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Uterine Contraction - Anatomy & Physiology (view source)
Revision as of 07:45, 8 July 2008
, 07:45, 8 July 2008no edit summary
'''''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 [[Female_Reproductive_Tract_-The_Uterus_-_Anatomy_%26_Physiology|lower uterine segment]] and the [[Female_Reproductive_Tract_-The_Cervix_-_Anatomy_%26_Physiology|cervix]] to create a '''birth canal'''.
* Reduces the uterine volume and causes retraction of the [[Female_Reproductive_Tract_-The_Uterus_-_Anatomy_%26_Physiology|lower uterine segment]] and the [[Female_Reproductive_Tract_-The_Cervix_-_Anatomy_%26_Physiology|cervix]] to create a '''birth canal'''.
*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'''''
Two hormones directly regulate myometrial contractions:
* '''[[Endocrine_System_-_Pituitary_Gland_-_Anatomy_%26_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.