Innervation of the external acoustic meatus The outer third (cartilaginous portion) contains hair and cerumen producing glands. The entire length of the external acoustic meatus is covered with skin ( keratinised squamous epithelium). There is a slightly raised constriction located at the junction of the cartilaginous and bony portion.The medial two-thirds of the external acoustic meatus is bony, derived from the temporal bone of the skull.The lateral one-third of the external acoustic meatus is cartilaginous, which extends slightly deeper on the inferior portion external acoustic meatus.The composition of the walls of the external acoustic meatus changes the deeper it travels: The external acoustic meatus is a tube that travels from the deepest aspect of the concha to the tympanic membrane, which marks the divide of the external and middle ear. The shape of the auricle helps to capture sound waves and direct them into the external acoustic meatus and assist in determining where the sound is coming from. Lymphatic drainage from the auricle passes into the parotid and mastoid lymph nodes and eventually into the upper deep cervical nodes. The superficial temporal artery gives rise to the anterior auricular arteries, which supplies the anterior aspect of the auricle.The external carotid artery gives rise to the posterior auricular artery, which supplies the posterior aspect of the auricle.The auricle is supplied by three main arteries: The deep part of the auricle is supplied by the vagus nerve (cranial nerve X) and facial nerve (cranial nerve VII).The superficial surface is supplied by the great auricular nerve and lesser occipital nerve, both of which are branches of the cervical plexus (C2 & C3), and the auriculotemporal branch of the mandibular nerve, which is a branch of the trigeminal nerve (cranial nerve V).The auricle has several sources of sensory innervation: The tragus forms a protective barrier to the external acoustic meatus, partially covering it to prevent the passage of large foreign objects down the external acoustic meatus. In the centre of the auricle, there is a depression called the concha of the auricle, which gives rise to the external acoustic meatus.Īnterior to the opening of the external acoustic meatus is an elevation of cartilage called the tragus. Parallel and anterior to the helix is a smaller curve, aptly called the antihelix. The outer curve of the auricle is called the helix, which connects with the lobule of the ear. 1,2,3 The auricleĪpart from the lobule, which contains fat and connective tissue, the auricle is a cartilaginous structure covered by skin. It is attached to the lateral aspect of the head and is characteristically divided into two parts: the auricle or pinna and the external acoustic meatus (more commonly referred to as the ear canal). The external ear is the part of the ear we can see with the naked eye. You might also be interested in our Anatomy Flashcard Collection which contains over 2000 anatomy flashcards in addition to advanced features such as spaced repetition.
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