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The zona pellucida (plural zonae pellucidae) is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it. The zona pellucida first appears in multilaminar primary oocytes.

This structure binds spermatozoa, and is required to initiate the acrosome reaction.The zona glycoprotein, ZP3, is responsible for sperm binding, adhering to proteins on the sperm plasma membrane. There is evidence that ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle.

In humans, five days after the fertilization, the blastocyst performs zona hatching; the zona pellucida degenerates and decomposes to be replaced by the underlying layer of trophoblastic cells.

The zona pellucida is essential for oocyte death and fertilization.

In some older texts, it has also been called zona striata and stratum lucidum (not to be confused with the stratum lucidum of the skin).

Immunocontraception

Glycoproteins in ZP1, 2, and 3 are targets for immunocontraception.

In non-mammalian animals, the zona pellucida (called vitelline layer) plays an important role in preventing breeding of different species, especially in species that fertilize outside of the body (e.g. fish).

The zona pellucida is commonly used to control wildlife population problems by immunocontraception. When the zona pellucida of one animal species is injected into the bloodstream of another, it results in sterility of the second species due to immune response. This effect can be temporary or permanent, depending on the method used. In New Jerseymarker, Porcine zona pellucida is used to keep deer populations low, and this process is commonly referred to as "spay-vac".

Four Major Glycoproteins

  • ZP3 allows species-specific sperm binding
  • ZP2 mediates subsequent sperm binding
  • ZP1 cross-links ZP2 and ZP3. It is important for structural integrity of zona pellucida but not essential for fertilization.
  • ZP4 Its true function is still quite unknown but evidence shows in a pig, the primary sperm receptor is a heterocomplex of ZP3 and ZP4.


Additional images



Image:Gray9.png|First stages of segmentation of a mammalian ovum.Image:Gray1164.png|Section of vesicular ovarian follicle of cat. x50.

References







  • Bagnell C (2005). "Animal Reproduction". Rutgers University Department of Animal Sciences.












External links

  • - "Female Reproductive System: ovary, cumulus oophorus "
  • - "Female Reproductive System: ovary, multilaminar primary follicle"
  • - "Mammal, canine ovary (LM, High)"
  • Image at um.edu.mt
  • Image at um.edu.mt



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