Ovarian and Endometrial Regulation

Question 1

Define: Menstrual Cycle

Answer 1

periodic preparations for fertilization and pregnancy, including cyclic changes in ovary and uterus- typically 28 days, day 1 is the start of menstruation

Question 2

Does estrogen exhibit positive or negative feedback to the hypothalamus-pituitary-gonad axis?

Answer 2

normally negative feedback, but about day 12 of menstrual cycle there is a brief positive feedback from rapidly increasing estrogen which stimulates the release of LH and FSH

Question 3

Describe: Ovarian Cycle

Answer 3

1. starting each cycle, several follicles enlarge to form antrum surrounding ovum
2. one dominant follicle, other undergo atresia, around day 14 of menstrual cycle dominant follicle ruptures and oocyte picked up by fimbriated ends of uterine tube
3. ruptured follicle filled with blood- corpus hemorrhagicum
4. corpus luteum- granulosa and theca cells start to proliferate and blood replaced with yellowish, lipid-rich luteal cells
5. regressing corpus luteum if no pregnancy

Question 4

Define: Atresia

Answer 4

immature ovarian follicles (including the ovum, the surrounding granulosa, and theca cells) degenerate (breakdown) and are subsequently re-absorbed during the follicular phase of the menstrual cycle

Question 5

Describe the developmental stages of oocytes

Answer 5

-the mature oocyte ovulated in mid-cycle begins to develop will before the menstrual cycle
-pre-antral period is independent of FSH/LH (does not require)
-development from early antral stage of ovulation requires FSH

Question 6

Where does fertilization occur?

Answer 6

fallopian tube

Question 7

What hormone is secreted after implantation of the fertilized egg?

Answer 7

human chorionic gonadotropin (hCG)

Question 8

What is the role of hCG?

Answer 8

stimulates corpus luteum to remain viable and continue secreting progesterone (pregnancy tests detect this hormone)

Question 9

During what phase of the menstrual cycle is estrogen the highest?

Answer 9

follicular phase, because the follicle secretes estrogen

Question 10

During what phase of the menstrual cycle is progesterone the highest?

Answer 10

luteal phase, because the corpus luteum secretes estrogen + progesterone

Question 11

Describe the hormonal regulation during the menstrual cycle

Answer 11

-day 1-12: dominant follicle secretes high levels of estrogen- rapidly increasing its concentration= estrogen stimulates endometrial proliferation
-day 12: a brief positive feedback occurs from estrogen stimulating release of LH and FSH
-40h after the LH and FSH surge: follicle ruptures and ovulation occurs
-day 15-28: corpus luteum secretes progesterone and estrogen- progesterone induces endometrium to transition to secretory phase (protein synthesis, increase blood flow) to prepare for embryo transplantation

Question 12

What is the composition of menstrual flow?

Answer 12

approx. 30mL- 3/4 arterial blood, tissue debris, prostaglandins, fibrinolysin

Question 13

What is the dominant estrogen found naturally in females?

Answer 13

E2: estradiol

Question 14

How is estradiol made naturally in the female body?

Answer 14

mostly made by ovary follicular phase by follicles or in the luteal phase by corpus luteum

Question 15

What is the role of thecal cells?

Answer 15

LH receptor activation stimulates enzymes to convert cholesterol to androgens

Question 16

What is the role of granulosa cells?

Answer 16

FSH receptor activation stimulates aromatase activity which converts androgens to estrogens

Question 17

What are the physiological effects of ESTROGEN?

Answer 17

-breast development
-maturation of ovaries
-endometrial proliferation
-peripubertal growth spurt and long bone growth cessation
-preserve bone density- prevents osteoporosis
- feedback regulation on hypothalamic and pituitary neuroendocrine cells
-protective effects on neurons
-increase hepatic production of proteins and cholesterol
-increase HDL, decrease LDL
-enhanced blood coagulation

Question 18

What are the physiological effects of PROGESTERONE?

Answer 18

-maturation of secretory changes of endometrium
-induces changes in cervical mucus
-increase body temperature mid-cycle
-CRUCIAL for maintaining pregnancy
-development of mammary glands (+ estrogen)
-increases insulin resistance during pregnancy contributing to gestational diabetes