What is the Difference Between Folliculogenesis and Oogenesis

The main difference between folliculogenesis and oogenesis is that folliculogenesis is the maturation of the ovarian follicle, whereas oogenesis is the formation process of female gametes. 

Folliculogenesis and oogenesis are two processes that occur in the ovary. The ovary is the organ of the female reproductive system that produces the ovum.      

Key Areas Covered

1. What is Folliculogenesis
– Definition, Process, Importance
2. What is Oogenesis
– Definition, Process, Importance
3. Similarities Between Folliculogenesis and Oogenesis
– Outline of Common Features
4. Difference Between Folliculogenesis and Oogenesis
– Comparison of Key Differences

Key Terms 

Folliculogenesis, Oogenesis

What is Folliculogenesis 

Folliculogenesis is the maturation process of the ovarian follicle, which is the densely packed somatic cells forming a shell around the immature ovum. It involves the development of several primordial follicles into large preovulatory follicles. A primordial follicle is an ovarian follicle. A single layer of flattened granulosa cells surrounds the immature ovum. Ideally, an ovarian follicle has to progress through several developmental stages until it becomes mature, suitable for ovulation. This developmental process is called folliculogenesis; the primordial follicle is the first stage of folliculogenesis.

Figure 1: Folliculogenesis

Furthermore, the process of folliculogenesis progresses through the primary, secondary, tertiary, and Graafian follicles. The primary follicle contains cuboidal granulosa cells that occur in a single layer surrounding the oocyte. Also, the secondary follicle contains a follicular antrum within a granulosa layer. Additionally, the secondary follicle contains a fluid-filled cavity, while the Graafian follicle contains a mature fluid-filled cavity. The Graafian follicle releases the ovum in the mid of the menstrual cycle. It is known as ovulation. 

What is Oogenesis

Oogenesis is the process of producing female gametes, ova, from oogonia in the ovary. The primary oocyte is the diploid cell, which is divided by meiosis, forming a single ovum. Two polar bodies are formed, one from each of the two stages of meiosis. Oogenesis occurs once a month from puberty to menopause. Oogenic germ cells or oogonia are the stem cells that are self-renewing and differentiating into ova. During embryonic development, roughly 7 million germ cells are produced by dividing thousands of oogonia during the second to the seventh months of the embryo. Primary oocytes are produced from oogonia by mitosis. Primary oocytes are processed until the diplotene stage of the first meiotic division during the embryonic period. The cell division is arrested as it is until puberty.

Figure 2: Oogenesis

Moreover, some primary oocytes arrest their cell division for about 50 years. Most of the primary oocytes are destroyed during their lifetime; ultimately, only around 400 primary oocytes become gametes after puberty. Puberty starts the arrested cell division, forming a secondary oocyte from the primary oocyte. The primary oocyte produces one secondary oocyte and one polar body by unequal cell division. The cytoplasm of the secondary oocyte remains, and the nucleus of the polar body is destroyed. A secondary oocyte is released from the ovary during ovulation.

Similarities Between Folliculogenesis and Oogenesis

• Folliculogenesis and oogenesis are two processes that occur in the ovary, the female reproductive organ.
• They are responsible for the production of the ovum. 

Difference Between Folliculogenesis and Oogenesis

Definition

Folliculogenesis refers to the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte. In contrast, oogenesis refers to the process of the production of the ovum that takes place in the ovaries of Females.

Process

Folliculogenesis is the maturation of the ovarian follicle, while oogenesis is the process of formation of female gametes. 

Product

The product of folliculogenesis is the ovarian follicle that contains a densely packed shell of somatic cells around the ovum, while the product of the oogenesis is the ovum. 

Function

Folliculogenesis produces hormones that influence the menstrual cycle stages, while oogenesis forms the female reproductive cell. 

Conclusion

In brief, folliculogenesis and oogenesis are two processes that occur in the ovary. Their function is to produce an ovum. Folliculogenesis is the process of maturation of the ovarian follicle. The ovarian follicle is a cellular aggregation that is roughly spheroid. It secretes hormones affecting the stages of the menstrual cycle. In comparison, oogenesis is the process of formation of female gametes. It produces the ovum. The ovum is the female reproductive cell. Therefore, the main difference between folliculogenesis and oogenesis is their process. 

References:

1. Folliculogenesis. Folliculogenesis – an overview | ScienceDirect Topics. (n.d.). 
2. Gilbert SF. Developmental Biology. 6th edition. Sunderland (MA): Sinauer Associates; 2000. Oogenesis.

Image Courtesy:

1. “Follicle development stages” By Tnhath – Own work (CC-BY SA 4.0) via Commons Wikimedia
2. “Oogenesis” By Acedatrey2 – Own Work (CC-BY SA 4.0) via Commons Wikimedia