Endocrine regulation of Female Reproductive tract

Question 1

what are the different phases of the menstrual cycle, in order

Answer 1

follicular(proliferative) phase, ovulation and luteal(secretory) phase

Question 2

how long does the follicular and luteal phases last

Answer 2

follicular = variable, usually 14 days, +/- 7days
luteal = more constant, 14 days
(around 28days total)

Question 3

describe what happens at the start of the menstrual cycle

Answer 3

FSH stimulates growth of ovarian follicles, associated with increase in oestrogen levels
(follicular phase)

Question 4

describe what happens as a result of the initial rising oestrogen levels in the follicular phase

Answer 4

exert negative feedback on hypothalamus/pituitary, temporarily lowering FSH levels

Question 5

describe what happens when oestrogen levels reach a certain conc. threshold in the follicular phase

Answer 5

exerts positive feedback regulation resulting in an increase in FSH levels and the LH ‘surge’

Question 6

what does the LH surge lead to and what does it regulate

Answer 6

leads to ovulation and regulates formation of corpus luteum and progesterone production and secretion

Question 7

what effect does increased progesterone in the luteal phase have

Answer 7

decreases LH secretion by influencing GnRH pulsatility

Question 8

what does a follicle consist of

Answer 8

an oocyte surrounded by follicular cells(granulosa and theca cells)

Question 9

what does follicular growth involve

Answer 9

increase in number of follicular cells(not oocytes), and accumulation of follicular fluid both resulting in increased diameter and overall size of follicle
(oocyte remains dormant)

Question 10

what effect does oestrogen and progesterone have on the endometrium

Answer 10

endometrium thickens due to oestrogen

endometrium becomes secretory tissue due to progesterone

Question 11

although onset of ovulation is variable between women and from one cycle to another, describe how timing of ovulation can be predicted

Answer 11

can be predicted with reasonable accuracy with LH surge, the surge precedes ovulation by 34-36 hours

Question 12

what is the threshold of oestrogen required for ovulation to occur

Answer 12

200pg/ml, needed for increased GnRH pulsatility and LH surge, therefore ovulation

Question 13

describe how LH stimulates increase in progesterone production by the corpus luteum

Answer 13

LH stimulates angiogenesis(ensures efficient delivery of cholesterol for progesterone synthesis), also stimulates enzymes in conversion of cholesterol to progesterone

Question 14

what happens to granulosa and theca cells in the luteal phase

Answer 14

transform to luteal cells as part of the corpus luteum

Question 15

what are the recognised functions of oestrogens

Answer 15

increase thickness of vaginal wall, regulate LH surge, reduce vaginal pH by increasing lactic acid production, decrease viscosity of cervical mucous to facilitate sperm penetration

Question 16

what are the recognised function of progesterone’s

Answer 16

maintain endometrium thickness, responsible for infertile thick mucus, relaxes the myometrium, functional progesterone withdrawal thought to regulate birth

Question 17

what is the sperms ability to penetrate the cervical mucus regulated by

Answer 17

thickness of mucus, motility of sperm, interaction with reactive oxygen species, interaction with mucins