Spermatogenesis and Oogenesis

Spermatogenesis is the process by which male sex cells are produced. It takes place in the testes of males. Oogenesis is the process by which female sex cells are produced. It takes place in the ovaries. The male gametes are called sperms and the female gametes are called eggs. Sperm fuses with the egg to form a zygote. 

Spermatogenesis and Oogenesis: Difference

Area of Differentiation                                   Oogenesis                                        Spermatogenesis           

Spermatogenesis 

The development of mature spermatozoa called sperms from the primary spermatogonia is called spermatogenesis. It is the formation of male sex cells and occurs in the male testes. The time taken by spermatogonia to develop into mature spermatozoa is 74 days. The process of spermatogenesis occurs in 4 stages- 

• The stage of proliferation

• The stage of growth

• The stage of maturation, and

• The stage of formation

Stage of Proliferation: Each spermatogonium contains a diploid number of chromosomes. One member of each pair is derived from mother and father respectively. During this stage, the spermatogonia undergo the process of mitosis hence no change in the number of chromosomes occurs. Usually, there are 7 stages of spermatogonia. During this stage, the spermatogonia moves towards the lumen of seminiferous tubules. They are accompanied by the Sertoli cells. 

Stage of Growth: In this stage, the primary spermatocyte grows in size and becomes larger. Besides growth, no change whatsoever takes place in the growth stage. 

Stage of Maturation: When the primary spermatocyte reach their full size, they undergo quick meiotic or maturation division which takes place in two phases- 

  First Phase: In this, each primary spermatocyte is divided into two secondary spermatocytes. The secondary spermatocytes receive only haploid i.e half the number of chromosomes. 

 Second Phase: In this, each secondary spermatocyte undergoes a second meiotic division to form two spermatids. The spermatids contain haploids i.e half the number of chromosomes. 

Stage of Transformation: Transformation occurs in two stages, 

Spermatogenesis: In this process, the spermatids become mature spermatozoa. Changes taking place are:

1. Nuclear material gets condensed

2. Acrosome, tail structures, and axial filament are formed.

3. Removal of unwanted cytoplasm. 

Spermination: It is the process by which matured sperms are released from Sertoli cells into the lumen of seminiferous tubules. 

Hormones Required for Spermatogenesis

Oogenesis

The formation of female sex cells from oogonia is called oogenesis. It takes place in the ovary. The primary oocyte divides to form a single ovum. The primary oocyte undergoes meiosis. In the embryo, millions of germ cells are produced from the second month to the seventh-month in-utero. 

Oogonia divides to form primary oocytes by mitosis. They are processed until the diplotene stage of the first meiotic division is attained in the embryo. The cell division is arrested until the female reaches puberty. Most primary oocytes are destroyed during their lifetime and only 400 primary oocytes live the day to become gametes after puberty.

 On reaching puberty, the cell arrest is revoked and the primary oocyte is divided to form a secondary oocyte. Each primary oocyte forms one secondary oocyte and one polar body. Therefore, two polar bodies are formed from the two meiotic stages. The secondary oocyte gets the entire cytoplasm and the polar body nucleus is destroyed. During ovulation, the secondary oocyte from the ovary is released. 

Spermatogenesis and Oogenesis: Differences

• Spermatogenesis occurs in males while oogenesis occurs in females

• Sperms are formed by spermatogenesis while eggs are formed by oogenesis

• Spermatogenesis occurs in testes while oogenesis occurs in the ovary

• Spermatogenesis occurs continuously while oogenesis occurs cyclically 

• Primary spermatocytes form two secondary spermatocytes while primary oocytes form one secondary oocyte and one polar body 

• Four spermatozoa are produced by one spermatocyte while one oocyte produces a single ovum

• Sperms are smaller than the spermatocytes while ovum is larger than oocytes

• The sperm has a condensed nucleus while no nuclear condensation happens in the ovum

• Sperms have very less reserved food while ovum is rich in reserved food and biochemicals

• Motile gametes are formed as a result of spermatogenesis while non-motile gametes are formed by oogenesis

Conclusion

Gametogenesis in the human body occurs by two processes- oogenesis and spermatogenesis. Sperms are produced in the testes of a male body through the process of spermatogenesis. Ova are produced in a female’s ovary through oogenesis. Both the processes undergo multiplication, growth, and maturation phases. One spermatocyte produces four spermatozoa while one ovum is produced by one oocyte.