Biology of the Spermatogenesis Process and Men Infertility - Essay Example

Spermatogenesis Spermatogenesis is the process when male gametogonia, or germs cell, develop into mature spermatozoa, which is the mature male gametes. It takes approximately sixty-four days for spermatogenesis to form in the male. Spermatogenesis is an essential process for sexual reproduction. The process of spermatogenesis begins around puberty, and does not stop until death, though a decrease can be seen in the quantity of sperm produced as the age of the male increases. (Carrell 167) Spermatogenesis takes place in several of the structures in the male reproductive system. The whole of the stages take place in the testes, and advance to the epididymis. The process begins in the seminiferous tubules of the testes, where the stem cells are adjacent to the inner tubule wall are divided in a centripetal direction. This is where immature sperm is produced, followed by maturation, which takes place in the epididymis, where the tail is involved. (UWYO) The process of spermatogenesis can be broken down into several steps, with each step involving a specific type of cell: spermatocytogenesis (which is also called mitosis), spermatidogenesis (also known as meiosis), and spermiogenesis. Spermatocytogenesis is the stage in which the spermatogonia cells are grown by mitosis. Numerous types of spermatogonia have been distinguished: A-0 through A-4, intermediate, and B. The process of mitosis is complete when the B spermatogonia produce two primary spermatocytes. During meiosis, the number of spermatocytes is cut in half. During meiosis I, spermatocytes are created into two spermatocytes, and then, during meiosis II, are converted into spermatids. Spermatocytes and spermatids are often larger in size than when they first began as spermatogonia. During the process of spermatidogenesis, spermatids are created from the secondary spermatocytes. Other spermatocytes that were produced earlier quickly enter meiosis II, dividing into haploid spermatids. Due to the quickness of this stage, secondary spermatocytes are not often seen during histological preparations. During the process of spermiogenesis, the spermatids start to grow a tail and a thickened middle. This thickened section is where the mitochondria group and form themselves into an axoneme. Spermatid DNA is grouped together, becoming contracted. The Golgi apparatus surrounds the contracted nucleus, thus turning into the acrosome. One of the centrioles of the acrosome becomes the tail of the sperm. After that process, maturation begins, ridding of the remaining unimportant organelles and cytoplasm. The excess cytoplasm surrounds the Sertoli cells in the testes, resulting in mature spermatozoa that lack motility, making them sterile. These spermatozoa are carried to the epididymis by means of testicular fluid. They develop motility in the epididymis, and are able to fertilize. The role of Sertoli cells in spermatogenesis is one of providing structural and metabolic support to the sperm cells during development. There are numerous functions that the Sertoli cells see to during spermatogenesis: they protect the environment that is needed for development and maturation; they secrete the substances and fluids that are needed to initiate meiosis; concentrates testosterone in the vicinity of the developing gametes; and they secrete the hormones that effect the pituitary gland, which has control over spermatogenesis and the polypeptide hormone known has inhibin. (Brehm) Some of the influencing factors or spermatogenesis is that the process is extremely sensitive to changes in the environment, such as hormones and temperature. Seminiferous epithelium is sensitive to high temperature, and can be affected if the temperature exceeds a few degrees below the normal body temperature. Other things that can affect the rate of spermatogenesis, or the overall outcome of the process, are vitamins B, E, and A, steroids, alcohol, and infectious diseases. Infertility affects close to ten percent of couples, and in roughly half of these cases the defect can be traced back to the male. Physiological studies have shown that spermatogenesis and the final steps of sperm maturation and activation can be subjected to complex regulation, which has been proven to cause infertility in men. There are roughly two thousand genes that regulate spermatogenesis. Most of these genes are found on the autosomes, while about thirty of the genes can be found on the Y chromosome. Y chromosomes are only essential when in regards to vital male reproductive processes. There are genetic factors that are involved in the infertility of males, and are considered to be chromosomal disorders, monogenic disorders, multi-factorial disorders, and endocrine disorders of a genetic origin. Abnormalities involving chromosomes are common in men that are infertile, such as those that have Klinefelter’s syndrome. Men can also have structural abnormalities that can lead to phenotypic male reproductive disorder or a severe congenital abnormality when gametes are formed. In one survey of infertile men, the incidence of chromosomal abnormalities was 5-8% and of these, sex chromosomal abnormalities accounted for 4-2% and autosomal abnormalities, 1-5%. (Seshagiri) There are numerous genes that are required for fertility. Mutations in these genes have been found to cause infertility because of the defects in the development of the germ-cell lineage, despite the fact that the organism can be considered healthy. One of the diseases that can occur during, and because of, spermatogenesis is spermatogenesis arrest. During spermatogenesis arrest, there is a delay in the distinction of germinal cells, which extracts a modified spermatozoa formation. Spermatogenesis arrest is usually caused by genetic factors that can create irreversible azoospermia. Other causes may involve thermic, hormonal, and toxic factors. In these cases, the affected azoospermia cause is reversed on its own or after treatment. The cancer disease process can also affect a man’s fertility by influencing spermatogenesis. There are multiple factors that can lead to this: preexisting defects in germ cells; systemic effects of cancer; and endocrine and immunological disturbances. Spermatogenesis can improve after the cure of the cancer disease. (Agarwal) Spermatogenesis is the process when male gametogonia develop into mature spermatozoa. The three major stages in spermatogenesis are spermatocytogenesis, spermatidogenesis, and spermiogenesis. Each of these stages plays an important role in the maturation of spermatozoa. Mutated cells that affect the process of spermatogenesis can cause infertility in males. A few diseases can also be caused by spermatogenesis, as well as affect the processes of spermatogenesis. Male infertility is a problem so common that it can be seen in one out of twenty-five men. There are numerous causes to male infertility, and many of these causes are still unknown. However, it has been found out that most of these causes are of a variety of new genetic causes. With the sequencing of the human genome, and with the help of advanced functional genomic programs, new genetic causes of male infertility will be able to be identified and the affects that they have on normal testicular functions will be understood. This can allow room for new and effective treatments for men that are infertile. (Cram et al). While there is still much to be learned, an immense lot has already come to light and progress has been made in the ways of the clinical delineation of the genetic forms of male infertility, and in the characterizing of the genes that are responsible for male infertility, as well as their mutations. (Meschede and Horst) The future, in concerns of male infertility, its numerous causes, and possible treatments, is moving in a positive direction. Scientists and researchers still have a long way to go, but with each day, they are coming upon more information that can help males with infertility. References Agarwal, Ashok. “Disruption of Spermatogenesis by the Cancer Disease Process.” 2005. Online. Available http://jncimono.oxfordjournals.org/cgi/content/full/2005/34/9. July 14, 2007. Brehm, Ralph. Regulation of Sertoli Cell and Germ Cell Differentiation. Springer-Verlag New York, 2005. Carrell, Douglas. Genetics of Male Fertility. Springer-Verlag New York, 2006. Seshagiri, Polani. “Molecular Insights into the Causes of Male Infertility.” 2001. Online. Available http://www.ias.ac.in/jblooci/nov2001/429.pdf. July 13, 2007. “Spermatogenesis.” 2004. Online. Available www.uwyo.edu/wjm/Repro/spermat.htm. July 13, 2007. Read More