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Bio 40B – Dr. Kandula Exercise 24: Eye Accessory Structures Eyebrows Palpebrae / eyelids Eyelashes Ciliary glands – modified sweat glands Small sebaceous glands Sty is inflamed ciliary glands or small sebaceous glands Eyeball = 1 inch diameter 5/6 of Eyeball inside orbit protected Eyelashes eyebrows help protect from foreign objects, perspiration sunlight Sebaceous glands are found at base of eyelashes (sty) Palpebral fissure is gap between the eyelids Eyelids or palpebrae: protect lubricate; layers in eyelids - epidermis, dermis, CT, orbicularis oculi m., tarsal plate, tarsal glands conjunctiva Tarsal glands: oily secretions keep lids from sticking together Conjunctiva: palpebral bulbar - stops at corneal edge Tears / Lacrimal fluid a watery physiologic saline, with a plasma-like consistency, contains the bactericidal enzyme lysozyme; it moistens the conjunctiva and cornea, provides nutrients and dissolved O2 to the cornea. Extrinsic Eye MusclesEye movements controlled by six extrinsic eye muscles Four recti muscles - Superior, inferior, lateral and medial - move in direction of name Two oblique muscles Superior inferior - rotate eyeball on its axis Superior rotates inferiorly and laterally Inferior rotates superiorly and laterally Tunics of eye Fibrous tunic – outer layer Vascular tunic / uvea – middle layer Nervous tunic / retina – inner layer Internal Structures of Eye Outer fibrous tunic sclera cornea Fibrous tunic: Sclera the outermost layer of the eye. Made up of sclera and cornea Sclera “White” of the eye, covers posterior ? of the eye Dense irregular connective tissue layer -- collagen fibroblasts Provides shape support At the junction of the sclera and cornea is an opening (scleral venous sinus) Posteriorly pierced by Optic Nerve (CNII) Cornea Transparent Helps focus light(refraction) astigmatism 3 layers nonkeratinized stratified squamous collagen fibers fibroblasts simple squamous epithelium Transplants: common successful; no blood v