Spermeiogenesis / spermetoleosis, Biology

Assignment Help:

SPERMEIOGENESIS / SPERMETOLEOSIS

It is the gradual differentiation of a stationary rounded and undifferentiated spermatid into an active and motile sperm.

The spermatids formed as a result of maturation divisions are typical undifferentiated animal cells containing mitochondira, golgi body and centriole but with a haploid set of chromosomes.

In spermeiogenesis following changes take place -

(i) Formation of acrosome

  1. The acrosome of spermatozoan is derived from golgi complex of the spermatid.
  2. In a spermatid the golgi compelx is in the form of a spherical body, comprising of numerous vesicles or small vacuoles in the centre surronded by several rows of concentrically arranged cisternae.
  3. As the differentaition proceeds, the arrangement of cisternae becomes irregular and one or two vacuoles enlarge to replace the vesicles.
  4. Inside each large vacuole appears a small dense body, the proacrosomal granule.
  5. The vacuole with its acrosomal granule enlarges in size, migrates towards the anterior pole and gets attached to the tip of elongated nucleus forming a sort of cap.
  6. The proacrosomal granule enlarges further and forms the acrosomal granule.
  7. It forms core of the acrosome. The vacuole loses its liquid content spreads over the acrosomal granule and half of the nucleus forming of spermatozoan.
  8. The remainder of golgi body undergoes a gradual regression and is discardd as golgi rest together with the cytoplasm of spermatid.

357_formation of acrosome.png

Formation of Acrosome

(ii) Formation of Perforatorium

A rounded small pit present below the nucleus, in this part G actin and Ca++  ions are present. This spaces is called perforatorium space.

(iii) Nuclear changes

  1. The nucleus shrinks by losing water from the nuclear sap and the chromosome closely packed.
  2. The step is essential, since it reduces the weight of spermatozoon and enhances its motility.
  3. Even RNA and other accessory materials are also removed leaving only the hereditary material.

(iv) Tail

  1. The axial filament of the tail of spermatozoan is formed the centriole of spermatid.
  2. The distal centriole gives rise to the axial filament of the flagellum and acts as a basal granule.
  3. The proximal centriole enters the ovum along with sperm nucleus and mitotic spindle formation for the first division of the zygote nucleus.

(v) Formation of mitochondrial spiral and middle piece

  1. The proximal part of axial filament and distal centriole in the middle piece of spermatozoan.
  2. Gradually, these mitochondria lose their individuality and partly fuse together forming two densely packed bodies one on either side of axial filament.
  3. The mitochondrial sheath provides energy and strength to the sperm when it swims or moves towards the ovum.
  4. During the process of spermeiogenesis all the mitochondria of the spermatid fuse to form a nebenkern or Jensen's sheath.
  5. The nebenkern provide required energy to the sperm.
  6. The nebenkern along with little cytoplasm form a spiral sheath around the anterior end of the axial filament which is called as manchette.

(vi) Changes in the cytoplasm

  1. During the acrosome formation cytoplasm move to backside and maximum part store in the middle piece of sperm.
  2. Tail formation occurs and mitochondria's are arranged in middle piece and cytoplam arranged as manchette.

(vii) Sperm sheath

Sperm sheath is form of mucopolysaccharide. It is also called glycocalyx. This sheath probably function as antigen.


Related Discussions:- Spermeiogenesis / spermetoleosis

Mrna molecule codifies only one kind of protein, Q. An mRNA molecule codifi...

Q. An mRNA molecule codifies only one kind of protein? Eukaryotic cells have monocistronic mRNA, that is each mRNA codifies only one polypeptide chain, Prokaryotes can present

Define excretion of methyl malonic acid in urine, Define Excretion of Methy...

Define Excretion of Methyl malonic acid in urine (Methyl malonil aciduria)? Methyl malonic acid is found only in traces in normal urine (1-2 mg/day). In vitamin  B 12 deficie

Role of wter, What is the role of water in metabolism and photosynthesis I

What is the role of water in metabolism and photosynthesis I

Hypoglycaemia, Hypoglycaemia is defined as state of low blood glucose level...

Hypoglycaemia is defined as state of low blood glucose level of less than 50mg/dl. Low blood sugar level varies from person to person. Causes Since hypoglycaemia can occur in

Describe the regulation of pyruvate dehydrogenase, Describe the regulation ...

Describe the regulation of pyruvate dehydrogenase through covalent modification. PDH exists in 2 forms :  Inactive, phosphorylated and Active, dephosphorylated. The active form

Transport system in higher animals, Transport system in higher animals ...

Transport system in higher animals The circulatory system in higher animals has undergone several changes during evolution. The heart has become totally muscular. It p

Define the agar shake tube method, Define the Agar Shake Tube Method Th...

Define the Agar Shake Tube Method The agar shake tube method is useful for isolation of anaerobic microorganisms. What are anaerobic microorganisms? You may recall the theory c

How do biodiversity vary during the ecological succession, Q. How do biodiv...

Q. How do biodiversity, the total number of living beings and the biomass respectively vary during the ecological succession? The Biodiversity, the biomass of an ecosystem and

Different from all the other cellular microbes, How are the bacteria and th...

How are the bacteria and the archaea different from all the other cellular microbes? -They have cell walls? -They can move? -They reproduce asexually? -They have no nucleus?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd