Connection lost. Please refresh the page.
Get help How to study Login Register
Ready to learn?
Pick your favorite study tool

Zona pellucida

Recommended video: Female reproductive system [18:21]
Main organs of the female reproductive system.

The zona pellucida (ZP) is an extracellular matrix layer that forms between the cell membrane of the oocyte and the first layer of granulosa cells during primary ovarian follicle development.

This layer measures about 5 to 10 μm in thickness and is composed of four main glycoproteins: ZP1, ZP2, ZP3 and ZP4. These glycoproteins, produced by the oocyte, form an irregular meshwork structure.

The filopodia (cytoplasmic processes) of granulosa cells in contact with the zona pellucida, penetrate this layer and interdigitate with microvilli of the oocyte, establishing a pathway for communication between the cells via gap junctions.

The zona pellucida plays important roles in sperm binding and fertilization. ZP3 and ZP4 serve as primary sperm receptors within the zona pellucida. These receptors bind to specific proteins on the sperm's surface, triggering a process called acrosomal reaction. This reaction enables the sperm to release hydrolytic enzymes, which then degrade the zona pellucida, allowing access to the oocyte.

Once the first sperm fuses with the oocyte plasma membrane, a process called cortical reaction ensues, resulting in the release of enzymes (proteases) from the cortical granules. These enzymes induce biochemical changes in the zona pellucida, rendering it resistant to further sperm binding and impermeable to additional sperm in a process termed the zona reaction. This mechanism effectively prevents polyspermy, ensuring that an oocyte is fertilized by a single sperm.

Terminology English: Zona pellucida
Synonyms: Pellucid zone

Zona pellucida
Definition Glycoprotein envelop surrounding plasma membrane of the oocyte
Function Facilitates sperm binding and fertilzation
Prevents polyspermic fertilization

Learn more about the zona pellucida of the ovarian follicle in the following study unit:

Zona pellucida: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more.

Kim Bengochea Kim Bengochea, Regis University, Denver
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Register now and grab your free ultimate anatomy study guide!