Biology today

through proliferation of their granulosa cells, addition of

thecal covering on the outside.

• The FSh stimulates ovarian follicle to secrete estrogen.
Estrogen stimulates the proliferation of the endometrium of
the uterine wall.

• after about a week of development only one ovarian follicle
(dominant follicle) continues growth while the rest begin
to degenerate.

• New blood capillaries develop. Uterine glands elongate and
get coiled. Epithelial lining of oviduct develops more cilia. The
activity of secretory cells is enhanced. muscles of the genital
tract become more active. cervix develops mucous strings
which form channels for guiding movements of sperms.

ovulatory phase

• The rapid rise in plasma Lh level, known as the LH surge
leads to final maturation of Graafian follicle.

• Follicle ruptures and a secondary oocyte is released on about
Day 14.

• Shortly after onset of midcycle Lh surge, plasma estradiol
levels drop and a further rise in plasma progesterone occurs.

luteal phase or secretory phase

• It represents time between ovulation and the onset of next
menses.

• Following ovulation, Lh stimulates the remnants of ovulated
follicle to develop into corpus luteum, which secretes
progesterone and some estradiol.

•    Both Lh and progesterone help in further growth and

thickening of endometrium. The major change is that

the endometrial glands become secretory. Thickness of

endometrium becomes 5-6 mm.

•    The uterine wall becomes ready for nourishing and anchoring

blastocyst if fertilisation takes place.

•    Progesterone inhibits uterine movements as well as proliferation

of new ovarian follicles. The phase lasts for about 10 days. If

the oocyte is not fertilised, corpus luteum activity declines and

it degenerates into corpus albicans.

•    With decrease in ovarian hormones, release of Gnrh, FSh,

and Lh occurs due to loss to of negative feedback suppression

by ovarian hormones. This resumes follicular growth.

0246810 12 14 16 18 20 2224 2628

Days

Estrogens LH Progesterone

O v u la t ion

FSH

M e n s t r u a t i o n

Fig.:Relative concentration of anterior lobe of pituitary hormones(FSH and LH)

and ovarian hormones (estrogens and progesterone) during a normal menstrual cycle.

Hormone concentration

menopause

•    menopause is a phase in woman’s life when ovulation

and menstruation stop. During this condition, ovaries fail

Fig.:Changes in ovary and uterus during a menstrual cycle in woman

Uterine

phase

Luteal

phase

Ovulatory

phase

Follicular

phase

Menstrual

phase

Bleeding

Anterior pituitary

FSH rises as progesterone falls

Growing

follicle

Proliferation Secretion

Fall in progesterone

Progesterone

Estrogen Ovulation

Endometrium

Graafian

follicle

Ruptured

follicle

Corpus

luteum

FS

FSH LH H

LH

InhibitsLH

LHfa

lls a

ses

troge

nfa

lls

Ovarian

event

FSH

Regressing

corpus luteum