Medical Terminology Glossary: [L]
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L-Thyroxine The major natural hormone produced by the thyroid gland, given in synthetic form to counter underactivity of the gland.

Labour, Third Stage of The period between the complete delivery of the infant and the complete delivery of the placenta and membranes.

Labyrinth The interconnecting canals of the inner ear that contain the organs of hearing and balance. 

Laceration (Tear), Vaginal, 4th Degree A tear of the vagina extending to and including the anal sphincters.

Laceration (Tear), Vaginal, 3rd Degree A tear of the vagina extending to, but not including, the anal sphincters.

Laceration A clean cut with a surgical instrument or other sharp object.

Lactic Acid Breakdown product of sugar metabolism.

Lactic Acidosis Accumulation of lactic acid as a result of inability to metabolise further this breakdown product of sugar metabolism.

Lactose Intolerance A pathological inability to hydrolyse the sugar in milk into its component simple sugars, because of a deficiency of the enzyme lactase, often leading to indigestion, gassiness, bloating and abdominal discomfort.

Lactose Tolerance Test A test for lactase deficiency in which the blood glucose is measured at regular intervals after drinking a standard lactose solution, and the results compared with the normal ranges.

Lamina, of Vertebra The flattened portion of the arch of the vertebra, extending from the spinous process to the pedicle on each side.

Lamina Flattened part of the vertebral arch, the ring of bone which, with the vertebral body, surrounds and encloses the spinal cord within that segment of the vertebral column.

Laminaria Tent A medical device which, when inserted into the cervix of the uterus, slowly increases the calibre of (dilates) the channel.

Laminectomy Surgical removal of the lamina of a vertebra.

Laminotomy Surgical shaving of bone from the lamina of a vertebra.

Laparoscopy Use of lighted hollow instruments introduced into the abdomen or pelvis, for diagnostic and/or surgical purposes.

Laparotomy An incision into the abdomen or loin, for diagnostic and/or surgical purposes.

Laparotomy, Exploratory An incision into the abdomen or loin, for diagnostic purposes.

Large for Gestation Age Beyond the 90th centile for size of a fetus at a given number of completed weeks of pregnancy.

Laryngectomy Surgical removal of the voice box, including the vocal cords.

Larynx Voice-box, containing the vocal cords.

Last Normal Menstrual Period (LNMP) First day of the last regular, normal menstrual bleeding before conception, which generally takes place, therefore, about 2 weeks into the 40 weeks or 280 days of pregnancy.

Lateral Away from the midline of the body.

Lavage The washing out of the cavity of a hollow organ with copious amounts of fluid for therapeutic or diagnostic purposes.

Left Ventricular Hypertrophy Pathological increase in the bulk of the muscle in the largest pumping chamber of the heart, which delivers oxygen-rich blood from lungs to aorta.

Left Atrium The chamber of the heart which receives oxygen-rich blood from the lungs.

Left Ventricle The largest and most muscular chamber of the heart concerned with the pumping of oxygen-rich blood from the lungs (via the left atrium) to all the other tissues of the body, via the aorta.

Left Ventricular Dilatation Pathological increase in the amount of blood remaining in the left ventricle at the end of contraction.

Leiomyoma A benign tumour of muscle of internal organs, in this the uterus (= fibroid).

Lesion Pathological change in tissue.

Lesser Curve The right side of the stomach from the cardia (entrance at the end of the esophagus or gullet) to the pylorus (exit into the duodenum or beginning of the small bowel).

Lesser Sac Pouch of peritoneum lying below the liver, behind the stomach, in front of the pancreas and to the right of the spleen.

Leucocytes White Blood Cells.

Leukemia Malignant proliferation of abnormal White Blood Cells, leading to replacement of the blood-producing tissues of the body, particularly the bone marrow and spleen.

Leukopenia (Leucopenia) Pathologically decreased concentration of White Blood Cells in the blood.

Ligament, Broad The fold of visceral peritoneum overlying the fallopian tube and other structures connecting ovary and uterus.

Ligate Tie off.

Lipid Member of the chemical family of fats.

Lipoma A benign tumour of fatty tissue, of cosmetic importance or nuisance value only.

Liquor The [amniotic] fluid which, contained in the sac of membranes known as the amnion, surrounds the fetus and provides a shock absorber and a secondary vehicle for the exchange of body chemicals with the mother.

Lithotomy Position Supine, with buttocks at the end of the examining or operating table, hips and knees both flexed at right-angles.

Lithotomy Position Supine on the operating or examining table, with the buttocks at the end and the knees and hips flexed, feet in stirrups.

Lobe Anatomically distinct part of an organ, particularly lung, liver, ear.

Lobulated Having more than one lobe or part.

Locked In Syndrome Cluster of disabilities caused by irreversible injury to the mid-brain, consisting of full consciousness, paralysis of all extremities, ability to communicate by eye and eyelid movements but not by speaking, and ability to move eyes vertically but not horizontally.

Loculated, of fluid collections Having more than one compartment.

Loop Colostomy Surgically formed opening of the large bowel on to the skin, with an intact channel to the lower bowel.

Low Density Lipoprotein (LDL) A type of fat in the blood, measured as cholesterol, which when pathologically increased promotes narrowing of the arteries (atherosclerosis).

Low Forceps Delivery Childbirth using obstetric forceps applied to the head of the fetus after it has descended into the lower vagina.

Low-grade, of Inflammation Not acute or vigorous.

Lower Uterine Segment Cesarian Section, Emergency Unplanned delivery of the labouring o nonlabouring pregnant woman by an incision into the narrowed lower third of the uterus, through either a horizontal or vertical abdominal incision.

Lower Uterine Segment Cesarian Section, Elective (ELUSCS) or Emergency Planned or previously unplanned delivery of the nonlabouring pregnant woman by an incision into the narrowed lower third of the uterus, through either a horizontal or vertical abdominal incision.

Lower Respiratory Tract The airways below the voicebox or larynx.

Lown-Ganong-Levine Syndrome A permanent and congenital short-circuit of the electrical conducting system of the heart, making it liable to potentially serious irregularities of rhythm.

Lumbar (Spine) The lower (usually 5) flexible segment of the spinal column.

Lumbar Puncture (Spinal Tap) Introduction of a needle into the spinal canal in the lumbar region of the spine, for the purpose of diagnosis or introduction of medication.

Lumen The space in the interior of a tubular organ.

Lymph Clear fluid collected from the body tissues by the lymphatic system.

Lymphadenectomy Surgical removal of lymphnodes for diagnostic and therapeutic purposes.

Lymphadenopathy Pathological increase in size of lymphglands.

Lymphangiogram Radiological imaging of the tissue-fluid channels and the accompanying lymphnodes, which drain infection and cancer cells, after the injection of a dye opaque to xrays.

Lymphatic Pertaining to vascular channels that transport lymph.

Lymphedema Swelling of tissues from accumulation of fluid because of impaired drainage by lymphatic vessels.

Lymphnode Round, oval or bean-shaped aggregation of infection- and cancer-fighting immune cells located along the lymph channels throughout the body.

Lymphocytes The physiologically smaller class of infection-fighting white blood cells, characteristically more numerous in generalised viral infections.

Lysis Physiological or therapeutic freeing.

Lytic Causing destruction of bone.

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