Placental Hormones That Maintain Pregnancy

Question 1

HCG (Human chorionic gonadotropin)

Answer 1

Prevents degeneration of corpus luteum
Corpus luteum continues to secrete progesterone and estrogens until placenta matures
Prevents menses
Levels rise over first 2 months of pregnancy, then drop sharply

Question 2

Placental Estrogen & Progesterone

Answer 2

Between 2nd-3rd month, levels of estrogens and progesterone (produced by placenta) rise and remain high throughout pregnancy
Inhibit menses

During first part of pregnancy, HCG secreted by the chorion contributes to:

• formation of the placenta
• sustains life of corpus luteum→ secretes estrogen and progesterone into the blood

In later pregnancy, the placenta becomes principal source of estrogen and progesterone

Question 3

Somatomammotropin

Answer 3

Blocks maternal insulin leading to increase in maternal blood glucose levels (ensure adequate fetal nutrition)
Develops maternal breasts

Question 4

Embryonic Period duration

Answer 4

Weeks 3-8 (first trimester)

Most critical period –Differentiation of all major systems occurs during this time

Question 5

Development during Embryonic Period

Answer 5

Heart
Main blood vessels
GI tract with very large liver
Lungs with branching bronchioles
Cerebral cortex, meninges, ventricles, CSF
Spinal cord
Ossification in occipital bone, mandible and humerus, Eye and internal ear beginning to develop
Testes/ovaries and sexless external genitals

Question 6

Fetal Period duration

Answer 6

Week 9-42

By week 9, all body systems are present in some form

Question 7

Birth

Answer 7

Accomplished by coordination of uterine myometrium (smooth muscles)

Facilitated by positive feedback loop mediated partly by hypothalamus oxytocin & cervix prostaglandins secretion → contraction more powerful→ forces the cervix to open wide → the fetus to be born

Question 8

Mammary Glands

Answer 8

Each breast has one pigmented projection (nipple) that has a series of closely spaced openings (lactiferous ducts)
Circular pigmented area = areola -contains modified sebaceous glands
Breasts are attached to fascia by suspensory ligaments (become loose with age or excessive strain)

With each breast is a mammary gland:

• consists of 15-20 lobes separated by various amounts of adipose tissue
• each lobe contains smaller compartments called lobules composed of a grape-like cluster of glands (alveoli)

Question 9

Lactation

Answer 9

Def: synthesis, secretion and ejection of milk

Milk production (produced in alveoli) stimulated by prolactin; ejection by oxytocin
Suckling stim secretion of prolactin and oxytocin by pituitary gland
Other neural signals (activated by infant’s cry), can stimulate oxytocin (but not prolactin) secretion and promote milk ejection