Changes

* Uterus enlarges slightly

* Uterus enlarges slightly

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

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

* [[Female_Reproductive_Tract_-The_Vagina/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 [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vagina_2|vaginal]] epithelium.

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

** Superficial layers become cornified.

** Superficial layers become cornified.

* The '''[[Female_Reproductive_Tract_-Oestrous_Cycle_- Anatomy & Physiology#Bitch|bitch]]''' shows external evidence:

* The '''[[Female_Reproductive_Tract_-Oestrous_Cycle_- Anatomy & Physiology#Bitch|bitch]]''' shows external evidence:

** [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vulva|Vulval]] oedema

** [[Vagina and Vestibule - Anatomy & Physiology#Vulva|Vulval]] oedema

** Hyperaemia

** Hyperaemia

** Sanguinous [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vulva|vulval]] discharge

** Sanguinous vulval discharge

=== Oestrus ===

=== Oestrus ===

* 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]], [[Female_Reproductive_Tract_-The_Cervix_- Anatomy & Physiology#Histology|cervical]] and [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vagina_2|vaginal glands]] secrete increased amounts of mucus.

* [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Histology|Uterine]], [[Female_Reproductive_Tract_-The_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 [[Female_Reproductive_Tract_-The_Uterus_- Anatomy & Physiology#Endometrium|uterine endometrium]] becomes hyperaemic and congested.

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

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

* 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]], [[Female_Reproductive_Tract_-The_Cervix_- Anatomy & Physiology#Histology|cervical]] and [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vagina_2|vaginal glands]].

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

=== Dioestrus ===

=== Dioestrus ===

* [[Female_Reproductive_Tract_-The_Cervix_- Anatomy & Physiology|Cervix]] becomes constricted

* [[Female_Reproductive_Tract_-The_Cervix_- Anatomy & Physiology|Cervix]] becomes constricted

* Secretions of the tract are scant and sticky.

* Secretions of the tract are scant and sticky.

* [[Female_Reproductive_Tract_-The_Vagina/Vestibule_- Anatomy & Physiology#Vagina_2|Vaginal mucosa]] becomes pale.

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

* Ends with the [[Female_Reproductive_Tract_-The_Ovary_- Anatomy & Physiology#Corpus_Luteum_Regression|regression of the corpus luteum]] (luteolysis).

* Ends with the [[Female_Reproductive_Tract_-The_Ovary_- Anatomy & Physiology#Corpus_Luteum_Regression|regression of the corpus luteum]] (luteolysis).