Dictionary

Body systems

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

pepsinAn enzyme in the stomach that begins breaking down proteins.

percentileA number from 1 to 99 that shows how a measurement compares with others, as the share of the group that falls below it.

perceptionThe brain's way of taking in and making sense of what the senses detect; also a person's own view or understanding of something.

perforationA hole that goes all the way through the wall of an organ or tissue.

perfusionThe flow of blood through the body's tissues, bringing them oxygen and nutrients.

pericarditisInflammation of the pericardium, the thin sac that surrounds the heart.

pericardiumThe thin, two-layered sac that surrounds the heart.

perimenopauseThe years leading up to menopause, when hormone levels rise and fall and periods become irregular.

perinealHaving to do with the perineum, the area between the genitals and the anus.

perineal hematomaA collection of blood under the skin of the perineum, the area between the vagina and the anus.

perineumThe area of skin and muscle between the genitals and the anus.

perioralAround the mouth.

peripheralAt or toward the outer parts of the body, away from the center, such as the arms, legs, hands and feet.

peripheral artery diseaseNarrowing of the arteries that carry blood to the legs, and sometimes the arms, usually from fatty plaque.

peripheral nervous systemAll the nerves outside the brain and spinal cord, which link them to the rest of the body.

peripheral neuropathyDamage to the nerves outside the brain and spinal cord, most often in the feet and hands.

peripheral vascular diseaseDisease of the blood vessels outside the heart and brain, most often narrowed arteries or damaged veins in the legs.

peristalsisWaves of muscle squeezing that push food and waste along the digestive tract.

peristomalAround a stoma, the surgical opening of the bowel or urinary tract on the abdomen.

peritonealHaving to do with the peritoneum, the thin lining of the belly cavity and the organs inside it.

peritoneal dialysisA kind of dialysis that uses the lining of the abdomen as a filter, with fluid run in and out through a catheter.

peritoneumThe thin membrane that lines the belly cavity and covers most of the organs inside it.

peritonitisInflammation of the peritoneum, the thin membrane that lines the inside of the belly and covers the organs there.

pernicious anemiaAn anemia from a lack of vitamin B12 because the stomach does not make intrinsic factor, a protein needed to absorb it.

peronealHaving to do with the outer side of the lower leg, near the fibula bone.

personality disorderA long-lasting pattern of thinking, feeling and behaving that differs strongly from what the person's culture expects.

pertussisA very contagious infection of the airways caused by the bacterium Bordetella pertussis; also called whooping cough.

petechiaeTiny flat red or purple dots on the skin from small amounts of bleeding under the surface.

phagocytosisThe process by which some white blood cells swallow and destroy germs, dead cells and debris.

pharyngitisInflammation of the pharynx, the throat behind the mouth and nose.

pharynxThe throat: the passage behind the nose and mouth that carries air to the voice box and food to the esophagus.

phenylketonuriaAn inherited disorder in which the body cannot break down phenylalanine, an amino acid found in protein foods.

phlebitisInflammation of a vein.

phobiaA strong, lasting fear of a particular thing or situation that is out of proportion to any real danger.

phospholipidA fat molecule with a phosphate group that forms the double layer around every cell.

photophobiaDiscomfort or pain in the eyes caused by light; sensitivity to light.

phototherapyTreatment with light, most often special blue light on a newborn's skin to lower the bilirubin level.

physiologicRelating to the normal working of the body.

physiologic jaundiceYellowing of a newborn's skin and eyes from a normal, short-lived rise in bilirubin in the first days after birth.

physiologyThe study of how the body and its parts work.

pineal glandA small gland deep in the brain that makes melatonin, the hormone that helps control sleep.

pitting edemaSwelling in which pressing a finger into the skin leaves a dent that stays for a while after the finger is lifted.

pituitary glandA gland the size of a pea, hanging below the brain, whose hormones control many other glands.

placentaThe organ that grows in the uterus during pregnancy and passes oxygen and food from the parent's blood to the fetus.

placenta previaA placenta that lies low in the uterus and partly or completely covers the opening of the cervix.

placentalRelating to the placenta, the organ that grows in the uterus in pregnancy and links the mother's blood supply to the baby's.

plantarHaving to do with the sole of the foot.

plaqueA deposit that builds up on a surface in the body, such as a sticky film of bacteria on teeth or a fatty buildup in an artery wall.

plasmaThe pale yellow liquid part of the blood, which carries the blood cells, proteins, nutrients and wastes.

plateletA tiny cell fragment in the blood that sticks together at a wound to help form a clot.