Follicles

Question 1

what do germ cells make indifferent supporting cells do

Answer 1

form granulosa cells, which surround the oocyte to form a follicle

Question 2

primordial follicle

Answer 2

• oocyte surrounded by single layer of flattened epthelial cells
• inactive, non-growing
• stimulation to grow is independent of gonadotropin stimulation

Question 3

primary follicle

Answer 3

• precursor granulosa cells become cuboidal
• commence mitosis
• formation of zona pellucida begins
• gap junctions between oocyte and granulosa cells
• still independent of FSH action

Question 4

secondary follicle

Answer 4

• more layers are added
• migration of another cell to the outside of the follicle
• form a fibroblast layer around the follicle (precursor to theca interna and externa)
• formation of network of capillaries
• LH receptors
• can occur in the absence of gonadotropins, but connection to systemic vasculature signals the onset of gonadotropin depenence

Question 5

antral/tertiary follicle

Answer 5

• pools of follicular fluid –> coalesce to form antrum
• rodents: transition from secondary to tertiary is FSH dependent
• larger animals: transition is FSH responsive but not dependent

Question 6

is growth of follicles through antral stage FSH dependent or independent

Answer 6

dependent –> inadequate FSH leads to atresia

Question 7

3 populations of cells in granulosa layer of antral follicles

Answer 7

• mural granulosa cells (steroids)
• antral granulosa cells (line cavity)
• cumulus cells (surround oocyte)

Question 8

graadian follicles

Answer 8

large, mature, tertiary follicles

Question 9

stages of follicular growth (3)

Answer 9

• preantral
• tonic
• exponential

Question 10

-preantral growth phase

Answer 10

• entry of the primordial follicle into growing pool until it is a secondary fillicle
• FSH independent
• slow

Question 11

tonic growth phase

Answer 11

• secondary follicle to a small antral (tertiary) follicle

- FSH responsive in larger species

Question 12

exponential growth phase

Answer 12

• sub-population of follicles (cohort) are recruited and enter this phase
• result in a large, dominant follicle
• FSH dependent until near the end

Question 13

follicle dominance

Answer 13

• actions of FSH are amplified by estrogen and IGF-1
• dominant follicle becomes independent of systemic (hormonal) environment
• estradoil/inhibin reduce FSH levels
• follicle can use LH in place of FSH

Question 14

when are follicles vulnerable to atresia

Answer 14

at all stages of formation

Question 15

what does follicular atresia first affect

Answer 15

granulosa cells –> without their support, oocyte dies

Question 16

patterns of antral follicle development

Answer 16

• cohort of small antral follicles is recruited and grows rapidly
• selection is applied, some follicles undergo atresia
• dominant follicle(s) arise

Question 17

dominant follicle development and LH

Answer 17

• if it develops at a time when it can trigger an LH surge, it will ovulate
• if it becomes dominant when there is still an active CL, it can’t trigger LH surge –> atresia
• allows increase in FSH and another cohort to develop

Question 18

3 stages of dominant anovulatory follicular development

Answer 18

• active growing phase
• static phase
• regressing phase

Question 19

ovulation

Answer 19

• gonadotropin surge starts cascade
• may be spontaneous or induced
• the result of an inflammatory cascade that weakens the follicular wall
• egg and cumulus oophorus are usually expelled within 2 minutes of follicular rupture

Question 20

induced ovulation

Answer 20

• LH surge caused by neuroendocrine reflex activated by mating
• sensory receptors or fields must be activated
• may need several matings
• causes GnRH release –> triggers LH release
• female needs to be estrogen dominanted