Question

1. Describe the hormonal changes and regulation that occurs as a result of fertilization (pregnancy). Specifically outline the role that Progesterone (5 pts) and hCG (2 pts) play in the creation of an optimal environment for implantation and development of the fetus. Make sure to include the cells/structure that secretes the hormone. There is no need to go beyond the first trimester in your description. Finally describe what cell/structure will take over secreting hormones (hint provide 2 hormones) after the first trimester AND why it needed to take over in the first place (2 pts). 1 pts for essay formatting, grammar, spelling.

Answer 1

The ratio between progestrone and estrogen is very important for implantation and further growth of embryo. Progestrone decreases the tone and muscular activity of uterus which helps in retaining blastocyst in the uterine lumen.

Progestrone

• It is the key hormone in maintaining pregnancy.
• secreted by luteal cells of corpus luteum intially. later by adrenal glands and placenta.
• Functions in pregnancy:
• 1) Action on oviduct: promotes oviductal secretions necessary for nourishment of young embryo.
• 2) influence on uterus: acts synergisticaly with estrogen to cause endometrial growth. it maintain pregnancy by increasing activity of secretory glands in endometrium and by inhibiting the motility of myometrium.
• 3) promotes lobuloalveoar growth in mammary gland.
• 4) inhibits LH secretion.
• 5)Effect on electrolyte balance - in pregnant- large quantity of progestrone increases reabsorption of sodium and water.
• 6) protein stores of motheer mobilized for fetal growth
• 7) prevent uterine contraction.
• 8) development of preimplantation embryo

Human chrionic gonadotrophin (hCG)

• Maternal recognition of pregnancy.
• It is produced by syncitiotrophoblast cells of human placenta.
• It is a glycoprotein and has LH like activity.
• It is detectable in urine of women just 8 days after ovulation if pregnancy is established.
• its concentration is usually seen high from 7 to 9th week of pregnancy and decreases in the 20th week of pregnancy.
• Functions in pregnancy:
• 1) It stimulates CL of cycle and coverts into CL of pregnancy
• 2) Causes ICSH production-
• 3) enhances progestron production by the CL.

Hormones that will take over secreting hormones: estrogen, relaxin  and human chronic somatotropin. These hormmones are increased by replacing progestrone and hcg during 3rd trimester because- they are the ones needed for the smooth expulsion of the fetus. Progestroon and HCG mainly functions to maintain the pregnancy only, they function to prevent the fetus expulsion.

Estrogen -

• Towards the end of gestation, syncytiotrophoblast cells of placenta secrete estrogen.
• the estrogen secreted is primarily estriol which is synthesized from dehydroepiandrosterone (DHEA) in fetal cortex which s very large at this stage of gestation.
• Functions-
• 1) enlargement of uterus
• 2) enlargement of mammary gland
• 3) growth off duct syste in mammary gland
• 4) enlargement of external genitalia in mother and fetus, if it is female.
• 5)induces myometrial oxytocin receptors in late gestation.

Human chronic somatotropin

• it is secreted from 5th week of gestation and increases till the end of parturition.
• it has same function as growth hormone. but is 1/200 times potent.
• Functions-
• it increases glucose availability to foetus from mother.
• fatty acids are made available to detus as an alternate source of energy

Relaxin

• it is produced by granulosa cells of CL and placenta.
• It has synergistic action with progestrone to maintain pregnancy.
• Functions:-
• 1) Separation of pubic symphysis
• 2) Loosens sacroiliac union
• 3) Enlarges birth canal
• 4) Dilate cervix
• 5) Relax pelvic ligaments
• 6) Increases the distensibility of uterus.