Special Senses

Question 1

Eye

Answer 1

3 layered sphere filled with fluid

Question 2

Structural features of the Eye

Answer 2

1. Fibrous Tunic
2. Vascular Tunic
3. Nervous (Sensory) Tunic
4. Lens
5. Anterior Segment
6. Posterior Segment

Question 3

Fibrous Tunic

Answer 3

• Sclera (white)
  
  • Avascular connective tissue (CT)
• Cornea (transparent)
  
  • Avascular CT
• Conjunctiva
  
  • Covers anterior sclera
  • Vascular mucous membrane
    
    • When vessels dilate = bloodshot eyes

Question 4

Vascular Tunic

Answer 4

• Choroid (posterior)
  
  • Contains melanin
  • Highly vascular
• Ciliary body (anterior)
  
  • Ciliary muscle and ciliary processes - focus the lens
• Iris
  
  • Coloured part of eye
• Pupil
  
  • Hole in iris

Question 5

Nervous (Sensory) Tunic = Retina

Answer 5

• Outer pigmented layer
• Inner neural layer
• Fovea contrails
• Optic disc

Question 6

Inner neural layer (Nervous Tunic)

Answer 6

• 3 layers of neurons
  
  • Photoreceptors (2 types)
    
    1. Rods - black and white
    2. Cones - colour
  • Bipolar Cells
  • Ganglion Cells
    
    • Axons from optic nerve (= Cranial Nerve II)

Question 7

Fovea contrails (Nervous Tunic)

Answer 7

• Where light is focused
• = Area of greatest visual acuity
• No rods, just cones

Question 8

Optic disc (Nervous Tunic)

Answer 8

• Blind spot where blood vessels + optic nerve exit eye
• No rods or cones

Question 9

Lens

Answer 9

• Avascular, transparent
• Cataracts = clouding of lens

Question 10

Anterior Segment

Answer 10

• Anterior to lens
• Contains aqueous humor
  
  • Fluid similar to plasma

Question 11

Posterior Segment

Answer 11

• Posterior to lens
• Contains vitreous humor
  
  • gel-like

Question 12

Structural Features of the Ear

Answer 12

1. External Ear
2. Middle Ear
3. Inner Ear (Labyrinth)
4. Cochlea
5. Receptors

Question 13

External Ear

Answer 13

• Conducts sounds
• Parts:
  
  • Auricle (pinna)
    
    • Elastic cartilage, covered with skin
  • External auditory canal (meatus)
  • Tympanic membrane (eardrum)

Question 14

Middle Ear

Answer 14

• Conducts sound
• Parts:
  
  • Eustachian tube
    
    • Also called pharyngotympanic tube
  • Ear ossicles
    
    • Malleus
      
      • Secured to tympanic membrane
    • Incus
    • Stapes
      
      • Transmits sound to inner ear via oval window

Question 15

Inner Ear (Labyrinth)

Answer 15

• Conducts sound
• Parts:
  
  • Bony Labyrinth
  • Membranous Labyrinth

Question 16

Bony Labyrinth

Answer 16

• Tunnels in temporal bone
  
  • Contain perilymph
• Parts:
  
  • Semicircular canals
    
    • Equilibrium
  • Vestibule
    
    • Equilibrium
  • Cochlea
    
    • Hearing

Question 17

Membranous Labyrinth

Answer 17

• Surrounded and protected by bony labyrinth
• Contains endolymph
• Parts:
  
  • Semicircular duct
    
    • Inside canals
  • Utricle and saccule
    
    • Inside vestibule
  • Conchlear duct
    
    • Inside cochlea

Question 18

Cochlea (Channels)

Answer 18

1. Scala vestibuli
   
   • Upper; perilymph
2. Scala tympani
   
   • Lower; perilymph
3. Conchlear duct
   
   • Middle; endolymph

Question 19

Cochlea (Membranes)

Answer 19

1. Vestibular membrane
   
   • Between cochlear duct + scala vestibuli
2. Basilar membrane
   
   • Between conchlear duct + scala tympani
3. Tectorial membrane
   
   • Covers hair cells (= receptor cells)

Question 20

Receptors

Answer 20

• Called hair cells that synapse with neurons
  
  • Send impulses to brain via cranial nerve VIII
• Hairs are cilia that extend into endolymph
  
  • Tips of cilia embedded in tectorial membrane (stability)