Where is the conjunctival sac located in the eye?

The conjunctival sac is a pouch-like space located between the eyelids and the eyeball, formed by the palpebral conjunctiva, bulbar conjunctiva, and fornix conjunctiva. Specifically, it is a mucous membrane that covers the inner surfaces of the upper and lower eyelids and the anterior surface of the eyeball, creating a cavity enclosed by the palpebral and bulbar conjunctivae. When the eyelids are closed, the opening of this sac closes, while the sac communicates with the outside environment through the palpebral fissure. Additionally, the conjunctival sac contains abundant blood vessels, nerve endings, and mucous glands that secrete mucus. These structures play important roles in protecting the eyeball, facilitating eye movement, lubricating the eye surface, and reducing friction between the conjunctiva and cornea. Therefore, the conjunctival sac is a vital component of the eye.