Sequence of follicle formation
- primordial follicle
- primary follicle
- secondary follicle
- graafian follicle
- ovulation
what are the stages of the menstrual cycle?
- follicular phase
- ovulation
- luteal phase
The follicular phase
- This phase begins on the first day of bleeding.
- LH levels rise steadily
- FSH levels also rise
- LH and FHS stimulate follicle growth
- low oestrogen
- as follicle grows it secretes oestrogen
- LH surge which triggers ovulation
draw the menstual cycle diagram
4 hormones
Follicular phase pre ovulation
a) which hormone is secreted from the hypothalamus? and its action
b) which hormones are secreted from the anterior pituitary and what are their action?
c) as the follicle is developing what does it secrete and what does this do?
a) GnRH, positive feedback to the A.pit and causes FSH and LH to be secreted.
b) LH and FSH, cause the follicle to develop
c) inhibin, and v. low oestrogen, these have negative feedback on the A.pit and low oestrogen on the hypothalamus.
The late follicular phase
a) as the follicle develops into a mature follicle and produces more oestrogen what does this cause?
b) what is positive feedback?
c) what does oestrogen do?
d) what does the LH surge trigger?
a) positive feedback from the high oestrogen levels causes a LH surge
b) when a signal causes something to move further and further away from the normal
c) causes the endometrium to thicken
d) ovulation
Luteal phase
What does the hypothalamus secrete? and what does the A.pit secrete?
Hypo=GnRH
A.pit=LH and FSH
What does the corpus lute produce?
moderate oestrogen wich positive feedback to the hypo and A.pit
high progesterone levels which negative feedback to the hypo and A.pit… negative feed back dominates
What does the progesterone produced by the CL do?
Keeps the LH and FSH down
what happens if there is no pregnancy?
- CL degenerates and stops producing progesterone
- FSH and LH are no longer inhibited and so a new cycle starts
- menstruation occurs
What happened if fertilisation occurs?
- CL maintained by the hCG produced by the chorion … becomes the CL of pregnancy
- hCG maintains the utrine lining until the placenta takes over as main producer of progesterone at 3 months
what does the placenta take over maintaining the lining of the uterus by producing progesterone?
3 months
