External ear
The external ear (or outer ear) comprises the auricle (or pinna), the external auditory meatus, and the tympanic membrane ("eardrum"). The auricle concentrates and amplifies sound waves and funnels them through the outer acoustic pore into the external auditory meatus to the tympanic membrane.
Gross anatomy
Auricle (pinna)
The auricle is the part of the ear that projects laterally from the head. It is composed of an irregular concave plate of elastic cartilage and dense connective tissue, covered by skin which contains short hairs (tragi), sebaceous glands, and ceruminous glands.
Structure
The auricle has a complex shape that is composed of several ridges, notches, and grooves (see Figure 1):
-
helix: posterior free margin of the auricle
- crus helicis: anterior terminal portion of the helix superior to the external acoustic pore
-
antihelix: a ridge parallel to the helix
- crura antihelicis: a pair of limbs located above the external acoustic pore
- fossa triangularis: tiny depression between the crura
- scaphoid fossa / scapha: the depression between the helix and antihelix
-
tragus: prominence in front of the external acoustic pore
- can be manually pushed back over the pore, to mitigate noise
- antitragus: situated in the lower part of the antihelix and faces the tragus
- intertragic incisure: a notch separating the tragus from the antitragus
- cavum conchae: the deepest depression in the auricle, inferior to the crus of the helix
- cymba conchae: depression surrounded by the crus of the helix below and the inferior crus of antihelix above
- ear lobe (lobule): the lowest part of the ear and the only part that does not contain cartilage, situated below the intertragic incisure
Vascular supply
The auricle is supplied by
- the posterior auricular branch of the external carotid artery
- the superficial temporal artery
- a branch from the occipital artery
Innervation
- greater auricular nerve of the cervical plexus supplies the medial auricle and the lateral auricle posterior to the EAC
- auriculotemporal nerve from the mandibular division of the trigeminal nerve (CN V3) supplies the skin of the lateral auricle anterior to the EAC
- sometimes there is a small contribution from the small auricular branch of the vagus nerve (CN X)
- facial nerve (CN VII) innervates the external auricular muscles and probably the auricular skin as well
External auditory meatus
The external auditory meatus is a short S-shaped canal within the tympanic temporal bone leading from the external acoustic pore of the auricle to the tympanic membrane. It is approximately 3 cm long and is lined by skin containing hair follicles (tragi), sebaceous glands, and ceruminous glands (which produce cerumen).
Tympanum
The tympanic membrane (or tympanum) consists of two layers of collagen fibers:
- an outer layer with a radial fiber arrangement
- an inner layer with a circular fiber arrangement
It has an outer cover of extremely thin skin and an inner layer of cuboidal epithelium facing the tympanic cavity.
The tympanic membrane, is anatomically part of, and represents, the most medial extent of the external ear.
Related Radiopaedia articles
Anatomy: Head and neck
- skeleton of the head and neck
-
cranial vault
- scalp (mnemonic)
- fontanelle
-
sutures
- calvarial
- facial
- frontozygomatic suture
- frontomaxillary suture
- frontolacrimal suture
- frontonasal suture
- temporozygomatic suture
- zygomaticomaxillary suture
- parietotemporal suture (parietomastoid suture)
- occipitotemporal suture (occipitomastoid suture)
- sphenofrontal suture
- sphenozygomatic suture
- spheno-occipital suture (not a true suture)
- lacrimomaxillary suture
- nasomaxillary suture
- internasal suture
- basal/internal
- skull landmarks
- frontal bone
- temporal bone
- parietal bone
- occipital bone
- skull base (foramina)
-
facial bones
- midline single bones
- paired bilateral bones
- cervical spine
- hyoid bone
- laryngeal cartilages
-
cranial vault
- muscles of the head and neck
- muscles of the tongue (mnemonic)
- muscles of mastication
-
muscles of facial expression
- occipitalis muscle
- circumorbital and palpebral muscles
- nasal muscles
- buccolabial muscles
- elevators, retractors and evertors of the upper lip
- levator labii superioris alaeque nasalis muscle
- levator labii superioris muscle
- zygomaticus major muscle
- zygomaticus minor muscle
- malaris muscle
- levator anguli oris muscle
- risorius muscle
- depressors, retractors and evertors of the lower lip
- depressor labii inferioris muscle
- depressor anguli oris muscle
- mentalis muscle
- compound sphincter
- orbicularis oris muscle
- incisivus superior muscle
- incisivus inferior muscle
- muscle of mastication:
- elevators, retractors and evertors of the upper lip
- muscles of the middle ear
- orbital muscles
- muscles of the soft palate
- pharyngeal muscles
- suprahyoid muscles
- infrahyoid muscles
- intrinsic muscles of the larynx
- muscles of the neck
- accessory muscles of the neck
- deep cervical fascia
-
deep spaces of the neck
- anterior cervical space
- buccal space
- carotid space
- danger space
- deep cervical fascia
- infratemporal fossa
- masticator space
- parapharyngeal space
- stylomandibular tunnel
- parotid space
- pharyngeal (superficial) mucosal space
- perivertebral space
- posterior cervical space
- pterygopalatine fossa
- retropharyngeal space
- suprasternal space (of Burns)
- visceral space
- surgical triangles of the neck
- orbit
- ear
- paranasal sinuses
- nose
- oral cavity
- pharynx
- larynx
- viscera of the neck
- blood supply of the head and neck
-
arterial supply
-
common carotid artery
- carotid body
- carotid bifurcation
- subclavian artery
- variants
-
common carotid artery
- venous drainage
-
arterial supply
- innervation of the head and neck
-
cranial nerves
- olfactory nerve (CN I)
- optic nerve (CN II)
- oculomotor nerve (CN III)
- trochlear nerve (CN IV)
-
trigeminal nerve (CN V) (mnemonic)
- trigeminal ganglion
- ophthalmic division
- maxillary division
- mandibular division
- abducens nerve (CN VI)
- facial nerve (CN VII)
-
vestibulocochlear nerve (CN VIII)
- vestibular ganglion (Scarpa's ganglion)
- glossopharyngeal nerve (CN IX)
-
vagus nerve (CN X)
- superior laryngeal nerve
- recurrent laryngeal nerve (inferior laryngeal nerve)
- (spinal) accessory nerve (CN XI)
- hypoglossal nerve (CN XII)
- parasympathetic ganglia of the head and neck
- greater occipital nerve
- third occipital nerve
-
cervical plexus
- muscular branches
- longus capitis
- longus colli
- scalenes
- geniohyoid
- thyrohyoid
-
ansa cervicalis
- omohyoid (superior and inferior bellies separately)
- sternothyroid
- sternohyoid
- phrenic nerve
- contribution to the accessory nerve (CN XI)
- cutaneous branches
- muscular branches
- brachial plexus
- pharyngeal plexus
-
cranial nerves
- lymphatic drainage of the head and neck
- embryological development of the head and neck