Zona Pellucida (Inferior)

Structure

The zona pellucida is a 6-8 μm dense, acellular transparent membrane that encircles the oocyte (Harrison, Bonnar and Thompson, 2012).

The zona pellucida is produced during folliculogenesis. The primary oocyte is located within the primordial follicle in the ovary. During the ovarian cycle, granulosa epithelial cells make intimate contact with the oocyte and deposit an acellular glycoprotein layer around the surface of the oocyte. As it increases in thickness, it forms the zona pellucida and remains present up until the end of the pre-implantation phase of pregnancy. The zona pellucida can only be penetrated by sperm, which must undergo an acrosomal reaction.

Key Features/Anatomical Relations

The zona pellucida is situated immediately internal to the corona radiata, to which it is adherent to, and external to the perivitelline space. The perivitelline space is an area that lies between the zona pellucida and the plasma membrane of the oocyte. The perivitelline space is the site where the contents of cortical granules were discharged following the fusion of the oocyte and the sperm (Plant and Zeleznik, 2014).

Function

The zona pellucida plays a vital role in ensuring that the processes of fertilization and implantation occur efficiently. Glycoproteins present in the zona pellucida allow for sperm binding, acrosomal activation, and species-specific fertilization. The zona pellucida plays a vital role in preventing polyspermy during the sperm-oocyte fusion (Gupta et al., 2009).

List of Clinical Correlates

- Infertility

- Contraception

- Assisted reproductive technology

References

Chiras, D. D. (2005) Human Biology. Jones and Bartlett Publishers.

DePamphilis, M. L. (2002) Gene Expression at the Beginning of Animal Development. Elsevier Science.

Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.

Gupta, S. K., Bansal, P., Ganguly, A., Bhandari, B. and Chakrabarti, K. (2009) 'Human zona pellucida glycoproteins: functional relevance during fertilization', J Reprod Immunol, 83(1-2), pp. 50-5.

Harrison, R. F., Bonnar, J. and Thompson, W. (2012) Fertility and Sterility: The Proceedings of the XIth World Congress on Fertility and Sterility, Dublin, June 1983, held under the Auspices of the International Federation of Fertility Societies. Springer Netherlands.

Plant, T. M. and Zeleznik, A. J. (2014) Knobil and Neill's Physiology of Reproduction. Elsevier Science.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edition: Elsevier Limited.