Dictionary

Body systems

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

radialHaving to do with the radius, the forearm bone on the thumb side, or spreading out from a center.

radial pulseThe pulse felt at the wrist, on the thumb side, over the radial artery.

radiationEnergy that travels as waves or particles, such as X-rays, used to make images or treat cancer; also pain that spreads from its starting point.

radiation therapyTreatment that uses high-energy rays or radioactive material to kill cancer cells or shrink tumors.

range of motionHow far a joint can move in each of its normal directions, and the exercises that move joints through it.

Raynaud phenomenonA condition in which small arteries of the fingers and toes narrow too much in response to cold or stress.

reabsorptionThe taking back of water and dissolved substances from the fluid in the kidney tubules into the blood.

reality testingThe ability to tell the difference between one's own thoughts and feelings and what is really happening in the outside world.

receptorA structure on or in a cell that a specific chemical, such as a hormone or drug, attaches to in order to act.

rectalRelating to the rectum, the last part of the large intestine; also, given or measured through the rectum.

rectumThe last part of the large intestine, between the colon and the anus, where stool is held until it leaves the body.

rectusLatin for straight; the name of several straight muscles, such as the rectus abdominis of the abdomen and the rectus femoris of the thigh.

recurrenceThe return of a disease or symptom after a period when it had gone away.

recurrentHappening again after it has gone away, often more than once.

red blood cellA blood cell that carries oxygen from the lungs to the body's tissues; also called an erythrocyte.

refeedingStarting food or nutrition support again in a person who has been starved or severely malnourished.

refeeding syndromeDangerous shifts in fluids and minerals that can happen when a starved or severely malnourished person starts eating or being fed again.

reflexAn automatic body response to something that stimulates it, which happens without thought, such as the knee jerk.

refluxA backward flow of fluid, most often of stomach contents up into the esophagus.

regurgitationA flowing backward: blood leaking back through a heart valve, or stomach contents coming back up into the mouth.

rehydrationReplacing the water and salts the body has lost, by mouth or through an IV.

relapseThe return of a disease or its symptoms after a period of improvement, or a return to substance use after a time without it.

remissionA period when the signs and symptoms of a disease lessen or disappear.

renalRelating to the kidneys.

renal failureLoss of the kidneys' ability to filter waste and extra fluid from the blood.

renin-angiotensin-aldosterone systemA chain of hormones that raises blood pressure and helps the body hold on to salt and water.

reproductionThe process by which living things produce offspring.

reproductive systemThe organs that make eggs or sperm and sex hormones, and that allow a pregnancy to begin and grow.

resilienceThe ability to cope with stress, hardship or trauma and to recover from it.

respirationBreathing air in and out, and the exchange of oxygen and carbon dioxide between the air, the blood and the cells.

respiratoryRelating to breathing or to the organs used for breathing.

respiratory acidosisA state in which the blood becomes too acidic because the lungs do not remove enough carbon dioxide.

respiratory alkalosisAn acid-base imbalance in which breathing out too much carbon dioxide makes the blood too alkaline.

respiratory distressDifficulty breathing severe enough that a person has to work hard to move air in and out.

respiratory distress syndromeA breathing disorder of newborns, mostly premature babies, whose lungs do not yet make enough surfactant.

respiratory failureA state in which the lungs cannot put enough oxygen into the blood, or cannot remove enough carbon dioxide from it.

respiratory rateThe number of breaths a person takes in one minute.

respiratory syncytial virusA common virus that infects the nose, throat and lungs, most often in babies and young children.

respiratory systemThe organs that bring air into the body and move oxygen into the blood and carbon dioxide out of it.

respiratory therapistA licensed health worker who treats breathing problems and runs equipment such as oxygen, inhaled treatments and ventilators.

respiratory tractThe passages that air moves through: the nose, mouth, throat, voice box, windpipe and the airways of the lungs.

retentionThe keeping in of something the body would normally let go, such as urine, fluid or stool.

retinaThe thin layer of light-sensing tissue at the back of the inside of the eye.

retinalRelating to the retina, the thin layer at the back of the eye that senses light and sends images to the brain.

retinopathyDisease or damage of the retina, the light-sensing layer at the back of the eye.

retractionA drawing back or pulling in of tissue; in breathing, the skin sinking in between, below or above the ribs with each breath.

reuptakeThe taking back of a chemical messenger into the nerve cell that released it.

Reye syndromeA rare illness that causes swelling of the brain and liver damage, mostly in children and teenagers.

rhabdomyolysisThe rapid breakdown of damaged skeletal muscle, which releases the muscle's contents into the blood.

rheumatic feverAn inflammatory disease in which the immune system attacks the heart, joints, skin and brain weeks after a strep throat infection.