Accessory Structures of the Eye

The accessory structures of the eyes protect and support the eye but are not directly involved in vision.      

Eyebrows, located above the eyes, consisting of dense short hairs. They help shade the eyes from sunlight and prevent sweat on the forehead from entering the eyes.

Eyelids or palpebrae are thin skin folds that cover the eyeball.

The upper and lower eyelids, separated by a palpebral fissure —meet at medial and lateral commissures. They protect the eyeball from external agents by covering it in front.

The conjunctiva is a transparent mucous membrane that lines the eyelids. It covers the sclera—the white of the eye, but not the cornea. It lubricates the eyes and prevents them from drying. 

The inner side of the eye holds the lacrimal apparatus, which consists of a lacrimal gland and ducts that carry lacrimal secretion, commonly known as tears.

Eyelids blink with the help of muscles orbicularis oculi, and levator palpebrae superioris, spreading the tears across the eye.

The tears pass through the lacrimal puncta and the lacrimal canaliculi and drain into the lacrimal sac.