Question

In humans, the oocyte is maintained in a state of meiotic arrest by the secretion of-
A) Granulosa cells
B) Zona pellucida
C) Cumulus cell
D) Theca interna

Answer 1

An oocyte is an immature egg (an immature ovum). Oocytes develop to maturity from within a follicle. These follicles are found in the outside layer of the ovaries.

Complete Answer:
A granulosa cell- it is also called a follicular cell. These are somatic cells which are closely associated with the developing oocyte in the ovary of mammals. Its major functions involve folliculogenesis which is formation of primordial ovarian follicle and its development. The granulosa cells produce sex steroids, myriad growth factors which interact with the oocyte during its development. The sex steroid production is stimulated by follicle-stimulating hormone (FSH) secreted from the anterior pituitary, it stimulates granulosa cells to convert androgens to estradiol by the action of aromatase during the follicular phase of the menstrual cycle. After ovulation, the granulosa cells form granulosa lutein cells which produce progesterone. The progesterone maintains a potential pregnancy and produces a thick cervical mucus that inhibits entry of sperm into the uterus.

Advancement in granulosa cells form a multilayered cumulus oophorus, which surrounds the oocyte in the Graafian follicle. Cumulus cells provide nutrients to the oocyte and influence the development of the oocyte, they also produce a mucified matrix required for ovulation
.
Zona pellucida surrounds the plasma membrane of mammalian oocytes, it is made up of glycoproteins. It constitutes a vital part of the oocyte. The zona pellucida starts appearing in the primary oocytes. It is produced by both the oocyte and the ovarian follicles. It is necessary as it binds spermatozoa and initiates the acrosome reaction. The zona pellucida is surrounded by the corona radiata which provides care to the egg when it is emitted from the ovary.

Theca interna cells transform into the theca lutein cells of the corpus luteum after the rupture of mature ovarian follicle. They secrete androgens and progesterone. Theca lutein cells are also known as small luteal cells

Hence the correct answer is option ‘A’.

Note: Where a gene resides on a DNA molecule, one strand is a coding strand (or meaning strand) and the other is a non-coding strand (also called an antisense strand, anticoding strand, template strand, or transcribed strand).