Lecture 19 - Placentation Flashcards
What is the function of the placenta?
Connects the mother to the fetus
- blood supply
- nutrient uptake
- waste elimination
- gas exchange
What ate the types of placentas?
Diffuse
Cotyledonary
Zonary
Discoid
What is the Diffuse placenta?
Site of exchange are distributed over the entire placenta
Sow and mare
What is the Cotyledonary placenta?
Exchange takes place at placentomes
Ruminants (cow, sheep)
What is a placentome?
Maternal caruncle + fetal cotelydon
What is a caruncle?
Button-like projections from the endometrium
What is a cotelydon?
Fetal membranes
What is a Zonary placenta?
Complete or incomplete band of attachment surrounding the fetus
Carnivores (dogs, cats, bears and seals) elephants
What is a discoid placenta?
Single placenta is formed in a discoid shape
What does the fetus do to trigger parturition?
High cortisol levels
What happens to the hormones during parturition?
What does the high cortisol from the fetus trigger?
Decrease in high progesterone
Increase in estrogen, oxytocin, prostaglandins, prolactin, and relaxin
Regression of the CL
What does relaxin do?
Stimulates the pelvic muscles and ligaments to lead in preparation for passage of the fetus through the birth canal
- secreted from placenta
What does oxytocin do?
Cause gradually increasing uterine contractions required for fetus expulsion
released from the posterior pituitary due to stretching of uterus and cervix
What does prolactin do?
Stimulates milk let down and nesting behavior
Secreted by the anterior pituitary
What does estrogen do?
Stimulates oxytocin release, sensitized uterus to effects of oxytocin, cervical dilation
also secreted fro the placenta, helps prepare mammary glands for milk synthesis
What is prostaglandins
Luteolytic effect on the CL, stimulates oxytocin and cervical dilation
What is the first stage of parturition?
Dilation of the Cervix
- softening of the cervix, hormones stimulate epithelial cells to secrete mucous
- uterine contractions move the fetus in to the pelvic canal
What is the second stage of parturition?
Expulsion of the fetus
Allanto-chorionic sac is expelled through vulva
Rupture leads to release of fluids surrounding fetus
Fetus is expelled
- intense uterine and abdominal contractions
- umbilical cord is separated
- rapid progression from this stage
What is the third stage of parturition?
Expulsion of the placenta
Horses need intervention
Cows will expel on their own
What is dystocia?
Difficult parturition
What are the common reasons of dystocia?
- fetus is too large to pass through birth canal (90%)
- fetus is in an abnormal position (5%)
- maternal issues (uterine inertia) (5%)
What assistance maybe used for dystocia?
- “Pulling calves”
- C-section
- fetotomy
