Normal Menstrual Cycle

Question 1

What are the four hormones involved in the menstrual cycle?

Answer 1

Follicle stimulating hormone
Luteinising hormone
Oestrogen
Progesterone

Question 2

What are the phases of the menstrual cycle in the ovary?

Answer 2

Follicular phase
Ovulatory phase
Luteal phase

Question 3

What is the normal length of a cycle?

Answer 3

~21 - 28 days - can be shorter or longer

Question 4

If the cycle is shorter or longer, which phase stays constant and which phase changes?

Answer 4

The follicular phase changes in duration

Luteal phase is always 14days

Question 5

What does the hypothalamus secrete?

Answer 5

Gonadotrophin releasing hormone GRH

Question 6

What does the GRH act on?

Answer 6

The anterior pituitary gland

Question 7

What does the anterior pituitary gland release?

Answer 7

Follicule stimulating hormone

Luteinising hormone

Question 8

What is the role of the FSH?

Answer 8

Acts on the ovaries and stimulates the development of follicles

Question 9

What is the role of LH?

Answer 9

Causes ovulation

Question 10

What happens in the follicular phase?

Answer 10

FSH stimulates the development of 15-20 follicles in the ovary
The surrounding granulosa cells secrete increasing oestrogen

Question 11

What is the role of oestrogen?

Answer 11

Oestrogen = steroid sex hormone
Development of secondary sex characteristics e.g. breast tissue & genital development
Influences the endometrium to proliferate - causing increase in capillary formation (proliferative phase of the menstrual cycle)
Causes thinning of the cervical mucous for sperm to fertilise the egg easily
Rise in oestrogen suppresses FSH and LH in the negative feedback loop

Question 12

When does ovulation happen?

Answer 12

Day 14 in a 28 day cycle

Question 13

What happens in the luteal phase?

Answer 13

After ovulation, the follicle that release the ovum collapses to form the corpus luteum

Question 14

What is the purpose of the corpus luteum?

Answer 14

It secretes high levels of progesterone which maintain the endometrial lining

Question 15

What is the role of progesterone?

Answer 15

Thickens and maintains the endometrium
Thickens the cervical mucus to become less penetrable
Causes a slight increase in body temp

Question 16

What else does the corpus luteum secrete?

Answer 16

Small amounts of oestrogen

Question 17

What happens if the egg is fertilised?

Answer 17

The synctiotrophoblast of the embryo releases human chorionic gonadtrophin (HCG)
The placenta takes over production of progesterone from 5-10 weeks

Question 18

What is the role of the HCG?

Answer 18

It keeps the corpus luteum alive

Pregnancy tests check for the levels of HCG

Question 19

What happens if the egg is not fertilised?

Answer 19

No HCG is released

The CL degenerates and stops producing oestrogen and progesterone

Question 20

Why does menstruation occur?

Answer 20

Due to the fall in oestrogen and progesterone when the CL degenerates causing the endometrium to break down

Question 21

What do stromal cells of the endometrium release and what does this do?

Answer 21

They release prostaglandins

Prostaglandins encourage the endometrium to break down and the uterus to contract

Question 22

When does menstruation start?

Answer 22

Day 1 of the menstrual cycle

Question 23

What happens to the levels of FSH and LH?

Answer 23

The cycle restarts –> The drop in oestrogen and progesterone removes the negative feedback loop to the hypothalamus and FSH and LH will rise again

Question 24

Which layers of the endometrium are involved in menstruation?

Answer 24

The superficial and middle layers - the functionalis layer - separates from the lower one third of the endometrium - the basalis layer

Question 25

What are the endometrial phases of the menstrual cycle?

Answer 25

Menstrual phase
Proliferative phase
Secretory phase