The process of formation of male gametes i.e. , sperms is called spermatogenesis. It occurs in the seminiferous tubules of the testes.
Formation of spermatids
Multiplication phase : The undifferentiated germ cells divide mitotically to form large number of spermatogonia .
Growth phase : Each spermatogonium accumulates large amount of nutrients and chromatin material , grows to a larger primary spermatocyte by the process called spermatocytogenesis .
Maturation phase : Each primary spermatocyte undergoes first meiotic division to form two secondary haploid spermatocytes which in turn produce four spermatids via second meiotic division . The first meiotic division is a homotypic division, whereas the second meiotic division is heterotypic.
Formation of spermatozoa
The transformation of spermatids into spermatozoa ( sperm ) is called spermiogenesis or spermateliosis or differentiation phase .
The different changes occurring during spermiogenesis are :
( i ) Formation of acrosome by Golgi apparatus . The latter then degenerates
( ii ) Elongation and condensation of nucleus
( iii ) Separation of centrioles into anterior proximal centriole and posterior distal centriole
( iv ) Formation of axial filament from distal centriole
( v ) Development of mitochondrial spiral around upper parts of axial filament.
( vi ) Formation of flagellum
After their maturation , spermatozoa detach from Sertoli cells . The process is called spermiation .
Four sperms are differentiated from a spermatogonium cell . The released sperms are stored in epididymis and first portion of vasa deferentia where they complete their maturation and become capable of fertilising an ovum . Nutrition is provided by epithelium of epididymis .
Sperm or Spermatozoon
Sperm is a microscopic structure composed of a head , neck , a middle piece and a tail . A plasma membrane envelops the whole body of sperm
The sperm head contains an elongated haploid nucleus . The anterior portion of head forms acrosome containing proteolytic and lysosomal enzyme
The middle piece possesses numerous mitochondria which provide energy for sperm motility.
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MANISH MEVADA
M. Sc, M. Phil, B. Ed
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