External ear

EXTERNAL EAR

• External ear consists of following structures:

1. Pinna/ Auricle
2. External auditory canal (or external auditory meatus)
3. Tympanic membrane (or eardrum)  

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:

Pinna/Auricle

• Irregularly concave, faces forwards with many eminences and depressions

1. Helix
2. Crus of helix
3. Auricular tubercle (Darwin’s tubercle)
4. Antihelix & its 2 cruras
5. Triangular fossa
6. Scaphoid fossa
7. Concha & Cympa concha
8. Tragus
9. Antitragus
10. Intertragic notch
11. Lobule of pinna

Cartilagenous framework of auricle

• Single thin plate of elastic fibrocartilage (yellow)
• Continous with the cartilage of external auditory canal (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 separated by sulcus anti-helicis transversus 
• E. conchae is crossed by a oblique ridge – Ponticulus 

Ligaments

Extrinsic – connects auricle to temporal bone

1. Anterior Lig – tragus & spine of helix to root of zygomatic process
2. Posterior Lig – post surf. of concha to lat. surf of mastoid process

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

• Great Auricular Nr – most of medial surface & post. part of lateral surface (inclu. lobule)
• Lesser Occipital Nr – upper part of medial surface
• Auriculotemporal Nr – tragus, crus of helix & adjacent helix
• Auricular br of Vagus (Arnold’s Nr) & Facial Nr – Concha (lat.) & Eminentia concha (med.), post. auricular skin

Pinna is supplied by Vagus  nerve, Auriculotemporal nerve, Greater auricular nerve