Antral follicle

Antral follicle

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Antral Follicle

An antral follicle, also known as a secondary follicle, is a stage in the development of an ovarian follicle in the ovary. It is characterized by the presence of a fluid-filled cavity called the antrum. Antral follicles are crucial in the process of oogenesis and play a significant role in reproductive endocrinology.

Structure

Antral follicles are formed from primary follicles during the follicular phase of the menstrual cycle. The development of antral follicles is stimulated by follicle-stimulating hormone (FSH) secreted by the anterior pituitary gland.

The structure of an antral follicle includes several key components:

• Antrum: A fluid-filled cavity that forms within the follicle, distinguishing it from earlier stages of follicular development.
• Granulosa cells: These cells line the antrum and are responsible for the production of estrogen.
• Theca cells: Located outside the granulosa cells, these cells work in conjunction with granulosa cells to produce androgens, which are precursors to estrogen.
• Oocyte: The immature egg cell that is surrounded by the granulosa cells and is located within the antral follicle.

Function

Antral follicles are essential for the maturation of the oocyte and the production of hormones necessary for the regulation of the menstrual cycle. The growth and development of antral follicles are regulated by a complex interplay of hormones, including FSH and luteinizing hormone (LH).

During the follicular phase, several antral follicles begin to develop, but typically only one will become the dominant follicle that proceeds to ovulation. The dominant follicle continues to grow and eventually releases the mature oocyte during ovulation.

Clinical Significance

The number of antral follicles present in the ovaries is an important indicator of a woman's ovarian reserve, which refers to the capacity of the ovary to provide egg cells capable of fertilization. Antral follicle count (AFC) is often assessed using transvaginal ultrasound and is used in the evaluation of fertility and the planning of assisted reproductive technology (ART) treatments.

A low antral follicle count may indicate diminished ovarian reserve, which can be associated with reduced fertility. Conversely, a high antral follicle count may be seen in conditions such as polycystic ovary syndrome (PCOS).

Related Pages

• Ovarian follicle
• Oogenesis
• Menstrual cycle
• Follicle-stimulating hormone
• Luteinizing hormone
• Ovarian reserve
• Polycystic ovary syndrome