Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

involuntary muscleMuscle that works without a person's conscious control, such as smooth muscle and heart muscle.

involutionThe process by which the uterus shrinks back to its size and position from before pregnancy, after the birth.

iodineA mineral the thyroid gland uses to make thyroid hormone; it is also used to kill germs on the skin and in some contrast dyes.

IPFIdiopathic pulmonary fibrosis: a long-term lung disease of unknown cause in which lung tissue becomes thick and scarred.

irisThe colored ring of muscle in the eye that controls the size of the pupil.

iron-deficiency anemiaAnemia caused by too little iron in the body, so the bone marrow cannot make enough hemoglobin.

irritable bowel syndromeA long-term bowel condition with belly pain and changes in bowel habits, such as diarrhea, constipation or both.

ischemiaToo little blood flow to a part of the body, so the tissue does not get enough oxygen.

ischemic strokeA stroke caused by a blocked artery that cuts off blood flow to part of the brain.

isotonicHaving the same concentration of dissolved particles as blood, so water does not move into or out of cells.

jaundiceYellow color of the skin, the whites of the eyes and other tissues from too much bilirubin in the blood.

jejunumThe second of the three sections of the small intestine; it follows the duodenum and leads into the ileum.

judgmentThe ability to think a situation through and make sound, safe decisions.

jugularRelating to the neck, especially the large veins in the neck.

jugular veinOne of the large veins on each side of the neck that carry blood from the head back toward the heart.

Kaposi sarcomaA cancer that starts in the cells lining the blood and lymph vessels.

Kawasaki diseaseAn illness of young children in which the walls of medium-sized blood vessels throughout the body become inflamed.

keloidA raised, firm overgrowth of scar tissue that spreads beyond the edges of the original wound.

kernicterusA form of permanent brain damage in which bilirubin is deposited in a newborn's brain tissue.

ketoacidosisA state in which ketones build up in the blood and make it too acidic.

ketoneAn acid made by the liver when the body burns fat for energy instead of glucose.

kidneyOne of two bean-shaped organs in the back of the belly that filter the blood and make urine.

kidney infectionAn infection of one or both kidneys; the medical word is pyelonephritis.

kidney stoneA hard, pebble-like lump of minerals that forms inside the kidney.

knee painPain felt in or around the knee joint.

Korsakoff syndromeA long-lasting brain disorder of memory that results from a severe lack of thiamine (vitamin B1).

kyphosisAn outward curve of the upper spine that makes the back look rounded or hunched.

laborThe process of childbirth, from the start of regular contractions that open the cervix to the delivery of the baby and placenta.

lacerationA cut or tear in the skin or other tissue, often with jagged edges.

lactationThe making and release of milk by the breasts.

lacticRelating to milk, or to lactic acid, a substance cells make when they break down glucose without enough oxygen.

lactic acidosisA type of metabolic acidosis in which lactic acid (lactate) builds up in the blood.

lanugoFine, soft, downy hair that covers the body of a fetus.

large for gestational ageDescribes a newborn who weighs more than 90 out of 100 babies born after the same number of weeks of pregnancy.

large intestineThe last part of the digestive tract, from the end of the small intestine to the anus, where water is absorbed and stool forms.

laryngitisInflammation of the larynx, the voice box.

laryngopharynxThe lowest part of the throat, below the back of the mouth, where the airway and the food passage separate.

larynxThe voice box: the part of the airway in the neck, above the windpipe, that holds the vocal cords.

last menstrual periodThe first day of a person's most recent menstrual period.

late decelerationA gradual drop in the fetal heart rate that starts and hits its lowest point after the peak of a contraction.

lateralToward the side of the body, away from the middle line.

latex allergyAn allergic reaction to proteins in natural rubber latex, found in some gloves, catheters and other products.

lead poisoningHarm to the body from a buildup of lead, a toxic metal, usually over months or years.

left lower quadrantThe lower left quarter of the abdomen, when it is divided into four parts by lines crossing at the navel.

left ventricleThe heart's lower left chamber, which pumps oxygen-rich blood into the aorta and out to the body.

left-sided heart failureHeart failure in which the left ventricle cannot pump enough blood out to the body.

lesionAn area of tissue that has been damaged or has changed from normal, such as a sore, wound, lump or spot.

letdownThe reflex that pushes milk out of the breast's milk glands toward the nipple during breastfeeding.

leukemiaA cancer of the blood-forming cells in the bone marrow, in which abnormal white blood cells are made in large numbers.

level of consciousnessHow awake, alert and aware of their surroundings a person is.