Changes

* 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 [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]] secrete increased amounts of mucus.

* [[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.

* 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

* [[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.

** The cow [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulates]] ~12 hours after the end of oestrus.

** The cow [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulates]] ~12 hours after the end of oestrus.

* 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 [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]].

* 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]].

=== Dioestrus ===

=== Dioestrus ===

* High progesterone levels prompt the uterus to prepare a suitable environment for development of the embryo, and eventual [[Fertilisation%2C_Implantation_and_Early_Embryonic_Development_-Implantation- Anatomy & Physiology|attachment of the conceptus to the endometrium]] (implantation).

* High progesterone levels prompt the uterus to prepare a suitable environment for development of the embryo, and eventual [[Fertilisation%2C_Implantation_and_Early_Embryonic_Development_-Implantation- Anatomy & Physiology|attachment of the conceptus to the endometrium]] (implantation).

* Uterine glands undergo hyperplasia and hypertrophy.

* Uterine glands undergo hyperplasia and hypertrophy.

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

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

* Secretions of the tract are scant and sticky.

* Secretions of the tract are scant and sticky.

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

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

* Follicular development is minimal and corpora lutea have regressed and are non-functional.

* Follicular development is minimal and corpora lutea have regressed and are non-functional.

* Secretions are scanty

* Secretions are scanty

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

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

* Vaginal Mucosa is pale

* Vaginal Mucosa is pale