Spermatogenesis & Oogenesis

Important notes

before we start on the nitty gritty details, let's do a simple comprehensive introduction and note some terminology.

1. Gametogenesis is the production of sperm and eggs, just like we learned in basic biology these gametic cells are different from all other cells (aka somatic cells). This is mainly because these cells are haploid (n), so they have half of the amount of chromosomes in comparison with diploid (2n) somatic cells.
2. The main process that is unique to these gamete cells is that they undergo meiosis.
3. Spermatogenesis refers to the sperm production while oogenesis refers to the egg production.
4. Both undergo three similar phases: proliferation, growth and maturation.
5. Hormones play a huge role in both process which mainly occurs during puberty.
6. Egg is also known as ovum (plural-ova). Sperm is also known as spermatozoa.
7. SperMIOgenesis is the process of spermatid maturation to spermatozoa which is the last stage of sperMATOgenesis.

Spermatogenesis

In this part, we cover everything male related. Spermatogenesis is the process of sperm production which occurs in the male gonads, the testes. Spermatogenesis undergoes three main phases:

1. Proliferation: increase spermatogonia numbers via mitosis. The spermatogonia reside on the seminiferous tubes, there are two kinds of known as Type A and Type B.
2. Growth: spermatogonia will produce primary spermatocyte (2n) through mitotic division. This occurs with the aid of nursing cells that provides the required material and nutrients.
3. Maturation: primary spermatocyte will undergo the first meiotic division resulting in secondary spermatocyte (n). The second meiotic division will produce four spermatids (n).

Check this file for more in depth understanding of this process including the hormonal role!

Oogenesis

In this part, we cover everything female related. Oogenesis is the process of egg production which occurs in the female gonads, the ovaries. This process is relatively more complex than spermatogenesis. Oogenesis undergoes three main phases:

1. Proliferation: increase oogonia numbers via mitosis. Interestingly, this happens during foetal development, in the first trimester of uterine life. The sizes of oogonia differ, some might be larger than others. The oogonia will undergo mitosis multiplying in numbers reaching around 7 million. This phase is also referred to as the Multiplication phase, since the numbers of oogonia multiply.
2. Growth: selection of oogonia. The oogonia will either enlarge or die. This causes a reduction in the number of oogonia from the previous phase. The enlarged oogonium give rise to the primary oocyte.
3. Maturation: primary oocyte will enter the first meiotic division which results in a secondary oocyte (large) and a polar body (small). The division will halt at prophase I until puberty.

Note that primary oocyte similar to spermatocyte undergo TWO maturation divisions.

Check this file for more in depth understanding of this process!