Lecture 11 - Parturition (Labor and Delivery)

Question 1

Parturition=labor and delivery.
How does it start?

Answer 1

• CRH from placenta triggers ACTH pathway and stimulates release of prostaglandins.
• Prostaglandins causes smooth muscle contraction.
• More CRH→ more prostaglandins→ early delivery Less CRH→ less prostaglandins→ late delivery

Question 2

What does CRH do in labor and delivery?

Answer 2

• Releases prostaglandins, and prostaglandins are involved in muscle contraction
• Release Estrogen.
• Estrogen stimulates: expression of oxytocin receptors which result in muscle contractions.
• Also stimulate release of prostaglandins.
• And estrogen also softens collagen of the cervix so that it’s easier to deliver baby.

Question 2

What does CRH do in labor and delivery?

Answer 2

• Releases prostaglandins, and prostaglandins are involved in muscle contraction
• Release Estrogen.
• Estrogen stimulates: expression of oxytocin receptors which result in muscle contractions. Oxytocin makes muscle contractions stronger.
• Also stimulate release of prostaglandins.
• And estrogen also softens collagen of the cervix so that it’s easier to deliver baby.

Question 3

If prostaglandins and estrogen are releasing all these signals to help with delivery, why does it take 9 months for the baby to come out?

Because…one hormone is inhibiting a lot of those synthesis.

What is that hormone?

Answer 3

Progesterone.

It inhibits the synthesis of Prostaglandins and receptor expression of oxytocin.

Eventually the positive feedback loop of CRH is too much and it overtakes progesterone. So eventually we get muscle contractions.

Question 4

What can make delivery difficult?

Answer 4

1. Fetal position
2. Pelvis too small
3. Fetus too large
4. Fetal distress

Question 5

How to handle difficult deliveries?

Answer 5

• Forceps (Kind of like tongs)
• Vacuum
• Cesarean section

Question 6

Multiples: Monozygotic (Identical twins)

Answer 6

• Usually one placenta
• Genetically identical
• Single inner cell mass divides in two

One sperm, one ovum

Question 7

Multiples: Dizygotic (fraternal twins)

Answer 7

• Two sperm, two ovum
• Either one or two placentas, depends on proximity during implantation

Question 8

Parturition: CRH pathway

Answer 8

Placenta releases CRH→ it triggers ACTH→ triggers CRH again to make Prostaglandins

Placenta releases CRH→ it triggers ACTH→ triggers DHEA-S→ this releases Estrogen→ with Estrogen, oxytocin gets released

Question 9

Parturition: EP1 is used for ________ and is expressed in the upper uterus.

EP2 is used for_________ and is expressed in the lowest portion near the cervix

Answer 9

EP1 is used for contractions and is expressed in the upper uterus.

EP2 is used for relaxation and is expressed in the lowest portion near the cervix.