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Gestation & Parturition
ANS 316 Notes
40
Veterinary Medicine
Undergraduate 3
06/04/2013

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Cards

Term
Gestation
Definition
Time or duration from conception to parturition
Term
Major hormone of pregnancy
Definition
Progesterone
Term
What is the original source of P4?
Definition
CL of ovulation
Term
Important source of P4 during pregnancy?
Definition
Placenta
Term
Exceptions for P4 production
Definition
In several species, the placenta does not produce sufficient P4 to maintain pregnancy and these females require the CL and luteal P4 throughout pregnancy
Term
Parturition
Definition
The physiologic process by which the pregnant uterus delivers the fetus and placents from the maternal organism
Term
Inituation of Parturition
Definition

During pregnancy, P4 domination has been exerting a quiescent effect on the mymetrium

 

Note the rise in fetal cortisol precedes all the hormonal changes occuring during parturition

 

Destruction of the fetal pituitary or adrenalectomy prolongs gestation

 

Timing of parturition is linked to genetic contraol of the fetal adrenal maturation

Term

Initiation of Parturition

 

 

(Stress)

Definition

Fetus is proposed to perceive a stress

 

Perception of this stress activated the hypothalamic-pituitary-adrenal cortex axis to cause the release of fetal cortisol

 

Stressor is proposed to be a physical or mechanical factor

Ex: attainment of a critical fetal size & weight

 

Secretion of fetal cortisol dramatically changes placental endocrine function

Term

Coritsol

 

(mechanism of hormone action)

Definition
Induces expression of 3 enzymes in the placenta that redirect steroidogenesis from P4 to E2 synthesis
Term

Initiation of Parturition

 

(hormone changes)

Definition
  • Decreasing P4 removes the block on myometriam contractility
  • E2 production stimulates PGF-2alpha synthesis
  • Both E2 and PGF-2alpha exert myokinetic effects on the myometrium and stimulate contractility
  • PGF-2alpha stimulates relaxin release
  • E2 upregulates relaxin and oxytocin receptors
  • Enhanced contractility in the uterus causes the fetus to press against the cervix stimulating oxytocin release via neuroendocrine reflex arc
Term

Initation of Parturition

 

(hormone flow chart)

Definition

Cholesterol-->

 

Pregnelone-->

 

Progesterone--(17alpha-hydroxylase)-->

 

17alpha-Hydroxyprogesterone--(17-20 Desmolase)-->

 

Androstendione-->

 

Testosterone--(Aromatase)-->

 

Estradiol

Term

Parturition Cascade

 

 

Definition

Fetal Stress-->


Fetal Hypothalamus(perceives stress)

--(corticotropin releasing factor)-->

 

Fetal Puitary Gland

--(corticotropin)-->

 

Fetal Adrenal Cortex

--(cortisol)-->

 

Placenta (Target Tissue)

--> Decreased Progesterone

--> Increased Estradiol

--> Increased PGF-2alpha

--> Increased Relaxin

 

 

Term

Parturition Cascade

 

(decreased progesterone....)

Definition
Leads to Increased Estradiol
Term

Parturition Cascade

 

 

(Increased Estradiol....)

Definition
  • Increased secretion for lubication-->

Fetus & Fetal Membrane explusion

 

  • Increased Oxytocin-->

Fetus and Fetal Membrane explusion

 

  • Increased myometrial contractions-->

increased cervical stimulation-->

increased oxytocin-->

fetus and fetal membrane explusion

 

  • increased PGF-2alpha
  • increased relaxin

 

Term

Parturition Cascade

 

(Increased PGF-2alpha...)

Definition
  • Increased myometrial contractions-->

increased cervical stimulation-->

increased Oxytocin-->

Fetus and fetal membrane explusion

 

  • Luteolysis

 

  • Increased Relaxin
Term

Parturition Cascade

 

 

(Increased Relaxin)

Definition
  • Cervical dilation & relaxation of pelvic ligaments-->

fetus and fetal membrane explusion

Term
Dexamethasone
Definition
Synthetic glucocorticoid used for induction of parturition
Term
Stage 1 of labor
Definition

Dilation of cervix

 

 

Term
Mechanical Forces during Stage 1 labor
Definition
Regular uterine contractions
Term
Period of stage 1 labor
Definition
Beginning of uterine contractions until the cervix is fully dilated and continuous with the vagina
Term
Related events of stage 1 of labor
Definition

Maternal restlessness

 

elevated pulse and respiration rate

 

changes in fetal position and posture

Term
Stage 2 of labor
Definition
Explusion of fetus
Term
Mechanical forces of stage 2 labor
Definition
Strong uterine and abdominal contractions
Term
Period of stage 2 labor
Definition
From complete cervical dilation to end of delivery of fetus
Term
Related events of stage 2 labor
Definition

Maternal recumbency and straining

 

Rupture of allantochorion and escape of fluid from vulva

 

appearance of amnion at vulva

 

rupture of amnion and delivery of fetus

Term
Stage 3 of labor
Definition
Expulsion of placenta
Term
Mechanical forces of stage 3 of labor
Definition
uterine contractions decrease in amplitude
Term
Period of stage 3 of labor
Definition
following delivery of fetus to explusion of placenta
Term
Related events of stage 3 of labor
Definition

maternal straining ceases

 

loosening of chorionic villi from maternal crypts

 

inversion of chorioallantois

 

straining and expulsion of fetal membranes

Term
Physiologic adjustments of the neonate
Definition

Cortisol stimulates surfacant production in the fetal lungs

 

Vascular changes

Term
Cortisol stimulates surfacant production in the fetal lungs
Definition

surfacatn decreases alveolar surface tension allowing lung expansion

 

 

preparation for breathing in extra-uterine life

Term
Vascular changes
Definition
  • During fetal life, oxygenated blood is delivered to the fetus by the umbilical vein; the fetal lungs are bypassed
  • closure of the foramen ovale- higher pressures in the left atria press a flap of tissue against the right atria closing the foramen ovale; occurs at birth
  • construction on the ductus arteriosus and the ductus venosus- complete closure of both requires some months
Term
Ductus Arteriosus
Definition
Vessel between the pulmonary artery and the aorta
Term
Foramen ovale
Definition
hole between the left and right atria
Term
Ductus Venosus
Definition
Hepatic shunt that carries blood from the umbilical vein to the post cava; absent in pig and horse
Term
Puerperium
Definition
Period following parturition required for the reproductive tract to return to its pre-pregnancy status
Term
Postpartum interval
Definition
period between parturition and conception
Term
Puerperium and Postpartum Interval
Definition

Period of uterine involution and endometrial repair

 

Principal forces driving involution are myometrial contractions

 

Lochia

Term
Lochia
Definition
Uterine discharg observed during this time; comprised of mucus, blood and shreds of fetal membrane and endometrium
Term
Principal forces driving involution are myometrial contractions caused by....
Definition

Due to sustained release of PGF-2alpha for uterine postpartum

 

augmented by oxytocin release during episodes of suckling

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