The Process of Spermatogenesis in the Male Testis
Spermatogenesis is an intricate process that involves mitotic cell division, meiosis, and its process. The regulation of spermatogenesis involves the endocrine and the paracrine mechanisms. The spermatogenesis endocrine stimulation involves the follicle stimulating hormones (FSH) and the luteinizing hormone. The luteinizing hormone acts through the intermediary testosterone that is produced by the leydig cells in the testis. A male fertility requires the production by the testis with large number of normal spermatozoa by spermatogenesis process. There are three major steps subdivided in the process; the mitosis, meiosis, and the transformation of the round spermatid. The multiplication of spermatogonia is through the process of mitosis. The meiosis reduces the numbers of chromosome from the diploid to haploid. It commences with the entry of type B spermatogonia in the first meiotic division prophase. The primary spermatocytes are divided to form secondary spermatocytes. It is divided again to form round spermatids, the successful transformation of the round spermatid in the complex structure of the spermatozoon that is called the spermiogenesis.
The male genitalia consist of the scrotum, inside is the testicles and ducts associated to it or the epididymis and vas deferens, and the penis. The testes are covered and protected by a tough white fibrous layer, the tunica albuginea; it extends inward and divides the testis in many lobules. Every 200 to 300 lobules contain one to three extra long and tight-coiled seminiferous tubules; it serves as nurse cells that provide important nutrients to the sperm. The absence of spermatogenesis, the sertoli cells are seen on microscopic inspection of the testicular biopsy. The leydig cells are the other important cell type within the testis; it makes testosterone that is essential to the male hormone. The testosterone is responsible for a normal male development of secondary sex characteristics, libido, and normal erections. In addition, the testosterone is important for sperm production to levels of hormones that is 50 folds higher within the testis as in the blood.
Meiosis is a part of spermatogenesis, the production of sperm cells. The sex organs mature after puberty. Spermatogenesis is constant in the testes of human males. The primary spermatocytes (diploid) divide during the meiosis I forming two secondary spermatocytes (haploid). The secondary spermatocytes divide during the meiosis II and produce four spermatids (haploid). In the secondary spermatocytes, the chromosomes are duplicated consisting two chromatoids while spermatids consists only one chromatoid.
Process of Oogenesis in Female
Oogenesis is a type of gametogenesis; it is the process of the production of female gametes as sex determination occurred in the embryo. It is the differentiation of the ovum, the gamete formed by oogenesis contains all the materials necessary to initiate and maintain the development and its metabolism. The female gonad development is at default state. The ova is created egg cells during the process of oogenesis and completed although the lifetime of a female. Oogenesis involves the creation of haploid sex cells through the process of meiosis. In addition, aside from the forming of a haploid nucleus, oogenesis builds up a group of cytoplasmic enzymes, organelles, mRNAs, and metabolic substrates. The egg develops s complex cytoplasm.
Oogenesis starts with the formation of primary oocytes in oocytogenesis process that occurs before birth. The oogonia or the primordial oocyte migrates through the embryo from the germinal epithelium, to the ridges of genital, and undergo mitosis that produces the primary oocytes. The first meiotic block meets and the process is arrested in the prophase of meiosis I until puberty. The oocytes made up of granulosa; the theca cells derived from the germinal epithelium called follicles in the ovaries. During puberty, every oocyte enters again in the meiosis before it is ovulated. It implies that some oocytes remain dormant for up to 50 years . In ovulation, a reproductive hormone or gonadotrophin-releasing hormone is released from the hypothalamus of the brain that stimulates the release of the two reproductive hormones such as luteinizing hormone and follicle stimulating hormone from an anterior lobe of the pituitary gland of the brain, and promotes the development in a secondary follicle.
The granulosa cells reproduce to form a thick layer. The theca cells are engaged to the oocyte forming two different layers such as theca interna and theca externa, respectively. The oestrogen starts to increase that looks like a stoma theca cells that secretes androgens. This oestrogen is converted by the granulosa cells in the oestrodiol that serves two purposes. These purposes are preparing the female for the chance of an embryo in thickening the endometrium and thinning cervical mucus as well. The oestrogen performs on the hypothalamus and pituitary gland to switch off gonadotrophin-releasing hormone, follicle-stimulating hormone, and luteinizing hormone secretion by non-positive feedback. The meiosis I is completed and the secondary oocyte occurs with the primary polar body inside a secondary follicle. The polar body goes through atresis and degrades eventually. The meiosis continues and again meets a meiotic block at the metaphase II stage of meiosis II.
The development of the secondary follicle continues and forms a mature ovarian follicle or graafian follicle. The layers of follicular cells are attached to the zona pellucid that forms the corona radiate. The secretion of granulosa cells, a follicular fluid that produced fluid that is filled with cavity adjacent to the oocyte, the antrum. As the theca thickens, more oestrogen is released. The entire follicle is attached to the ovary through the formed of cumulus oophorus or a stalk that is produced by the granulosa cells. A developed mature follicle trigger the oestrogen to increase that leads to a rush in the luteinizing hormone that stimulates an ovulation. The oocyte burst out of the follicle; however, it is remained attached to the ovary, with a loosened cumulus oophorus on a wall-weakened through the hormone rush. The matured oocyte is ovulated, travels freely to the uterus, and meets a sperm cell along the way. With an increased of progesterone levels, it stimulates glandular activity, maintains the endometrium during a pregnancy, and later, it depends whether the oocyte is fertilized or not.
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