Changes

=== Species that depend on the Corpus Luteum===

=== Species that depend on the Corpus Luteum===

To produce progesterone throughout pregnancy (Goat, Cow, Sow, Bitch)

To produce progesterone throughout pregnancy (goat, cow, sow, bitch)

[[Image:Endocrine Control of Parturition 1.jpg|thumb|right|150px|The Onset of Parturition, Copyright RVC 2008]]

[[Image:Endocrine Control of Parturition 1.jpg|thumb|right|150px|The Onset of Parturition, Copyright RVC 2008]]

* The foetus initiates parturition.

* The foetus initiates parturition.

* For parturition to occur, progesterone production by the Corpus Luteum must be terminated.

* 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 leades to a rise in foetal [[Pituitary_Gland_-_Anatomy_%26_Physiology#Hormones_of_the_Anterior_Pituitary_Gland|ACTH]].  The rise in ACTH causes production of Cortisol from the foetal [[Adrenal_Glands_-_Anatomy_%26_Physiology|Adrenal Glands]].

* As the foetus grows in a restrictive environment it becomes stressed.  Stress leads to a rise in foetal [[Pituitary_Gland_-_Anatomy_%26_Physiology#Hormones_of_the_Anterior_Pituitary_Gland|ACTH]].  The rise in ACTH causes production of Cortisol from the foetal [[Adrenal_Glands_-_Anatomy_%26_Physiology|adrenal Glands]].

* The rise in foetal cortisol leased to an increased Oestrogen:Progesterone ratio by upregulating '''aromatase''' enzymes which convert Androgens to Oestrogens.  Cortisol also reduces Progesterone production.

* The rise in foetal cortisol leased to an increased oestrogen:progesterone ratio by upregulating '''aromatase''' enzymes which convert androgens to oestrogens.  Cortisol also reduces progesterone production.

=== Species that depend on Placental Progesterone===

=== Species that depend on Placental Progesterone===