External Ear Anatomy: High-Yield Revision for ENT Exams and Clinical Practice

A. Overview & Functions of the Ear (2 Points)

1. Functions of the Ear – “HEAR” Mnemonic
   • Hearing: Converts sound waves to nerve impulses.
   • Equilibrium: The Vestibular system maintains balance.
   • Alarm: Detects threatening sounds from the environment, acting as a warning system.
   • Reception: Essential for speech and communication.
2. Three Main Divisions of the Ear
   • External Ear: Auricle (Pinna) + External Acoustic Canal + Tympanic Membrane.
   • Middle Ear: Tympanic cavity + Ossicles + Eustachian tube.
   • Internal Ear: Cochlea (hearing) + Vestibular apparatus (balance).

 

B. External Ear (Auricle/Pinna)

1. Prominent Landmarks of the Pinna – “HAT CAG”
   • Helix, Antihelix, Tragus, Concha, Antitragus, Groove (intertragic notch)
2. Muscles, Blood & Nerve Supply
   • Muscles: Extrinsic (3) & Intrinsic (6) – both by Facial Nerve (CN VII)
   • Arterial supply: Posterior auricular (ECA), Anterior auricular (STA), Occipital (assist)
   • Nerve supply:
     • Greater auricular (C2–C3) – Posterior & medial pinna
     • Auriculotemporal (V3) – Tragus, anterosuperior pinna
     • Facial (VII), Vagus (X), Lesser occipital (C2) – Concha & postauricular region
3. Lymphatic Drainage of the Pinna
   • Medial Surface → Mastoid nodes
   • Tragus/Upper Lateral → Preauricular nodes
   • Rest of Pinna → Upper deep cervical nodes

 

  C. External Auditory Canal (EAC)

1. Structure of EAC
   • Cartilaginous outer 1/3 (8 mm) – Has hairs, ceruminous and pilosebaceous glands which produce earwax, furuncles are seen only in this part
   • Bony inner 2/3 (16 mm) – Has isthmus (narrowing 5-6 mm lateral to the TM), making medial foreign body removal difficult. It also has an anterior recess that collects discharge but is hard to access; wax here or in the attic may signal cholesteatoma, and posterosuperior sagging can suggest mastoiditis.
   • Shape  of EAC: S-shaped; pull upward, backwards, and laterally for otoscopy
2. Infection Pathways
   • Fissure of Santorini – Present in cartilaginous EAC, increases flexibility but allows infections and neoplasms to spread to and from the parotid and temporomandibular regions.
   • Foramen of Huschke – Present in bony EAC, acts the same as Fissure of Santorini
   • Hitzelberger sign – Hypoesthesia of posterior meatal wall = Acoustic neuroma
3. Important Relationships of EAC
   • Anterior: TMJ
   • Posterior: Mastoid, facial nerve
   • Superior: Middle cranial fossa
   • Inferior: Parotid gland
   • Medial: Tympanic membrane
   • Lateral: Environment
4. Nerve Supply of EAC
   • Anterior & Superior: Auriculotemporal (V3)
   • Posterior & Inferior: Arnold’s nerve (Vagus, CN X) – → Vasovagal reflex
   • Posterior Wall: Facial nerve (CN VII)

D. Tympanic Membrane (Drumhead)

1. Basic Features
   • Size: 9–10 mm (height) × 8–9 mm (width)
   • Thickness: ~0.1 mm
   • Angle: 55° with the floor of the EAC
   • Set obliquely: Posterosuperior is more lateral
   • Colour: Pearly white
2. Tympanic membrane has 3 Layers
   • Outer Epithelial – continuous with skin
   • Middle Fibrous – with radial & circular fibres
   • Inner Mucosal – continuous with the middle ear
3. Pars Tensa vs. Pars Flaccida
   • Pars Tensa: Thick, has a fibrous layer, shows cone of light
   • Pars Flaccida: Above malleus, lacks robust fibrous layer → cholesteatoma site
4. Blood Supply
   • Lateral surface: Auricular branch of maxillary artery
   • Medial surface: Anterior tympanic, Stylomastoid branch (PAA), Middle meningeal
5. Nerve Supply
   • Lateral side:
     • Anterior half: Auriculotemporal (V3)
     • Posterior half: Auricular branch of Vagus (CN X) → Arnold’s Reflex
   • Medial side: Jacobson’s nerve (Tympanic branch of Glossopharyngeal CN IX)
6. Clinical Pearls for Otoscopy
   • Normal TM: Shiny, pearly grey, visible cone of light
   • Siegelization: Tests mobility using pneumatic otoscope
   • Cholesteatoma suspicion: Wax/debris on pars flaccida or attic = red flag

 

———— End of the chapter ————

Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Glasscock-Shambaugh, Textbook of Surgery of the Ear.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Salah Mansour, Middle Ear Diseases – Advances in Diagnosis and Management.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Rob and smith, Textbook of Operative surgery.
• Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.

Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India

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Keywords: PPT Free Download, External ear nerve supply, Ear plugs, Ear lobe, Auricle or pinna, Anatomy of Ear, Muscles & Blood supply of pinna, Fissures of Santorini, Huschke.