Kõvakesta

Kõvakesta is the Estonian word for the sclera, the tough, white outer layer of the eyeball. It is primarily composed of dense connective tissue, largely collagen, which provides structural integrity and protection to the delicate inner components of the eye. The sclera is continuous with the cornea at the front of the eye and the optic nerve sheath at the back. Its opaque nature gives the eye its characteristic white appearance, although variations in pigment can occur.

The primary functions of the sclera include maintaining the shape of the eyeball, protecting it from external trauma, and serving as an attachment point for the extraocular muscles that control eye movement. These muscles, responsible for rotating and moving the eye, insert into the sclera, allowing for precise and coordinated visual tracking. The sclera is relatively avascular, meaning it has few blood vessels, which contributes to its white color. However, it does receive nutrients from the underlying choroid.

In some medical contexts, the sclera can be involved in various conditions. Scleritis, for instance, is an inflammation of the sclera that can cause pain and redness. Diseases like Marfan syndrome or osteogenesis imperfecta can lead to a bluish discoloration of the sclera due to underlying connective tissue abnormalities. Medical procedures, such as corneal transplants, involve working with the sclera. The term "kõvakesta" in Estonian directly translates to "hard shell," aptly describing its protective and rigid nature.