ANATOMY AND PHYSIOLOGY OF THE EXTERNAL EAR Flashcards
What part of the human skull houses the outer, middle, and inner ear?
The temporal bone.
What is the significance of the temporal bone in neonates?
The fontanels enclose it, the sutures are not fused, and the mastoid bone is absent.
What causes the elongated shape of the mastoid bone in adults?
The anteroinferior pull of the neck muscles, including the sternocleidomastoid (SCM) and posterior belly of the digastric muscle.
Which bones articulate with the temporal bone posteriorly, superiorly, anteriorly, and medially?
Posteriorly: Occipital Bone; Superiorly: Parietal Bone; Anteriorly: Zygomatic Bone; Medially: Sphenoid Bone.
What is the 3D shape of the temporal bone?
A pyramid.
What forms the base of the temporal bone pyramid?
The lateral surface of the temporal bone, including the squamous portion.
What is the most medial portion (apex) of the temporal bone pyramid?
The petrous portion.
What forms the superior and posterior portions of the temporal bone pyramid?
Superior: Middle cranial fossa floor;
Posterior: Anterior surface of the posterior cranial fossa.
What is located at the lateral side of the temporal bone pyramid?
The musculocutaneous side of the head, including the temporalis and masseter muscles.
What is the broad, pan-like portion of the temporal bone?
The squamous portion.
What structures are located in the squamous portion of the temporal bone?
External auditory canal, temporal line, zygomatic process.
Where is the tympanic portion of the temporal bone located, and what exits from it?
It is near the styloid process and stylomastoid foramen, where extratemporal branches of the facial nerve exit.
What are the major components of the mastoid portion of the temporal bone?
SCM, posterior belly of digastric, mastoid tip, mastoid cortex, mastoid air cells.
What is the significance of mastoid air cells?
They should be well-pneumatized. Sclerotic mastoid air cells can indicate chronic infection.
What happens to the mastoid bone in children compared to adults?
It is not developed in children and becomes prominent as they grow older due to muscle attachments.
What is the apex of the temporal bone pyramid called, and what passes through it?
The petrous portion; the internal auditory canal where the facial nerve and vestibulocochlear nerve pass through.
What is Eagle syndrome?
An abnormal elongation of the styloid process causing dysphagia, odynophagia, and foreign body sensation in the throat.
What is the normal size of the styloid process?
2.5 – 3 cm.
What are the four parts of the temporal bone?
Squamosa, Petrosa, Mastoid, Tympanic.
Where does the external ear develop from embryologically?
The first branchial pharyngeal cleft ectoderm.
What happens to the external ear by the 20th week of gestation?
The outer, middle, and inner ear are fully developed and functional.
What are the six hillocks of the external ear, and what do they form?
1st: Tragus, 2nd: Crus of helix, 3rd: Helix, 4th: Antihelix, 5th: Antitragus, 6th: Lobule.
What is the funnel-shaped cartilaginous structure of the auricle called?
The auricle, continuous with the meatus and EAC.
What is the blood supply to the auricle and external auditory canal (EAC)?
External carotid artery, posterior auricular artery, and superficial temporal artery.
What are the two parts of the external auditory canal?
Lateral 1/3 fibrocartilage and medial 2/3 bony.
What is the narrowest portion of the external auditory canal?
The bony-cartilaginous junction (isthmus).
What nerves are associated with the sensory innervation of the ear?
Facial nerve, vagus nerve (Arnold’s nerve), great auricular nerve, and auriculotemporal nerve.
What happens if the tympanic membrane is not visible during otoscopy?
Possible causes include cerumen obstruction, a perforated eardrum, or an improperly straightened ear canal.
What is the purpose of the fissures of Santorini?
They are vestigial lymph channels draining into the superficial parotid gland.
What is the significance of the foramen of Huschke?
It represents incomplete ossification in the anterior EAC and may allow inflammation to spread intraorally.
