Spermatogenesis in Human - Process and Description

Spermatogenesis

The process by which male gametes  or sperms are formed from the primary germ cells inside the male  gonads  is called spermatogenesis. Spermatogenesis is a type  of gametogenesis in male. Spermatozoa are the mature male gametes. In mammals spermatozoa  are formed  in the male Testes but maturation of male gamete takes place in Epididymis.

👌👌Remember - The process of spermatogenesis takes approximately 74 days in male humans.

Spermatogenesis starts at puberty and generally continues uninterrupted until death. There could be a slight decrease in the quantity of sperm with increase in age.

Site of Spermatogenesis
The site  of the spermatogenesis  is male gonad or testes. The initial stages of this process occur inside the testes and further progress to the epididymis. In epididymis, the male  gametes mature and are stored till ejaculation. Process of Spermatogenesis include Spermatocytogenesis, Spermatidogenesis and Spermiogenesis

Spermatocytogenesis 
It is the type of gametocytogenesis that takes place in male and results in the formation of spermatocytes.
In spermatocytogenesis, a diploid spermatogonium which is present   in the compartment of seminiferous tubules, divides mitosis division and  to form  two diploid  cells called primary spermatocytes.
Each primary spermatocyte duplicates its DNA and undergoes meiosis-I  or reduction division to produce two haploid secondary spermatocytes.
This division involves genetic variations. These variations occur due to  either parental chromosomes or chromosomal crossover.

Spermatidogenesis
Spermatidogenesis is the process of formation of spermatids from secondary spermatocytes. Secondary spermatocytes rapidly enter meiosis-II  or equational division and divide to produce haploid spermatids. 

Spermiogenesis
During this process of spermiogenesis, the spermatids develop a tail and  middle piece. In this middle piece, the mitochondria  are accumulated to form an axoneme. During this process, spermatid DNA is  packed and  condensed.

👌👌 Remember -The Golgi apparatus surrounds the condensed nucleus and forms a cap-like structure called acrosome.  Acrosome has Hyaluronidase enzyme.

Proximal and distal centriole also develops in sperm. Maturation of sperm is triggered by testosterone Although spermatozoa are  matured but they lack motility. These spermatozoa are released from testes  through a process called spermiation. The non-motile spermatozoa are transported to the epididymis with the help of testicular fluid secreted by the Sertoli cells with peristaltic contraction. The spermatozoa gain motility and become capable of fertilization in the epididymis..

Factors  affecting Spermatogenesis
The process of spermatogenesis is highly influenced by hormones and temperature. Testosterone is required to maintain the process of spermatogenesis.  Testosterone is produced by interstitial cells, also known as Leydig cells, which reside adjacent to the seminiferous tubules. Temperature is another factor that affects the process of spermatogenesis. So the testes are located outside the body in the scrotum. The optimal temperature is maintained at 2°C  below body temperature. Dietary deficiencies like vitamins B, E and A  x-ray exposure, alcohol, and infectious diseases will also adversely affect the rate of spermatogenesis.

Hormonal control of Spermatogenesis
Spermatogenesis occurs at puberty due to the interaction of the hypothalamus, pituitary gland and Leydig cells. Gonadotropin releasing hormone is secreted  by the hypothalamus and released by the anterior pituitary. This Gonadotropin releasing hormone stimulates. luteinizing hormone and Sertoli cells to secrete testosterone  Hormone and Follicle stimulating hormonal The Sertoli cells provide nourishment for the complete process of spermatogenesis under Follicle stimulating Hormone  production.

The Leydig cells are also capable of producing Androgen in addition to their main product testosterone.