Oogenesis

Question 1

How do primordial follicles form from primordial germ cells?

Answer 1

PGCs undergo mitosis and then germ cell cysts form

These are then broken down and primordial follicles are formed

Question 2

What shape are the granulosa cells in the resting phase and active phase of oogenesis?

Answer 2

Flat in resting phase
Become cuboidal when activation happens

Question 3

What changes occur in the progress of a primary follicle to secondary follicle?

Answer 3

Increased diameter
Cytodifferentiation phase occurs
Production and secretion of glycoproteins to form Zona Pellucida
Granulosa-oocyte interaction through gap junctions

Question 4

What changes occur in the progress of a preantral follicle to antral follicle?

Answer 4

Granulosa cells continue to proliferate and cavities filled with follicular fluid appear - eventually coalescing to form a single follicular antrum

Nuclear DNA becomes less active and starts to compact

Follicle is responsive to FSH and LH at this stage

Question 5

How is the dominant follicle selected?

Answer 5

The dominant follicle as a high rate of mitosis in the granulosa cells

It is more fit to cope with declining FSH levels and is the only follicle that has managed to have an LH receptor

Question 6

What happens to all other follicles that aren’t the dominant one?

Answer 6

Atresia

Question 7

Meiosis in oocytes will only be completed when?

Answer 7

If the oocyte is fertilised

Question 8

GnRH is released in a pulsatile/constant manner in males/females?

Answer 8

Pulsatile in females
Constant in males

Question 9

High frequency of GnRH release results in secretion of what hormone?

Answer 9

LH

Question 10

Low frequency of GnRH release results in secretion of what hormone?

Answer 10

FSH

Question 11

Concentration of which hormone above a threshold will increase GnRH secretion?

Answer 11

Oestrogen

Question 12

Increased concentration of which hormone will reduce the frequency of GnRH pulses?

Answer 12

Progesterone

Question 13

What happens at the LH surge?

Answer 13

Ovulation
Maturation of granulosa and theca cells into luteal cells and final maturation of the oocyte

Granulosa and theca cells switch hormone production from oestrogen to progesterone

Question 14

What is the corpus luteum?

Answer 14

An endocrine gland within the ovary which forms from the follicle wall after ovulation

Question 15

Function of corpus luteum?

Answer 15

Secretes progesterone

Question 16

What happens to corpus luteum if the oocyte is not fertilised?

Answer 16

Degrades after approx. 14 days and becomes the corpus albicans

Question 17

What happens to the corpus luteum if fertilisation and implantation occurs?

Answer 17

Continues to secrete progesterone until the implanted trophoblasts (placenta) takes over at around 12 weeks gestation