Medical Terminology
Glossary
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radiographic anatomy - diagnostic branch of anatomy that includes the use of X-rays
rales - sounds sometimes heard in lungs; resemble bubbling or rattling; due to presence of an abnormal amount or type of fluid or mucus inside bronchi or alveoli or to bronchoconstriction, so that air cannot enter or leave the lungs normally
rami communicantes - branches of a spinal nerve; singular, ramus communicans
Raynaud's disease - vascular disease, primarily of females, characterized by bilateral attacks of ischemia, usually of the fingers and toes; the skin becomes pale and exhibits burning and pain as a result of exposure to cold or to emotional stimuli
reactivity - the ability of an antigen to react specifically with the antibody whose formation it induced
reciprocal innervation - the phenomenon by which action potentials stimulate contraction of one muscle and simultaneously inhibit contraction of antagonistic muscles
recruitment - the process of increasing the number of active motor LETTERs; also called motor LETTER summation
rectum - the last 20 cm (7 in.) of the gastrointestinal tract, from the sigmoid colon to the anus
recumbent - lying down
refraction - the bending of light as it passes from one medium to another
refractory period - the time during which an excitable cell cannot be made to respond to a stimulus that is usually adequate to evoke an action potential
regeneration - the natural renewal of a structure
regimen - strictly regulated scheme of diet, exercise, or activity designed to achieve certain ends
regurgitation - a return of solids or fluids from the stomach to the mouth; blood flow backward through incompletely closed heart valves
relapse - return of a disease, weeks or months after its apparent cessation
renal corpuscle - the glomerular (Bowman's) capsule and its enclosed glomerulus
renal erythropoietic factor - an enzyme released by the kidneys and liver in conditions of hypoxia; acts on a plasma protein to bring about production of eyrthropoietin, a hormone that stimulates red blood cell production
renin - an enzyme released by the kidney into plasma, where it converts angiotensinogen into angiotensin I
renin-angiotensin pathway - mechanism for the control of aldosterone secretion by angiotensin II; initiated by secretion of renin from the kidney, in response to low blood pressure
reproduction - the formation of new cells for growth, replacement, or repair, or the production of a new individual
residual volume - the volume of air still contained in the lungs after maximal expiration; about 1,200 ml
resistance - resistance to blood flow as a result of viscosity, blood vessel length, and blood vessel radius; hindrance to the flow of electricity; hindrance to the flow of air as it moves through the respiratory pasageways; the abililty to ward off disease
respiration - overall exchange of gases among the atmosphere, the blood, and the body cells; it consists of pulmonary ventilation, external respiration, & internal respiration
respirator - apparatus fitted to a mask over the nose and mouth, or hooked directly to an endotracheal or tracheostomy tube; it is used to assist or support ventilation or to provide nebulized medication to the air passages under positive pressure
resuscitation - the act of bringing a person back to full consciousness
rete testis - the network of ducts in the testis
retention - a failure to void urine due to obstruction, nervous contraction of the urethra, or absence of sensation of the desire to urinate
reticular activating syst. - the extensive network of branched nerve cells running through the core of the brain stem; when these cells are activated, a generalized alert or arousal behavior results
reticulocyte - an immature red blood cell
reticulum - a network
retina - inner coat of the eyeball, lying only in the posterior portion of the eye and consisting of nervous tissue and a pigmented layer comprising epithelial cells lying in contact with the choroid; also called the nervous tunic
retinal - the pigment portion of the photopigment rhodopsin; also called visual yellow
retraction - movement of a protracted part of the body backward on a plane parallel to the ground, as in pulling the lower jaw back into line with the upper jaw
retroflexion - positioning of the uterus in which it is tilted posteriorly
retrograde degeneration - the changes occuring in the proximal portion of a damaged axon only as far as the first neurofibral node (of Ranvier); similar to the changes that occur during Wallerian degeneration
retroperitoneal - external to the peritoneum lining the abdominal cavity
rheumatism - a painful state of the supporting structures of the body, bones, ligaments, joints, tendons, or muscles
rhinology - the study of the nose and its disorders
rhinoplasty - the surgical procedure in which the structure of the external nose is altered
rhodopsin - the photopigment in rods of the retina, consisting of a protein scotopsin plus retinal; it is sensitive to low levels of illumination; also called visual purple
ribonucleic acid (RNA) - a single-stranded nucleic acid; nucleotides consist of a base (adenine, cytosine, guanine, or uracil), ribose, and phosphate; the three types are messenger (m-RNA), transfer (tRNA), and ribosomal (rRNA), all of which are necessary for protein synthesis
ribosome - organelle in the cytoplasm of cells; composed of ribosomal RNA and ribosomal proteins; nicknamed the protein factory because of its role in protein synthesis
rickets - condition affecting children deficient in vitamin D; characterized by soft and deformed bones, resulting from abnormal calcium metabolism
rigidity - hypertonia characterized by increased muscle tone; reflexes are not affected
roentgen - internation LETTER of radiation; a standard quantity of X or gamma radiation
roentgenogram - image produced by X-rays on a photographic film
rotation - movement of a bone around its own axis, with no other movement
rugae - large folds in the mucosa of an empty hollow organ, such as the stomach or the vagina