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Transcript
Eye Notes I. II. Accessory Structures of the eye: a. Eyelids – aka. Palpebral i. Meets at medial and lateral canthus b. Eyelashes i. Meibomian glands – modified sebacious glands produce an oily secretion to lubricate the eye 1. Chalazion - inflammation ii. Ciliary glands – modified sweat glands between the eyelashes 1. Sty - inflammation c. Conjunctiva: membrane that lines the eyelids i. Connects to the surface of the eye ii. Secretes mucus to lubricate the eye 1. Conjunctivitis – inflammation of – sometimes known as “pink eye” d. Lacrimal apparatus i. Lacrimal gland – produces lacrimal fluid ii. Lacrimal canals – drains lacrimal fluid from eyes iii. Lacrimal sac – provides passage of lacrimal fluid towards nasal cavity iv. Nasolacrimal duct – empties fluid the nasal cavity v. Functions: 1. Dilute salt solution (tears) 2. Contains antibodies and lysozyme 3. Protects, moistens, and lubricates the eye 4. Empties into the nasal cavity e. Extrinsic Eye muscles i. Six eye muscles attach to the outer surface of the eye ii. Produce gross eye movements iii. Rectus muscles: lateral, medial, superior, inferior iv. Oblique muscles: inferior, superior Structure of Eye a. The wall is composed of three tunics i. Fibrous tunic – Outer layer (Sclera) ii. Vascular tunic (uvea) – middle layer (Choroid) iii. Sensory tunic – inside layer (Retina) b. The Fibrous Tunic i. Sclera: White connective tissue layer 1. Seen anteriorly as the “white of the eye” ii. Cornea: Transparent, central anterior portion 1. Allows for light to pass through 2. Repairs itself easily 3. The only human tissue that can be transplanted without fear of rejection c. Vascular Tunic: d. e. f. g. i. Choroid – posterior portion 1. Blood-rich nutritive tunic 2. Dark pigment prevents light from scattering ii. Ciliary body – anterior 1. Smooth muscle 2. Attached to lens iii. Iris: Pigmented layer that gives eye color 1. Pupil – rounded opening in the iris for light passage 2. Circular & radial fibers regulate opening Sensory Tunic (Retina) i. Contains receptor cells (photoreceptors) 1. Rods & Cones ii. Leave the retina toward the brain through the optic nerve iii. Rods: 1. Allow dim light vision and peripheral vision 2. Edges of Retina 3. Perception is all in gray tones iv. Cones: 1. Allow for detailed color vision 2. Densest in the center of the retina v. Fovea centralis 1. Area of the retina with only cones 2. Area of greatest visual acuity vi. Optic disk (Blind Spot) 1. No photoreceptor cells, 2. Site of optic nerve leaving eyeball Lens i. Biconvex crystal-like structure ii. Held in place by a suspensory ligament attached to the ciliary body iii. Cataracts: clouding of lens Aqueous humor in Anterior Segment i. Watery fluid found in chamber between the lens and cornea ii. Similar to blood plasma iii. Helps maintain intraocular pressure iv. Provides nutrients for the lens and cornea v. Reabsorbed into venous blood 1. Blocked drainage = glaucoma Vitreous humor: Gel-like substance behind the lens i. Keeps the eye from collapsing ii. Lasts a lifetime and is not replaced iii. Keeps retina firmly against wall of eyeball