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Female reproductive system (organa genitalia feminina) 309

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14.11 Stigma following rupture of the
follicle with folding and fragmentation
of the follicle wall. Haematoxylin and
eosin stain (x14).

CORPUS LUTEUM foRmation of the coRPus luteum
The corpus luteum (Figures 14.12 to 14.14) is a transient Formation of the corpus luteum commences with tear-
endocrine gland that forms after ovulation from the ing of the basal lamina between the basal cells and theca
remaining cells of the follicle wall and stromal cells of the interna. This is followed immediately by ingrowth of
theca. Hormones synthesised by the corpus luteum include capillaries into the avascular follicle wall. Together with
progesterone, oestrogens and possibly oxytocin. If fer- hairpin-like arterioles of the theca externa, the capillaries
tilisation does not occur, the corpus luteum undergoes sprout into the former cavity of the follicle.
further development before regressing (corpus luteum
cyclicum). In the event that fertilisation takes place, the Species variation
corpus luteum persists for the duration of pregnancy Horse, ox, pig and dog: In the mare, cow, sow and, to
(corpus luteum graviditatis). When the corpus luteum a lesser extent, the bitch, the lumen of the postovula-
regresses, it is replaced by fibrous scar tissue (corpus albi- tory follicle is filled with serum, coagulated blood and
cans). Development and regression of the corpus luteum remnants of follicular fluid (corpus haemorrhagicum).
involves reorganisation of cellular, vascular and connective Vessels growing into the former antrum are accompa-
tissue of the follicle and surrounding theca. nied by stromal cells, fibroblasts and macrophages.
Within the first 5 days after ovulation, these cells begin
to reorganise the corpus haemorrhagicum. Remnants
of blood components and follicle fragments are phago-
cytosed by macrophages. Vascularisation of the interior
of the follicle leads to formation of the corpus luteum.

14.12 Corpus luteum (sheep). Azan stain (x15).

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