External Ear

External Ear

The external ear consists of:

1. Auricle or Pinna
2. External Auditory Canal
3. Tympanic Membrane

Auricle or Pinna

• Made up of single elastic cartilage except the lobule.
• Continuous medially with the external auditory meatus.
• Covered by skin.

External Auditory Canal (EAC)

• Extends from the pinna to the tympanic membrane.
• Approximately 24 mm in length.
• Not a straight tube:
  • Inner part is directed upwards and backwards.
  • Outer part is directed downwards and forwards.
• Two parts:
  • Outer one-third: Cartilaginous (8 mm).
    • Contains hair follicles, sebaceous glands, and ceruminous glands.
  • Inner two-thirds: Bony (16 mm).
    • No hair follicles.

Relations of EAC

• Superiorly: Middle cranial fossa.
• Posteriorly: Mastoid air cells and the facial nerve.
• Inferiorly: Parotid gland.
• Anteriorly: Temporomandibular joint.

Tympanic Membrane

• Semi-transparent, pearl-white oval membrane.
• Separates the external and middle ear.
• Obliquely placed.
• Dimensions: 9–10 mm tall, 8–9 mm wide.
• Two parts:
  • Pars Tensa: Pearl white.
  • Pars Flaccida: Pinkish.

Layers of Tympanic Membrane

1. Outer epithelial layer: Continuous with the skin lining the meatus.
2. Inner mucosal layer: Continuous with the mucosa of the middle ear.
3. Middle fibrous layer.