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External acoustic meatus - Bony or Cartilaginous

 # Which of the following about external acoustic meatus is correct?
A. External acoustic meatus is purely cartilaginous in nature
B. External acoustic meatus is totally bony in nature
C. Medial side is bony in nature, whereas lateral side is cartilaginous in nature
D. Medial side is cartilaginous in nature, whereas lateral side is bony in nature


The correct answer is C. Medial side is bony in nature, whereas lateral side is cartilaginous in nature

External ear consists of auricle and the external acoustic meatus. 

External acoustic meatus is 24 mm long, of which medial two thirds (16 mm) are bony and lateral one third (8 mm) is cartilaginous. It can be examined by pulling the pinna upwards, backwards and outwards. The skin  lining the anterior half of the meatus is supplied by the auriculotemporal nerve and lining the posterior half by the auricular branch of the vagus. External auditory meatus contains modified sebaceous glands. Its floor is longer than its roof. It is narrowest near the tympanic membrane. 

Auricle is made of elastic cartilage. Nerve supply is from facial, vagus and mandibular nerve. Inflammation of the external ear is extremely painful  because its skin is highly vascular and firmly adherent to the underlying tissue. 

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