Ear Anatomy

Question 1

What is the function of the external pinna?

Answer 1

Transmission of sound waves to TM

Question 2

What antibodies are contained in cerumen?

Answer 2

IgG, IgM, IgA

Question 3

Where is the “normal landmark tuft of hair” located in the canal?

Answer 3

At the external acoustic meatus in the ventral half fo the canal

Question 4

What pattern do cells migrate from the ear drum?

Answer 4

• Start at TM and migrate in centrifugal pattern
• Normal cleaning mechanisms of the ear canal

Question 5

What does the TM separate?

Answer 5

External from middle ear

Question 6

What are the 3 parts of the middle ear?

Answer 6

1. Dorsal
   
   1. smallest
   2. contains head of malleus and incus
2. Middle
   
   1. aka “Tympanic Cavity Proper”
   2. adjacent ot TM
   3. Auditory tube opens here
3. Ventral
   
   1. largest
   2. contains septum bulla
      
      1. *in cats, this is complete and divides
   3. difficult to access/assess this area

Question 7

What differs regarding the septum bulla in cats?

Answer 7

• Cats: Septum bulla complete
• Divides ventral bulla into two parts:
  
  • Pars tympanica (dorsolateral)
  • Pars endotympanica (ventromedial)

Question 8

What structures run through the middle ear?

Answer 8

• Facial nerve (CN VII)
• Vagus nerve (CN X)
• Carotid and Lingual arteries

Question 9

What parts of the ear make up the vestibular system?

Answer 9

1. Saccule
2. Utricle
3. Semi-circular canals
   
   1. filled with endolymph

Question 10

What is/are the macula?

Answer 10

• Neurosensory epithelial hairs on the wall of the cavities (saccule, utricle, semi-circular canals).

Question 11

What surrounds the Macula? What is its function?

Answer 11

• a gelatinous layer of polysaccharide overlies the macula
• within it are Otoliths = Ca+carbonate crystals
  
  • determine head rotation with movement