Lecture 19 - Placentation

Question 1

What is the function of the placenta?

Answer 1

Connects the mother to the fetus

• blood supply
• nutrient uptake
• waste elimination
• gas exchange

Question 2

What ate the types of placentas?

Answer 2

Diffuse
Cotyledonary
Zonary
Discoid

Question 3

What is the Diffuse placenta?

Answer 3

Site of exchange are distributed over the entire placenta

Sow and mare

Question 4

What is the Cotyledonary placenta?

Answer 4

Exchange takes place at placentomes

Ruminants (cow, sheep)

Question 5

What is a placentome?

Answer 5

Maternal caruncle + fetal cotelydon

Question 6

What is a caruncle?

Answer 6

Button-like projections from the endometrium

Question 7

What is a cotelydon?

Answer 7

Fetal membranes

Question 8

What is a Zonary placenta?

Answer 8

Complete or incomplete band of attachment surrounding the fetus

Carnivores (dogs, cats, bears and seals) elephants

Question 9

What is a discoid placenta?

Answer 9

Single placenta is formed in a discoid shape

Question 10

What does the fetus do to trigger parturition?

Answer 10

High cortisol levels

Question 11

What happens to the hormones during parturition?

What does the high cortisol from the fetus trigger?

Answer 11

Decrease in high progesterone

Increase in estrogen, oxytocin, prostaglandins, prolactin, and relaxin

Regression of the CL

Question 12

What does relaxin do?

Answer 12

Stimulates the pelvic muscles and ligaments to lead in preparation for passage of the fetus through the birth canal

• secreted from placenta

Question 13

What does oxytocin do?

Answer 13

Cause gradually increasing uterine contractions required for fetus expulsion

released from the posterior pituitary due to stretching of uterus and cervix

Question 14

What does prolactin do?

Answer 14

Stimulates milk let down and nesting behavior

Secreted by the anterior pituitary

Question 15

What does estrogen do?

Answer 15

Stimulates oxytocin release, sensitized uterus to effects of oxytocin, cervical dilation
also secreted fro the placenta, helps prepare mammary glands for milk synthesis

Question 16

What is prostaglandins

Answer 16

Luteolytic effect on the CL, stimulates oxytocin and cervical dilation

Question 17

What is the first stage of parturition?

Answer 17

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

Question 18

What is the second stage of parturition?

Answer 18

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

Question 19

What is the third stage of parturition?

Answer 19

Expulsion of the placenta

Horses need intervention
Cows will expel on their own

Question 20

What is dystocia?

Answer 20

Difficult parturition

Question 21

What are the common reasons of dystocia?

Answer 21

• fetus is too large to pass through birth canal (90%)
• fetus is in an abnormal position (5%)
• maternal issues (uterine inertia) (5%)

Question 22

What assistance maybe used for dystocia?

Answer 22

• “Pulling calves”
• C-section
• fetotomy