Stages of Spermatogenesis - Mitosis and Meiosis
Mitosis:
Mitosis covers just one step in the eukaryotic cell cycle: G1 > S > G2 > M > C.
Meiosis:
Steps involved in meiosis are outlined as follows:
Interphase: Replication of DNA (4N)
Metaphase I: One face of each homolog centromere attaches to a spindle fiber
Anaphase I: Homologous pairs split and start to move
Telophase I: Chromosomes travel to each pole, cell division (2N)
Prophase II: Spindle fibers reschedule and chromosome recondense
Metaphase II: Chromosomal pairs line up along spindle equator
Anaphase II: Sister chromatids divide and move to opposite poles
Telophase II: Every daughter cell nucleus has a single set of chromosomes (1N)
Throughout the process of spermatocytogenesis, the primitive cells are known as spermatogonia proliferate by mitosis. Various types of spermatogonia like A-0 through A-4, intermediate [IN], and B have been identified. Discriminating anatomist alone can actually differentiate among types of spermatogonia. The process of mitosis ends when a B spermatogonium yields two primary spermatocytes.
Endogenous damage to the genetic material is predictable in proliferative cells. A battery of repair devices guarantees that the DNA fidelity of gametes is sustained.
During spermiogenesis, the spermatids undergo a dramatic change in form into the streamline spermatozoa modified for fertilization. It engages nuclear condensation, the formation of the acrosomal cap, and tail development. Using the Golgi apparatus, the acrosome is derived from. Centrioles i.e. the points of the organization of spindle fibers migrate to a post-nuclear area after the completion of the phase of meiosis. The distal centriole provides a pattern for the accumulation of cytoskeletal elements consisting of the contractile lattice of the tail. Mitochondria become concentrated into the cover of the middle piece. During the phase of spermiogenesis, the cells don’t divide.
FAQs on Spermatogenesis
1. What is spermatogenesis in simple terms?
Spermatogenesis is the biological process through which male germ cells, called spermatogonia, develop into mature sperm cells, also known as spermatozoa. This entire process occurs within the seminiferous tubules of the testes and starts at puberty.
2. What are the main steps involved in the spermatogenesis process?
The process of spermatogenesis can be broken down into three main phases:
- Spermatocytogenesis (Mitosis): Diploid spermatogonia multiply and grow to become primary spermatocytes.
- Meiosis: The diploid primary spermatocytes undergo meiotic divisions. Meiosis I produces two haploid secondary spermatocytes, and Meiosis II results in four haploid spermatids.
- Spermiogenesis: The non-motile spermatids transform and differentiate into motile, mature spermatozoa (sperm cells).
3. What is the difference between spermatogenesis and spermiogenesis?
Spermatogenesis is the entire process of producing mature sperm from germ cells. Spermiogenesis, on the other hand, is just the final stage of spermatogenesis. It specifically refers to the transformation of the circular, non-motile spermatids into the typical, tadpole-shaped, motile sperm (spermatozoa).
4. How long does it take for spermatogenesis to complete in humans?
The entire process of spermatogenesis, from the spermatogonial stem cell to the formation of mature spermatozoa, takes approximately 64 to 74 days in human males. This is a continuous process, ensuring a constant supply of sperm.
5. Which hormones are important for regulating spermatogenesis?
Several hormones are crucial for initiating and maintaining spermatogenesis. The key ones include:
- Gonadotropin-releasing hormone (GnRH): Released by the hypothalamus to stimulate the pituitary gland.
- Luteinizing Hormone (LH): Stimulates Leydig cells in the testes to produce testosterone.
- Follicle-Stimulating Hormone (FSH): Acts on Sertoli cells, which help in the process of spermiogenesis.
- Testosterone: Essential for the development and maturation of sperm cells.
6. How does spermatogenesis differ from oogenesis?
Spermatogenesis and oogenesis are both processes of gamete formation but differ significantly. Spermatogenesis produces four small, motile sperm from one parent cell, begins at puberty, and is a continuous process. In contrast, oogenesis produces one large, non-motile ovum and smaller polar bodies, begins during fetal development, and occurs in monthly cycles after puberty.
7. Why is the process of meiosis so important for spermatogenesis?
Meiosis is critical because it reduces the chromosome number by half. The parent cells (spermatogonia) are diploid (46 chromosomes), but the final sperm cells must be haploid (23 chromosomes). This ensures that when the sperm fertilises a haploid egg, the resulting zygote will have the correct diploid number of chromosomes (46), maintaining the species' chromosome count.
8. What is the specific function of Sertoli cells in this process?
Sertoli cells, often called 'nurse cells', play a vital supporting role. They provide structural support and nourishment to the developing sperm cells inside the seminiferous tubules. They also help regulate the process by responding to FSH and secreting substances that aid in spermiogenesis.
9. What would be the consequence if spermiogenesis failed to occur?
If spermiogenesis failed, the male would still produce haploid spermatids through meiosis. However, these spermatids are non-motile and lack the structures needed for fertilisation, such as the acrosome and flagellum (tail). As a result, even though the cells have the correct genetic information, they would be unable to travel to or penetrate an egg, leading to infertility.
