Pregnancy/Parturition

Question 1

Fertilization process

Answer 1

1. Sperm binds to zona pellucida
2. Acrosomal reaction triggered–fusion of the acrosome with sperm cell plasma membrane (exocytosis: Ca dependent)
3. Hydrolytic enzymes released from acrosome penetrate the zona pellucida.
4. Sperm and oocyte fuse
5. Cortical reaction–prevents entry of other sperm (Ca, IP3 dependent)
6. Oocyte completes 2nd meiotic divison–2nd polar body expelled
7. Sperm head swells and becomes the male pronucleus
8. Male and female pronuclei fuse and form the zygote

Question 2

How many days after fertilization does implantation occur?

Answer 2

-6 days

Question 3

Human chorionic gonadotropin

Answer 3

• hCG
• Produced in the syncytiotrophoblasts by the blastocyst
• Closely related to LH
• Sustains the corpus luteum
• Immunosuppresive agent, promotes placental development
• Also leads to male sex organ development by stimulating testosterone production

Question 4

Estrogen and parturition

Answer 4

-Initiates parturition

Question 5

Key hormones supplied by the placenta

Answer 5

• Steroid hormones: progesterones and estrogens remain high during pregnancy
• hCG: placental peptide hormone
• Somatomammotropins: similar to growth hormone

Question 6

Maternal-fetal placental unit

Answer 6

• Work together to produce steroid hormones
• Placenta doesn’t make adequate amounts of cholesterol and lacks 3-beta-hydroxysteroid dehydrogenase, aromatase, and 16 alpha-hydroxylase and 17,20-desmolase, and 17 alpha hydroxylase

Question 7

Parturition

Answer 7

-May be triggered by an increase in fetal production of cortisol near term which increases the ratio of estrogen/progesterone and thus the sensitivity of the uterus to contractile stimuli

Question 8

What initiates contractions?

Answer 8

• Prostaglandins
• Sustained by oxytocin and more prostaglandins
• PGE2 and PGF2a

Question 9

Estrogen impact on oxytocin receptors

Answer 9

-Increases the number on myometrial tissue in the uterus

Question 10

Ferguson reflex

Answer 10

-Distension of the cervix due to maternal oxytocin release

Question 11

Relaxin

Answer 11

• Produced by corpus luteum, placenta, and decidua

- May help to soften/dilated cervix

Question 12

What promotes milk let down?

Answer 12

-Oxytocin

Question 13

What promotes milk synthesis

Answer 13

-Prolactin

Question 14

What prevents the secretion of milk?

Answer 14

-Estrogen and progesterone

Question 15

What must happen to allow prolactin to work?

Answer 15

-Dopamine release must be inhibited