A Brief Overview to the Beginning of the Human Embryologic Development

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Humandevelopment begins when a male gamete or sperm unites with a female gamete or ovum to form a single cell called a zygote. Gametogenesis process involving the chromosomes and cytoplasm of the gametes, prepares these cells for fertilization. During gametogenesis, the chromosome number is reduced by half and the shape of the cells is altered. Gametes develop in the gonads (sex cells). In males, its name is spermatogenesis, formation of sperm. In females, its name is oogenesis, formation of oogonesis. The process of gametes formation that occurs in the gonads (ovary or testis). It is defined as a process by which diploid or haploid cells undergo cell division and differentiation to form mature haploid gametes. Spermatogenesis and oogenesis are both forms of gametogenesis, in which a diploid gamete cell produces haploid sperm and egg cells.

Primordialgerm cells are the progenitor cells that give rise to the gametes. Primordial germ cells migrating from the vitellus sac to the reproductive organ developmental zone are distributed among the cells in the region. After a while, changes start in the male testes. The differentiation in primordial germ cells, which started in the third month of uterine life in female, but it, starts in puberty in male. A newborn males, sex cord’s shape are like a column. In this case, all of the primordial germ cells are seated on the basal membrane of the sex cord and are mixed with the modified cell that Sertoli cells (Sustentaculer). Along with the formation of the lumen, the primordial germ cells turn into spermatogoniums. At the meiosis cleavage stages they enter into a tight relationship with the Sertoli cell. Sertoli cells, the structural cells of the reproductive epithelium of the sex cord, perform vital tasks such as supplementing, feeding, hormone secretion, mitosis and regeneration. Sertoli cells are nurse cells.

Spermatogenesisis a complex period that relies on coordinated cell proliferation and apoptosis. Spermatogenesis is a temporal event during which a relatively undifferentiated diploid cell called spermatogonium slowly evolves into a highly specialized haploid cell called spermatozoon. The main aim of spermatogenesis is to produce a genetically unique male gamete that can fertilize an ovum and produce offspring. Spermatogenesis can be divided into three stages.