Click on the alphabet and there you go!

Labia majora: The larger (major) outside pair of labia (lips) of the vulva (the female external genitalia).

Labia minora: The smaller (minor) inside pair of labia (lips) of the vulva (the female external genitalia).

Labial: Pertaining to the lips.

Labile: Unstable.

Labium: A lip. Labium is the singular of the Latin neuter noun meaning "a lip." The plural is labia.

Labor: The journey of the baby and placenta (afterbirth) from the uterus to the vagina to the outside world. Synonymous with childbirth, confinement, delivery, parturition, and travail (the French word for work).

Labyrinth: The maze of canals in the inner ear. The labyrinth is the portion of the ear that is responsible for sensing balance. Inflammaton of the labyrinth (labyrinthitis) can be accompanied by vertigo.

Labyrinthitis: Inflammation of the labyrinth.

Laceration: Severed skin. A cut. Washing a cut or scrape with soap and water and keeping it clean and dry is all that is required to care for most wounds. Putting alcohol, hydrogen peroxide, and iodine into a wound can delay healing and should be avoided. Seek medical care early if you think that you might need stitches. Any delay can increase the rate of wound infection. Any puncture wound through tennis shoes has a high risk of infection and should be seen by your healthcare professional. Any redness, swelling, increased pain, or pus draining from the wound may indicate an infection that requires professional care.

Lacrimal: Pertaining to tears.

Lacrimation: Shedding tears.

Lactase: Enzyme that breaks down the milk sugar lactose.

Lactase deficiency: Lack of the enzyme lactase resulting in failure to digest lactose in milk (lactose intolerance).

Lactation: Giving milk.

Lactobacillus: Literally milk bacteria, normally found in the mouth, intestinal tract and vagina.

Lactobacillus acidophilus: Bug that produces acidophilus milk.

Lactose intolerance: inability to digest the milk sugar lactose.

Lacuna: A small pit, cavity, defect or gap.

Lamella: A thin leaf, plate, disk, wafer.

Lamina: A plate or layer. For example, the lamina arcus vertebrae, usually just called the lamina, are plates of bone in each vertebral body.

Lancet: Small pointed knife used to do a finger prick for a blood test. Also the name of a medical journal in England.

Lanugo: The fine hair on the body of a newborn baby.

Laparoscopy: Laparoscopy is a type of surgery where small incisions are made in the abdominal wall through which instruments are placed that can help in visualizing structures in the abdomen and pelvis.

Laparotomy: An operation to open the abdomen.

Large cell carcinoma: A group of lung cancers in which the cells are large and look abnormal.

Large intestine: Comes after the small intestine. Large because it is wider than the small intestine.

Laryngeal: Having to do with the larynx.

Laryngeal papilloma: A warty growth in the larynx, ususally on the vocal cords. Persistent hoarseness is a common symptom.

Laryngeal papillomatosis: Numerous warty growths on the vocal cords. Most common in young children. Recurrences are, unfortunately, frequent. Remission may occur after several years. The disease can be due to the baby contracting human papilloma virus (HPV) during birth through the vaginal canal from a mother with genital warts (which are due to HPV). Each year, about 300 infants are born with the virus on their vocal cords because of maternal transmission.

Laryngectomee: A person who has had his or her voice box removed.

Laryngectomy: An operation to remove all or part of the larynx.

Laryngitis: Inflammation of the larynx (voice box).

Laryngomalacia: A soft floppy larynx.

Laryngoscope: A flexible, lighted tube used to examine the larynx.

Laryngoscopy: Examination of the larynx with a mirror (indirect laryngoscopy) or with a laryngoscope (direct laryngoscopy).

Laryngostasis: More commonly known as croup. An infection of the larynx, trachea, and the bronchial tubes, largely in children. Caused usually by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling. Treatment can include moist air, salt water nose drops, decongestants and cough suppressants, pain medication, fluids, and occasionally antibiotics. The major concern in croup is breathing difficulty as the air passages narrow. Close monitoring of the breathing of a child with croup is important, especially at night. While most children recover from croup without hospitalization, some children can develop life-threatening breathing difficulties. Therefore, close contact with the doctor during this illness is important.

Larynx: The larynx is the portion of the breathing, or respiratory, tract containing the vocal cords which produce vocal sound. It is located between the pharynx and the trachea. It is also called the "voice box." Its outer wall of cartilage forms the area of the front of the neck referred to as the "Adams apple."

Laser: A powerful beam of light used in some types of surgery to cut or destroy tissue.

Lateral: The side of the body or body part that is farther from the middle or center (median) of the body. Typically, lateral refers to the outer side of the body part, but it is also used to refer to the side of a body part. For example, when referring to the knee, lateral would mean the side of the knee that is farthest from the opposite knee. The opposite of lateral is medial.

Lavage: Washing out. Gastric lavage is washing out the stomach, for example, to remove drugs or poisons.

Lazy eye: An eye that diverges in gaze. More formally called strabismus. Can be esotropia (cross-eyed) or exotropia (wall-eyed).

lb.: The abbreviation for pound, the measure of weight, lb. (plural: lb. or lbs.) stands for "libra" (Latin for pound).

LDL: Low-density lipoprotein.

LDL cholesterol: Low-density lipoprotein cholesterol (the "bad" cholesterol).

Lead poisoning: An environment hazard (for example, from lead-containing paint, leaded gasoline,etc) capable of causing brain damage.

Legg-Perthes disease: A hip disorder in children due to interruption of the blood supply to the head of the femur (the ball in the ball-and-socket hip joint). Also called Legg disease and Legg-Calve-Perthes disease.

Legionaire's disease: A disease (first identified at the 1976 American Legion convention) due to bacteria (Legionella) found in plumbing, shower heads and water-storage tanks. Outbreaks of Legionella pneumonia have been attributed to evaporative condensors and cooling towers.

Legionella: The bacteria causing Legionaire's disease.

Leiomyoma: A benign tumor of smooth muscle, the type of muscle found in the heart and uterus. A leiomyoma of the uterus is commonly called a fibroid.

Leiomyosarcoma: a malignant tumor of smooth muscle origin. Smooth muscle is the major structural component of most hollow internal organs and the walls of blood vessels. Can occur almost anywhere in the body but is most frequent in the uterus and gastrointestinal tract. Complete surgical excision, if possible, is the treatment of choice.

Leishmania: A group of parasites causing considerable human disease (leishmaniasis).

Leishmaniasis: Diseases due to Leishmania involving the organs (kala-azar), skin plus mucous membranes (espundia), or skin alone (usually named for the place plus boil, button or sore as, for example, Jericho boil, Bagdad button, Dehli sore).

Lennox syndrome: See Lennox-Gastaut syndrome.

Lennox-Gastaut syndrome: A severe form of epilepsy that usually begins in early childhood and is characterized by frequent seizures of multiple types, mental impairment, and a particular brain wave pattern (a slow spike-and-wave pattern). The seizures that are notoriously hard to treat and may lead to falls and injuries can be reduced in frequency by treatment with lamotrigone, a chemically novel antiepileptic drug. The syndrome is named for W.G. Lennox and H. Gastaut who described it.

Leprosy: A skin infection caused by a bacteria, which can also be associated with nerve damage. The bacteria involved is called Mycobacterium leprae.

Lesbian: Female homosexual. The name "lesbian" comes from the Greek island of Lesbos in the Aegian Sea where in antiquity the women were said to be homosexual. The poet Sappho who lived on Lesbos (circa 600 BC) was a lesbian in both geographic location and sexual orientation.

Lesbianism: Female homosexuality. Also called sapphism (after the lesbian poet Sappho).

Lesion: An area of abnormal tissue change.

Lethal: Deadly.

Lethargy: Abnormal drowsiness, stupor.

Leucemia: See leukemia.

Leukemia: Cancer of the blood cells.

Leukemia, accelerated phase of: Refers to chronic myelogenous leukemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase.

Leukemia, smoldering: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Smoldering leukemia also is called myelodysplastic syndrome or preleukemia.

Leukemoid reaction: A benign blood picture resembling leukemia. For example, in infectious mononucleosis.

Leuko-: Prefix meaning white.

Leukocytes: Cells that help the body fight infections and other diseases. Also called white blood cells (WBCs).

Leukocyte count: A white blood cell (WBC) count.

Leukocytosis: Increase in the number of white blood cells.

Leukodystrophy: Disorder of the white matter of the brain. The white matter mainly consists of nerve fibers (not the nerve cells themselves) and is concerned with conduction od nerve impulses.

Leukopenia: Shortage of white blood cells.

Leukoplakia: A white spot or patch in the mouth.

Levo-: From the Latin laevus meaning on the left side. For example, a molecule that shows levorotation is turning or twisting to the left. The opposition of levo- is dextro- (from the Latin dexter meaning on the right side) so the opposite of levorotation is dextrorotation.

Levocardia: Reversal of all of the abdominal and thoracic organs (situs inversus) except the heart which is still in its usual location on the left. This situation is far more of an anatomic mess than when all the organs including the heart are reversed to create a complete mirror image. Levocardia virtually always results in congenital heart disease (malformation of the heart or great vessels).

LHRH agonists: Compounds that are similar to LHRH (luteinizing hormone-releasing hormone).

Libido: The word "libido" in Latin means "desire, longing, fancy, lust, or rut." Although the adjective "libidinous" meaning lustful has been used in English for 500 or so years, "libido" made a belated entry into the English language in1913, thanks to Sigmund Freud and other psychoanalysts who applied the term to psychic energy or drive, especially the sexual instinct.

Library: In genetics, a library is an unordered collection of clones (i.e., cloned DNA from a particular organism), whose relationship to each other can be established by physical mapping. For example, you can have an E. coli library or a human DNA library. Among the types of libraries, there are genomic libraries and arrayed libraries. (See Library, genomic and Library, arrayed).

Library, arrayed: In genetics, arrayed libraries of DNA clones are used for many purposes, including screening for a specific gene or genomic region of interest as well as for physical mapping. An arrayed library consists of (in technical terms) individual primary recombinant clones (which are hosted in phage, cosmid, YAC, or another vector) that have been placed in two-dimensional arrays in microtiter dishes (plastic dishes with an orderly array of tiny wells). Each primary clone can be identified by the identity of the plate and the clone location (row and column) on that plate. The information gathered on individual clones from various genetic linkage and physical map analyses is then entered into a relational database and used to construct physical and genetic linkage maps.

Library, genomic: A collection of DNA clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism. As a molecular genetic sequel to John Steinbeck’s "Of Mice and Men", today you can have a mouse genomic library or a human genomic library.

Li-Fraumeni syndrome: A family tendency to cancers due to a mutation in a gene that normally serves to curb cancer: the p53 tumor-suppressor gene.

Ligament: A ligament is a band or sheet of connective tissue that connects two bones together.

Ligate: To tie. As, for example, the surgeon ligated the artery.

Ligature: Material (silk, gut, wire, etc) used to ligate.

Limb: The arm or leg.

Lingual: Having to do with the tongue.

Linkage: Tendency for genes to be inherited together because of their location near one another on the same chromosome.

Linkage analysis: Study aimed at establishing linkage between genes. Today linkage analysis serves as a way of gene-hunting and genetic testing.

Linkage map: A map of the genes on a chromosome based on linkage analysis. A linkage map does not show the physical distances between genes but rather their relative positions, as determined by how often two gene loci are inherited together. The closer two genes are (the more tightly they are linked), the more often they will be inherited together. Linkage distance is measured in centimorgans (cM).

Lipid: Fatty substance.

Lipid storage diseases: A series of disorders due to inborn errors in lipid metabolism resulting in the abnormal accumulation of lipids in the wrong places (Examples include Gaucher, Fabry and Niemann-Pick diseases and metachromatic leukodystrophy).

Lipid profile: Pattern of lipids in the blood. (A lipid profile usually includes the total cholesterol, high density lipoprotein (HDL) cholesterol, triglycerides, and the calculated low density lipoprotein (LDL) cholesterol.

Lipoma: A benign fatty tumor.

Lipoprotein: A complex of lipid and protein, the way lipids travel in the blood.

Lips: Aside from the lips of the mouth, there are two pairs of lips at the entrance to the vagina. They are the labia majora (the larger outside pair) and the labia minora (the smaller inside pair). Together they form part of the vulva (the female external genitalia).

Listeria: A group of bacteria named after the English surgeon and apostle of antisepsis, Joseph Lister (1827-1912).

Listeriosis: Infection with one of the Listeria bacteria capable of causing miscarriage (spontaneous abortion), stillbirth and premature birth.

Litho-: Prefix meaning stone.

Lithotomy: Surgical removal of a stone.

Lithotripsy: Procedure to break a stone into small particles that can be passed in the urine.

Liver: An organ in the upper abdomen that aids in digestion and removes waste products and worn-out cells from the blood.

Livid: Black and blue.

Living will: A living will is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic types of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).

Lobar: Having to do with a lobe. For example, lobar pneumonia.

Lobe: 1. A subdivision of an organ, divided by fissures, connective tissue or other natural boundaries. 2. A rounded projecting portion, such as the lobe of the ear.

Lobectomy: An operation to remove an entire lobe of the lung.

Lobule: A little lobe.

Local therapy: Treatment that affects only a tumor and the area close to it.

Local treatment: Treatment that affects the tumor and the area close to it.

Lochia: The fluid that weeps from the vagina for a week or so after delivery of a baby.

Lockjaw: See Tetanus.

Locomotion: Moving from one place to another.

Locus: The place, in Latin.. In genetics, a locus is the place a gene occupies on a chromosome. One locus, two loci.

Locus minoris resistentiae: A place of less resistance, in Latin. For example, a damaged heart valve may act as a locus minoris resistentiae where bacteria released into the blood stream (bacteremia) tend to settle.

Loin: The portion of the lower back from just below the ribs to the pelvis.

Longevity: Lifespan. (With increasing longevity, women will soon be postmenopausal for one third of their lives).

Longitudinal: The word come from the Latin longitudo meaning length. Hence, longitudinal means along the length, running lengthwise, or (by extension) over the course of time.

Longitudinal section: A section that is cut along the long axis of a structure. The opposite is a cross section.

Longitudinal study: A study done over the passage of time. For example, a longitudinal study of children with Down syndrome (trisomy 21) might involve the study of 100 children with this condition from birth to 10 years of age. Also called a diachronic study. The opposite of a cross-sectional (synchronic) study.

Lordosis: Swayback.

Louse-borne typhus: A severe acute disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called epidemic, European, classic typhus and jail fever.

Lower GI series: A series of x-rays of the colon and rectum that is taken after the patient is given a barium enema. (Barium is a white, chalky substance that outlines the colon and rectum on the x-ray.)

Low-set ear: An ear positionned below its normal location. Classified as a minor anomaly. Technically, the ear is low-set when the helix (of the ear) meets the cranium at a level below that of a horizontal plane through both inner canthi (the inside corners of the eyes). The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.

Lubricant: An oily or slippery substance. A vaginal lubricant may be helpful for women who feel pain during intercourse because of vaginal dryness.

Lues: An old name for syphilis, a sexually transmitted disease (STD) that has been around for centuries and is caused by Treponema pallidum, a microscopic organism called a spirochete, a worm-like spiral-shaped organism that infects by burrowing into the moist mucous membranes of the mouth or genitals. From there, the spirochete produces the classic non-painful ulcer known as a chancre. There are 3 stages of syphilis. The first ("primary") stage is formation of the chancre.. It is highly contagious and can last 1-5 weeks. The disease can be transmitted from any contact with one of the ulcers, which are teeming with spirochetes. If the ulcer is outside the vagina or on the scrotum, the use of condoms may not help preventitransmission of the disease. Likewise, if the ulcer is in the mouth, merely kissing can spread syphilis. Even without treatment, an early infection resolves on its own in most women. However, 25% will proceed to the next stage of the disease called "secondary" syphilis, which lasts 4-6 weeks. This secondary phase can include hair loss, a sore throat, white patches in the nose, mouth, and vagina, fever, headaches, and a skin rash. There can be lesions on the genitals that look like genital warts but are caused by spirochetes rather than the wart virus. These wart-like lesions, as well as the skin rash, are highly contagious. The rash can occur on the palms of the hands and the infection can be transmitted by casual contact. The third stage of the disease involves the brain and heart and is usually no longer contagious. At this point, however, the infection can cause extensive damage to the internal organs, such as the brain, and can lead to death.

Lumbar puncture: A lumbar puncture or "LP" is a procedure whereby spinal fluid is removed from the spinal canal for the purpose of diagnostic testing. It is particularly helpful in the diagnosis of inflammatory diseases of the central nervous system, especially infections, such as meningitis. It can also provide clues to the diagnosis of stroke, spinal cord tumor and cancer metastasis to the central nervous system.

Lumpectomy: A lumpectomy is a partial mastectomy, and quadrentectomy refer to removing only a portion of the breast.

Lungs: The lungs are a pair of breathing organs located with the chest which remove carbon dioxide from and bring oxygen to the blood. There is a right and left lung.

Luteinizing hormone-releasing hormone: A hormone that controls sex hormones in men and women. Also called LHRH.

Luxation: Complete dislocation of a joint. A partial dislocation is a subluxation.

Lymph: The almost colorless fluid that travels through the lymphatic system and carries cells that help fight infection and disease.

Lymph nodes: Small, bean-shaped organs located throughout the lymphatic system. The lymph nodes store special cells that can trap cancer cells or bacteria that are traveling through the body in lymph. Also called lymph glands.

Lymphadenopathy: Disease of the lymph nodes.

Lymphangiogram: X-rays of the lymphatic system. A dye is injected to outline the lymphatic vessels and organs.

Lymphangioma: A structure consisting of a collection of blood vessels and lymph vessels that are overgrown and clumped together. Depending on their nature, these structures may grow slowly or quickly. They can cause problems because of their location. For example, a lymphangioma around the voicebox (larynx) might cause a breathing problem.

Lymphatics: Lymphatics are small thin channels similar to blood vessels. They do not carry blood, but collect and carry tissue fluid from the body to ultimately drain back into the blood stream.

Lymphatic system: The tissues and organs, including the bone marrow, spleen, thymus, and lymph nodes, that produce and store cells that fight infection and disease. The channels that carry lymph are also part of this system.

Lymphedema: A condition in which excess fluid collects in tissue and causes swelling. It may occur in the arm or leg after lymph vessels or lymph nodes in the underarm or groin are removed.

Lymphocytes: White blood cells that fight infection and disease.

Lymphocytic: Referring to lymphocytes, a type of white blood cell.

Lymphocytosis: Too many lymphocytes.

Lymphoid: Referring to lymphocytes, a type of white blood cell. Also refers to tissue in which lymphocytes develop.

Lymphoid tissue: The part of the body's immune system that helps protect it from bacteria.

Lymphoma: Tumor of the lymphoid tissue.

Lyon hypothesis: See Lyonizatioon.

Lyonization: The inactivation of an X chromosome. One of the two X chromosomes in every cell in a female is randomly inactivated early in embryonic development. Named after geneticist Mary Lyon.

Lysis: Destruction. Hemolysis (hemo-lysis) is the destruction of red blood cells with the release of hemoglobin.

Lytic: Suffix having to do with lysis. For example, hemolytic anemia.