| external iliac plexus | A lymphatic plexus formed by the lymph nodes along the external iliac artery on either side, and their afferent and efferent vessels. Synonym: plexus iliacus externus. (05 Mar 2000) |
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| external iliac vein | <anatomy, vein> A direct continuation of the femoral vein superior to the inguinal ligament, uniting with the internal iliac vein to form the common iliac vein. Synonym: vena iliaca externa. (05 Mar 2000) |
| external lip of iliac crest | The roughened outer margin of the crest that gives attachment to the external oblique and latissimus dorsi muscles above and to the fasciae latae and the tensor fascia lata muscle below. Synonym: labium externum cristae iliacae. (05 Mar 2000) |
| abdominal canal | A passage in the lower anterior abdominal wall which in the male allows passage of the spermatic cord and in the female contains the round ligament. Because of the weakness it creates in the abdominal wall, it is the most frequent site for a hernia. (12 Dec 1998) |
| accessory canal | A channel leading from the root pulp laterally through the dentin to the periodontal tissue; may be found anywhere in the tooth root, but is more common in the apical third of the root. Synonym: lateral canal. (05 Mar 2000) |
| adductor canal | The space in middle third of the thigh between the vastus medialis and adductor muscles, converted into a canal by the overlying sartorius muscle. It gives passage to the femoral vessels and saphenous nerve, ending at the adductor hiatus. Synonym: canalis adductorius, Hunter's canal, subsartorial canal. (05 Mar 2000) |
| Alcock's canal | The space within the obturator internis fascia lining the lateral wall of the ischiorectal fossa that transmits the pudendal vessels and nerves. Synonym: canalis pudendalis, Alcock's canal. (05 Mar 2000) |
| alimentary canal | <anatomy> The digestive tract. (27 Sep 1997) |
| anal canal | The terminal portion of the alimentary canal; it extends from the pelvic diaphragm to the anal orifice. Synonym: canalis analis. (05 Mar 2000) |
| 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) |
| 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) |