Female Reproductive Endocrinology Flashcards
What is the function of luteinising hormone?
Supports theca cells
LH surge triggers ovulation
What is the function of follicle stimulating hormone?
Initiates recruitment of follicles
Supports growth of follicles, especially the granulosa cells
What is the function of the theca cells?
They produce the oestrogen precursor androtenedione.
What is the function of the granulosa cells?
They convert androtenedione to oestrogen with aromatase
What happens to the concentration of oestrogen as the follicles develop?
It increases, because there are more theca interna cells and more granulosa cells.
What is a primordial follicle?
An oocyte surrounded by pre-granulosa cells, covered in a thin basal lamina
Stimulated by FSH
What is a primary follicle?
Once a primordial follicle has been acted on by FSH, it becomes a primary follicle.
Is surrounded by a single layer of granulosa cells
Cells begin to secrete oestrogen rich fluid into the antrum
Briefly describe the hypothalamic-pituitary-ovarian axis.
The hypothalamus secretes GnRH
GnRH stimulates the anterior pituitary to release FSH and LH
The ovary reacts to these hormones and secretes sex hormones
What is a secondary follicle?
The theca develops and the follicle gains an independent blood supply
Theca externa forms a fibrous capsule around the follicle
Granulosa cells develop FSH, androgen and oestrogen receptors to allow faster growth
Cumulus cells attach the oocyte to the follicle wall, covering the mature ovum
Describe the effect of oestrogen on the pituitary during most of the follicular phase.
It has a negative feedback effect on the secretion (not the synthesis) of the LH and FSH molecules.
What happens to oestrogenic effect on the pituitary around 36 hours before ovulation?
It switches to positive feedback, and all the built up LH is released (and FSH)
This enormous surge causes ovulation
What happens to the levels of oestrogen and progesterone after ovulation?
Oestrodiol peaks and then starts to decrease
Progesterone levels start to increase
How does LH cause ovulation?
Stimulates enzymes that initiate breakdown of the follicular wall and release a mature oocyte.
Triggers the first meiotic division of the oocyte
What effects does oestrogen have on the endometrium (normally during the follicular/proliferative stage)?
Stimulates stratum basalis to proliferate and for a new functional layer
Elongates the uterine glands
Grows spiral arteries
Stimulates watery cervical mucus that helps sperm cross the cervix
What effects does progesterone have on the endometrium? (Normally during the luteal/secretory phase)
Glands became more tortuous
Excess of secretory substances accumulate in the glandular epithelium
Cytoplasms of secretory cells increase in lipid and glycogen deposits
Spiral arteries increase further and become very tort
