Question

Ovulation, explain particularly the hormones directly associated with it.

Answer 1

The gamete formation in females is a cyclic activity (The Mentrual Cycle) that takes about 28 days.

Ovulation is an event occuring in the mid of the menstrual cycle i.e the 14th day.
It results in the rupture of Graafian Follicle to release an Ovum. (The Female Gamete).

The hormones that are directly involved in ovulation are:

• FSH-Follicle Stimulating Hormone
  (released from anterior pituitary under action of FSH-Releasing Hormone from hypothalamus of the brain)
• LH-Lutienising Hormone
  (released from anterior pituitary under action of LH-Releasing Hormone from hypothalamus of the brain)
• Estrogen
  (From the Follicular Cells)
  
  The following paragraph will explain their respective role with sequence of events.

Primary Follicles (Primary Oocyte surrounded by granulosa cells) are present in the ovary from the time of birth. During each Menstrual Cycle, a single primary follicle matures into an Ovum and is made available for fertilisation.

Mentrual Cycle has the following four Phases: ( explaining only the relevant phases and aspects here)
1. The Mentrual Phase (Usually 4-5 days)

2. The Follicular or the Pre Ovulatory Phase:
Under the action of FSH released from Anterior Pituitary of the brain, the primary follicle grows and transfroms first into a secondary follicle and then into a tertiary follicle by acquiring layers of cells repeatedly.
The fully grown and mature follicle is called a Graafian Follicle. The follicular cells of this Graafian follicle secretes Estrogen.  
Estrogen sends positive feedback to the anterior pituitary which triggers it to release more LH and FSH. Estrogen also increases the No. of LH Receptors present in the Follicle.


3. Ovulatory Phase : Both the Gonadotropins (LH and FSH) reach their peak value in the middle of the cycle. ( around the 14th Day )
The rapid secretion of LH leading to its maximum value is called LH Surge. It induces the rupture of Graafian Follicle and thereby the release of Ovum ( Ovulation).

4. Luteal Phase (13-14 days)