| germinal pole | <cell biology> In most animal oocytes the nucleus is not centrally placed and its position can be used to define two poles. That nearest to the nucleus is the animal pole and the other is the vegetal pole, with the animal vegetal axis between the poles passing through the nucleus. During meiosis of the oocyte the polar bodies are expelled at animal pole. In many eggs there is also a graded distribution of substances along this axis, with pigment granules often concentrated in the animal half and yolk, where present, largely in the vegetal half. (12 Nov 1997) |
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| germinal rod | One of the minute elongated bodies resulting from the repeated division of the oocyst during sporogony. In the case of the malarial parasite, it is the form that is concentrated in the salivary glands and introduced into the blood by the bite of a mosquito; it enters the liver cells (exoerythrocytic cycle), whose progeny, the merozoites, infect the red blood cells to initiate clinical malaria. Synonym: germinal rod, zoite, zygotoblast. Origin: sporo-+ G. Zoon, animal (05 Mar 2000) |
| germinal streak | An ectodermal ridge in the midline at the caudal end of the embryonic disk from which arises the intraembryonic mesoderm; achieved by inward and then lateral migration of cells; in human embryos, it appears on day 15 and gives a cephalocaudal axis to the developing embryo. Synonym: germinal streak. (05 Mar 2000) |
| acoustic vesicle | One of the paired sacs of invaginated ectoderm that develop into the membranous labyrinth of the internal ear. Synonym: acoustic vesicle, otic vesicle. (05 Mar 2000) |
| acrosomal vesicle | A vesicle derived from the Golgi apparatus during spermiogenesis whose limiting membrane adheres to the nuclear envelope; together with the acrosomal granule within, it spreads in a thin layer over the pole of the nucleus to form the acrosomal cap. (05 Mar 2000) |
| allantoic vesicle | The hollow portion of the allantois. (05 Mar 2000) |
| amniocardiac vesicle | The rostral portion of the most primitive intraembryonic celom. (05 Mar 2000) |
| auditory vesicle | One of the paired sacs of invaginated ectoderm that develop into the membranous labyrinth of the internal ear. Synonym: acoustic vesicle, otic vesicle. (05 Mar 2000) |
| Baer's vesicle | An obsolete term for vesicular ovarian follicle. (05 Mar 2000) |
| blastodermic vesicle | In mammalian development, cleavage produces a thin walled hollow sphere, whose wall is the trophoblast, with the embryo proper being represented by a mass of cells at one side. The blastocyst is formed before implantation and is equivalent to the blastula. (18 Nov 1997) |
| gas vesicle | The hollow, cylindrical, gas-filled structure in the gas vacuole. It confers ability for gas vacuole to float. (09 Oct 1997) |
| vesicle | <pathology> A closed membrane shell, derived from membranes either by a physiological process (budding) or mechanically by sonication. Vesicles of dimensions in excess of 50nm are believed to be important in intracellular transport processes. See: coated vesicles. (18 Nov 1997) |
| vesicle hernia | Protrusion of a segment of the bladder through the abdominal wall or into the inguinal canal and into the scrotum. (05 Mar 2000) |
| cerebral vesicle | Each of the three divisions of the early embryonic brain (prosencephalon, mesencephalon, and rhombencephalon). Synonym: encephalic vesicle, primary brain vesicle. (05 Mar 2000) |
| cervical vesicle | An abnormally persisting vestige of the cervical sinus or its associated branchial grooves. (05 Mar 2000) |