| superior recess of lesser peritoneal sac | Pneumoenteric recess, a recess of the embryonic celom between the right lung bud and the gut; it is normally largely obliterated before birth, leaving only the superior recess of the vestibule of the lesser peritoneal sac as a vestige. (05 Mar 2000) |
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| dental sac | Dense fibrous layer formed from mesodermal tissue that surrounds the epithelial enamel organ. The cells eventually migrate to the external surface of the newly formed root dentin and give rise to the cementoblasts that deposit cementum on the developing root, fibroblasts of the developing periodontal ligament, and osteoblasts of the developing alveolar bone. (12 Dec 1998) |
| double decidual sac | <radiology> DDS, visualization correlates with presence of pregnancy in 98%, may be seen at less than 5 weeks on transvaginal scans see: gestational sac (12 Dec 1998) |
| Douglas' cul-de-sac | <anatomy> A pocket formed by the deflection of the peritoneum from the rectum to the uterus. Synonym: excavatio rectouterina, cavum douglasi, cul-de-sac, Douglas' cul-de-sac, Douglas' pouch, pouch of Douglas, rectovaginouterine pouch. (05 Mar 2000) |
| omental sac | <anatomy> An isolated portion of the peritoneal cavity lying dorsal to the stomach and extending craniad to the liver and diaphragm and caudad into the greater omentum; it opens into the general peritoneal cavity at the epiploic foramen. Synonym: bursa omentalis, lesser peritoneal cavity, lesser peritoneal sac, omental sac. (05 Mar 2000) |
| tear sac | The upper portion of the nasolacrimal duct into which empty the two lacrimal canaliculi; empty. Synonym: saccus lacrimalis, dacryocyst, sacculus lacrimalis, tear sac. (05 Mar 2000) |
| tooth sac | A capsule that encloses the developing tooth. (05 Mar 2000) |
| embryo sac | <botany> See Embryonic. Source: Websters Dictionary (01 Mar 1998) |
| endolymphatic sac | The blind pouch at the end of the endolymphatic duct. (12 Dec 1998) |
| yolk sac | <embryology, ornithology> One of the set of extra embryonic membranes, growing out from the gut over the yolk surface, in birds formed from the splanchnopleure, an outer layer of splanchnic mesoderm and an inner layer of endoderm. (18 Nov 1997) |
| yolk sac carcinoma | Malignant germ cell tumour commonly found in the ovary. The tumour arises from primitive germ cells and develops into extra-embryonic tissue resembling the yolk sac. Synonym: yolk sac carcinoma. (05 Mar 2000) |
| yolk sac tumour | An unusual and aggressive tumour of germ-cell origin that reproduces the extraembryonic structures of the early embryo. It is the most common malignant germ cell tumour found in children. It is characterised by a labyrinthine glandular pattern of flat epithelial cells and rounded papillary processes with a central capillary (schiller-duval body). The tumour is rarely bilateral. Before the use of combination chemotherapy, the tumour was almost invariably fatal. (12 Dec 1998) |
| featureless thecal sac | <radiology> No nerve roots seen (in lumbar spine; roots not seen in T-spine) Differential diagnosis: arachnoiditis, Pantopaque, infection, haemorrhage, surgery / RT, subdural injection, contrast flows, unlike epidural injection, nerve roots seen as they exit, but not between disc levels (12 Dec 1998) |
| lacrimal sac | The upper portion of the nasolacrimal duct into which empty the two lacrimal canaliculi; empty. Synonym: saccus lacrimalis, dacryocyst, sacculus lacrimalis, tear sac. (05 Mar 2000) |
| fornix of the lacrimal sac | Fornix of the lacrimal sac; the upper, blind end of the lacrimal sac that extends above the openings of the lacrimal canaliculi. Synonym: fornix sacci lacrimalis. (05 Mar 2000) |