Changes

* Follicular growth and [[Ovary - Anatomy & Physiology#Corpus_Luteum_Regression|regression of the corpus luteum]] of the previous cycle (in polyoestrous species).

* Follicular growth and [[Ovary - Anatomy & Physiology#Corpus_Luteum_Regression|regression of the corpus luteum]] of the previous cycle (in polyoestrous species).

* Uterus enlarges slightly

* Uterus enlarges slightly

* [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|Endometrium]] becomes congested and oedematous, glands show secretory activity.

* [[Uterus - Anatomy & Physiology#Endometrium|Endometrium]] becomes congested and oedematous, glands show secretory activity.

* [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|Vaginal]] mucous becomes hyperaemic.  

* [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|Vaginal]] mucous becomes hyperaemic.  

** Increase in cell numbers in the [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal]] epithelium.

** Increase in cell numbers in the [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal]] epithelium.

* The onset and end of oestrus are the only stages of the oetrous cycle that can be accurately measured.  They are therefore used to determine cycle length.

* The onset and end of oestrus are the only stages of the oetrous cycle that can be accurately measured.  They are therefore used to determine cycle length.

* Female seeks out the male and 'stands' to be mounted.

* Female seeks out the male and 'stands' to be mounted.

* [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Histology|Uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]] secrete increased amounts of mucus.

* [[Uterus - Anatomy & Physiology#Histology|Uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]] secrete increased amounts of mucus.

* Vaginal epithelium and [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|uterine endometrium]] becomes hyperaemic and congested.

* Vaginal epithelium and [[Uterus - Anatomy & Physiology#Endometrium|uterine endometrium]] becomes hyperaemic and congested.

* [[Cervix - Anatomy & Physiology|Cervix]] is relaxed

* [[Cervix - Anatomy & Physiology|Cervix]] is relaxed

* [[The_Ovary_-_Ovulation_- Anatomy & Physiology|Ovulation]] occurs during this phase in all domestic species except the cow.

* [[The_Ovary_-_Ovulation_- Anatomy & Physiology|Ovulation]] occurs during this phase in all domestic species except the cow.

* Granulosa cells of the [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulated]] [[The_Ovary_-_Follicles_- Anatomy & Physiology|follicles]] give rise to lutein cells, which are responsible for the [[Corpus Luteum Formation - Anatomy & Physiology|formation of the corpus luteum]] (luteinisation).

* Granulosa cells of the [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulated]] [[The_Ovary_-_Follicles_- Anatomy & Physiology|follicles]] give rise to lutein cells, which are responsible for the [[Corpus Luteum Formation - Anatomy & Physiology|formation of the corpus luteum]] (luteinisation).

* Progesterone secretion is detectable soon after [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]], with significant quantities produced in 2-5 days.  This marks a transition from oestrogen to progesterone dominance.

* Progesterone secretion is detectable soon after [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]], with significant quantities produced in 2-5 days.  This marks a transition from oestrogen to progesterone dominance.

* Reduction in secretion from [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Histology|uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]].

* Reduction in secretion from [[Uterus - Anatomy & Physiology#Histology|uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]].

=== Dioestrus ===

=== Dioestrus ===

* Oestrogen dominant

* Oestrogen dominant

* Includes proliferation of the [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|endometrium]].

* Includes proliferation of the [[Uterus - Anatomy & Physiology#Endometrium|endometrium]].

=== Secretory Phase ===

=== Secretory Phase ===

* Oestrus:

* Oestrus:

** Uterus is congested

** Uterus is congested

** [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|Endometrium]] contains oedematous fluid, which causes its surface to glisten.

** [[Uterus - Anatomy & Physiology#Endometrium|Endometrium]] contains oedematous fluid, which causes its surface to glisten.

** Muscularis is contractile, so when palpated per rectum, the uterus feels turgid and the horns feel erect and coiled.

** Muscularis is contractile, so when palpated per rectum, the uterus feels turgid and the horns feel erect and coiled.

*** Tonicity is present the day before and the day after oestrus, but is at its maximum during heat.

*** Tonicity is present the day before and the day after oestrus, but is at its maximum during heat.

*** In heifers, there is also often perimetral subserous petechiae.

*** In heifers, there is also often perimetral subserous petechiae.

* Dioestrus:

* Dioestrus:

** [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|Endometrium]] is covered with scanty secretion from the uterine glands.

** [[Uterus - Anatomy & Physiology#Endometrium|Endometrium]] is covered with scanty secretion from the uterine glands.

=== Cyclic Changes in the Ovaries ===

=== Cyclic Changes in the Ovaries ===

=== Cyclic Changes in the  Uterus ===

=== Cyclic Changes in the  Uterus ===

* The [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|endometrium]] shows considerable change during the oestrous cycle.

* The [[Uterus - Anatomy & Physiology#Endometrium|endometrium]] shows considerable change during the oestrous cycle.

* In pro-oestrus and oestrus, endometrial glands are loosely coiled with obvious lumina and a deep epithelial lining.

* In pro-oestrus and oestrus, endometrial glands are loosely coiled with obvious lumina and a deep epithelial lining.

* During metoestrus, the glands become larger.  Lumina become smaller and the basal layer of the [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|endometrium]] becomes more tortuous.

* During metoestrus, the glands become larger.  Lumina become smaller and the basal layer of the [[Uterus - Anatomy & Physiology#Endometrium|endometrium]] becomes more tortuous.

* As the bitch reaches anoestrus, there is a reduction in the number of glands and the amount that they coil.

* As the bitch reaches anoestrus, there is a reduction in the number of glands and the amount that they coil.

* In metoestrus (~98 days after the onset of oestrus), there is desquamation of the [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|endometrial]] epithelium.

* In metoestrus (~98 days after the onset of oestrus), there is desquamation of the [[Uterus - Anatomy & Physiology#Endometrium|endometrial]] epithelium.

* By day 120-130, the [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|endometrium]] is restored by proliferation of cells from crypts of the endometrial glands.

* By day 120-130, the [[Uterus - Anatomy & Physiology#Endometrium|endometrium]] is restored by proliferation of cells from crypts of the endometrial glands.

=== Cyclic Changes in the Ovaries ===

=== Cyclic Changes in the Ovaries ===