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Normal Parturition - Anatomy & Physiology (view source)
Revision as of 18:27, 3 July 2012
, 18:27, 3 July 2012no edit summary
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==Stages of Parturition==
*Stage 1: this is the preparatory stage, starting at the onset of regular uterine contractions followed by cervical dilatation and the foetus assuming the correct disposition for passage through the birth canal.
*Stage 2: the expulsive stage, characterised by the onset of abdominal contractions which together with uterine contractions lead to foetal expulsion
*Stage 3: separation and expulsion of the foetal membranes. In polycotous species second and third stages are often inter-mixed.
The following table summarises the normal time taken to progress through the stages of parturition in different species.
{| style="width:75%; height:200px" border="1"
{| style="width:75%; height:200px" border="1"
| '''Stage 2: Foetal Expulsion'''
| '''Stage 2: Foetal Expulsion'''
| 12-30 minutes
| 12-30 minutes
| 30-60 minutes
| 30 minutes - 4 hours
| 30-120 minutes
| 30-120 minutes
| 150-180 minutes
| 150-180 minutes
|-
|-
|}
|}
The step in the reproductive process that immediately precedes lactation, uterine involution and return to cyclicity. It is initiated by the foetus and involves a complex cascade of endocrine events. Parturition is the process by which the conceptus (foetus, placenta and placental membranes) is expelled from the [[Uterus - Anatomy & Physiology|uterus]]; this requires [[Cervical Softening - Anatomy & Physiology|cervical softening]],[[Uterine Contraction - Anatomy & Physiology|coordinated myometrial contractions]] and contraction of abdominal muscles
to occur
== Placental Changes ==
During the last 5 days of gestation, there are changes in the placenta.
* Collaginisation of the placentome.
* Flattening of maternal crypt epithelium.
* Leucocyte migration and increased activity.
* Reduction of binucleate cells in the trophectoderm.
* Weakening of the acellular protein layer between cotyledonary and caruncular epithelium.
== Contractions ==
* Open endometrial crypts
* Foetal villi have shrunk due to the escape of blood from the foetal side of the placenta when the umbillical cord ruptures.
* [[Uterine Contraction - Anatomy & Physiology|Myometrial contractions]] aid exsanguination of the placenta.
* Separation of foetal membranes.
* Apex of the allantochorionic sac becomes inverted.
* As the sac is 'rolled' down the uterine horns, foetal villi are drawn out of the crypts.
* When a large portion becomes detached and inverted, it forms a mass in the maternal pelvis.
** Stimulates reflex contractions of abdominal muscles.
** Completes expulsion of the allantochorionic sac.
* In polytocious species, dehisence and expulsion of foetal membranes are interspersed with births of the young.
** Only expulsion of the last afterbirth stimulates abdominal contractions.
* The final stage of allantochorionic expulsion lasts 1 hour (mare) - 6 hours (cow).
* Domestic animals normally eat the afterbirth.
** Not the mare or camelids.
== Placental Expulsion ==
In most species, expulsion of foetal membranes quickly follows expulsion of the foetus.
* After the birth of the young, regular abdominal contractions largely cease.
* Myometrial contractions persist.
** Decreased amplitude, but become more frequent and less regular.
** Important for dehiscence and expulsion of foetal membranes.
* Waves of contractions from uterus to the cervix persist.
** Act in a peristaltic fashion in the cow and sow in the reverse direction.
== Parturition Behaviour ==
=== [[Parturition Behaviour - Mare|Mare]] ===
===[[Parturition Behaviour - Cow| Cow]] ===
===[[Parturition Behaviour - Ewe| Ewe]] ===
===[[Parturition Behaviour - Sow| Sow]] ===
===[[Parturition Behaviour - Bitch| Bitch]] ===
===[[Parturition Behaviour - Cat| Cat]] ===
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[[Category:Parturition]]
[[Category:Bullet Points]]