SPL on Hormonal Regulation of Pregnancy and Childbirth

Question 1

1. a. Describe the glandular function of the corpus luteum during the first week of pregnancy.


Answer 1

The corpus luteum release progesterone and estrogen in order to maintain the endometrium.

Question 2

1. b. Describe the glandular function of the blastocyst.

Answer 2

When the
blastocyst imbeds itself in the lining of the uterus it secretes human chorionic gonadotropin - hCG.

Question 3

1.C What is the function of human chorionic gonadotropin (hCG)?

Answer 3

Hcg prevents the ovarian corpus luteum from degenerating and thus maintains the secretions of estrogen and progesterone.

Question 4

1.d Explain why menstruation does not occur.

Answer 4

Because the estrogen and progesterone levels are maintained.

Question 5

2.
Describe the glandular role of the corpus luteum and the chorion
over the first two- three months of pregnancy.

Answer 5

Estrogen and progesterone are primarily secreted by the corpus
luteum, maintaining nutritional support for the embryo and fetus. hCG production increases and peaks about 8 weeks and triggers the corpus luteum to produce ever increasing levels of estrogen and progesterone

Question 6

3 Identify the shift in estrogen production by the ninth week.

Answer 6

By the 9th’ week the placenta becomes the primary source of estrogen
and progesterone.

Question 7

4. Describe CG production changes after the fourth month.

Answer 7

After the 4’ month the levels of hCG significantly decrease and stay at a low level.

Question 8

5
Identify the placental produced hormones that regulate activities
during months 4-9.

Answer 8

Following the 4’ month the rising levels of placental estrogen and
progesterone are sufficient to maintain the pregnancy.

Question 9

Describe regulatory effects of placental produced estrogens and
progesterone during months 4-9.

Answer 9

The estrogens increase uterine blood flow and maintain the
endometrium during pregnancy. The high levels of estrogen and
progesterone also inhibit the synthesis of milk. Progesterone inhibits
myometrial contractions of the uterus to prevent premature birth.

Question 10

7 Describe the roles of placental produced relaxin.

Answer 10

Relaxin inhibits myometrial contraction and increases the flexibility of the pubic
symphysis.

Question 11

8 Describe the roles of human chorionic somatomammotropin
(hCS).

Answer 11

hCS enhances maternal breast growth and development by
increasing protein synthesis. It also prepares the mammary glands for lactation and inhibits glucose uptake by the maternal cells leaving more glucose for the fetus.

Question 12

9.
What effect does placental produced corticotropic releasing
hormone have on the fetus?

Answer 12

This stimulates the fetal anterior pituitary gland to secrete ACTH. ACTH stimulates fetal cortisol production.

Question 13

10. What effect does ACTH, secreted by the fetal anterior pituitary
    gland have on the fetal adrenal glands?

Answer 13

The release of ACTH stimulates the fetal adrenal gland to start
producing cortisol.

Question 14

11. What effect does cortisol, secreted by the fetal adrenal glands,
    have on fetal lungs?

Answer 14

The release of fetal cortisol triggers fetal lung maturation and surfactant
production.

Question 15

12. Describe CRH and Estrogen changes and functions through months 4-9.

Answer 15

Levels of placental CH increase toward the end of pregnancy and stimulate
the fetus and the placenta to produce more estrogens. Increased levels of
estrogen act as a timer for birth and for lactation.

Question 16

13 Explain how blood levels of prolactin build throughout the
pregnancy but lactation does not begin until AFTER delivery.

Answer 16

Prolactin increases steadily throughout the pregnancy. However the high
levels of estrogen and progesterone during pregnancy inhibit the action of
Prolactin on the mammary tissue so no milk production occurs. After birth the
levels of estrogen and progesterone rapidly drop and their inhibitory action
ends.

Question 17

a. Describe the role of breast stretch receptors.

Answer 17

The stretch
receptors in the breast are activated by the sucking action of the baby and
serve to send impulses to the hypothalamus.

Question 18

Describe hypothalamus activity resulting from suckling stimulation.

Answer 18

The impulses from the breast reaching the hypothalamus inhibit a Prolactin
inhibiting hormone (PIH) and stimulate Prolactin-releasing hormone (PRH)

Question 19

14 c Describe effects caused by prolactin.

Answer 19

Increased PRH triggers the release of Prolactin from the anterior pituitary
gland. This circulates to the alveoli of the mammary glands and promotes
lactation.

Question 20

15. Explain production and effect of oxytocin.

Answer 20

The sucking action of the
baby stimulates the hypothalamic hormone oxytocin. Oxytocin circulates to
the myoepithelial cells that surround the alveoli of the mammary gland and
cause contraction. This forces the milk from the alveoli into the ducts where it
then can be suckled.

Question 21

16. a. Corticotropin-releasing hormones stimulate increased estrogen
    secretion just prior to birth. What affect do these high levels of
    estrogen have on the uterine muscles?

Answer 21

The high estrogen levels overcome the inhibitory effects of progesterone on
uterine
smooth muscle. This is done by promoting the formation of gap
junctions between the smooth muscle cells and the myometrium. It also
increases the number of smooth muscle cell receptors for oxytocin that
promote uterine contractions.

Question 22

What effect does the increase in uterine oxytocin receptors have?

Answer 22

Promotes uterine contraction.

Question 23

Describe the effects of relaxin.

Answer 23

Promotes the dilation of the cervix and increases the flexibility of the pubic
symphysis.

Question 24

18. Describe the positive feedback loop that results in childbirth.
    (Stretch Receptors, Nerve Impulses, Hypothalamus, Anterior Pituitary,
    Oxytocin, More Stretch)

Answer 24

Initial contraction of the uterus begins the cycle and pushes the fetus towards the cervix. As the fetus enters the cerix, it stretches and stimulates stretch
receptors. Impulses are sent to the neurosecretory cells of the hypothalamus
and oxytocin is released into the capillaries of the pituitary gland. The blood
carries the hormone to the uterine tissue. Oxytocin targets the myometrium
and causes the smooth muscle to contract forcefully. This pushes the fetus
further into the cervix and stretches it even more. This sends additional
impulses to the hypothalamus and a positive feedback loop is created. This
continues until the fetus is expelled from the uterus and the cervix is no
longer stretched.

Question 25

19. Describe events for each of the three stages of parturition.

Answer 25