Question

Which of the following layers in an antral follicle is acellular
A. Zona pellucida
B. Granulosa
C. Theca Interna
D. Stroma

Answer 1

Hint: The structure of antral or Graafian follicle consists of the antrum, fluid-filled cavity, secondary oocyte surrounded by an acellular layer and outer to it, corona radiata which is composed of several layers.

Complete answer: An antral follicle is also called Graafian follicle. First, the meiotic division leads to this follicular stage. Inside this follicle, secondary oocytes and fluid-filled cavities called antrum are present. The secondary oocyte is surrounded by layers, namely a cellular layer called zona pellucida and an acellular layer called corona radiata. After the release of secondary oocytes, Graafian follicles produce the corpus luteum. The Zona pellucida is an acellular layer surrounding the secondary oocyte which also contains enzymes that catalyses penetration of sperms. Follicular development of the primary follicle and Graafian follicle occurs in the follicular or proliferative phase of the menstrual cycle. A follicle-stimulating hormone secreted by the anterior pituitary gland stimulates the proliferation of granulosa cells in developing follicles. Under the influence of FSH, granulosa cells secrete estrogen, which in turn stimulates the release of Gonadotropin releasing hormones (GnRH). GnRH stimulates the release of LH which leads to ovulation. This is known as the ovulatory phase. It takes place 34-36 hours after the LH surge. Ovulation occurs on day 14, in the middle of the cycle. The ovum or egg dies after 24 hours if fertilization doesn't occur. In case of fertilization, the remaining Graafian follicle becomes corpus luteum and secrete progesterone for thickening of the endometrium. If fertilization doesn't occur, the endometrium sloughs off along with blood and this phase is called the menstrual phase.
Hence, the correct answer is option A.

Note: The zona pellucida is a translucent matrix of glycoproteins that surrounds the mammalian oocyte. Its formation is critical to successful fertilization. In non-mammals, it is called the vitelline membrane or vitelline envelope.