Physiology - Lassies

Question 1

List the major female reproductive hormones?

Answer 1

Gonadotrophin releasing hormone (GnRH)

Gonadotrophins - FSH & LH

Steroid hormones - Estrogen, progesterone & Testosterone

Question 2

Trace the Hypothalamo-Pituitary-Ovarian Axis (HPO)

Answer 2

Hypothalamus produces GnRH

GnRH act on Pituitary –> FSH & LH

FSH & LH act on ovaries –> Ova & Oestrogen/progesterone

Question 3

Describe the normal feedback effect of the HPO axis?

Answer 3

Oestrogen and progesterone normally have a -ve feedback effect on the Hypothalamus & Ant Pit

Question 4

When & how does the feedback effect of the HPO axis change?

Answer 4

Roughly day 12-14 of the menstrual cycle.

Oestrogen reaches a peak level that flips it from -ve to +ve feedback resulting in a surge of Gonadotrophins (mainly LH)
–> LH surge leads to Ovulation

Question 5

What do we call the phases of the ovarian cycle?

Answer 5

Follicular stage

Luteal phase

The switch happens at ovulation

Question 6

What occurs during the follicular phase of the ovarian cycle?

Answer 6

FSH & LH initiate the growth of new follicles

Primary Oocyte –> Developing follicle –> mature graafian follicle

Question 7

What occurs during the Luteal phase of the ovarian cycle?

Answer 7

The now empty follicle forms a corpus luteum that then degenerates to scar tissue known as a corpus albicans

FSH & LH fall

Question 8

What are the phases of the menstrual cycle?

Answer 8

Menstrual Phase (0-4 days)
Proliferative Phase (4-14 days) - Then ovulation
Secretory Phase (14-26 days)
Premenstrual phase (26-28 days)

Question 9

.What type of hormone are oestrogen and progesterone?

Answer 9

Steroid Hormones

Question 10

Describe how the gonadotrophins change over the course of the month?

Answer 10

They rise a bit then remain fairly steady throughout Follicular phase then spike at ovulation before falling away again during the luteal phase

Question 11

Describe how ovarian hormones change throughout the month?

Answer 11

Oestrogen & PRogesterone start very low.

Oestrogen rises during the follicular phase and peaks at ovulation before falling away again near the end of the luteal phase

Progesterone starts to rise after ovulation, peaking & overtaking oestrogen in the middle of the luteal phase and falling away again before the start of the next follicular phase

Question 12

Describe how the endometrial wall changes throughout the month?

Answer 12

Starts thick
Sheds during the menstrual phase (aka 0-4days aka start of follicular phase)

Thickens during the proliferative stage from 4-14 days

After ovulation the secretory phase starts at which point glands develop (14-26 days)

Premenstrual phases features high vascularisation (26-28 days)

Question 13

Describe the process of Oogenesis BEFORE BIRTH

Answer 13

Oogonium (Stem cell) undergo mitosis to form Primary Oocytes.

These undergo Meiosis but pause in the prophase

Question 14

Describe the process of Oogenesis after Menarche?

Answer 14

Every month 1 Primary Oocyte completes meiosis to form a 2nd* Oocyte & a polar body.

Secondary oocyte is releasd in ovulation

Question 15

Describe the process of Oogenesis after fertilization?

Answer 15

The secondary oocyte that was released in ovulation is fertilized with sperm

Only then does it undergo meiosis II to form a mature Ovum & polar body

Question 16

What is the purpose of the menstrual cycle?

Answer 16

To prepare the endometrium for pregnancy
Should no fertilization occur the menstrual phase happens, clearing the way for the next cycle

Question 17

How does follicle number decline with age?

Answer 17

Roughly 1,000,000 at birth
~half that at 18
~Down to 100,000 by 30

Considered non-fertile by 41 when egg number hits ~10,000

Irregular cycles start from around 45

Menopause occurs at roughly 50

Theses are rough numbers and don’t matter specifically, just important to understand how ovarian reserve changes with age