Main Difference – Spermatogenesis vs Oogenesis
Spermatogenesis and oogenesis are two types of reproductive divisions found in the sexual reproduction of animals. Reproductive division, also called gametogenesis, occurs in the germ cells in gonads by meiosis. It is involved in the production of gametes. Diploid germ cell produces haploid gametes. Two different types of gametes are found: male gametes and female gametes. Male gametes are known as sperms and female gametes are known as eggs. One sperm is fused with an egg in order to form the diploid zygote, which is then divided and differentiated into a new organism. The main difference between spermatogenesis and oogenesis is that spermatogenesis is the production process of sperms from male germ cells and spermatogonia in males whereas oogenesis is the production of eggs from female germ cells oogonia in females.
This article explains,
1. What is Spermatogenesis
– Definition, Characteristics, Function
2. What is Oogenesis
– Definition, Characteristics, Function
3. What is the difference between Spermatogenesis and Oogenesis
What is Spermatogenesis
The production of male gametes, sperms, from spermatogonia in testis is called spermatogenesis. The spermatogonium consists of diploid cells. It is found in the tiny tubules of the testis, which is the primary reproductive organ in males. Each spermatogonium is responsible for the production of four, haploid spermatozoa. The cell division occurs by meiosis. Spermatogenesis starts with the males’ puberty. Literally, millions of sperms are produced per day for the rest of the males’ life.
Spermatogenic germ cells are called spermatogonia. Spermatogonia are stem cells that are capable of self-renewing. They differentiate into intermediate spermatogonium, which is committed to differentiating into spermatozoa. Mitosis of the intermediate spermatogonium produces type B spermatogonia, which further undergo mitosis, producing primary spermatocytes. Primary spermatocytes then undergo meiosis 1, producing two secondary spermatocytes. The resulting haploid cells are called spermatids, which are still connected to the border of the testis lumen through cytoplasmic bridges. Spermatids are round, unflagellated cells, maturing and differentiating into sperms during spermiogenesis. Human spermatic development takes around 70 days to complete the process. Per day, 100 millions of sperms are produced by testis in humans.
Figure 1: Spermatogenesis
What is Oogenesis
The production of female gametes, ova, from oogonia in the ovary is called oogenesis. 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. Oogensis occurs once a month from puberty to menopause.
Oogenic germ cells are called oogonia, which are stem cells, self-renewing and differentiating into ova. During embryonic development, roughly 7 million germ cells are produced by the division of thousands of oogonia during 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. Some primary oocytes arrest their cell division for about 50 years. Most of the primary oocytes are destroyed during the lifetime and ultimately, only around 400 primary oocytes become gametes after the puberty. Puberty starts the arrested cell division, forming secondary oocyte from the primary oocyte. Here, primary oocyte produces one secondary oocyte and one polar body by unequal cell division. The entire cytoplasm is contained by the secondary oocyte and the nucleus of the polar body is destroyed. Secondary oocyte is released from the ovary during ovulation.
Figure 2: Oogenesis
Difference Between Spermatogenesis and Oogenesis
Definition
Spermatogenesis: The production of sperms from spermatogonia is called spermatogenesis.
Oogenesis: The production of eggs from oogonia is called oogenesis.
Location
Spermatogenesis: Spermatogenesis occurs inside the testis in males.
Oogenesis: Oogenesis occurs inside the ovary in females.
Stages
Spermatogenesis: All the stages of spermatogenesis occur inside the testis.
Oogenesis: All the stages of oogenesis, other than the last stage, occurs inside the ovary. The last stage occurs inside the oviduct.
Releasing
Spermatogenesis: Sperms are released from the testis.
Oogenesis: Oocytes are released from the ovary, which matures later.
Continuity
Spermatogenesis: Spermatogenesis is a continuous process, occurring after the puberty till death.
Oogenesis: Early stages of the oogenesis occurs during the fetal period. The rest of the process occurs after the puberty. Only one ovum is produced per month until menopause.
Spermatogonia/Oogonia
Spermatogenesis: Spermatogonia is developed from the germinal epithelial lining of the seminiferous tubules.
Oogenesis: Oogonia is developed from the germinal epithelium, which overlays the ovary.
Sertoli Cells
Spermatogenesis: Sertoli cells are found in the germinal cell epithelium, supporting the germinal cells.
Oogenesis: No Sertoli cells are found in the germinal cell epithelium.
Cell Division
Spermatogenesis: All spermatogonia are divided by meiosis, producing sperms all the times.
Oogenesis: Some of the oogonia divide during the production of eggs, one at a time.
Growth Phase
Spermatogenesis: Growth phase is too short in spermatogonia.
Oogenesis: Growth phase is prolonged in oogonia.
Primary Gametocyte
Spermatogenesis: Primary spermatocyte is divided by meiosis 1, forming two secondary spermatocytes.
Oogenesis: Primary oocyte is divided by meiosis 1, forming a secondary oocyte and one polar body.
Secondary Gametocyte
Spermatogenesis: Secondary spermatocyte is divided by meiosis 2, forming two spermatids.
Oogenesis: Secondary oocyte is divided by meiosis 2, forming ovum and one polar body.
Cytokinesis
Spermatogenesis: Equal cytokinesis occurs during spermatogenesis, ultimately producing four sperms.
Oogenesis: Unequal cytokinesis occurs during oogenesis, ultimately producing a single ovum and three polar bodies.
Result
Spermatogenesis: One spermatocyte produces four spermatozoa.
Oogenesis: One oocyte produces only one ovum.
Size
Spermatogenesis: Sperms are smaller than spermatocyte.
Oogenesis: Ovum is larger than the oocyte.
Nucleus
Spermatogenesis: The nucleus undergoes condensation in the sperm.
Oogenesis: No nuclear condensation is found in the ovum.
Food Reservation
Spermatogenesis: Little food is reserved in the sperm.
Oogenesis: A lot of food and biochemicals are reserved in the ovum.
Motility
Spermatogenesis: Spermatogenesis produces motile gametes.
Oogenesis: Oogenesis produces non-motile gametes.
Conclusion
Spermatogenesis and oogenesis refer to the production of gametes in testis and ovary respectively. During spermatogenesis, sperms are produced from spermatocytes in the testis. One spermatocyte produces four sperms, which are smaller than spermatocytes. During oogenesis, ova are produced from oocytes in the ovary. One oocyte is responsible for the production of one ovum. Both spermatogenesis and oogenesis occur through three stages: multiplication phase, growth phase, and maturation phase. The main difference between spermatogenesis and oogenesis is their occurrence in different sexes of organisms.
Reference:
1. Gilbert, Scott F. “Spermatogenesis.” Developmental Biology. 6th edition. U.S. National Library of Medicine, 01 Jan. 1970. Web. 11 Apr. 2017.
2. Gilbert, Scott F. “Oogenesis.” Developmental Biology. 6th edition. U.S. National Library of Medicine, 01 Jan. 1970. Web. 11 Apr. 2017.
Image Courtesy:
1. “Figure 28 01 04” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Gray5” By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body. Bartleby.com: Gray’s Anatomy, Plate 5. (Public Domain) via Commons Wikimedia
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