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Parturition Endocrine Control - Anatomy & Physiology (view source)
Revision as of 16:59, 7 January 2011
, 16:59, 7 January 2011→Species that depend on the Corpus Luteum
[[Image:Endocrine Control of Parturition 1.jpg|thumb|center|250px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 1.jpg|thumb|center|250px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 3.jpg|thumb|right|250px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 3.jpg|thumb|center|250px|The Onset of Parturition, Copyright RVC 2008]]
The foetus initiates parturition. For parturition to occur, progesterone production by the corpus luteum must be terminated. As the foetus grows in a restrictive environment, it becomes stressed. Stress leads to a rise in foetal [[Pituitary_Gland_- Anatomy & Physiology#Hormones_of_the_Anterior_Pituitary_Gland|ACTH]]. The rise in ACTH causes production of cortisol from the foetal [[Adrenal_Glands_- Anatomy & Physiology|adrenal glands]]. The rise in foetal cortisol leads to an increased oestrogen:progesterone ratio by upregulating '''aromatase''' enzymes, which convert androgens to oestrogens. Cortisol also reduces progesterone production.
The foetus initiates parturition. For parturition to occur, progesterone production by the corpus luteum must be terminated. As the foetus grows in a restrictive environment, it becomes stressed. Stress leads to a rise in foetal [[Pituitary_Gland_- Anatomy & Physiology#Hormones_of_the_Anterior_Pituitary_Gland|ACTH]]. The rise in ACTH causes production of cortisol from the foetal [[Adrenal_Glands_- Anatomy & Physiology|adrenal glands]]. The rise in foetal cortisol leads to an increased oestrogen:progesterone ratio by upregulating '''aromatase''' enzymes, which convert androgens to oestrogens. Cortisol also reduces progesterone production.
In late pregnancy, the ewe, guinea pig, queen and mare depend on placental progesterone.
In late pregnancy, the ewe, guinea pig, queen and mare depend on placental progesterone.
[[Image:Endocrine Control of Parturition 4.jpg|thumb|right|250px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 4.jpg|thumb|center|250px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 5.jpg|thumb|right|150px|The Onset of Parturition, Copyright RVC 2008]]
[[Image:Endocrine Control of Parturition 5.jpg|thumb|center|150px|The Onset of Parturition, Copyright RVC 2008]]
As previously explained, parturition is dependent on a rise in foetal cortisol. However, in this case, the rise in foetal cortisol leads to a decrease in '''maternal''' progesterone. Foetal cortisol causes upregulation of the enzymes, '''17α hydroxylase, C17-C20-lyase and aromatase''' in order to increase the oestrogen:progesterone ratio.
As previously explained, parturition is dependent on a rise in foetal cortisol. However, in this case, the rise in foetal cortisol leads to a decrease in '''maternal''' progesterone. Foetal cortisol causes upregulation of the enzymes, '''17α hydroxylase, C17-C20-lyase and aromatase''' in order to increase the oestrogen:progesterone ratio.