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Oestrous Cycle - Anatomy & Physiology (view source)
Revision as of 12:23, 10 September 2008
, 12:23, 10 September 2008→Oestrous Cycle
* Only fertilized eggs can pass into the uterus.
* Only fertilized eggs can pass into the uterus.
* Non-fertilized eggs remain in the Utero-Tubal junction for months, where they finally disintegrate.
* Non-fertilized eggs remain in the Utero-Tubal junction for months, where they finally disintegrate.
*
== Changes on the Ovary ==
* Just before the onset of oestrus, several follicles enlarge to 1-3cm.
* By the first day of oestrus, one dominant follicle is significantly larger than the others, with a diameter of 2.5-3.5 cm.
* During oestrus, this dominant follicle matures and ruptures once it has attained a diameter of 3-7 cm.
* Several hours before ovulation, the ripe follicle becomes much less tense and can be recognised as an indentation on the surface of the ovary.
* There is usually haemorrhage into the follicle and the coagulum hardens within the next 24 hours.
* After ovulation, the other follicles regress.
* During the first 4-9 days of Dioestrus, there are no follicles over 1cm present on the ovary.
* For 3 days after ovulation, the leutinising mass can be felt, but later it normally has the same texture as the ovary.
* The corpus luteum reaches full size at 4-5 days after ovulation but does not protrude from the ovarian surface.
* On section of the ovary, the corpus luteum will appear brown and later yellow. It is triangular or conical in shape, with the narrow end on the ovulaiton fossa. The centre of the corpus luteum normally contains dark brown fibrin.
* The corpus luteum of the cycle (non-pregnant) starts to regress on about the 12th day of the cycle. At the time of regression, there is a fall in blood progesterone concentration.
* During winter Anoestrus, both ovaries are usually small and bean-shaped. They normally measure:
** 6cm pole-pole
** 4cm from the hilus to the free border
** 3 cm side-side
* During the cycle, the size of the ovary depends on the number and size of the follicles.
* During oestrus, the ovary may contain 2-3 follicles. These can each measure 4-7 cm. These, combined with other less developed follicles, give the ovary a huge size.
* During Dioestrus, there is an active corpus luteum and atretic follicles present. However, these only give the ovary a size a little larger than in Anoestrus.
=== Endocrine Changes During the Oestrous Cycle ===
=== Endocrine Changes During the Oestrous Cycle ===