Here's a breakdown of its roles and characteristics:

Functions:

* Protection: It acts as a protective barrier, shielding the yolk from damage and microbial invasion.

* Structural Support: It helps maintain the shape of the yolk.

* Sperm Entry: It has a specialized region called the micropyle that allows sperm to penetrate the egg during fertilization.

* Development: It plays a role in the early stages of embryonic development, facilitating cell division and differentiation.

Characteristics:

* Composed of: The vitelline membrane is primarily made of glycoproteins, specifically vitelline and chorionin.

* Location: It's located immediately outside the yolk, beneath the albumen (egg white).

* Thin and Flexible: It's very thin and flexible, allowing for the expansion of the yolk during development.

Important Note: The vitelline membrane is not the same as the shell membrane or the eggshell.

* The shell membrane is a tougher, more fibrous membrane that lies beneath the eggshell.

* The eggshell itself is a hard, calcified outer layer.

Understanding the vitelline membrane helps in understanding the intricate structure and function of an egg, particularly its role in reproduction and embryonic development.