Repro Flashcards
What is the age of onset of puberty in girls?
9-13
Starts with growth spurt and breast growth
Menarche starts at 13
What is the age of onset of puberty in boys?
10-14
Starts with growth spurt and increased testicular volume
What initiates puberty?
Pulsatile release of GnRH from the hypothalamus
This stimulates release of LH and FSH from the anterior pituitary
This stimulates release of androgens and oestrogen
What stimulates Leydig cells in the testes and what do they produce?
LH stimulates Leydig cells to produce testosterone
Production remains constant
What stimulates Sertoli cells and what do they produce?
Stimulated by testosterone (from Leydig cells)
Site of spermatogenesis
Also secretes inhibin for -ve feedback on anterior pituitary, reduce FSH
Located in seminiferous tubule
What cells in the ovaries respond to FSH?
Ovarian granulosa cells
Stimulates production of oestrogen production
What cells in the ovaries respond to LH?
Theca interna cells
Stimulates production of progesterone
What is the effect of different levels of oestrogen on GnRH?
Low levels - negative feedback on GnRH
High levels - positive feedback on GnRH, causes LH surge
What is the effect of progesterone?
Increases inhibitory effect of oestrogen
Prevents +ve feedback, so no LH surge
Prevents further ovulation
Where is inhibin produced in the ovary? And what is its effect?
Released from granulosa cells of corpus luteum
Inhibits secretion of FSH => only one egg develops
Also has a small inhibitory effect on LH
What are the stages of the ovarian cycle?
Follicular phase
Ovulation
Luteal phase
What occurs in the follicular phase?
Increasing FSH; Causes follicular development Theca interna and externa now appears Follicle now able to secrete oestrogen Inhibin starts to be secreted, inhibits FSH
Increasing oestrogen;
Rise causes positive feedback on LH
Causes LH surge => progesterone production
What occurs in ovulation?
Meiosis I completes
Meiosis II starts
Mature oocyte extruded through capsule of ovary
What occurs in the luteal phase?
Granulosa and theca cells become the corpus luteum which secrets oestrogen and progesterone
Progesterone counteracts the +ve feedback of oestrogen => reduced LH
FSH inhibited by inhibin
If fertilisation doesn’t occur, corpus luteum becomes the corpus albicans
What are the stages of the uterine cycle?
Proliferative phase
Secretory phase
What occurs in the proliferative phase?
Proliferation and thickening of the endometrium in response to oestrogen - functional layer doubles in size
Glands within the endometrium become coiled
What occurs in the secretory phase?
The glands become secretory due to progesterone
Glands lose their structure after hormones begin to fall
If implantation doesn’t occur then the functional layer is shed
What is the function of GnRH?
Released in pulses by the hypothalamus
Stimulates LH and FSH
Can become desensitised with constant exposure - given in endometriosis
What is the function of FSH?
Stimulates follicle development at the start of the cycle
Sustains development of a gamete
What is the function of LH?
Responsible for ovulation - LH surge
What is the function of inhibin?
Inhibits FSH
Produced by follicles
What is the function of oestrogen?
Promotes fertilisation
Proliferation of endometrium and myometrium
Fallopian tubes motility
Production of thick, alkaline cervical mucus
What is the function of progesterone?
Sustains a viable pregnancy
Secretory function of the endometrium
Reduced motility of myometrium
Production of thick, acidic cervical mucus - prevents further entry of sperm
What methods are used in contraception?
Blocks transport of sperm
Disrupts HPG axis
Inhibits implantation of conceptus
