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Uterine Contraction - Anatomy & Physiology (view source)
Revision as of 18:31, 3 July 2012
, 18:31, 3 July 2012→Endocrine Control
{{review}}
== Myometrial Contraction==
*'''Myometrium''' consists of:
** Non-striated smooth muscle fibres
** Nerves, Blood and Lymph
* Uterine contractions increase in both frequency and amplitude during labour. This causes an increase in '''uterine pressure''' from 10mmHg to 50-100mmHg.
* Uterine contractions increase in both frequency and amplitude during labour. This causes an increase in '''uterine pressure''' from 10mmHg to 50-100mmHg.
== The Birth Canal ==
'''''Brachystasis'''''
'''''Brachystasis'''''
* Myometrial cells contract and shorten, but do not regain their original length upon relaxation.
* Myometrial cells contract and shorten, but do not regain their original length upon relaxation.
* Reduces the uterine volume and causes retraction of the lower uterine segment and the cervix to create a '''birth canal'''.
* Reduces the uterine volume and causes retraction of the [[Uterus - Anatomy & Physiology|lower uterine segment]] and the [[Cervix - Anatomy & Physiology|cervix]] to create a '''birth canal'''.
'''''Retraction Ring'''''
'''''Retraction Ring'''''
*The Uterus is divided into two segments:
*The [[Uterus - Anatomy & Physiology|Uterus]] is divided into two segments:
** Upper segment: contractile
** Upper segment: contractile
** Lower segment: passive
** Lower segment: passive
*The junction between these segments is the retraction ring.
*The junction between these segments is the retraction ring.
* Palpation of the retraction ring is used as an indicator of progression through labour.
* Palpation of the retraction ring is used as an indicator of progression through labour.
== Endocrine Control ==
[[Image:Myometrial Contraction endocrinology.jpg|thumb|right|150px|Schematic Diagram to show the Endocrine Influence on Myometrial Contraction,Copyright RVC 2008]]
*Two hormones directly regulate myometrial contractions:
** '''[[Pituitary_Gland_- Anatomy & Physiology#Oxytocin|Oxytocin]]''': from the posterior pituitary gland (not the corpus luteum) lowers the excitation threshold of muscle cells to increase the likelihood of action potential firing. Oxytocin also stimulates prostaglandin release.
*** The uterine Oxytocin receptor is a G protein coupled receptor with a Gαq subinit. Thus the signalling pathway is via a calcium second messenger. Hence prostaglandin and oxytocin are complementory in action.
** '''Prostaglandins''': Stimulate liberation of calcium from intracellular stores to cause the rise in intracellular calcium concentration required for myometrial contraction.
[[Category:Parturition]]
[[Category:Bullet Points]]