The External Ear

Original Author: Oliver Jones
Last Updated: September 1, 2017
Revisions: 33

The ear can be split into three parts; external, middle and inner. This article is about the external ear. We shall look at its structural anatomy, vasculature, innervation, and the clinical conditions that can occur.

The external ear can be functionally and structurally split into two sections; the auricle (or pinna), and the external acoustic meatus.

The Auricle

Fig 1.0 - Anterior surface of the auricle (or pinna) of the ear

Fig 1 – Anterior surface of the auricle (or pinna) of the ear.

The auricle is an external, lateral paired structure positioned and can also be known as the pinna. Its function is to capture and transmit sound to the external acoustic meatus.

Structure

Most of the auricle has a cartilaganious framework, with the lobule the only part not supported by cartilage. The outer curvature of the ear is called the helix. Moving inwards, there is another curved elevation, which is parallel to the helix – this is known as the antihelix. The antihelix divides into two cura – the inferoanterior crus, and the superoposterior crus (see Fig 1).

In the middle of the auricle is a hollow depression, called the concha of auricle. It continues into the skull as the external acoustic meatus. The concha acts to direct sound into the external acoustic meatus. Immediately anterior to the start of the external acoustic meatus is an elevation of tissue – the tragus. Opposite the tragus is the antitragus.

Vasculature

With respect to the vasculature, the main vessels involved are the posterior auricular, superficial temporal and occipital arteries and veins.

Innervation

Cutaneous innervation to the skin of the auricle comes from the greater auricular, lesser occipital and branches of the facial and vagus nerves. Patients can complain of an involuntary cough when cleaning their ears – this is due to stimulation of the auricular branch of the vagus nerve, the nerve responsible for the cough reflex.

Lymphatic Drainage

Lymphatic drainage of the auricle is to the preauricular, posterior auricular and superficial temporal lymph nodes.


External Acoustic Meatus

The external acoustic meatus is a sigmoid shaped tube that extends from the deep part of the concha to the tympanic membrane. The walls are given their structure by cartilage from the auricle, and bony support from the temporal bone

Structure

The external acoustic meatus does not have a straight path, and travels in an S-shaped curve:

  • Initially travels in a superoanterior direction.
  • Turns slightly to move superoposterior.
  • Ends in an inferoanterior direction.

Vasculature

The outer part of the external acoustic meatus is supplied by superficial temporal and posterior auricular arteries. The inner part by deep auricular branch of maxillary artery.

Innervation

This part of the external ear gets its sensory innervation from branches of the mandibular and vagus nerves.

Lymphatic Drainage

Drainage of the external auditory meatus it to the preauricular, postauricular and superficial cervical lymph nodes


Tympanic Membrane

The external acoustic meatus ends at the tympanic membrane. The tympanic membrane has a double layered structure, covered with skin on the outside and a mucus membrane on the inside. At the core of the membrane is connective tissue. It is connected to the surrounding temporal bone by a fibrocartilaginous ring.

The tympanic membrane is translucent, therefore structures within the middle ear can be seen. On the inner surface of the membrane, the handle of malleus attaches to the tympanic membrane, at a point called the umbo of tympanic membrane.

The handle of malleus continues superiorly, and at its highest point, a small projection can be seen, called the lateral process of malleus. The parts of the tympanic membrane moving away from the lateral process are called the anterior and posterior malleolar folds.

Fig 2 - The tympanic membrane of the ear.

Fig 2 – The tympanic membrane of the ear.

Clinical Relevance: Perforation of the Tympanic Membrane

The two most common causes of tympanic perforation are trauma and infection. An infection of the middle ear (otitis media) causes pus and fluid to build up. This causes an increase in pressure, and eventually the eardrum ruptures.

In many cases the tympanic membrane heals itself, but in large perforations surgical intervention might be necessary.

Clinical Relevance: Auricular Haematoma

A auricular haematoma is when blood collects between the cartilage and the overlying pericondrium. It is usually a result of trauma, commonly seen in contact sports.

The accumulation of blood disrupts the vascular supply to the cartilage of the pinna. If it is not drained quickly, a gross deformity results, called ‘cauliflower ear‘.

Rate This Article

26

Average Rating:

Quiz

Question 1 / 8
What is the only part of the auricle to not be supported by cartilage?

Quiz

Question 2 / 8
What part of the auricle is found anterior to the external auditory meatus?

Quiz

Question 3 / 8
Which of the following is a consequence of an auricular haematoma?

Quiz

Question 4 / 8
Which structure marks the end of the external auditory meatus?

Quiz

Question 5 / 8
What infection of the middle ear can cause the tympanic membrane to rupture?

Quiz

Question 6 / 8
Which of the following features of cartilage make it vulnerable to vascular disruption by auricular haematoma leading to cauliflower ear?

Quiz

Question 7 / 8
The tympanic membrane is connected to the surrounding bone by a fibrocartilaginous ring. Which bone is it connected to?

Quiz

Question 8 / 8
What is the umbo of the tympanic membrane?

Results

Load 3d model