| internal intercostal muscle | <anatomy> Each arises from lower border of rib and passes obliquely downward and backward to be inserted into upper border of rib below; action, contract during expiration, also maintain tension in the intercostal spaces to resist mediolateral movement; nerve supply, intercostal. Synonym: musculus intercostalis internus. (05 Mar 2000) |
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| internal jugular vein | <anatomy, vein> Main venouus structure of the neck, formed as a continuation of the sigmoid sinus of the dura mater, contained within the carotid sheath as it descends the neck uniting, behind the sternoclavicular joint, with the subclavian vein to form the brachiocephalic vein. Synonym: vena jugularis interna. (05 Mar 2000) |
| internal lacrimal fistula | A fistulous communication between the lacrimal sac and the ethmoidal sinus. Synonym: internal lacrimal fistula. (05 Mar 2000) |
| internal limiting membrane | Formed by the expanded inner ends of Muller's fibres, outer limiting membrane, not a membrane but a row of junctional complexes. Synonym: membrana limitans. (05 Mar 2000) |
| internal lip of iliac crest | The roughened inner margin of the crest that gives attachment to parts of the transversus abdominis, quadratus lumborum, and erector spinae muscles. Synonym: labium internum cristae iliacae. (05 Mar 2000) |
| internal male genital organs | The internal masculine genital organs, the testes, epididymides, deferent ducts, seminal vesicles, prostate, and bulbourethral glands. Synonym: organa genitalia masculina interna. (05 Mar 2000) |
| internal malleolus | The process at the medial side of the lower end of the tibia, forming the projection of the medial side of the ankle. Synonym: malleolus medialis, inner malleolus, internal malleolus. (05 Mar 2000) |
| internal mammary artery | <anatomy, artery> Origin, subclavian; branches, pericardiacophrenic, anterior intercostal, sternal, mediastinal, thymic, bronchial, muscular, and perforating branches, and bifurcates into the musculophrenic and superior epigastric. Synonym: arteria thoracica interna, arteria mammaria interna, internal mammary artery. (05 Mar 2000) |
| internal mammary-coronary artery anastomosis | Direct myocardial revascularization in which the internal mammary artery is anastomosed to the right coronary artery, circumflex artery, or anterior descending coronary artery. The internal mammary artery is the most frequent choice, especially for a single graft, for coronary artery bypass surgery. (12 Dec 1998) |
| internal mammary plexus | An autonomic plexus on the internal thoracic artery derived from the subclavian plexus. Synonym: internal mammary plexus, plexus mammarius internus. (05 Mar 2000) |
| internal maxillary artery | <anatomy, artery> A branch of the external carotid artery which distributes to the deep structures of the face (internal maxillary) and to the side of the face and nose (external maxillary). (12 Dec 1998) |
| internal maxillary plexus | <anatomy, artery> An autonomic plexus on the maxillary artery derived from the external carotid plexus. Synonym: internal maxillary plexus, maxillary plexus, plexus maxillaris internus. (05 Mar 2000) |
| internal medicine | The speciality of the general medicine of the internal organs. In the Commonwealth, the specialist in internal medicine is called a Physician (in the us, an Internist). (16 Dec 1997) |
| internal medullary lamina | See: medullary laminae of thalamus. (05 Mar 2000) |
| internal membrane | General term for intracellular membrane systems such as endoplasmic reticulum. Not particularly helpful, but has the advantage of being noncommittal. (18 Nov 1997) |