Quick Facts
The plasma membrane is the structure enveloping a cell, enclosing the cytoplasm and forming a selective permeability barrier; it consists of a lipid bilayer with integral and peripheral proteins and contains channels and pumps to transport substances across the membrane, as well as receptors to receive stimuli from the external environment and transduce them into intracellular signals (Dorland, 2011).
Related parts of the anatomy
Structure
The plasma membrane of the oocyte is a fine, semipermeable membrane that encloses the cytoplasm and is produced by rough endoplasmic reticulum in synergy with the Golgi complex. It is made up of phospholipids, cholesterol, glycolipids, and proteins in roughly equal proportions (Standring, 2016).
The lipid component of the plasma membrane forms a lipid bilayer, each of which is approximately 7.5 nm thick. The lipid bilayer of the plasma membrane is predominantly fluid; hence, it selectively permits diffusion of a number of molecules across its plane. The protein components are submerged in the lipid bilayer in a uniform manner popularly referred to as the fluid mosaic model. While some of the plasma membrane proteins are affixed to the lipid bilayer in a superficial manner, a number of them known as transmembrane proteins spread across the entire width of the plasma membrane (Standring, 2016).
Key Features/Anatomical Relations
The plasma membrane surrounds the cytoplasm of the oocyte. It lies internal to the perivitelline space, which in turn lies internal to the zona pellucida.
Function
The plasma membrane (plasmalemma) of the secondary oocyte plays a role in facilitating fertilization, as well as preventing polyspermy. More specifically, at fertilization the “cortical reaction” is initiated where cortical granules fuse with the plasma membrane then release their contents into the perivitelline space. The cortical granules contain enzymes dismantle the receptor binding sites for the sperm head. As a result of this, no extra sperm can bind to the zona pellucida to penetrate the ovum (Chiras, 2005; Standring, 2016).
List of Clinical Correlates
- Infertility
- Polyspermy
- Assisted Reproductive Technology
References
Chiras, D. D. (2005) Human Biology. Jones and Bartlett Publishers.Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edition: Elsevier Limited.
