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Oestrous Cycle - Anatomy & Physiology (view source)
Revision as of 20:46, 3 January 2023
, 20:46, 3 January 2023no edit summary
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==Introduction==
Ovarian cycles are from oestrus to oestrus. Oestrus is the easily identifiable external marker. It should be noted that Oestrus is the noun and oestrous is the adjective.
'''Classification of Oestrous Cycles ''' can be done based on '''vaginal cytology''' or '''secretory patterns of the ovary'''.
==Based on Vaginal Cytology ==
= Classification of Oestrous Cycles =
=== Pro-Oestrus ===
* The phase immediately preceding oestrus.
* Lasts 2-5 days, depending on the species.
* Marked increase in reproductive activity.
* Endocrine transition from progesterone to oestrogen dominance under the influence of gonadotrophins LH and FSH.
* Follicular growth and [[Corpus Luteum Regression - Anatomy & Physiology|regression of the corpus luteum]] of the previous cycle (in polyoestrous species).
* Uterus enlarges slightly
* [[Uterus - Anatomy & Physiology#Endometrium|Endometrium]] becomes congested and oedematous, glands show secretory activity.
* [[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.
** Superficial layers become cornified.
* The '''[[Oestrous Cycle - Anatomy & Physiology#Bitch|bitch]]''' shows external evidence:
** [[Vagina and Vestibule - Anatomy & Physiology#Vulva|Vulval]] oedema
** Hyperaemia
** Sanguinous vulval discharge
=== Pro-Oestrus ===
=== Oestrus ===
* The period where the female will accept the male for [[Copulatory Behaviour - Anatomy & Physiology|copulation]].
* 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.
* [[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 [[Uterus - Anatomy & Physiology#Endometrium|uterine endometrium]] becomes hyperaemic and congested.
* [[Cervix - Anatomy & Physiology|Cervix]] is relaxed
* [[Ovulation - Anatomy & Physiology|Ovulation]] occurs during this phase in all domestic species except the cow.
** The cow [[Ovulation - Anatomy & Physiology|ovulates]] ~12 hours after the end of oestrus.
* [[Ovulation - Anatomy & Physiology|Ovulation]] is spontaneous in all domestic species except the cat, rabbit and camelids. In these species it is induced by the act of [[Copulatory Behaviour - Anatomy & Physiology|copulation]].
* During pro-oestrous and oestrus there is [[Ovary - Anatomy & Physiology#Folliculogenesis|follicular growth]] with no functional [[Corpus Luteum - Anatomy & Physiology|corpora lutea]] present on the [[Ovary - Anatomy & Physiology|ovary]] (aka follicular phase).
* The main ovarian hormone production is Oestrogen.
=== Metoestrus ===
=== Metoestrus ===
* The phase after oestrus
* During early metoestrus, both oestrogen and progesterone levels are relatively low.
* Granulosa cells of the [[Ovulation - Anatomy & Physiology|ovulated]] [[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 [[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 [[Uterus - Anatomy & Physiology#Histology|uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]].
=== Dioestrus ===
=== Dioestrus ===
* Longest phase of the oestrous cycle, which usually laste 10-14 days in polyoestrous females.
* The [[Corpus Luteum - Anatomy & Physiology|corpus luteum]] is present on the [[Ovary - Anatomy & Physiology|ovary]] and secreting large amounts of progesterone. The duration of this phase is directly related to the time that the corpus luteum remains functional.
* High progesterone levels prompt the uterus to prepare a suitable environment for development of the embryo, and eventual [[Implantation - Anatomy & Physiology|attachment of the conceptus to the endometrium]] (implantation).
* Uterine glands undergo hyperplasia and hypertrophy.
* [[Cervix - Anatomy & Physiology|Cervix]] becomes constricted
* Secretions of the tract are scant and sticky.
* [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|Vaginal mucosa]] becomes pale.
* Ends with the [[Corpus Luteum Regression - Anatomy & Physiology|regression of the corpus luteum]] (luteolysis).
=== Anoestrus ===
=== Anoestrus ===
* Genital system is quiescent
* Follicular development is minimal and corpora lutea have regressed and are non-functional.
* Secretions are scanty
* [[Cervix - Anatomy & Physiology|Cervix]] is constricted
* Vaginal Mucosa is pale
== Based on Secretory Patterns of the Ovary ==
== Based on Secretory Patterns of the Ovary ==
=== Follicular Phase ===
=== Follicular Phase ===
* Begins after luteolysis, which causes the decline in progesterone.
* Gonadotrophins LH and FSH are produced, which cause ovarian follicles to produce Oestrogen.
* Ends at ovulation.
* Oestrus is designated as day 0.
=== Luteal Phase ===
=== Luteal Phase ===
=Comparative Oestrous Cycles=
* Begins after ovulation
* Includes the development of corpora luta, which produce progesterone.
* Includes luteolysis, which is brought about by Prostaglandin F2α.
== Based on Vaginal Cytology ==
=== Proliferative Phase ===
* Oestrogen dominant
* Includes proliferation of the [[Uterus - Anatomy & Physiology#Endometrium|endometrium]].
=== Secretory Phase ===
* Progesterone dominant
* Includes secretions from the uterus, such as 'uterine milk' to sustain the fertilised ovum until implantaion.
==Comparative Oestrous Cycles==
{| style="width:75%; height:200px" border="1"
!'''Species'''
!'''Mare'''
!'''Cow'''
!'''Sow'''
!'''Ewe'''
!'''Bitch'''
!'''Queen'''
|-
| '''Length of Oestrous Cycle (days)'''
| 21
| 21
| 21
| 17
| 93
| Variable
|-
| '''Duration of Oestrus'''
| 4-8 days
| 12-36 hours
| 48-96 hours
| 24-48 hours
| 7-13 days
| 4-10 days
|-
| '''Duration of Follicular Phase (days)'''
| 7 (variable)
| 4
| 7
| 3
| 18
| Variable
|-
| '''Duration of Luteal Phase (days)'''
| 14
| 17
| 14
| 14
| 75
| 40
|
|}
<big><b>
Oestrus Cycles in:
:[[Oestrous Cycle - Horse|Mare]]
:[[Oestrous Cycle - Dog|Bitch]]
:[[Oestrous Cycle - Cat|Queen]]
:[[Oestrous Cycle - Cattle|Cow]]
:[[Oestrous Cycle - Sheep|Ewe]]
:[[Oestrous Cycle - Goat|Nanny Goat]]
:[[Oestrous Cycle - Pig|Sow]]
</b></big>
== Links ==
* [[Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology|Pharmacological Manipulation of Oestrous Cycles]]
* [[Oestrus Behaviour - Anatomy & Physiology| Oestrus Behaviour and Methods of Oestrus Detection]]
= Links =
==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
[[Oestrous_Cycle_-Pharmacological_Manipulation_of_Oestrous_Cycles_-_Anatomy_%26_Physiology|Pharmacological Manipulation of Oestrous Cycles]]
[[Category:Oestrous Cycles]]
[[Category:Bullet Points]]