This process occurs in the seminiferous tubules of the testis. It begins at puberty and continues throughout life. Type A spermatogonia, which are derived from the primordial germ cells that migrated from the wall of the yolk sac, undergo mitosis.
gametes gametes are mature haploid germ cell or sex cells male gametes at a sperm or female germ cell ovum fused with another mature haploid germ cell during fertilization to form a zygote gametogenesis is the formation and development of cells that form gametes or sex cells in male that is stones or females that is oocytes in the male and female gonads from precursor cells
gametogenesis in males are called as spermatogenesis the process in which undifferentiated germ cells are immature or primordial germ cell undergo differentiation to form mature sperm
gametogenesis in females are called as oogenesis this is the development of female sex cell or ugonia into mature ovum in the female gonad that is ovary formation of the primordial germ cells
formation of the primordial germ cells during the early embryogenesis the fifth week of gestation the primordial germ cells originate in the endodermal epithelium of yolk sac in the vicinity of alantoik stock these cells migrate to the gonadal ridges which later give rise to functional gametes in males and female gonads testis and ovary respectively these cells remain dormant until puberty and at puberty these cells differentiate to form mature sperms or ovum this process continues throughout the life but decreases at old age
the testis is a paired ovoid male reproductive organ situated in the scrotum
from the superior aspect it is suspended by spermatic cord the epididymis is a comma-shaped body situated on the lateral part of posterior border of testes it consists of head body and tail the head of epididymis receives and stores sperms released from the seminiferous tubules of testus
the sperms in the epididymis undergo maturation and travel through the tail of epididymis into the vas deferens the testis is enveloped by a double layered membrane known as tunica vaginalis
except at the superior and posterior border where the spermatic cord and epididymus adheres to the testis the testis is composed of convoluted seminiferous tubules in which the process of spermatogenesis takes place
it is held in a loose connective tissue with numerous elastic fibers and interspersed ladies cells these ladies cells often present in groups these cells are the prime source of testosterone that is male sex hormone the seminiferous tubules consist of a basement membrane on which the primordial germ cells lie these germ cells differentiate or mature as they advance towards the lumen of the seminiferous tubule also interspersed between the spermatogonia are the sertoli cells which are large pyramidal shaped cells with centrally placed nucleus and nucleoli with numerous cytoplasmic organelles such as golgi complexes ribosomes lysosomes these cells project inward from the basement to the lumen and provides support nutrition to the developing sperm cells secrete fluid into the lumen and are phagocytic in nature the spermatogonia and the spermatids are embedded in the resources of the sertoli cells throughout its development
the first stage of spermatogenesis occurs at puberty where the primordial germ cells differentiate to form type a dark spermatogonia these type a dark cells undergo mitotic division to produce more type a dark
and type a light spermatoconia
the type a dark spermatogonia have the ability to self-renew and the type a light spermatogonia cells differentiate and undergo mitotic division to form type b spermatogonia these type b cells further divide to form primary spermatocytes the primary spermatocytes consist of 46 chromosomes of which 44 are autosomes and two are sex chromosomes that is x and y chromosomes these deployed primary spermatocytes enter first meiotic division and produce haploid secondary spermatocytes that is 23 chromosomes in each spermatocyte these secondary spermatocytes then undergo second meiotic division to form spermatids which process 22x and 22 white chromosomes these spermatids gradually undergo a series of morphological changes to develop into a mature spermatozoa this process is known as spermiogenesis
in this process each spermatid comprises of a spherical nucleus golgi apparatus centrosome with proximal and distal centrioles mitochondria and cytoplasm the nucleus condenses
and the golgi apparatus with acrosomal granules coalesce and spread over the anterior pole of the nucleus to form a bilaminar cap that covers over two thirds of the nucleus the centrosome occupies the posterior pole of the nucleus and splits the proximal and distal centrioles to give rise to axial filaments of the body that is middle part.