question_answer

Directions : (51 - 55)

Read the passage given below and answer the following questions.

The process of formation of a mature female gamete is called oogenesis which is markedly different from spermatogenesis. Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells or oogonia are formed within each foetal ovary; no more oogonia are formed and added after birth. These cells start division and enter into prophase-I of the meiotic division and get temporarily arrested at that stage, called primary oocytes. Each primary oocyte then gets surrounded by a layer of granulosa cells and then called the primary follicle. A large number of these follicles degenerate, i.e. follicular atresia and sack rollicks are called atretic follicles during the phase from birth to puberty. Therefore, at puberty only 60, 000 to 80, 000 primary follicles are left in each ovary. The primary follicles get surrounded by more layers of granulosa cells and a new theca and called secondary follicles. The secondary follicle soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum or liquor folliculi. The theca layer is organised into an inner theca interna and an outer theca externa. A solid mass of follicular cells that the developing ovarian follicle is called cumulus oophorus or ovaricus formed by granulose cells, important to note that it is at this stage that the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body or polocyte. The secondary oocyte retains bulk of the nutrient rich cytoplasm of the primary oocyte. The tertiary follicle further changes into the mature follicle or Graafian follicle.

The secondary oocyte forms a new membrane called zona pellucida surrounding it. The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation. The empty follicles fill with a yellow pigment lutin to form.

After ovulation, the collapsed ovarian follicle shrinks and becomes filled with cells to form :

A) Corpus atresia

B) Corpus adiposum

C) Corpus luteum

D) Corpus albicans