Session 4- The Menstrual Cycle

Question 1

How does the hypothalamus-pituitary-gonadal axis differ in males and females

Answer 1

Males

• continuous gamete production required
• levels of hormones are maintained at a steady state

Females

• periodic gamete production
• tract needs to prepare for implantation
• waiting phase in case implantation occurs
• cyclical hormone changes

Question 2

Average length of mentrual cycle

Answer 2

28 days

Question 3

What is the purpose o the ovarian cycle

Answer 3

Preparation of the gamete for release

Question 4

What are the two phases of ovarian cycle

Answer 4

Follicular phase- early and late

Luteal phase

Question 5

Ovarian cycle- early follicular phase - 0-5

Answer 5

No ovarian hormone production
Granulosa cells secrete activin- stimulates FSH ONLY
-increased FSH production and receptors on granulosa cells
-reduced production of androgens by theca cells- less oestrogen

THIS STIMULATES FOLLICLE GROWTH

Question 6

Outcome of early follicular phase

Answer 6

Stimulate follicle growth
Theca interna appears
Enhanced aromatase function-> folllicle now capable of enhanced oestrigen production

Dominant follicle granulosa cells switch to produce inhibin which cause FSH to decrease which allows LH to increase

Question 7

Late follicular phase

Answer 7

Days 5-14
Dominant follicle granulosa cell produce oestrogen and inhibin

Oestrogen

• increase FSH receptors on follicle
• LH receptors on granulosa cells- prep for ovulation

Inhibin
-decrease FSH production and help LH to increase theca cell androgen production

Question 8

Ovulatory phase

Answer 8

Day 14

Oestrogen continues to rise independently of FSH

High levels of oestrogen exert positive feedback on hypothalamus and ant pituitary which causes a surge in LH production

Ovulation occur

Question 9

Ovulation

Answer 9

Meiosis 1 completes
Meiosis 2 begun but not completed yet

Mature oocyte travels through the capsule of the ovary not the Fallopian tube

Question 10

Luteal phase

Answer 10

Follicle is luteinised -Corpus luteum
Secrets oestrogen and progesterone in large quantiles
Inhibin also secreted so another follicle doesnt develop

Oestrogen and progesterone exert negative feedback on LH
FSH levels remain low

Question 11

What hormone causes proliferative epithelium to develop

Answer 11

Oestrogen

Question 12

What hormone causes secretory epithelium to develop

Answer 12

Progesterone and oestrogen

Question 13

What layers is the uterus mae up of

Answer 13

Endometrium- stroma and epithelium

Myometrium

Perimetrium

Question 14

What layers is the endometrium made up of

Answer 14

Functional layer- responsive to hormone shed in menstruation

Basal layer- develops into new functional layer

Question 15

Early proliferative phase of uterine cycle

Answer 15

Sparse glands, straight

Question 16

Late proliferative stage of uterine cycle

Answer 16

Thicker functional layer, glands coiled

Question 17

Secretory phase of uterine cycle

Answer 17

Endometrial thickness of maximum very coiled glands

Coiled arterioles

Question 18

What happens at the end of menstrual cycle if no fertilisation

Answer 18

Corpus luteum -> corpus albicans if no fertilisation

Dramatic fall in oestrogen, progesterone and inhibin as corpus luteum is gone

No negative feedback so sow rising FSH

Question 19

End of menstrual cycle- if fertilisation occurs

Answer 19

Syncytiotrophoblast produces hCG

Extends lifespan of corpus luteum-> before placenta forms

Question 20

What is teh normal duration of teh cycle

Answer 20

21 - 35 days

Variegation is due to length of follicular phase

Question 21

When is oestrogen mostly used

Answer 21

Follicular phase
-Thickening of endometrium Fallopian tube function Growth and motility of myometrium
Thin alkaline cervical mucus Vaginal changes Changes in Skin, hair, metabolism

Question 22

When is progesterone mostly used

Answer 22

Luteal phase
-Further thickening of endometrium (secretory)
Thickening of myometrium and reduction of motility
Thick, acidic cervical mucus Development of breast tissue Increased body temperature Metabolic changes Electrolyte changes

Question 23

what triggers ovulation

Answer 23

LH

LH surge