leech , n. bloodsucking worm.

Lethal       capable of causing death.

Lesion       1. a wound, injury, or other destructive change in body tissue. 2. any visible, local abnormality of the tissues of the skin, as a wound, sore, rash, or boil. A lesion may be described as benign (noncancerous), malignant (cancerous), gross (visible), occult (of unknown cause), or primary (first).

Leukemia , n. cancerous disease of  blood cells.

Leukocyte  /lö'kæsít/     a white blood cell. There are five types of leukocytes, classified by the presence or absence of small particles (granules) in the cytoplasm, the main substance of the cell. The agranulocytes, or those without granules, are lymphocytes and monocytes. The granulocytes, white cells with granules, are called neutrophils, basophils, and eosinophils. White cells are able to squeeze through spaces between cells and migrate by amebalike movements. Leukocytes are larger than red blood cells (erythrocytes). A cubic millimeter of normal blood usually contains 5,000 to 10,000 leukocytes. Among the most important functions of the leukocytes are the destruction of bacteria, fungi, and viruses, and rendering harmless poisonous substances that may result from allergic reactions and cellular injury. Also called leucocyte, white blood cell, white corpuscle.

Levator scapulae       a muscle of the back and sides of the neck. It acts to raise the scapula of

the shoulder.

Lithotomy  /lithot'æmè/     the surgical removal of a stone (calculus), especially one from the urinary tract.

Lhermitte's sign  /ler'mits/     sudden, temporary, electricity like shocks spreading down the body when the head is flexed forward. It occurs chiefly in multiple sclerosis but also in compression disorders of the spinal cord in the neck.

ligament       1. a white, shiny, flexible band of fibrous tissue binding joints together and connecting various bones and cartilages. Such ligaments are slightly elastic and composed of parallel bundles of connective tissue. When part of a joint membrane, they are covered with fibrous tissue that blends with surrounding connective tissue. Yellow elastic ligaments connect certain parts of adjoining vertebrae. Compare 16964tendon. 2. a layer of membrane with little or no stretching ability, extending from one abdominal organ to another. See also 2811broad ligament.

Ligature       1. a suture. 2. a wire, such as used in orthodontia to straighten teeth.

Linea alba  /lin'è×æ/     a seam that runs along the middle line of the abdomen beneath the skin, formed by the fusion of three sheets of tissue fibers into a single tendon extending from the breastbone to the pubic area. It contains the navel.

Lithotomy  /lithot'æmè/     the surgical removal of a stone (calculus), especially one from the urinary tract.

Lobe       1. a roundish projection of any structure. 2. a semidetached portion of any organ, outlined by clefts, furrows, or connective tissue, as the lobes of the brain, liver, and lungs.-lobar, lobular, adj.

Lochia  /lò'kè×æ/     the discharge that flows from the vagina following childbirth. During the first few days, the lochia is red and consists of blood, discarded cells from the uterus and placental tissue, and fetal body matter, such as hair or fat from the skin covering. After the third day, the amount of blood lessens, the lochia becomes darker and thinner, and then watery as evacuation of solid material is completed. During the second week, white blood cells and bacteria appear in large numbers along with fatty material, causing the lochia to appear yellow. During and after the third week, the amount of lochia decreases markedly. Cessation of the flow of lochia at about 6 weeks is usual.-lochial, adj.

Longitudinal       1. referring to a measurement in the direction of the long axis of an organ, object, or body, such as an imaginary line from head to toe. 2. referring to a scientific study that is conducted over a long period of time.

Loin       a part of the body on each side of the spinal column between the lowest ribs and the hip bones.

Lucid  /lö'sid/     clear, rational, and able to be understood.

Lumbago  /lumbà'gò/     pain in the lower back (lumbar region) caused by muscle strain, rheumatoid arthritis, osteoarthritis, or a ruptured spinal disk. Ischemic lumbago, characterized by pain in the lower back and buttocks, is caused by poor blood circulation to the area.

Lumbar  /lum'bær, lum'bär/     pertaining to the part of the body between the chest and the pelvis, particularly the lower back area.

Lumen  /lö'mæn/     pl. lumina, lumens, a cavity or the channel within any organ or structure of the body.

Luteal  /lö'tè×æl/     pertaining to the corpus luteum of the female ovary or its functions or effects.

Lymph       a thin, clear, slightly yellow fluid originating in many organs and tissues of the body. It circulates through the lymphatic vessels and is filtered by the lymph nodes. Lymph enters the bloodstream at the junction of the internal jugular and subclavian veins at the base of the neck. Its composition varies depending on the organ or tissue it is in, but generally contains about 95% water, a few red blood cells, and variable numbers of white blood cells. It is similar to blood plasma except for a lower amount of protein material. 4046

Lymphatic system       a vast, complex network of capillaries, thin vessels, valves, ducts, nodes, and organs. It helps to protect and maintain the fluid environment of the body by producing, filtering, and conveying lymph and by producing various blood cells. The lymphatic network transports fats, proteins, and other substances to the blood system. It also restores 60% of the fluid that leaks out of the blood capillaries and cells into spaces between cells during normal metabolism. Small valves throughout the lymphatic network help to control the flow of lymph. At the junction with the blood vein system, the valves prevent blood from flowing into the lymphatic vessels. The lymph collected throughout the body drains into the blood through two ducts situated in the neck.