Definition Learning disorders, or learning disabilities, are disorders that cause problems in speaking, listening, reading, writing, or mathematical ability. Description A learning disability, or specific developmental disorder, is a disorder that inhibits or interferes with the skills of learning. Under federal law, public schools consider a child to be learning disabled...

Definition Lead poisoning occurs when a person swallows, absorbs, or inhales lead in any form. The result can be damaging to the brain, nerves, and many other parts of the body. Acute lead poisoning, which is somewhat rare, occurs when a relatively large amount of lead is...

  Definition Laxatives are products that promote bowel movements. Purpose Laxatives are used to treat constipation—the passage of small amounts of hard, dry stools, usually fewer than three times a week. Before recommending use of laxatives, differential diagnosis should be performed. Prolonged constipation may be evidence of a significant problem, such as localized peritonitis...

Laser (light amplification by stimulated emission of radiation ) surgery uses an intensely hot, precisely focused beam of light to remove or vaporize tissue and control bleeding in a wide variety of non-invasive and minimally invasive procedures. Laser surgery is used to: ·         cut or destroy tissue...

Definition Laryngoscopy is a procedure used to view the inside of the larynx (the voice box). Purpose The purpose of seeing inside the larynx is to assess the vocal cords and to detect tumors, foreign bodies, nerve or structural injury, or other abnormalities. Precautions A patient undergoing a laryngoscopy should be assessed for allergies to local anesthetics or other pharmacologic...

Laryngitis is an inflammation of the larynx. Located at the upper end of the trachea, or windpipe, the larynx contains the vocal chords that are used to form sounds. Because the larynx plays such an important role in speech, it is sometimes called the voice box. When the larynx becomes inflamed in laryngitis, it swells and reddens. The major symptom of laryngitis is hoarseness. Other symptoms...

Definition A laryngectomy is the partial or complete surgical removal of the voice box (larynx). Purpose Because of its location, the voice box, or larynx, plays a critical role in breathing, swallowing, and speaking. The larynx is located above the windpipe (trachea) and in front of the food pipe (esophagus). It contains two small bands of muscle called the vocal cords that close to prevent food from...

Definition Laryngeal cancer is cancer of the larynx or voice box. Description The larynx is located where the throat divides into the esophagus and the trachea. The esophagus is the tube that takes food to the stomach. The trachea, or windpipe, takes air to the lungs. The area where the larynx is located is sometimes called the Adam's apple. The larynx has two main functions. It contains...

Definition Laparoscopy is a type of surgical procedure in which a small incision is made, usually in the navel, through which a viewing tube (laparoscope) is inserted. The viewing tube has a small camera on the eyepiece. This allows the doctor to examine the abdominal and pelvic organs on a video monitor connected to the tube. Other small incisions can be made to insert instruments to perform procedures. Laparoscopy can...

Definition Lactose intolerance is defined as the inability to digest the milk sugar, lactose, because of a deficiency of the digestive enzyme lactase. Description Lactose is the main sugar found in milk and other dairy products. Lactose is broken down by the enzyme lactase. Lactase is produced by cells in the inner lining of the small intestine. Lactase breaks down lactose into...

Definition Lactic acid is an acid produced by cells during chemical processes in the body that do not require oxygen (anaerobic metabolism). Anaerobic metabolism occurs only when too little oxygen is present for the more usual aerobic metabolism (oxygen requiring). Lactic acid is a contributing factor in muscle cramps. It is also produced in tissues when conditions such...

Definition Lactation refers to the formation of milk in the breasts during the period following childbirth . Breastfeeding is the process of the infant obtaining milk by suckling at the breast. Description Although breast development begins around puberty , development of mammary function is only completed in pregnancy. During the first half of pregnancy the mammary ducts proliferate...

Definition Lactate dehydrogenase, also called lactic dehydrogenase, or LDH, is an enzyme found in the cells of many body tissues, including the heart, liver, kidneys, skeletal muscle, brain, red blood cells, and lungs. It is responsible for converting muscle lactic acid into pyruvic acid, an essential step in producing cellular energy. Purpose Lactic dehydrogenase is present in almost all...

Definition The enzyme lactate dehydrogenase (also known as lactic dehydrogenase, or LDH) is found in the cells of almost all body tissues. The enzyme is especially concentrated in the heart, liver, red blood cells, kidneys, muscles, brain, and lungs. The total LDH can be further separated into five components or fractions labeled by number: LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5. Each of these...

Definition A lacrimal duct obstruction is blockage of the tear duct, the thin channel that normally drains tears from the surface of the eye. Description The lacrimal glands, located above each eyeball, produce tears. The tears flow over the eye, then drain through the nasolacrimal ducts. A tiny hole at the inner edge of each eyelid marks the opening of the ducts, which lead...

Definition Laceration repair includes all the steps required to treat a wound in order to promote healing and minimize the risks of infection, premature splitting of sutures (dehiscence), and poor cosmetic result. Purpose A laceration is a wound caused by a sharp object producing edges that may be jagged, dirty, or bleeding. Lacerations most often affect the skin, but any tissue may be lacerated,...

Definition Labyrinthitis is an inflammation of the inner ear that is often a complication of infection of the middle ear (otitis media ). It is usually caused by the spread of bacterial or viral infections from the head or respiratory tract into the inner ear. Description The labyrinth is a group of interconnected canals chambers located in the inner ear. It is made up of the cochlea and the semicircular...

Lymph nodes serve a protective function by helping to prevent the dissemination of germs, toxins, and foreign materials throughout the body. When an infection develops in a certain part of the body, the lymph nodes that serve this part will become inflamed. Lymph nodes, which normally are too small to be noticeable, now become enlarged, tender, and painful. If the infection is severe, the involved lymph nodes...

This symptom is usually of a functional nature; that is, it is not the result of actual disease but of anxiety. Typically the patient with this symptom faces some unsolved problem, and the resultant pent-up emotional tension causes him apprehension about his health. The lump in the throat is an unconscious result of a fear that he may have cancer of the throat or some other life-threatening disease. Sometimes...

(See Discharge, Purulent: G. From the Vagina.) The word leukorrhea, meaning "white discharge," includes all non bloody discharges from the vagina. A small amount of mucous discharge is normal, but when a white discharge from the vagina is sufficient to soil the underclothing; when this condition is associated with itching or with discomfort around the anus; or when sexual intercourse becomes uncomfortable,...

(See also Weakness) After performing prolonged mental or physical work, a person's capacity for this work is reduced. In muscle activity, loss of energy results from a reduction in the oxygen available in the muscle plus an accumulation of the chemical waste products of muscle activity. Both of these are accentuated by a limitation of blood supply to the muscle.  After a muscle has been used for a...

Lactase deficiency; Milk intolerance; Disaccharidase deficiency; Dairy product intolerance Definition of Lactose intolerance: Lactose intolerance is the inability to digest lactose (a type of sugar found in milk and other dairy products). Causes, incidence, and risk factors: Lactose intolerance happens when the small intestine does not make enough of the enzyme lactase. Babies' bodies make this enzyme...