Changes

== Regulation of Prostaglandins ==

== Regulation of Prostaglandins ==

The [[Uterus - Anatomy & Physiology|uterus]] is an important site of prostaglandin synthesis. During pregnancy, the presence of the foetus inhibits the production of prostaglandins in order to prevent luteolysis. At parturition, an increase in prostaglandin synthesis is required. Prostaglandins are synthesized from '''arachadonic acid''', which is derived from '''glycerophospholipids''' by the enzyme '''phospholipase A2''' (PLA2). '''Oestrogen''' liberates phospholipase A2 from lysosomes. '''Progesterone''' stabilises lysosomes, so phospholipase A2 cannot be liberated from lysosomes. An increase in '''oestrogen:progesterone ratio''' increases prostaglandin production. The increase in '''oestradiol''' (bioactive oestrogen) also increases expression of '''endometrial oxytocin receptors'''.

The [[Uterus - Anatomy & Physiology|uterus]] is an important site of prostaglandin synthesis. During pregnancy, the presence of the foetus inhibits the production of prostaglandins in order to prevent luteolysis. At parturition, an increase in prostaglandin synthesis is required. Prostaglandins are synthesized from '''arachadonic acid''', which is derived from '''glycerophospholipids''' by the enzyme '''phospholipase A2''' (PLA2). '''Oestrogen''' liberates phospholipase A2 from lysosomes. '''Progesterone''' stabilises lysosomes, so phospholipase A2 cannot be liberated from them. An increase in '''oestrogen:progesterone ratio''' increases prostaglandin production. The increase in '''oestradiol''' (bioactive oestrogen) also increases expression of '''endometrial oxytocin receptors'''.

== Regulation of Oxytocin ==

== Regulation of Oxytocin ==

[[Image:Parturition Cascade.jpg|thumb|right|250px|The Parturition Cascade, Copyright RVC 2008]]

[[Image:Parturition Cascade.jpg|thumb|right|250px|The Parturition Cascade, Copyright RVC 2008]]

Details of oxytocin synthesis and secretion may be found [[Pituitary_Gland_- Anatomy & Physiology#Oxytocin|here]].

Details of oxytocin synthesis and secretion may be found in [[Pituitary_Gland_- Anatomy & Physiology#Oxytocin|pituitary gland]] page.

Oxytocin acts to; increase [[Uterine Contraction - Anatomy & Physiology|myometrial contraction]] (positive feedback) and prostaglandin release.

Oxytocin acts to increase [[Uterine Contraction - Anatomy & Physiology|myometrial contraction]] (positive feedback) and prostaglandin release.

=== Furgesson Reflex ===

=== Furgesson Reflex ===

The furgesson reflex is a neuroendocrine reflex. Oxytocin is released in response to cervical stimulation by the foetus, this causes further synthesis and secretion of oxytocin, thus exibiting positive feedback. Oxytocin concentrations continue to rise until the foetus is expelled, thus the cervical stimulation ceases.

The furgesson reflex is a neuroendocrine reflex. Oxytocin is released in response to cervical stimulation by the foetus, this causes further synthesis and secretion of oxytocin, thus exhibiting positive feedback. Oxytocin concentrations continue to rise until the foetus is expelled, thus the cervical stimulation ceases.

=== Role of Relaxin ===

=== Role of Relaxin ===

Relaxin is a glycoprotein hormone. It is produced by either the, corpus luteum or placenta depending on species. Its synthesis is stimulated by '''PGF2α'''. This causes softening of the connective tissue in the [[Cervix - Anatomy & Physiology|cervix]] and promotes elasticity of the pelvic ligaments. This prepares the birth canal, so that the passage of the foetus can occur with relative ease.

Relaxin is a glycoprotein hormone. It is produced by either the corpus luteum or placenta depending on species. Its synthesis is stimulated by '''PGF2α'''. This causes softening of the connective tissue in the [[Cervix - Anatomy & Physiology|cervix]] and promotes elasticity of the pelvic ligaments, thus preparing the birth canal so that the passage of the foetus can occur with relative ease.

== Role of Oestrodiol Elevation prior to Parturition ==

== Role of Oestrodiol Elevation prior to Parturition ==

This elevation initiates the secretory activity of the reproductive tract, particularly the [[Cervix - Anatomy & Physiology|cervix]], resulting in the [[Cervix - Anatomy & Physiology|cervix]] and [[Vagina and Vestibule - Anatomy & Physiology|vagina]] producing mucus. This washes out the cervical seal of pregnancy and lubricates the cervical canal and vagina and reduces friction, enabling the foetus to exit the reproductive tract with relative ease.

This elevation initiates the secretory activity of the reproductive tract, particularly the [[Cervix - Anatomy & Physiology|cervix]], resulting in the [[Cervix - Anatomy & Physiology|cervix]] and [[Vagina and Vestibule - Anatomy & Physiology|vagina]] producing mucus. This washes out the cervical seal of pregnancy and lubricates the cervical canal and vagina to reduce friction, enabling the foetus to exit the reproductive tract with relative ease.

== Onset of Parturition ==

== Onset of Parturition ==

[[Image:Endocrine Control of Parturition 4.jpg|thumb|center|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|center|150px|The Onset of Parturition, Copyright RVC 2008]]

[[Image:Endocrine Control of Parturition 5.jpg|thumb|center|250px|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.

[[Category:Parturition]]

[[Category:Parturition]]

[[Category:Endocrine System - Anatomy & Physiology]]

[[Category:Endocrine System - Anatomy & Physiology]]

[[Category:To Do - AimeeHicks]][[Category:To Do - Review]]

[[Category:A&P Done]]