| CRAO | central retinal artery occlusion |
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| CRB | chemical, radiological, and biological; congenital retinal blindness |
| CRD | carbohydrate-recognition domain; chronic renal disease; chronic respiratory disease; child restraint... |
| CRP | chronic relapsing pancreatitis; corneal-retinal potential; coronary rehabilitation program; C-reacti... |
| CRV | central retinal vein |
| alveolar-arterial oxygen difference | The difference or gradient between the partial pressure of oxygen in the alveolar spaces and the arterial blood: P(A-a)02. Normally in young adults this value is less than 20 mm Hg. See: alveolar gas equation. (05 Mar 2000) |
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| arterial | <anatomy> Pertaining to an artery or to the arteries. (18 Nov 1997) |
| arterial arcades | A series of anastomosing arterial arches, as the intestinal arterial arcades between the branches of the jejunal and ileal arteries in the mesentery and the pancreaticoduodenal arteries on the head of the pancreas. (05 Mar 2000) |
| arterial arches of colon | Anastomosing branches of the colic arteries that form arch's in the mesocolon from which the walls of the colon are supplied. See: marginal artery of colon. (05 Mar 2000) |
| arterial arches of ileum | Arches formed in the mesentery by branches of the superior mesenteric artery from which vessels (vasa recta) arise to supply the wall of the ileum. See: intestinal arterial arcades. (05 Mar 2000) |
| arterial arches of jejunum | Arch's formed in the mesentery by branches of the superior mesenteric artery from which vessels (vasa recta) arise to supply the walls of the jejunum. See: intestinal arterial arcades. (05 Mar 2000) |
| arterial arch of lower eyelid | Formed by the medial palpebral artery which communicates with a branch of the lacrimal artery along the tarsal margin. Synonym: arcus palpebralis inferior. (05 Mar 2000) |
| arterial arch of upper eyelid | Formed by communicating branches of the medial and lateral palpebral arteries. Often two arches are present, one located near the free border of the tarsal plate, the other along the upper border of the tarsus. Synonym: arcus palpebralis superior. (05 Mar 2000) |
| arterial blood | Blood that is oxygenated in the lungs, found in the left chambers of the heart and in the arteries, and relatively bright red. (05 Mar 2000) |
| arterial blood gas | A test which analyses arterial blood for oxygen, carbon dioxide and bicarbonate content in addition to blood pH. Used to test the effectiveness of respiration. Acronym: ABG (17 Oct 1997) |
| arterial bulb | The dilated first part of the aorta containing the aortic semilunar valves and the aortic sinuses. Synonym: bulbus aortae, arterial bulb. (05 Mar 2000) |
| arterial canal | Before birth, the blood headed from the heart (via the pulmonary artery) for the lungs is shunted away from the lungs and returned to the greatest of arteries (the aorta). The shunt is through a short vessel called the ductus arteriosus. When the shunt is open, it is said to be patent (pronounced pa'tent). The patent ductus arteriosus (PDA) usually closes at or shortly after birth and blood is permtted from that moment on to course freely to the lungs. If the ductus stays open (patent), flow reverses and blood from the aorta is shunted into the pulmonary artery and recirculated through the lungs. The PDA may close later spontaneously (on its own) or need to be ligated (tied off) surgically. (12 Dec 1998) |
| arterial capillary | A capillary opening from an arteriole or metarteriole. (05 Mar 2000) |
| arterial circle of cerebrum | An anastomotic "circle" of arteries (roughly pentagonal in outline) at the base of the brain, formed, sequentially and in anterior to posterior direction, by the anterior communicating artery, the two anterior cerebral, the two internal carotid, the two posterior communicating, and the two posterior cerebral arteries. Synonym: circulus arteriosus cerebri, circle of Willis. (05 Mar 2000) |
| arterial cone | The left or anterosuperior, smooth-walled portion of the cavity of the right ventricle of the heart, which begins at the supraventricular crest and terminates in the pulmonary trunk. Synonym: arterial cone, pulmonary cone, pulmonary conus. (05 Mar 2000) |