SPECIAL SENSES

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SPECIAL SENSES

• THE EYES AND EARS
• CHAPTER 11

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THE STRUCTURES OF THE EYE

• CHOROID
• PUPIL
• IRIS
• SCLERA
• CORNEA
• RETINA

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THE EYE

• The eye contains three layers of tissue that form
  the eyeball
• Sclera
• Choroid
• Retina

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SCLERA CHOROID

• Sclera also known as the white of the eye
• Maintains the shape of the eye
• Protects the inner layers of tissue
• The front surface is called the cornea

• The choroid is the middle layer of the eye
• Contains many blood vessels
• Provides the blood supply for the entire eye

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THE CHOROID

• Associated with the choroid is the
• Iris--the colored muscular layer that surround
  the pupil
• Pupil--the black center of the iris
• Ciliary muscles which adjust the shape and
  thickness of the lens

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THE LENS

• The lens also known as the crystalline lens
• Is clear, flexible, and curved
• Located behind the iris and pupil
• Is held in place by a ligament attached to the
  ciliary muscle

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THE RETINA

• The retina is the innermost layer of the eye
• Located between the posterior chamber and the
  choroid layer at the back of the eye
• Contains microscopic receptor cells
• Rods
• Cones

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RODS CONES

• Rods are the receptors for night vision
• Dim lights can stimulate the rods

• Cones are stimulated by bright light
• There are three kinds of cones sensitive to a
  different color
• Allows you to distinguish colors
• Converts images into nerve impulses

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OTHER PARTS OF THE INNER EYE

• Optic Disk/Blind Spot--where the nerve endings of
  the retina gather to form the optic nerve
• Macula lutea--yellow spot in the center of the
  retina
• Fovea centralis--a pit located within the macula
  lutea

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OCULAR CHAMBERS

• ANTERIOR CHAMBER--LOCATED BEHIND THE INNER
  SURFACE OF THE CORNEA AND IN FRONT OF THE IRIS
• POSTERIOR CHAMBER--LOCATED BETWEEN THE BACK OF
  THE IRIS AND THE FRONT OF THE LENS
• AQUEOUS HUMOR
• VITREOUS HUMOR

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OUTER STRUCTURES

• ORBIT
• EYE MUSCLES
• EYELIDS
• CONJUNCTIVA
• LACRIMAL APPARATUS

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VISUAL PATHWAY

• There is a particular pathway that light travels
  to allow us to see objects and includes light
  traveling through
• Cornea, aqueous humor, lens, and vitreous humor
• Hits the Retina
• Goes to the Optic Nerve
• Goes to the Brain/Occipital Lobe

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ACTIONS OF THE EYES

• REFRACTION
• ACCOMMODATION
• EMMETROPIA
• CONVERGENCE

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THE EAR

• ENABLES HEARING
• HELPS MAINTAIN BALANCE
• CONTAINS
• EXTERNAL EAR
• MIDDLE EAR
• INNER EAR
• LETS EXAMINE EACH OF THESE AREAS

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EXTERNAL EAR

• The external ear sometimes known as the outer ear
  consists of two parts
• Auricle or Pinna
• External Auditory Canal

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MIDDLE EAR

• The middle ear contains three small bones
• Malleus
• Incus
• Stapes
• Bones end at the Oval Window
• Eustachian tube

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THE INNER EAR

• The inner ear or Labyrinth contains the receptors
  for hearing and balance and consists of
• The Cochlea
• The Cochlea Duct
• Auditory Nerve Fibers
• Semicircular Canals
• Organ of Corti

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EAR FLUIDS

• PERILYMPH--A watery fluid located in the inner
  ear
• ENDOLYMPH--A thick fluid located in the inner ear

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HOW DO WE HEAR?

• There is a specific sequence of events that takes
  place to allow us to hear
• Sound waves enter through the Auricle
• Strike the Tympanic membrane
• Vibrates the Ossicles
• Vibration opens the Oval Window
• Sound waves make the Perilymph Emdolymph move
• Sends a signal to the Temporal Lobe of the Brain

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