folliculogenesis

what is folliculogenesis

the process by which ovarian follicles develop from primordial follicles into mature follicles capable of ovulation

where does folliculogenesis occur

within the ovary and involves coordinated changes in the oocyte and surrounding somatic cells

what is folliculogenesis regulated by

both intra-ovarian factors and hormones from the hypothalamic-pituitary-ovarian axis and is essential for female fertility

how does folliculogenesis begin

with primordial follicles which are present in the ovary from foetal life

what does each primordial follicle consist of

a primary oocyte arrested in prophase I of meiosis surrounded by a single layer of squamous granulosa cells.

what happens to the primordial follicles

remain in a resting state until they are recruited into the growing pool majority do not develop further any further and undergo atresia

what is the first stage of follicular development

the transformation of a primordial follicle into a primary follicle.

what happens during the first stage

the granulosa cells change from squamous to cuboidal and the oocyte increases in size and a glycoprotein layer called the zona pellucida begins to form around it .

what is the second step

as development continues the follicle becomes a secondary follicle

what happens during secondary follicle formation

Granulosa cells form multiple layers surrounding oocyte, stromal cells differentiate into theca layers (separated from granulosa cells by basement membrane), distinct zona pellucida and oocyte bigger

what is the third stage

formation of the tertiary follicle.

what is the formation of the tertiary follicle characterised by

the appearance of a fluid-filled cavity - antrum.

Distinct zona pellucida surrounded by corona radiata granulosa cells

Corona radiata projects into antrum on a stalk of granulosa cells, the cumulus oophorus

Remainder of granulosa cell are mural granulosa cells forming folliclular wall

Theca has theca interna and theca externa

layers

what does the theca interna do

involved in hormones synthesis of androgens

what does the theca externa do

provides structural support

what do the granulosa cell do

convert androgens produced by the theca cells into oestrogen, contributing to rising oestrogen levels during the menstrual cycle.

what happens to the follicles

During each menstrual cycle, several follicles begin to develop, but usually only one becomes the dominant follicle.

what is special about the dominant follicle

has a greater sensitivity to follicle-stimulating hormone and is able to continue developing even as FSH levels decline.

what happens to remaining follicles

undergo astresia

what does the dominant follicle develop into

a mature graafian follicle

what is characteristic of a graafian follicle

large antrum and fully developed oocyte surrounded by corona radiata

what happens after the graafian follicle develops

a surge in LH triggers ovulation and causes the follicle to rupture and release the secondary oocyte into the fallopian tube

what stage is a secondary oocyte in

completed meiosis I and is arrested in metaphase II

what is atresia

the process by which follicles degenerate and are reabsorbed

what does atresisa ensure

only the most viable follicles proceed to ovulation.

what does FSH pomote

granulosa cell proliferation and follicular growth

what does LH promote

androgen production by the theca cells.

what is done with the androgens

converted into oestrogen by granulosa cells, creating a feedback system that regulates follicular development. This hormonal coordination is essential for normal ovulation and fertility.