Page 494 - Anatomy and Physiology of Farm Animals, 8th Edition

The Ovary and Estrous Cycles / 479

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Figure 27-3. A tertiary follicle from the ovary of a 1‐month‐old heifer. The antrum (a) of the follicle is
surrounded by a layer of granulosa cells, the membrana granulosa (b). Surrounding the oocyte itself (*),
the cumulus oophorus (c) is visible. A sheath of stromal cells, the theca folliculi (d), has formed around
the follicle and has an inner vascular layer (theca interna) and an outer connective tissue layer (theca
externa) which can be difficult to see at this magnification. Source: image courtesy of Library of
Reproduction Images (LORI: http://lorimainsection.blogspot.ca).

FSH, LH LH LH FSH
Mature Developing Mature Regressing Growing
tertiary follicle Ovulating follicle corpus luteum corpus luteum corpus luteum tertiary
follicle
Luteal
regression
triggered
by uterine
PGF 2
Estrogen Secondary Progesterone Progesterone Follicular
oocyte and estrogen and estrogen growth
day 19–21 day 1 day 2–8 day 9–14 Day 15–18

Endometrial Metror- Endometrial transformation from proliferative to secretory type: Endometrial, including
proliferative phase rhagia glandular hyperplasia and secretion glandular, involution

Proestrus Estrus Metestrus Diestrus
18 19 20 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Figure 27-4. Ovarian, uterine, and hormonal changes during the estrous cycle of the cow. The scale
indicates days 1–21 of the cycle. Relative blood levels of progesterone (***), estrogen ( ), FSH( ), and
_
LH ( ) are shown in the graph at the bottom of the figure. Source: Dellmann and Eurell, 1998. Reproduced
___
with permission of John Wiley & Sons, Inc.
during which there is no corpus luteum during which a corpus luteum is intact
and the dominant follicle is developing is and secreting progesterone. Formation of
the follicular phase of the estrous cycle. a corpus luteum and its functions are
The luteal phase is the part of the cycle discussed later in this chapter.