Black's Student Medical Dictionary by Harvey Marcovitch

Author:Harvey Marcovitch
Language: eng
Format: epub
ISBN: 9781472921741
Publisher: Bloomsbury Publishing
Published: 2015-10-15T00:00:00+00:00

L

Labetalol

Labetalol is an alpha- and beta-adrenoceptor blocker (see ADRENERGIC RECEPTORS) used to treat HYPERTENSION. Beta blockers block the beta-adrenoceptors in the heart, peripheral blood vessels and bronchi.

Labia

(Singular: labium.) Lips. The labia majora and labia minora are the outer and inner lip-like folds of skin surrounding the entrance to the VAGINA.

Labium

Labium is the Latin word for a lip or lip-shaped organ.

Labour

See PREGNANCY AND LABOUR.

Labyrinth

A convoluted system of structures forming the inner EAR and involved in hearing and balance.

Labyrinthitis

Inflammation of the LABYRINTH of the EAR. Usually caused by bacterial or viral infection – the former often the result of inadequately treated otitis media (see EAR, DISEASES OF – Diseases of the middle ear), or MEASLES. Symptoms are VERTIGO, nausea, vomiting, nystagmus (see EYE, DISORDERS OF), TINNITUS and loss of hearing. Bacterial infection needs treatment with ANTIBIOTICS; viral infection usually gets better without treatment. ANTIHISTAMINE DRUGS may help reduce vertigo. Rarely, surgery may be required to drain the infection in bacteria-based labyrinthitis.

Laceration

A wound to the skin or surface of an organ which results in a cut with irregular edges (cf. an incision produced with a knife, which has smooth, regular edges).

Lacrimal

See EYE – Lacrimal apparatus.

Lacrimal Bones

The smallest bones of the face, one forming part of the bony structure of each orbit containing an EYE.

Lacrimal Nerve

A branch of the ophthalmic nerve supplying the lacrimal gland and conjunctiva of the EYE.

Lacrimation

Crying, or the secretion of an excess quantity of tears.

Lactase

An ENZYME produced by glands in the small INTESTINE. It changes lactose (milk sugar) into glucose and galactose during the process of digestion.

Lactation

The production of milk by the mother’s breast, or the period during which an infant is suckled. (See also BREAST FEEDING; INFANT FEEDING.)

Lacteal

A lymphatic vessel that transmits CHYLE from the INTESTINE. (See also LYMPH.)

Lactic Acid

A colourless, syrupy, sour liquid, which is produced by the action of bacteria upon lactose, the sugar found in milk. The growth of this organism and consequent formation of lactic acid cause the souring of milk, and the same change takes place to a limited extent when food is retained in the stomach for a long time.

Lactic acid (CH3.CHOH.COOH) is produced in the body during muscular activity, from the breakdown of GLYCOGEN. Muscle fatigue is associated with an accumulation of lactic acid in the muscle. Recovery follows when enough oxygen reaches the muscle, part of the lactic acid being oxidised and most of it then being built up once more into glycogen.

Lactobacillus

A gram-positive (see GRAM’S STAIN), rod-shaped, non-motile bacterium (see BACTERIA). It produces LACTIC ACID by fermenting CARBOHYDRATE. Lactobacilli are found in fermenting animal and plant products, especially dairy products; they also occur in the GASTROINTESTINAL TRACT and the VAGINA. L. acidophilus occurs in milk and is a contributory cause to the development of dental caries (see TEETH, DISORDERS OF).

Lactose

The official name for milk sugar.

Lactose Intolerance

This is due to lack in the INTESTINE of the ENZYME known as LACTASE, which is responsible for the digestion of lactose, the sugar in milk. In people with lactose intolerance, drinking milk or eating

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