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quadrangular - Latin quadri = four and angulus = angle; hence square or rectangular.

Quadratus - (L. quadratus, square). More or less square-shaped muscles. Latin = square or rectangular.

Quadriceps - (L. quadi-, four + caput, head). A name given to a muscle having four heads, e.g., quadriceps femoris. Latin quadri = four, and caput = head; hence, a 4-headed muscle.

quadrigeminus - Latin quadri = four, and gemini = paired or twinned; hence four-fold.

Quinti - (L. quintus, fifth). Fifth, as in the fifth digit.

radiation - Latin radiatus = radiant; hence, divergence from a common centre (cf. radius).

radicle - diminutive of Latin radix = root; hence a small root, adjective - radicular.

Radio- - (L. radius, ray). Pertaining to muscles associated with the radius of the forearm.

Radioactive Isotope - Isotope refers to one of two or more atoms of the same element that have the same number of protons in their nucleus but different numbers of neutrons. A radioactive isotope is a natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached.

Radiotherapy - The treatment of disease with radiation (as X rays).

radius - Latin = spoke of a wheel, which rotates around the hub; hence, the lateral bone of the forearm, which rotates (though around an almost vertical axis); adjective - radial.

radix - Latin = root.

ramify - Latin ramus = a branch; and facere = to make; hence, to branch.

ramus - Latin = branch; hence, a branch of a nerve.

raphe - Greek a seam; hence, the line of junction of the edges of 2 muscles or areas of skin.

receptor - a sensing mechanism.

receptor proteins - provide binding sites for hormones or other trigger molecules.

recess - Latin recessus = a secluded area or pocket; hence, a small cavity set apart from a main cavity.

Rectalis - (L. rectus, straight). Pertaining to muscles associated with the distal segment of the large intestine.

rectum - adjective, Latin rectus = straight. (The rectum was named in animals where it is straight - which it is not in Man).

rectus - Latin rectus = straight.

recurrent - Latin re = back, and currere = to run; hence a structure that bends, and runs back toward its source.

red blood cells - (erythrocytes or RBCs)

reflex - an involuntary response - muscular or secretory - to a stimulus mediated by the central nervous system.

Refractory - Not readily yielding to treatment.

remodeling - the process of creating new bone and removing old bone.

renal - adjective, Latin ren = kidney.

Reportable List - A list that identifies all diagnoses and types of cases to be included in the cancer registry data base. For most registries in the world, the "reportable list" is everything listed in ICD- O-3 with a /2 or a /3 in the behavior code.

Reportable Malignancies - Tumors required to be reported. Typically, in most cancer registries, the reportable tumors are those that are listed in the International Classification of Diseases for Oncology, Third Edition which have a behavior defined as in situ (behavior code

reproduction - the production of eggs and sperm and the processes leading to fertilization.

Reproperitoneal - Having to do with the area outside or behind the peritoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen).

Residual Disease - The disease has not been eradicated.

respiratory system - delivers air to the lungs.

rete - Latin = a net; hence, a network of veins or tubules.

reticular - adjective, Latin reticulum = small net; hence having a network.

Reticuloendothelial system - A group of cells having the ability to take up and sequester inert particles and vital dyes, including macrophages or macrophage precursors, specialized endothelial cells lining the sinusoids of the liver, spleen, and bone marrow, and reticular cells of lymphatic tissue (macrophages) and of bone marrow (fibroblasts).

reticulum - diminutive of Latin rete = net; adjective - reticular.

retina - the inner nervous tunic of the eye that absorbs light in the pigmented epithelium and stores vitamin A by use of photoreceptor cells. Derivation uncertain - the innermost of the 3 layers of the eyeball.

retinaculum - Latin = a tether; hence, a thickened band of deep fascia which retains tendons or the patella.

Retinoblastoma - An ocular malignant neoplasm of the retina, usually arise in the first 2 years of life, it is the most form of intraocular malignancy in children.

retract - Latin re = back, and tractum = pulled; hence, to pull something back, and retraction - the act of retracting.

retro - prefix - Latin = backwards.

retroflexion - Latin retro = backwards, and flexion = bent; hence, the position of being bent backwards, applied to the angulation of the body of the uterus on the cervix.

retroversion - Latin retro = backwards, and version = turned; hence, the position of being turned backwards, applied to the angulation of the cervix uteri on the vagina.

Rh blood group - This is a complex group defined by the antigens produced by three different genes. The Rh factor determines positive or negative blood.

Rhabdomyosarcoma - Rhabdomyosarcoma tumors arise from a cell called a "rhabdomyoblast", which is a primitive muscle cell. Instead of differentiating into striated muscle cells, the rhabdomyoblasts grow out of control. Since this type of muscle is located throughout the body, the tumors can appear at numerous locations.

rhinencephalon - Greek rhinion = nostril, and enkephalos = brain; hence, the part of the brain concerned with smell (relatively large in lower animals).

rhombencephalon - Greek rhombos = rhomboid, and enkephalos = brain; hence, the hind-brain - the medulla oblongata, pons and cerebellum, which enclose the rhomboid fossa (the floor of the 4th ventricle).

Rhombo- - (G. rhombos, a rhomb). Resembling a rhomb, an oblique parallelogram of unequal sides. Relating to two superficial muscles of the back.

rhomboid - Greek rhombus = a figure with 4 equal sides, not at right angles, and eidos = shape or form, hence, the shape of a rhombus.

Ribosome - Any of the RNA-rich cytoplasmic granules that are sites of protein synthesis.

right atrium - located in the upper right side of the heart, along with the right auricle, acts as a temporary storage chamber so that blood will be readily available for the right ventricle.

right ventricle - the pumping chamber of the heart for pulmonary circulation.

rima - Latin = chink; hence, e.g., rima palpebrarum = the chink between the free edges of the eyelids.

Risorius - (L. risor, laughter). Pertaining to a facial muscle, i.e., musculus risorius.

risorius - Latin risor = scoffer; hence, muscle risorius is the facial muscle which expresses laughter by drawing the corner of the mouth laterally.

RNA (ribonucleic acid) - takes genetic instructions from DNA and directs various metabolic activities of the cell.

rods - photoreceptors that are most sensitive to light and more numerous than cones. The provide vision in dim light and are more capable of detecting movement.

Roentgen - The international unit of x- or gamma-radiation, abbreviated r or R; named after the German physicist, Wilhelm Roentgen, who discovered roentgen ray in 1895.

rostral - adjective, Latin rostrum = beak, implying nearness to the corpus callosum.

rostrum - Latin beak, which decorated the Roman orator's platform; hence, a platform or beak-like structure; adjective - rostral.

rotate - Latin rota = wheel; hence, to turn, and rotation, the act of turning.

rotundum - Latin rotnudus = round.

Rubric - A rubric is a chart or template which specifies the criteria to be used to evaluate an assignment.

rubro - prefix, Latin rubrum = red.

ruga - Latin = a wrinkle.

rugose - adjective, Latin ruga = a wrinkle, hence, wrinkled.