The term spermatogenesis is used to describe sperm formation. It begins at the onset of puberty and is a prerequisite for reproduction.
What is spermatogenesis?
Spermatogenesis is when the male germ cells are formed. These are known as sperm cells. Spermatogenesis is where the male germ cells are formed. These are known by the name spermatozoa. Spermatogenesis takes place in the sexually mature testes. Here, sperm cells go through various stages of development and eventually mature into sperm. Spermatogenesis lasts an average of 64 days and is subject to control by the pituitary gland and hypothalamus. Disruptions in spermatogenesis can affect male fertility.
Function and role
Spermatogonia are formed from the stem cells of the testis even before birth. This production cycle continues during puberty. Spermatogonia are primordial sperm cells. They are formed from the primordial germ cells when these, still in the womb, have migrated to the testicular anlage of the unborn child. Spermatogonia are formed by mitotic cell division of these primordial germ cells. The primordial sex cells, also called gonocytes, are located in the seminiferous tubules. During division, type A spermatogonia are formed. Further division gives rise to type B spermatogonia from the type A spermatogonia. One of these daughter cells remains with the original spermatogonia. This ensures that spermatocytes can be replicated throughout life. The B-type spermatogonia are connected by projections and form groups. Together, the groups pass through the different stages of spermatogenesis. They migrate through the so-called blood-testicular barrier towards the seminiferous tubules. The blood-testis barrier is located in the seminiferous tubules of the testis. It is impermeable to large proteins and immune cells. This barrier is important because spermatocytes have antigenic properties. This means that they would be rejected by the patient’s own immune system under certain circumstances. Once the B spermatogonia arrive in the seminiferous tubules, they are referred to as 1st order spermatocytes. In the seminiferous tubule, they undergo the first maturation division. During this meiosis, 2nd order spermatocytes are formed by haploidization. These are also called secondary spermatocytes. The first maturation division is directly followed by the second maturation division. During meiosis II, two spermatids are formed. Spermatids are the smallest cells of the germinal epithelium. They are significantly smaller than spermatocytes. Thus, in the course of spermatogenesis, four spermatids are formed from one spermatocyte. In the final step of spermatogenesis, in spermiogenesis, these spermatids mature into spermatozoa. The nucleus of the spermatids condenses during this process and there is also a loss of cytoplasm. The spermatids also form the typical tail. This is also called kinocilia. Furthermore, the acrosome develops from the Golgi region during spermiogenesis. The acrosome is the head cap of the spermatids. It covers the head and serves to penetrate the egg cell. Thus, one spermatogonium gives rise to four spermatozoa during spermiogenesis and spermatogenesis. Two of them carry an X chromosome and two carry a Y chromosome. The complete process of spermatogenesis takes 64 days. The first reproduction of spermatogonia takes 16 days. Meiosis I covers a period of 24 days and meiosis II covers a period of only a few hours. The maturation of spermatozoa during spermiogenesis lasts 24 days. At the end of spermatogenesis is the sperm, which serves to fertilize the female egg.
Diseases and disorders
Disorders of spermatogenesis can have different causes. With age, natural fertility decreases. From about the age of 40, sperm density decreases. Spermatozoa are then no longer as motile. During maturation division occurs more and more frequently. Thus, the number of abnormal spermatozoa increases. Chromosomal changes can also be observed more frequently. Spermatogenesis may also be disturbed due to genetic abnormalities. If there are no spermatozoa in the ejaculate, this is called azoospermia. Azoospermia is a typical symptom of Klinefelter syndrome. It is an abnormality that results in gonadal hypofunction. Klinefelter syndrome is a hypergonadotropic hypogonadism.If the disorder is present at the level of the pituitary gland or hypothalamus, it is hypogonadotropic hypogonadism. Typical disorders are Kallmann syndrome or pituitary adenoma. Damage to the anterior lobe of the pituitary gland in hemochromatosis can also affect spermatogenesis and thus impair sperm formation. Spermatogenesis and thus also the quality of the sperm is also determined by one’s own everyday behavior. Malnutrition, for example, can lead to a decrease in sperm quantity. An unhealthy diet low in vital nutrients and rich in saturated fatty acids, sweets, convenience foods and breaded dishes not only leads to a micronutrient deficiency, but also to impaired spermatogenesis. The same applies to regular consumption of alcohol, coffee and tobacco. Alcohol consumption in particular has a negative effect on sperm development. Due to alcohol-related liver damage, sex hormones can no longer be completely broken down in the organism. This leads to hormonal disorders at the hypothalamic-pituitary level. The quality of spermatozoa deteriorates and sperm density decreases. In turn, the percentage of malformed spermatozoa increases. Smoking limits the motility of spermatozoa. In addition, the DNA of smokers is less stable than the DNA of non-smokers. X-rays, ionizing radiation, heat, various drugs, and environmental toxins also damage spermatogenesis. Since spermatogenesis occurs in the testes, diseases of the testis can also interfere with spermatogenesis. Underdevelopment of testicular tissue, testicular injury, infection of the prostate, undescended testis, or mumps-related testicular inflammation can decrease sperm quality and quantity.