Question

Choose the correct sequence of the structure of the ear starting from external ear (entry of sound) to inner ear.
A. Helix
B. Oval window
C. Pinna
D. Cochlae
E. Tympanic membrane

• A. B, C, A, E and D
• B. C, A, E, B and D
• C. D, B, E, A and C
• D. A, C, E, B and D

Hint:

A helpful mnemonic for the major boundaries of the auditory system: Pinna (Outer receiver) $\rightarrow$ Tympanic Membrane (Middle ear border) $\rightarrow$ Oval Window (Inner ear border) $\rightarrow$ Cochlea (Neural processing center).

Answer 1

The Correct Option is D

Step 1: Concept:
The question requires tracing the precise anatomical pathway that acoustic sound waves take as they travel from the external environment, through the outer and middle ear, and finally into the inner ear for sensory processing.

Step 2: Step-by-step Explanation:

• Sound waves in the environment first encounter the most lateral structure of the external ear, the prominent cartilaginous rim known as the Helix (A).

• The waves are then captured and directed inward by the broader, bowl-like cartilaginous structure of the external ear, collectively referred to as the auricle or Pinna (C).

• Funneled through the external auditory canal, the acoustic waves strike the Tympanic membrane (E), commonly known as the eardrum, causing it to vibrate. This marks the boundary between the outer and middle ear.

• These vibrations are mechanically amplified by the three small ossicle bones (malleus, incus, and stapes) in the middle ear. The stapes bone pushes against the Oval window (B), a membrane-covered opening that serves as the entry portal to the inner ear.

• Once the vibrations pass through the oval window, they create fluid waves within the Cochlea (D), the snail-shaped, fluid-filled organ where mechanical waves are finally transduced into electrical neural signals by hair cells.

• Therefore, the sequential anatomical pathway is A $\rightarrow$ C $\rightarrow$ E $\rightarrow$ B $\rightarrow$ D.

Step 3: Final Answer:
Option (D) provides the correct anatomical sequence.