SPECIAL SENSES

THE EYE

• Properties of light• External eye

– Palpebra– Eyeball– Protection provided by – – Meibomian glands (eyelashes)– Conjunctiva– Lacrimal glands

EYE MOVEMENTS3 pairs of muscles• Medial rectus• Lateral rectus• Superior rectus• Inferior rectus• Superior oblique• Inferior oblique

Internal Eye3 tissue layers + 2 fluid filled cavities1) Outer, fibrous tunic

1) Sclera “Canal of Schlemm”2) Cornea

2) Middle vascular tunic1) Choroid2) Ciliary body (ciliary muscles + ciliary

process)3) Lens4) Iris

3) Inner retina or nervous tunic1) Photoreceptor cells

1) Rods (rhodopsin)2) Cones (cyanolabe, erythrolabe,

chlorolabe)

2) Fovea centralis (cones only)3) Optic disk 4) Macula lutea

CAVITIES

1. Anterior1. Aqueous humor

1. Ciliary process2. Canal of Schlemm

2. Posterior1. Vitreous humor

LENS

• Changes shape and focuses light onto retina

• Accommodation

DISORDERS

• Myopia

• Hypermetropia

• Astigmatism

• Cataract• Glaucoma• Presbyopia• Color blindness

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