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| + | <big><center>[[Reproductive System|'''BACK TO REPRODUCTIVE SYSTEM''']]</center></big> |
| − | ==Introduction==
| + | <big><center>[[Reproductive_System#Female Reproductive Tract|'''BACK TO FEMALE REPRODUCTIVE TRACT''']]</center></big> |
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| − | 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.
| + | [[Oestrous_Cycle_-Pharmacological_Manipulation_of_Oestrous_Cycles_-_Anatomy_%26_Physiology|Pharmacological Manipulation of Oestrous Cycles]] |
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| − | '''Classification of Oestrous Cycles ''' can be done based on '''vaginal cytology''' or '''secretory patterns of the ovary'''.
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| − | ==Based on Vaginal Cytology ==
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| − | === Pro-Oestrus ===
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| − | * The phase immediately preceding oestrus.
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| − | * Lasts 2-5 days, depending on the species.
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| − | * Marked increase in reproductive activity.
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| − | * Endocrine transition from progesterone to oestrogen dominance under the influence of gonadotrophins LH and FSH.
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| − | * Follicular growth and [[Corpus Luteum Regression - Anatomy & Physiology|regression of the corpus luteum]] of the previous cycle (in polyoestrous species).
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| − | * Uterus enlarges slightly
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| − | * [[Uterus - Anatomy & Physiology#Endometrium|Endometrium]] becomes congested and oedematous, glands show secretory activity.
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| − | * [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|Vaginal]] mucous becomes hyperaemic.
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| − | ** Increase in cell numbers in the [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal]] epithelium.
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| − | ** Superficial layers become cornified.
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| − | * The '''[[Oestrous Cycle - Anatomy & Physiology#Bitch|bitch]]''' shows external evidence:
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| − | ** [[Vagina and Vestibule - Anatomy & Physiology#Vulva|Vulval]] oedema
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| − | ** Hyperaemia
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| − | ** Sanguinous vulval discharge
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| − | === Oestrus ===
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| − | * The period where the female will accept the male for [[Copulatory Behaviour - Anatomy & Physiology|copulation]].
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| − | * 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.
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| − | * Female seeks out the male and 'stands' to be mounted.
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| − | * [[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.
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| − | * Vaginal epithelium and [[Uterus - Anatomy & Physiology#Endometrium|uterine endometrium]] becomes hyperaemic and congested.
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| − | * [[Cervix - Anatomy & Physiology|Cervix]] is relaxed
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| − | * [[Ovulation - Anatomy & Physiology|Ovulation]] occurs during this phase in all domestic species except the cow.
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| − | ** The cow [[Ovulation - Anatomy & Physiology|ovulates]] ~12 hours after the end of oestrus.
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| − | * [[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]].
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| − | * 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).
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| − | * The main ovarian hormone production is Oestrogen.
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| − | === Metoestrus ===
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| − | * The phase after oestrus
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| − | * During early metoestrus, both oestrogen and progesterone levels are relatively low.
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| − | * 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).
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| − | * 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.
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| − | * Reduction in secretion from [[Uterus - Anatomy & Physiology#Histology|uterine]], [[Cervix - Anatomy & Physiology#Histology|cervical]] and [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|vaginal glands]].
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| − | === Dioestrus ===
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| − | * Longest phase of the oestrous cycle, which usually laste 10-14 days in polyoestrous females.
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| − | * 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.
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| − | * 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).
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| − | * Uterine glands undergo hyperplasia and hypertrophy.
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| − | * [[Cervix - Anatomy & Physiology|Cervix]] becomes constricted
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| − | * Secretions of the tract are scant and sticky.
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| − | * [[Vagina and Vestibule - Anatomy & Physiology#Vagina_2|Vaginal mucosa]] becomes pale.
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| − | * Ends with the [[Corpus Luteum Regression - Anatomy & Physiology|regression of the corpus luteum]] (luteolysis).
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| − | === Anoestrus ===
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| − | * Genital system is quiescent
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| − | * Follicular development is minimal and corpora lutea have regressed and are non-functional.
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| − | * Secretions are scanty
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| − | * [[Cervix - Anatomy & Physiology|Cervix]] is constricted
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| − | * Vaginal Mucosa is pale
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| − | == Based on Secretory Patterns of the Ovary ==
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| − | === Follicular Phase ===
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| − | * Begins after luteolysis, which causes the decline in progesterone.
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| − | * Gonadotrophins LH and FSH are produced, which cause ovarian follicles to produce Oestrogen.
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| − | * Ends at ovulation.
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| − | * Oestrus is designated as day 0.
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| − | === Luteal Phase ===
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| − | * Begins after ovulation
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| − | * Includes the development of corpora luta, which produce progesterone.
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| − | * Includes luteolysis, which is brought about by Prostaglandin F2α.
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| − | == Based on Vaginal Cytology ==
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| − | === Proliferative Phase ===
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| − | * Oestrogen dominant
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| − | * Includes proliferation of the [[Uterus - Anatomy & Physiology#Endometrium|endometrium]].
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| − | === Secretory Phase ===
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| − | * Progesterone dominant
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| − | * Includes secretions from the uterus, such as 'uterine milk' to sustain the fertilised ovum until implantaion.
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| − | ==Comparative Oestrous Cycles==
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| − | {| style="width:75%; height:200px" border="1"
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| − | !'''Species'''
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| − | !'''Mare'''
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| − | !'''Cow'''
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| − | !'''Sow'''
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| − | !'''Ewe'''
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| − | !'''Bitch'''
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| − | !'''Queen'''
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| − | |-
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| − | | '''Length of Oestrous Cycle (days)'''
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| − | | 21
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| − | | 21
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| − | | 21
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| − | | 17
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| − | | 93
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| − | | Variable
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| − | |-
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| − | | '''Duration of Oestrus'''
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| − | | 4-8 days
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| − | | 12-36 hours
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| − | | 48-96 hours
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| − | | 24-48 hours | |
| − | | 7-13 days
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| − | | 4-10 days
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| − | |-
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| − | | '''Duration of Follicular Phase (days)'''
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| − | | 7 (variable)
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| − | | 4
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| − | | 7
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| − | | 3
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| − | | 18
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| − | | Variable
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| − | |-
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| − | | '''Duration of Luteal Phase (days)'''
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| − | | 14
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| − | | 17
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| − | | 14
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| − | | 14
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| − | | 75
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| − | | 40
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| − | |}
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| − | <big><b>
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| − | Oestrus Cycles in:
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| − | :[[Oestrous Cycle - Horse|Mare]]
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| − | :[[Oestrous Cycle - Dog|Bitch]]
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| − | :[[Oestrous Cycle - Cat|Queen]]
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| − | :[[Oestrous Cycle - Cattle|Cow]]
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| − | :[[Oestrous Cycle - Sheep|Ewe]]
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| − | :[[Oestrous Cycle - Goat|Nanny Goat]]
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| − | :[[Oestrous Cycle - Pig|Sow]]
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| − | </b></big>
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| − | == Links ==
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| − | * [[Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology|Pharmacological Manipulation of Oestrous Cycles]]
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| − | * [[Oestrus Behaviour - Anatomy & Physiology| Oestrus Behaviour and Methods of Oestrus Detection]]
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| − | ==Webinars==
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| − | <rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
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| − | [[Category:Oestrous Cycles]]
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| − | [[Category:Bullet Points]]
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