Hormonal Regulation of Menstrual Cycle

Question 1

Menstrual Cycle:

Answer 1

: Recurring cycle of events in uterus and ovaries under the influence of hormones in females (Menstruus means “monthly”)

Question 2

Anatomy of Ovaries

Answer 2

Question 3

Ovarian Follicles

Answer 3

Ovaries are made of many sac like structures called ovarian follicles

Ovarian follicles contain oocyte and cells that produce oestrogen and progesterone

Thecal cells and granulosa cells produce oestrogen and progesterone when stimulated with FSH and LH

Question 4

Development of Ovarian Follicles

Answer 4

Question 5

Stages of Oogenesis

Answer 5

Question 6

Overview of Menstrual Cycle

Answer 6

Question 7

Early Follicular Phase (pre-ovulation)

Answer 7

Question 8

Negative Feedback

Answer 8

Question 9

Late Follicular Phase (just before ovulation)

Answer 9

Question 10

Late Follicular Phase (just before ovulation)

Answer 10

Question 11

LH Surge

Answer 11

Re-starts meiosis in the oocyte…which becomes haploid

Activates enzymes - dissolve follicle wall and promote vascular leakage so that antrum swells and bulges

Follicle ruptures

OVULATION

Oestrogen production dives

Question 12

Ovarian Cycle and Corpus Luteum

Answer 12

Question 13

Luteal Phase (after ovulation)

Answer 13

Question 14

The Corpus Luteum (CL)

Answer 14

If fertilization does NOT occur:
CL degenerates spontaneously
Progesterone falls
Uterus loses its endocrine support
Menstruation
FSH & LH get to work again on the follicles
If fertilization DOES occur:
CL maintained by hCG from the chorion
Becomes the Corpus Luteum of Pregnancy
Maintains uterine lining until placenta takes over as main producer of progesterone at 3 months

Question 15

Mechanism of action of the combined contraceptive pill

Answer 15

Low dose of oestrogen
↓ FSH from Anterior Pituitary
↓ development of follicle
No ovulation

Progestogens:
Makes cervical mucus sperm-unfriendly
↓ LH from Anterior Pituitary
↓ GnRH from hypothalamus
↓ motility of fallopian tube

Question 16

Progestogen-only pill

Answer 16

Low dose progestogen taken continuously (e.g. either norethisterone or levonorgestrel);
Makes cervical mucus inhospitable to sperm;
Hinders implantation; through its effect on the endometrium and on the motility and secretions of the fallopian tubes;
Menstruation often ceases initially but usually returns with prolonged use;
Main adverse effects: Breakthrough bleeding and irregular menses.

Question 17

Answer 17

Oestrogen prepares the way:
promotes growth of endometrium & myometrium
promotes formation of progesterone receptors

Question 18

Answer 18

Progesterone acts on the oestrogen-primed endometrium..
Loosens and softens connective tissue - makes implantation easier
Promotes secretion of nutrients (glycogen)
Quietens uterine activity

Question 19

Answer 19

No occupants..(no embryo) no hCG so Corpus Luteum degenerates
Progesterone (and oestrogen) support lost
Uterine prostaglandins → vasoconstriction → tissue death
Blood and endometrial debris (menses) lost through vagina

Question 20

Menstrual Disorders

Answer 20

Dysmenorrhea – painful periods
Menorrhagia – heavy or prolonged periods
Amenorrhea – Absence of periods (primary or secondary)
Oligomenorrhea – light periods