What is the conjunctiva?

The conjunctiva is a mucous membrane that lines the eyelids and covers the surface of the eyeball, except for the part that is covered by the cornea. This membrane plays a crucial role in protecting the eye by providing a barrier against pathogens and environmental irritants. It also helps to keep the eye moist by producing mucus and tears, facilitating smooth eye movement and comfort.

The other options refer to distinctly different anatomical structures: blood cells are components of the circulatory system that transport oxygen and nutrients; parts of the heart are involved in the muscular and electrical functions of pumping blood; and muscle tissue is responsible for body movement and consists of specialized cells that can contract. The specific function and location of the conjunctiva make it essential for eye health, distinguishing it from these unrelated structures.