Question

(a) Explain the menstrual phase in a human female. State the levels of ovarian and pituitary hormones during this phase.

(b) Why is follicular phase in the menstrual cycle also referred as proliferative phase? Explain.

(c) Explain the events that occur in a graafian follicle at the time of ovulation and thereafter.

(d) Draw a graafian follicle and label antrum and secondary oocyte. [5]

Answer 1

(a) The cycle starts with the menstrual phase, when menstrual flow occurs and it lasts for 3-5 days. The menstrual flow results due to breakdown of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina. [1.5]
During this phase the levels of estrogen and progesterone are low. [0.5]

(b)

• The endometrium gets regenerated under the influence of estrogen.
• Primary follicle grows into graafian follicle under the influence of LH & FSH [0.5+0.5]

(c)

• During the mid cycle leutinizing hormone is secreted to its maximum level which induces rupture of Graafian follicle and thereby the release of ovum (ovulation)
• This is followed by the luteal phase during which the remaining parts of the Graafian follicle transforms as the corpus luteum which secretes large amounts of progesterone. [0.5+0.5]

(d) [0.5+0.5 Diagram and labelling]