Spermatogenesis and Spermiogenesis
Spermatogenesis refers to the entire process of converting the original diploid
precursor of spermatozoa (bearing 46 chromosomes), the spermatogonia into
haploid spermatozoa bearing 23 chromosomes).
Q. 1. At what age The spermatogenic cycle initiates ? Ans: The spermatogenic cycle from spermatogonia
to spermatozoa starts at puberty and last about 9 weeks. This process is
initiated by testosterone secreted by Leydig cells. Under the influence of
testosterone, spermatogonia proliferate rapidly by mitotic division to produce primary
spermatocyte.
Q 2. When doses first meiotic division initiates??
Ans. Primary spermatocyte enters
meiosis I or the first meiotic division and produces a secondary spermatocyte.
Q.3: Whan is the secondary spermatocytes ? It is the division
of secondary spermatocytes undergo
meiosis II and form haploid spermatids (23 chromosomes). The spermatid being haploid can be used for in vitro fertilization since
it has acquired the status of a mature spermatozoon.
Q, 4: What is then spermiogenesis? . Formation of spermatozoa involves three
events and this is known as spermiogenesis.(the finishing touch)
1.
Acrosome granule formation and acquisition
of acrosome cap : The acrosomal granule is made of coalition of Golgi membranes
and the granules wrap round the nucleus to form and acrosomal cap.
2.
The tail and midpiece formation of
the spermatozoon is formed by the movement of the centriole towards the tail
end of the acrosomal ends. 3. Centriole
forms the flagellum.
4.
Mitochondria group around the
junction of the tail and the head forming the midpiece.
5.
Nuclear condensation in the head :--The
matured spermatozoon now has a nuclear condensation in the head. The residual
tissues remaining after formation of spermatozoa is engulfed by Sertoli cell.
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