Case Histories in Human Physiology - Appendix C: Glossary

Glossary - Definitions

QRS complex The principal deflection of an electrocardiogram that is produced by depolarization of the ventricles.

ramus (ra´mus) A branch of a bone, artery, or nerve.

raphe (ra´fe) A ridge or a seamlike structure between two similar parts of a body organ, as in the scrotum.

receptor (re-sep´tor) A sense organ or a specialized distal end of a sensory neuron that receives stimuli from the environment.

rectum (rek´tum) The terminal portion of the GI tract, between the sigmoid colon and the anal canal.

red marrow (mar´o) A tissue that forms blood cells, located in the medullary cavity of certain bones.

red nucleus (noo´kle-us) An aggregation of gray matter of a reddish color located in the upper portion of the midbrain. It sends fibers to certain brain tracts.

reduced hemoglobin (he´muo-glo´´bin) Hemoglobin with iron in the reduced ferrous state. It is able to bond with oxygen but is not combined with oxygen. Also called deoxyhemoglobin.

reducing agent An electron donor in a coupled oxidation-reduction reaction.

reflex (re´fleks) A rapid involuntary response to a stimulus.

reflex arc The basic conduction pathway through the nervous system, consisting of a sensory neuron, an association neuron, and a motor neuron.

regional anatomy The division of anatomy concerned with structural arrangement in specific areas of the body, such as the head, neck, thorax, or abdomen.

renal (re´nal) Pertaining to the kidney.

renal corpuscle (kor´pus'l) The portion of the nephron consisting of the glomerulus and a glomerular capsule; also called the malpighian corpuscle.

renal cortex The outer portion of the kidney, primarily vascular.

renal medulla (mue-dul´ua) The inner portion of the kidney, including the renal pyramids and renal columns.

renal pelvis The inner cavity of the kidney formed by the expanded ureter and into which the calyces open.

renal plasma clearance rate The milliliters of plasma cleared of a particular solute per minute by the excretion of that solute in the urine. If there is no reabsorption or secretion of that solute by the nephron tubules, the plasma clearance rate is equal to the glomerular filtration rate.

renal pyramid A triangular structure within the renal medulla composed of nephron loops and the collecting ducts.

repolarization (re-po´´lar-u1-za´shun) The reestablishment of the resting membrane potential after depolarization has occurred.

respiration (res´´pu1-ra´shun) The exchange of gases between the external environment and the cells of an organism.

respiratory acidosis (ru1-sp=1r´ua-tor-e as´´u1-do´sis) A lowering of the blood pH to below 7.35 due to accumulation of CO2 as a result of hypoventilation.

respiratory alkalosis (al´´kua-lo´sis) A rise in blood pH to above 7.45 due to excessive elimination of blood CO2 as a result of hyperventilation.

respiratory center The structure or portion of the brain stem that regulates the depth and rate of breathing.

respiratory distress syndrome A lung disease of the newborn, most frequently occurring in premature infants, that is caused by abnormally high alveolar surface tension as a result of a deficiency in lung surfactant; also called hyaline membrane disease.

respiratory membrane A thin, moistened membrane within the lungs, composed of an alveolar portion and a capillary portion, through which gaseous exchange occurs.

rete testis (re´te tes´tis) A network of ducts in the center of the testis associated with the production of spermatozoa.

reticular formation (rue-tik´yuu-lar) A network of nervous tissue fibers in the brain stem that arouses the higher brain centers.

retina (ret´u1-nua) The principal portion of the internal tunic of the eyeball that contains the photoreceptors.

retraction (re-trak´shun) The movement of a body part, such as the mandible, backward on a plane parallel with the ground; the opposite of protraction.

retroperitoneal (ret´´ro-per´´u1-tuo-ne´al) Positioned behind the parietal peritoneum.

rhodopsin (ro-dop´sin) A pigment in rod cells that undergoes a photochemical dissociation in response to light, and in so doing stimulates electrical activity in the photoreceptors.

rhythmicity area (rith-mis´u1-te) A portion of the respiratory control center located in the medulla oblongata that controls inspiratory and expiratory phases.

ribosome (ri´bo-s=om) A cytoplasmic organelle composed of protein and RNA in which protein synthesis occurs.

rickets (rik´ets) A condition caused by a deficiency of vitamin D and associated with an interference of the normal ossification of bone.

right lymphatic duct (lim-fat´ik) A major vessel of the lymphatic system that drains lymph from the upper right portion of the body into the right subclavian vein.

rigor mortis (rig´or mor´tis) The stiffening of a dead body due to the depletion of ATP and the production of rigor complexes between actin and myosin in muscles.

RNA Ribonucleic acid; a nucleic acid consisting of the nitrogenous bases adenine, guanine, cytosine, and uracil; the sugar ribose; and phosphate groups. There are three types of RNA found in cytoplasm: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).

rod A photoreceptor in the retina of the eye that is specialized for colorless, dim-light vision.

root canal The hollow, tubular extension of the pulp cavity into the root of the tooth that contains vessels and nerves.

rotation (ro-ta´shun) The movement of a bone around its own longitudinal axis.

round window A round, membrane-covered opening between the middle and inner ear, directly below the oval window; also called the cochlear window.

rugae (roo´je) The folds or ridges of the mucosa of an organ.

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