Question

Which one of the following is fibrous layer of follicle?

• A. Theca externa
• B. Zona pellucida
• C. Membrana granulosa
• D. Vitelline membrane

Answer 1

Answer: (A)

Theca externa

At puberty, only 60,000-80,000 primary follicles are left in each ovary. The primary follicles get surrounded by more layers of granulosa cells and a new theca and are called secondary follicles.

The secondary follicle soon transforms into a tertiary follicle, which is characterised by a fluid filled cavity, called as antrum. The theca layer is fibrous and is organised into an inner theca interna and an outer theca externa. At this stage, 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. Thus the answer is option A.