External Ear

EMBRYOLOGY:
  • First branchial cleft is the precursor of external auditory canal.
  • Around the sixth week of embryonic life, a series of six tubercles appear around the first branchial cleft.
  • They progressively coalesce to form the auricle.
  • Branchial clefts are ectodermal in origin.
  • Pinna is formed at birth
ANATOMY:
Skin
  • Thin with no dermal palillae
  • Closely adherent to underlying cartilage & bony wall
  • Cartilagenous part has subcutaneous tissue -secretes wax
  • Active – collumnar & Quiescent – cuboidal
  • Ceruminous glands and hair follicles are limited to cartilagenous parts only
  • Skin over pinna is fixed Loosely on medial side
Pinna
  1. Irregularly concave, faces forwards with many eminences and depressions
  2. Helix
  3. Crus of helix
  4. Auricular tubercle (Darwin’s tubercle)
  5. Antihelix & its 2 cruras
  6. Triangular fossa
  7. Scaphoid fossa
  8. Concha & Cympa concha
  9. Tragus
  10. Antitragus
  11. Intertragic notch
  12. Lobule of pinna
Cartilagenous framework of auricle
  • Single thin plate of elastic fibrocartilage(yellow)
  • Continous with the cartilage of EAC
  • No cartilage in lobule and between tragus and crus of the helix
  • Helix and antihelix are separated by fissura anti-tragohelicinia
  • Medial aspect has Eminentia concha & Eminentia scaphae sep. by sulcus anti-helicis transversus (corresp. to inf. crus of antihelix)
  • E. conchae is crossed y a oblique ridge – Ponticulus (atch. of auricularis posterior)
Ligaments
  • Extrinsic - connects auricle to temporal bone
  • Anterior Lig - tragus & spine of helix to root of zygomatic process
  1. Posterior Lig - post surf. of concha to lat. surf of mastoid process
  2. Intrinsic - connects individual auricular cartilages
  • Strong fibrous band between tragus and helix
  • Another band between antihelix and tail of helix
MUSCLES:

TYPES MUSCLES NERVE SUPPLY BLOOD SUPPLY ACTION
EXTRINSIC MUSCLES Auricularis Anterior
Auricularis Superior
Auricularis Posterior
Ant & Sup – Temporal br. of Facial Nerve
Post. – Post auricular br of Facial Nerve.
Post. Auricular artery Ant – forwards & upwards
Sup – elevates
Post – backwards
INTRINSIC MUSCLES Helicis Major
Helicis Minor
Tragicus Antitragicus
Transversus Auriculae
Obliquus auriculae
lat asp. – Temporal br of Facial Nerve
med asp. – Post. Auricular br of Facial Nerve
Post auricular & superficial temporal artery minimal change in shape of auricle
INNERVATION OF AURICLE

  1. Pinna is supplied by Vagus nerve, Auriculotemporal nerve, Greater auricular nerve
  2. Great Auricular Nr – most of medial surface & post. part of lateral surface (inclu. lobule)
  3. Lesser Occipital Nr – upper part of medial surface
  4. Auriculotemporal Nr – tragus, crus of helix & adjacent helix
  5. Auricular br of Vagus (Arnold’s Nr) & Facial Nr – Concha (lat.) & Eminentia concha (med.), post. auricular skin
Exam Question
  • Pinna is ectodermal in origin
  • Pinna is formed at birth
  • Pinna is composed of a thin plate of yellow elastic cartilage, covered with integument
  • Pinna develops from the cleft of Ist arch
  • Sensory nerve supply of pinna is by V3
  • Major part of the skin of pinna is supplied by Great auricular nerve
  • Pinna is supplied by Vagus nerve, Auriculotemporal nerve, Greater auricular nerve
  • Skin over pinna is fixed Loosely on medial side
Don't Forget to Solve all the previous Year Question asked on External Ear