Spermatogenesis and ovogenesis are the processes of formation and formation of germ cells.
The process by which cells occur is called gametogenesis. It is subdivided into spermatogenesis and ovogenesis. Formation begins in the uterine period, during the differentiation of sex, and continues until the completion of the reproductive age. Sex cells are secreted by special glands - gonads. In humans and animals, female gametes develop in the ovaries, and in the testes - male.
The process of ovogenesis and its features
The development of female germ cells takes quite a long time. The process begins in the cortical layer of the primary ovarian follicles. Completion is observed after ovulation in the egg line. Ovogenesis is a three-phase process that includes the stages of reproduction, growth and development.
Breeding phase and growth phase
At the first stage of ovogenesis, multiple mitotic divisions occur in the cells of the ovarian wall. As a result, a large number of diploid ovogoniums are formed.In humans, gonad reproduction starts in embryogenesis and ends by the third year of life.
The growth period is characterized by an increase in the nucleus and cytoplasm in the cells. Substances necessary for subsequent fission processes accumulate, chromosome doubling occurs. In this phase, ovogonia are converted into first-order oocytes. They grow in the ovary and store nutrients. Each oocyte is surrounded by epithelial cells. It forms a bubble - follicle.
Ovogenesis is a long process. Features of the ripening phase
The ripening phase has a number of features. The prophase of meiosis I passes even during embryonic development, and the remaining stages proceed after the organism reaches puberty. Every month, one follicle matures in one of the ovaries. At this stage, the first division of meiosis ends, a large secondary oocyte and a small body are formed. These structures enter the second phase of meiosis. At the metaphase stage of meiosis II, ovulation occurs — the oocyte leaves the ovary, finds itself in the abdominal cavity and passes into the oviduct.
If there is a fusion of the egg with the sperm,then the further maturation of the oocyte begins. As a result of the completion of meiosis II, a mature ovotide egg and a second polar body are formed.
Ovogenesis is a complex, multistep process, as a result of which cells with a haploid chromosome set are formed from a diploid gamete: one mature egg cell and three polar bodies.
The egg cell has a spherical shape and large size. Its diameter in mammals and humans varies from 0.110 to 0.140 mm. In terms of its volume, the egg is larger than the sperm 10-20 thousand times and 2 times longer.
Maturation Phase Based on the Example of the Human Body
Maturation begins at 12-13 years of age, during puberty. The gonads contain multiple follicles containing oocytes. Under the action of follicle-stimulating hormone, one after another, they begin to develop, reaching the size of a pea. As the egg cells inside these vesicles grow, they reach the lumen of the ovary. As a result, the most viable follicle is isolated, and the rest are reduced. This usually happens on the 10th day of the onset of menstruation. The follicle remaining on the surface of the ovary, and the grapha vesicle, continue to grow.Having reached the maximum development, the formation bursts, and the mature egg leaves into the oviduct.
Ovulation occurs. Under the influence of the lutein-forming hormone, the bursting of graaf vial changes - now it is a yellow body. Its cell walls acquire a yellow tint due to the fat content. They occupy the area in which the egg cell was previously located. The corpus luteum produces the hormone progesterone, which is aimed at preparing the uterus mucosa for fertilization.
If a meeting of the egg and sperm did not occur, after a few days the regeneration and reduction of the corpus luteum begins. The mucous membrane of the uterus in the absence of progesterone is destroyed and rejected. This process is characterized by blood discharge from the vagina lasting 2-7 days (menstruation).
The process of spermatogenesis and its features
Ovogenesis and spermatogenesis are similar, the difference is that maturation of male gametes occurs in 4 stages.
Spermatogenesis is the formation and formation of male germ cells - sperm. It starts from the moment of sexual differentiation and intensively develops during the period of maturity of the organism.
At the stage of reproduction, multiple mitotic cell divisions begin in the testes, resulting in the formation of numerous spermatogonia that have a diploid set of chromosomes. The phase of development in men begins from the moment of puberty and lasts almost the entire life.
At the growth stage, the cells are called 1st order spermatocytes. They gradually increase in size due to the accumulation of nutrients, doubling of DNA and chromosomes.
The maturation phase is characterized by two successive divisions of meiosis. As a result, 4 spermatids with a haploid chromosome set are formed from each primary spermatocyte.
Features of the development of male gonads
The maturation phase is characteristic only for spermatogenesis. Its essence lies in the fact that spermatids acquire the structure and motor function characteristic of sperm cells.
The process of spermatogenesis from dividing the original cell to the release of the sperm cell in the epididymis is 35-55 days. During the day, in the sexual gland matures up to 7 billion sperms. Male gonads retain their mobility for 2-3 months, and the ability to fertilize - more than 30 days.The formation of sperm cells is directly dependent on the state of the body, nutrition and external conditions. Their viability may be reduced under the action of adverse factors, inadequate diet, internal violations.
Spermatogenesis and ovogenesis are the most important processes that are responsible for the reproduction, development and extension of the genus of all living things.