Primordial follicle

Primordial follicle is the earliest stage of folliculogenesis, the process by which ovarian follicles mature and release eggs. It is a crucial component of female reproduction.

Overview

A primordial follicle consists of an immature oocyte surrounded by a single layer of flat granulosa cells. These follicles are formed during fetal life in humans and are present at birth. They represent the initial pool of follicles that can potentially develop into mature Graafian follicles and release eggs for fertilization.

Development

The development of primordial follicles begins in the fetus during gestation. The oogonia (immature egg cells) in the fetal ovaries divide by mitosis to increase in number. Some of these cells then enter meiosis, a type of cell division that reduces the number of chromosomes by half. These cells, now called primary oocytes, are surrounded by a layer of flat granulosa cells to form the primordial follicles.

Activation

The activation of primordial follicles is a complex process regulated by various hormones and growth factors. The transition from a primordial follicle to a primary follicle marks the beginning of folliculogenesis. This process involves the growth and differentiation of the oocyte and granulosa cells, and the formation of a fluid-filled cavity called the antrum.

Clinical significance

The number and quality of primordial follicles in the ovaries determine a woman's ovarian reserve, which is a key factor in her fertility potential. Conditions such as premature ovarian failure and polycystic ovary syndrome can affect the number or quality of primordial follicles, leading to infertility.