Dictionary

Body systems

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

PACAn abbreviation with more than one meaning, most often premature atrial contraction or pulmonary artery catheter.

pacemakerA small device that sends electrical pulses to the heart to keep it beating at a set rate; also the heart's own natural rhythm center.

packed red blood cellA blood product made of red blood cells with most of the plasma removed, given by transfusion.

PADAn abbreviation that most often means peripheral artery disease, a narrowing of the arteries outside the heart and brain.

palmarHaving to do with the palm of the hand.

palmar grasp reflexA newborn reflex in which the baby's fingers close tightly around an object placed in the palm.

palpitationThe feeling of your own heartbeat as pounding, racing, fluttering or skipping.

pancreasA long, flat gland behind the stomach that makes digestive enzymes and the hormones insulin and glucagon.

pancreatitisInflammation of the pancreas, which may come on suddenly (acute) or last for years (chronic).

panic attackA sudden wave of intense fear that peaks within minutes.

papuleA small, solid, raised bump on the skin, less than 1 cm across, with no fluid inside.

paraThe number of pregnancies a person has carried to 20 weeks or more, whatever the outcome.

paralysisLoss of the ability to move a part of the body, and sometimes loss of feeling in it.

paralytic ileusA stop in the normal movement of the intestines that happens without anything physically blocking them.

paraplegiaParalysis of both legs and the lower part of the body.

parasympatheticRelating to the part of the autonomic nervous system that calms the body and supports "rest and digest" functions.

parasympathetic nervous systemThe part of the autonomic nervous system that calms the body, slows the heart and helps digestion during rest.

parathyroid glandOne of four small glands behind the thyroid that control the amount of calcium in the blood.

parathyroid hormoneA hormone from the parathyroid glands in the neck that raises the calcium level in the blood.

parenteral nutritionNutrition given as a liquid straight into a vein instead of through the digestive tract.

paresthesiaAn abnormal feeling in the skin, such as tingling, prickling or "pins and needles," with nothing touching it.

parietalRelating to the wall of a body cavity; also names a lobe of the brain and two bones of the skull.

parietal lobeThe part of the brain at the top and back of the head that processes touch, pain, temperature and the body's position in space.

Parkinson diseaseA slowly worsening brain disease in which the nerve cells that help control movement die off.

patent ductus arteriosusA heart defect in which the ductus arteriosus, a blood vessel between the aorta and pulmonary artery, stays open after birth.

patent foramen ovaleAn opening between the heart's two upper chambers that did not close after birth as it normally does.

pathologyThe study of disease and its causes and effects, or the disease changes found in a person or tissue.

pathophysiologyThe study of how normal body functions change when disease or injury is present.

PEAn abbreviation that most often means pulmonary embolism; it can also mean physical examination or pleural effusion.

pedicleA narrow stem or stalk that attaches a structure, such as a tumor or a skin flap, to the body.

pediculosisInfestation with lice, tiny wingless insects that live on the body and feed on blood.

pelvicHaving to do with the pelvis, the bowl-shaped ring of bones at the base of the spine, or the organs inside it.

pelvic inflammatory diseaseInfection of the female upper reproductive organs: the uterus, fallopian tubes and ovaries.

pelvisThe ring of bones at the base of the spine that joins the legs to the trunk, or the lower part of the trunk it encloses.

penetrationPassing into or through something, such as an object entering the body through 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.