Special Senses: EYE & EAR BIOL 221L

• Fibrous tunic


  Sclera and Cornea; outermost layer
• Sclera

  Optic nerve penetrates

  
• Cornea

  The clear tissue that covers the front of the eye

  
• Vascular tunic

  Middle layer of the eye; contains the choroid, ciliary body, lens, iris, pupil
• Choroid

  Layer of connective tissues and blood vessels, provides nourishment to the outer layers of retina

  
• Ciliary body

  accommodation, holding the lens in place and producing aqueous fluid

  
• Ciliary muscle


  control the shape of the lens, and it secretes aqueous humor
• Lens


  curvature and shape allow for fine focusing of an image

  
• Refraction

  bending of light waves
• Anterior segment (Aqueous humor)


  Watery fluid found between lens and cornea
• Posterior segment (*Vitreous humor)

  Gel-like substance posterior to the lens

  
• Pupil


  The opening through which light enters the eye
• Sensory tunic

  innermost layer contains retina, optic disc, optic nerve, macula lutea, and fovea centralis
• Retina

  Light sensitive layer of the eye; contains rods and cones

  
• Optic disc


  blind spot

  
• Optic nerve


  carries neural impulses from the eye to the brain
• Macula lutea


  a yellowish central area of the retina that is rich in cones and that mediates clear detailed vision

  
• Fovea centralis


  Concentrated area of cones

  
• Emmetropic eye

  normal eye
• Myopic eye (near sighted)

  Concave lens
• Hyperopic eye (farsighted)

  Convex lens
• Conjunctiva


  Thin mucous membrane lining of the eye and eyelid
• Lacrimal gland


  produces tears
• Lacrimal canals (canaliculi)

  Drain tears from at medial side of eyes into lacrimal sac
• Lacrimal sac


  structure that collects tears before emptying into the nasolacrimal duct
• Nasolacrimal duct


  drains tears into nasal cavity
• Superior rectus


  elevates eye

  
• Inferior rectus

  looking down
• Medial rectus

  rotates eye medially

  
• Lateral rectus

  Deviates eye laterally

  
• Superior oblique

  Deviates eye inferior

  
• Inferior oblique


  Deviates eye superior, up and out
• Circular muscles (Sphincters)

  Muscles found in the iris that contract in bright light and relax in dim light
• Radial Muscles (Dilator Pupillae)

  contract when stimulated by the sympathetic nervous system, causing pupil to dilate
• Central retinal vessels

  artery and vein entering and exiting the eyeball at the back in the area of the optic disc
• Pathway of light through the eye

  Cornea, aqueous humor, pupil, lens, vitreous humor, fovea centralis, optic nerve, optic chiasm, optic tract, thalamus, occipital lobe
• Pathway of sound entering the ear

  External auditory canal/meatus, tympanic membrane, malleus, incus, stapes, oval window, cochlea, cochlear branch of the vestibulocochlear nerve, thalamus, temporal lobe
• Outer ear


  pinna and auditory canal

  
• Pinna (auricle)


  the visible part of the outer ear

  
• External acoustic canal/meatus

  Directs sounds to the tympanic membrane