Question

Give reason for the following :
(a) The first half of the menstrual cycle is called follicular phase as well as proliferative phase.
(b) The second half of the menstrual cycle is called luteal phase as well as secretory phase.

Answer 1

Dear student,

The hormones involved in the menstrual cycle are -

1. Pituitary hormones - FSH (Follicle stimulating hormone) , LH (Luteinizing hormone)
2. Ovarian hormones - progesterone and estrogen

a). During the first half of the menstrual cycle, the FSH stimulates the ovaries to start the formation and maturation of eggs with the beginning of menstrual cycle (day 1) LH and FSH increases gradually during this phase. This stimulates follicular development and secretion of estrogen by growing follicles. Since this phase involves the formation and maturation of the follicles thus it is known as the follicular phase. Due to maturation of the follicles , this phase is also called proliferative phase.


b). The LH and FSH peak during 14th day and this LH surge causes ovulation (release of ovum).(Ovulatory phase)
The remaining part of follicle transforms into corpus luteum and hence the phase is known as the luteal phase.
The corpus luteum secretes progesterone which maintains endometrium.Hence it is also known as the secretory phase.


Regards.