Lec: 11 Dr.Sajida
Reproduction and hormonal function in female
Anatomy
The female reproductive organs include the ovaries, fallopian tubes and
the uterus. During reproductive years (13-50 Years) about 450 follicles
developed and expel their ova once each month.
Gonadotropic hormones and their effect on ovaries:
The ovarian changes during the female sexual cycle depend completely
on the hormones FSH and LH secreted by the anterior pituitary.
The ovaries that are not stimulated by these hormones remain inactive,
that’s what occurs in childhood when no FSH and LH secreted. At ages
of 9-10 years the anterior pituitary begin to secrete FSH and LH which
results in female sexual cycle between age of 11-16 years. This period is
called puberty and the first menstrual cycle is called menarche. During
fetal life, the ovaries are stimulated by hCG from the placenta but after
birth the stimulation is lost.
Both FSH and LH are glycoproteins, during each month the is a cyclical
increase or decrease of both FSH and LH, FSH and LH stimulate their
ovarian target cells by combination with highly specific FSH and LH
receptors in the cell membrane, the activated receptors in turn increase
the rate of secretion of these cells and their growth and their proliferation.
Ovarian cycle (Menstrual cycle):
The normal reproductive years in female is characterized by monthly
changes in rate of secretion of female hormones, in the ovaries and sexual
organs. The duration of menstrual cycle average 28 days but maybe as
short as 20 days or as long as 45 days. As a result of this cycle, only one
mature ovum is released from the ovaries each month, the uterine
endometrium is prepared for implantation of the fertilized ovum.
Note: The absence of the cycle is called amenorrhea:
1- Primary amenorrhea: no cycle at the age of puberty.
2- Secondary amenorrhea: physiologically like in pregnancy or
pathologically.
Note (2): the ovarian cycle consist of follicular phase and luteal phase.
Follicular phase (development of ovarian follicle):
At childhood, the primordial follicle consists of an ovum surrounded by
single layer of granulose cells, and it is believed that it secrete an oocyte
maturation inhibitory factor that keeps the ovum in primordial state.
After puberty, when large quantities of LH and FSH secreted, the ovaries
and the follicles begin to grow so moderate enlargement of the ovum and
additional layer of granulosa cells formed.
Function of granulosa cells:
1- Nourish oocyte.
2- Secrete chemical messengers that influence the oocyte and the
thecal cells.
3- Secrete antral fluid.
4- Are the sites of action for estrogen and FSH in the control of
follicle development during early and middle follicular phases.
5- Express aromatase, which converts androgen (from theca cells) to
estrogen.
6- Secrete inhibin, which inhibits FSH secretion via an action on the
pituitary.
7- Are the site of action of LH induction of changes in the oocyte and
follicle culminating in ovulation and formation of the corpus
luteum.