Chapter 122: Pinna and External Ear Canal Flashcards
What is the scutiform cartilage?
Boot-shaped or cartilage sitting within the rostroauricular muscles medial to the ear. Was attached to other stuff at birth but separated.
What is the annular cartilage?
Connects the horizontal canal to the osseous external auditory meatus. Attached to both the auricular cartilage and the external auditory meatus (part of temporal bone) by fibrous connective tissue.
What is cerumen?
Secretions of the superficial sebaceous glands and deeper tubular ceruminous glands, mixed with desquamated epithelium.
What nerves supply sensory and motor function to the external ear canal?
Sensory: Vagus
Motor: Facial
What important vessels surround the bulla?
- Rostral: retroglenoid vein
- Ventral: External carotid artery and maxillary vein
- Medial: internal carotid artery
Trace the path of the facial nerve from it’s exit of the cranial vault at the internal acoustic meatus:
It leaves through the meatus with the vestibular and cochlear nn. -> runs through facial canal of the temporal bone and middle ear before -> exiting through the stylomastoid foramen caudodorsal to the osseous ear canal.
What vein causes severe hemorrhage in TECA-BO?
Retroglenoid vein. It sits rostral to the osseous ear canal/meatus.
Where does the facial nerve exit the middle ear?
Through the stylomastoid foramen caudodorsal to the osseous ear canal.
Rostral to the osseous ear canal is what vein?
Retroglenoid vein, bleeds in TECA-BO
What is the purpose of the pinna?
Focusing and localizing device to direct sound to middle ear.
The auricular cartilage of the pinna is called the what?
Scapha - covered by skin that is tightly adhered on the inner/concave surface and a little loose on the outer/convex.
What is the antihelix?
A cartilaginous protuberance that separates the flat scapha from the the beginning of the funnel shaped external ear canal.
What is the tragus?
Rectangular plate opposite the antihelix that marks the lateral margin of the external canal opening.
What is the blood supply to the pinna?
Caudal auricular artery (branch from external carotid).
This forms lateral, intermediate and medial vascular rami on outside of pinna.
*There are tiny channels in the scapha that allow blood to pass between surfaces.
Where does the external ear canal begin?
Where does it go next?
At the external acoustic opening, formed by tragus, antitragus, and antihelix.
2-3 cm ventrally and a little rostrally before turning medially to become the horizontal canal.
