Follicle

A follicle is a cellular aggregation in the ovaries of females, which secrete hormones that affect the menstrual cycle. It contains an ovum encapsulated in a single layer of cells. When puberty sets in a woman’s life, they are 3,00,000 to 4,00,000 lakhs in number initially. Each one of them releases an egg for fertilization. We will study further about this topic in this article and the characteristics and related phenomena to the follicles in the ovaries.

What is a follicle, and where is it present?

A follicle is a mass of cells enclosed in a single layer of cells and is present inside the ovaries of women. They release egg for fertilization. If the egg meets a sperm in the ovarian duct, fertilization occurs and the zygote forms. The zygote then grows and develops into a blastocyst which further develops into an embryo. The embryo is attached to the endometrium with the help of placenta and umbilical cord. If the egg doesn’t get fertilised, the wall of the endometrium will shed and the remnant of the follicle disintegrates. The remaining follicle is known as corpus luteum and is responsible for the luteal discharge post-menstruation. The corpus luteum secretes oestrogen and progesterone.

Important things to be learned about follicles 

•   The number of follicles in your ovaries speaks about your fertility state. The more follicles you have, the more fertile you are.
•   The quantity and quality of follicles and thus, the eggs depend on the health of the women and their bodies. They are greatly affected by the eating habits and the lifestyle of an individual.
•   If you have a good number of follicles in your ovaries, it tells that you have the potential to conceive. This is because the follicles contain immature eggs and speak a lot about your fertility status. One follicle ruptures and one egg is released each time you menstruate. Just one healthy follicle and a healthy egg is required for a successful pregnancy.
•   The fertilisation is a totally different thing and it in no way depends on the follicle. A follicle’s part is just to get ruptured and release the egg. Fertilisation occurs when sperm meets the egg in the fallopian tubes.

The size of follicle 

Do you know what size is the follicle when you ovulate? The size of the follicle when a woman ovulates is approximately 18 – 20 mm. When the diameter of the follicle reaches 18 mm, it is ready to release an egg. The egg then can implant itself in the endometrium of the uterus as a zygote if it gets fertilised by an incoming competent sperm.

At what size does the follicle rupture?

The follicle usually ruptures when it acquires a size of 20mm. In the bodies of the women menstruating regularly, the follicle gets ruptured to release the egg just two weeks before the expected menstruation date.

The follicle wall diagram 

Looking at the follicle wall diagram, we can say that the follicular membrane is surrounded by specialised somatic cells (called the granulosa cells). They are composed of egg mother cells which make up the basis of intercellular connections. Each of them contains a single oocyte which forms the basis of reproduction. The granulosa cells are surrounded by the follicular membrane cells. The granulosa cells are derived from the surficial epithelium of the ovaries. The granulosa cells then form the squamous epithelium which releases oestrogen.

The FSH and what it does?

FSH stands for Follicular stimulating hormone. It is released by the anterior pituitary in response to the secretion of Gonadotropin releasing hormone released by the hypothalamus. The quantity of FSH released in the body of the females is greater than the quantity of FSH released in the body of the males. It stimulates the maturation of the primordial germ cells in both males and females.

The main feature and characteristic of the follicular stimulating hormone is that it initiates the follicular growth. It also helps in controlling the menstrual cycle in the body of a female. It stimulates the ovary to produce an egg as well as increases the rate of oestradiol production. Besides these functions, the most important functions performed by the FSH are –

•   Secretion of androgen binding proteins from the Sertoli cells in the bodies of the males.
•   Stimulates sperm production in the testicles. The process of formation of sperms is called spermatogenesis.
•   It stimulates the ovary to release an egg.
•   It controls the regulation of the growth and development of the secondary sexual characters in both the genders (particularly in females).
•   It controls the growth of the ovarian follicles which release an egg during ovulation.

The normal level of FSH in body-

If it is a male’s body, the optimum level of FSH during puberty must be :  0.3 to 10.0 mIU/mL

Similarly, if it is a female’s body, we can say that the right level of FSH during puberty is 0.3 to 10.0 mIU/mL. After menopause however, the amount of FSH released increases in females. It jumps up to 25.8 to 134.8 mIU/mL.

Conclusion – 

In this chapter we learned about follicles and the roles it plays in the bodies of humans (primarily females). The follicle is an essential part of the body as it affects an individual’s reproductive system and influences her progeny. Along with the follicles, the FSH parallelly plays an important role. If any abnormality occurs with FSH, many problems could happen.. For example, if FSH is not being released properly or in proper amounts in any individual’s body, it may cause Turner syndrome, ill or no production of eggs, damage to testicles, non-functioning of the reproductive organs, etc.