| 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) |
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| 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) |
| fossa of lacrimal sac | A fossa formed by the lacrimal bone and the frontal process of the maxilla, lodging the lacrimal sac. Synonym: fossa sacci lacrimalis. (05 Mar 2000) |
| lesser cul-de-sac | The initial portion of the pyloric part of the stomach, which may temporarily become partially or completely shut off from the remainder of the stomach during digestion by peristaltic contraction of the prepyloric "sphincter"; it is demarcated, sometimes, from the second part of the pyloric part of the stomach (pyloric canal) by a slight groove. Synonym: antrum pyloricum, antrum, lesser cul-de-sac. (05 Mar 2000) |
| lesser peritoneal 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) |