. The science and art of midwifery. OGY OF THE OVUM. fluid, the cylindrical cells are pressed against the membrana propria,and form a third coating, or layer, termed the membrana granulosa. A glance at a transverse section through the ovary of a maturemammal exhibits follicles of different ages. To recapitulate : The young follicles are composed of primordial ova, surrounded byepithelium, and imbedded in the ovarian stroma. The fully developed follicles possess a vesicular character. Theyare surrounded by a connective-tissue wall (theca folliculi), which iscomposed of two layers (tunica propri
. The science and art of midwifery. OGY OF THE OVUM. fluid, the cylindrical cells are pressed against the membrana propria,and form a third coating, or layer, termed the membrana granulosa. A glance at a transverse section through the ovary of a maturemammal exhibits follicles of different ages. To recapitulate : The young follicles are composed of primordial ova, surrounded byepithelium, and imbedded in the ovarian stroma. The fully developed follicles possess a vesicular character. Theyare surrounded by a connective-tissue wall (theca folliculi), which iscomposed of two layers (tunica propria and tunica fibrosa). The tunicapropria is lined by cells (membrana granulosa) which are gathered inheaps (discus proligerus) around the ova. The discus proligerus isseated sometimes superficially, sometimes in the deepest portion of thefollicle. Each ovum is surrounded by a special layer of cylindricalepithelium (epithelium of the ovum). Henle estimates the entire number of Graafian follicles in each ovaryat thirty-six thousand.*. Fig. 32.—Ovum from a Graafian follicle in the rabbit, a, epithelium of ovum; 6, zona radi-ate s. pellucida; <?, germinative vesicle; d, gcrminative spot; e, vitellus. (Waldeyer.) The ovum, at the time of its discharge from the ovary, is no longera simple cell, composed of ordinary protoplasm, but presents the fol-lowing characteristic peculiarities : It is of large size. In the humanfemale the ovum measures about jfo of an inch. It possesses a thick,transparent envelope, termed the vitelline membrane, or, from the man- * Henle, Handbuch der Eingcwcidelehre, Braunschweig, I860, p. 483. DEVELOPMENT OF THE OVUM. 39 ner in which it transmits light, the zona pellunda. The zona pellu-cida was formerly thought to be due to a thickening of the cell-mem-brane. It is now more commonly regarded as something superaddedto the primordial ovum. Probably the attached portions of the radiatecells which surround the ovum in the discus proligerus contribute toits
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
