Anatomical Location of the External Ear Canal
The external ear canal (also called the external auditory canal or EAC) extends from the auricle (pinna) to the tympanic membrane (eardrum), forming an osseous-cartilaginous tube that connects the outer ear to the middle ear. 1
Structural Components and Boundaries
The external ear canal is one of two parts that comprise the external ear, with the other being the auricle 1. Specifically:
- Lateral boundary: The canal begins at the auricle (pinna), which is the visible portion of the outer ear 1
- Medial boundary: The canal terminates at the tympanic membrane (eardrum), which separates the external ear from the middle ear cavity 2, 1
- Composition: The canal is an osseous-cartilaginous structure, meaning it has both cartilaginous (lateral third) and bony (medial two-thirds) portions 1
Relationship to Adjacent Structures
The external auditory canal serves as a physical conduit between the outside environment and the tympanic membrane 3. Key anatomical relationships include:
- Connection to middle ear: The tympanic membrane at the medial end of the canal separates it from the middle ear cavity, which contains the ossicles (malleus, incus, and stapes) 2
- Connection to nasopharynx: The middle ear cavity connects to the nasopharynx via the Eustachian tube, though this is beyond the external canal itself 2
- Temporal bone location: The bony portion of the canal is located within the temporal bone 2
Clinical Significance of Canal Anatomy
Understanding the canal's anatomical location is essential because:
- Medial canal location: Exostoses (bony growths) typically occur in the medial ear canal near the eardrum, while osteomas are usually lateral in the bony canal 2
- Visualization challenges: The canal's depth and curvature can limit direct visualization of the tympanic membrane, particularly when narrowing or debris is present 2
- Specialized epithelium: The canal is lined with highly specialized skin that migrates outward and contains cerumen glands, distinguishing it from other skin appendages 4, 3