Human Eye Anatomy: Layers, Muscles, and Protective Structures

Fibrous layer

Outer layer of the eyeball, includes sclera and cornea.

Vascular layer

middle layer of eye; contains choroid, ciliary body, iris

nervous layer

Inner layer of the eye, contains retina.

eyebrows

overlie supraorbital margins; shade eye from sunlight, prevent perspiration from reaching eye

Eyelids (Palpebrae)

thin, skin-covered folds that protect eye anteriorly; offer protection from foreign objects and spread secretions to moisten eye

conjunctiva

transparent mucous membrane; produces a lubricating mucous secretion

Lacrimal apparatus

consists of lacrimal gland and ducts that drain into the nasal cavity; tears contain mucus, antibodies, and antibacterial lysozyme

extrensic eye muscles

originate from bony orbit and insert on eyeball; enable eye to follow moving objects, maintain shape of eyeball, and hold it in orbit

lateral rectus

muscle that moves eye laterally

medial rectus

muscle that moves eye medially

Superior rectus

elevates eye and turns it medially

inferior rectus

depresses eye and turns it medially

inferior oblique

elevates eye and turns it laterally

Superior oblique

depresses eye and turns it laterally