Difference between revisions of "Normal Parturition - Anatomy & Physiology"

Revision as of 09:11, 15 July 2008

The Process by which the conceptus (foetus, placenta and placental membranes) are expelled from the Uterus requires:
- Cervical Softening
- Coordinated Myometrial Contraction
- Voluntary contraction of abdominal muscles

In most species, expulsion of foetal membranes quickly follows expulsion of the foetus.
Expulsion of the foetus requires that the chorionic villi become dislodged from the crypts of the maternal side of the placenta.
- Brought about by powerful vasoconstriction of arteries in the villi.
  - Vasoconstriction reduces pressure and allows villi to be released from crypts.

Normal Parturition

Species	Mare	Cow	Ewe	Sow	Bitch
Stage 1: Contractions and Cervical Dilation	1-4 hours	2-6 hours	2-6 hours	2-12 hours	6-12 hours
Stage 2: Foetal Expulsion	12-30 minutes	30-60 minutes	30-120 minutes	150-180 minutes	6 hours (up to 24 hours with large litters)
Stage 3: Placental Expulsion	1 hour	6-12 hours	5-8 hours	1-4 hours	Placenta Exits with Foetus

@@ Line 1: / Line 1: @@
-{{OpenPagesTop}}
+* The Process by which the conceptus (foetus, placenta and placental membranes) are expelled from the [[Female_Reproductive_Tract_-The_Uterus_-_Anatomy_%26_Physiology|Uterus]] requires:
-==Stages of Parturition==
+** [[Parturition - Cervical Softening - Anatomy & Physiology|Cervical Softening]]
+** [[Parturition - Coordinated Myometrial Contraction - Anatomy & Physiology|Coordinated Myometrial Contraction]]
+** Voluntary contraction of abdominal muscles
-*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.
+* In most species, expulsion of foetal membranes quickly follows expulsion of the foetus.
+* Expulsion of the foetus requires that the chorionic villi become dislodged from the crypts of the maternal side of the [[Female_Reproductive_Tract_-Placenta_-_Anatomy_%26_Physiology|placenta]].
+** Brought about by powerful vasoconstriction of arteries in the villi.
+*** Vasoconstriction reduces pressure and allows villi to be released from crypts.
+'''Normal Parturition'''
 {| style="width:75%; height:200px" border="1"
@@ Line 25: / Line 31: @@
 | '''Stage 2: Foetal Expulsion'''
 | 12-30 minutes
-| 30 minutes - 4 hours
+| 30-60 minutes
 | 30-120 minutes
 | 150-180 minutes
@@ Line 38: / Line 44: @@
 |-
 |}
-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]] ===
-{{OpenPages}}
-[[Category:Parturition]]
-[[Category:Bullet Points]]

Difference between revisions of "Normal Parturition - Anatomy & Physiology"

Revision as of 09:11, 15 July 2008

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