| RC | an electronic circuit containing a resistor and capacitor in series; radiocarpal; reaction center; r... |
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| RCT | radiotherapy and chemotherapy; randomized clinical trial; randomized controlled trial; registered ca... |
| RF | radial fiber; radio frequency; receptive field; regurgitant fraction; Reitland-Franklin [unit]; rela... |
| SC | conditioned stimulus; sacrococcygeal; Sanitary Corps; scalenus [muscle]; scapula; Schwann cell; scia... |
| LSCC | lateral semicircular canal |
| anterior condyloid canal of occipital bone | The canal through which the hypoglossal nerve emerges from the skull. Synonym: canalis hypoglossalis, anterior condyloid canal of occipital bone, anterior condyloid foramen. (05 Mar 2000) |
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| archenteric canal | Invagination of the blastopore into the notochordal process to form a cavity. See: neurenteric canal. Synonym: notochordal canal. (05 Mar 2000) |
| Arnold's canal | <anatomy, nerve> The small opening in the petrous bone lateral to the hiatus of facial canal that gives passage to the lesser petrosal nerve. Synonym: hiatus canalis nervi petrosi minoris, Arnold's canal, canalis nervi petrosi superficialis minoris. (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) |
| artery of pterygoid canal | Usually arises from the third part of the maxillary artery, but frequently from the greater palatine artery, within the pterygopalatine fossa. Passes posteriorly to run through the pterygoid canal with the corresponding nerve, supplying the contents and wall of the canal, the mucous membrane of the upper pharynx, the auditory tube and the tympanic cavity. Synonym: arteria canalis pterygoidei, vidian artery. (05 Mar 2000) |
| atrial ventricular canal defect | A defect caused by deficient or absent septal tissue immediately above and below the normal level of the atrioventricular valves, including the region normally occupied by the A-V septum in hearts with two ventricles. The A-V valves are abnormal to a varying degree. (05 Mar 2000) |
| atrioventricular canal | The canal in the embryonic heart leading from the common sinuatrial chamber to the ventricle. (05 Mar 2000) |
| atrioventricular canal cushions | A pair of mounds of embryonic connective tissue covered by endothelium, bulging into the embryonic atrioventricular canal; located one dorsally and one ventrally, they grow together and fuse with each other and with the lower edge of the septum primum, dividing the originally single canal into right and left atrioventricular orifices. Synonym: endocardial cushions. (05 Mar 2000) |
| auditory canal | The passage leading inward through the tympanic portion of the temporal bone, from the auricle to the tympanic membrane; it consists of a bony (inner) portion and a fibrocartilaginous (outer) portion, the cartilaginous external acoustic meatus. Synonym: meatus acusticus externus, acoustic meatus, antrum auris, auditory canal, external auditory meatus. (05 Mar 2000) |
| A-V canal | The canal in the embryonic heart leading from the common sinuatrial chamber to the ventricle. (05 Mar 2000) |
| basipharyngeal canal | An opening between the vaginal process of the sphenoid and the ala of the vomer on either side. It conveys a branch of the sphenopalatine artery. Synonym: canalis vomerovaginalis, basipharyngeal canal, vomerine canal. (05 Mar 2000) |
| Bernard's canal | The excretory duct of the head of the pancreas, one branch of which joins the pancreatic duct, the other opening independently into the duodenum at the lesser duodenal papilla. Synonym: ductus pancreaticus accessorius, Bernard's canal, Bernard's duct, ductus dorsopancreaticus, Santorini's canal, Santorini's duct. (05 Mar 2000) |
| Bichat's canal | <anatomy, vein> An expansion of the subarachnoid space extending forward between the corpus callosum and the thalamus; it encloses the internal cerebral veins which caudally join to form the vena magna cerebri (Galen's vein). Synonym: ambient cistern, Bichat's canal, Bichat's foramen, cistern of great vein of cerebrum, cisterna ambiens, cisterna superioris, cisterna venae magnae cerebri, superior cistern. (05 Mar 2000) |
| birth canal | Cavity of the uterus and vagina through which the foetus passes. Synonym: parturient canal. (05 Mar 2000) |
| blastoporic canal | An obsolete term for primitive pit. (05 Mar 2000) |