Special Senses

Question 1

Eye

Answer 1

• 3 layered sphere filled with fluid
• Special features:
  1) Fibrous Tunic
  2) Vascular Tunic
  3) Nervous (Sensory) Tunic
  4) Lens
  5) Anterior Segment
  6) Posterior Segment

Question 2

Fibrous Tunic (Eye)

Answer 2

• Parts:
  1) Sclera (white)
• Avascular CT
  2) Cornea (Transparent)
• Avascular CT
  3) Conjunctiva
• Covers anterior sclera
• Vascular mucous membrane - when vessels dilate = bloodshot eyes

Question 3

Vascular Tunic (Eye)

Answer 3

• Parts:
  1) Choroid (posterior)
• Contains melanin
• Highly vascular
  2) Ciliary Body (anterior)
• Ciliary muscles + ciliary processes- focus the lens
  3) Iris
• Coloured part of eye
  4) Pupil
• Hole in Iris

Question 4

Nervous (Sensory) Tunic (Eye)

Answer 4

= Retina

• Parts:
  1) Outer Pigmented Layer
  2) Inner Neural Layer
  3) Fovea Centralis
  4) Optic Disc

Question 5

Inner Neural Layer (Nervous Tunic)

Answer 5

• 3 layers of neurons
  1) Photoreceptors (2 types)
  a) Rods - black + white
  b) Cones - colour
  2) Bipolar
  3) Ganglion
• Axons form optic nerve (cranial nerve II)

Question 6

Fovea Centralis (Nervous Tunic)

Answer 6

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

Question 7

Optic Disc (Nervous Tunic)

Answer 7

• Blind spot where blood vessels + optic nerve exit eye

- No rods or cones

Question 8

Lens (Eye)

Answer 8

• Avascular, transparent

- Cataracts = clouding of lens

Question 9

Anterior Segment (Eye)

Answer 9

• Anterior to lens

- Contains aqueous humour - fluid similar to plasma

Question 10

Posterior Segment (Eye)

Answer 10

• Posterior to lens

- Contains vitreous humour - gel-like

Question 11

Ear

Answer 11

• Structural Features:
  1) External Ear
  2) Middle Ear
  3) Inner Ear
  4) Cochlea
  5) Receptors in Inner Ear

Question 12

External Ear

Answer 12

• Conducts sound
• Parts:
  a) Auricle (Pinna)
• Elastic cartilage, covered with skin
  b) External auditory (acoustic) canal (meatus)
  c) Tympanic Membrane (eardrum)

Question 13

Middle Ear

Answer 13

• Conducts Sound
• Parts:
  a) Eustachian tube
• Also called pharyngotympanic tube
  b) Ear ossicles
  1) Malleus - secured to tympanic membrane
  2) Incus
  3) Stapes - Transmits sound to inner ear via oval window

Question 14

Inner Ear (Labyrinth)

Answer 14

• Detects sound, involved with equilibrium
• Parts:
  1) Bony Labyrinth
  2) Membranous Labrinth

Question 15

Bony Labyrinth (Inner ear)

Answer 15

• Tunnels in temporal bone
• Contains perilymph
• Parts:
  1) Semicircular Canals - equilibrium
  2) Vestibule - Equilibrium
  3) Cochlea - Hearing

Question 16

Membranous Labyrinth (Inner Ear)

Answer 16

• Surrounded and protected by bony labyrinth
• Contains endolymph
• Parts:
  1) Semicircular ducts - inside canals
  2) Utricle + Saccule - inside vestibule
  3) Cochlear duct - inside cochlea

Question 17

Cochlea

Answer 17

• Coiled
• Each coil has 3 channels:
  1) Scala Vestibuli - upper; perilymph
  2) Scala Tympani - lower; perilymph
  3) Cochlear duct - middle; endolymph
• Membranes:
  1) Vestibuler membrane - between cochlear duct + Scala vestibuli
  2) Basilar Membrane - between cochlear duct + Scala tympani
  3) Tectorial Membrane - covers hair cells (=receptor cells)

Question 18

Receptors In Inner Ear

Answer 18

• Hair cell that synapses with an associated neuron - send impulses to brain via cranial nerve VIII
• Hair = cilia that extend into endolymph - tips of cilia embedded in tectorial membrane (stability)