Describe the auricle. Which part is elastic cartilage and which is fatty connective tissue?
The auricle (L. auricula) is composed of elastic cartilage covered by thin skin. The auricle has several depressions and elevations. The concha is the deepest depression, and the elevated margin of the auricle is the helix (Fig. 7.69C). The helix is is made of elastic cartilage. The non-cartilaginous lobule (earlobe) consists of fibrous tissue, fat, and blood vessels.
Define the tragus, helix and antihelix.
The tragus is a tongue-like projection overlapping the opening of the external acoustic meatus.
The elevated margin of the auricle is the helix (Fig. 7.69C).
The anithelix is the curved margin prominence anterior to the helix.
Describe the external acoustic meatus (Fig 7.69). Which part is bony and which is cartilaginous?
The external acoustic meatus is a canal that leads inward through the tympanic part of the temporal bone from the auricle to the tympanic membrane, a distance of 2 to 3 cm in adults (Fig. 7.69B). The lateral third of this slightly S-shaped canal is cartilaginous and lined with skin, which is continuous with the skin of the auricle. Its medial two thirds is bony and lined with thin skin that is continuous with the external layer of the tympanic membrane.
What is cerumen?
The ceruminous and sebaceous glands produce cerumen (earwax). Cerumen is a yellowish, waxy substance secreted in the ear canals. It plays an important role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from bacteria, fungi, and insects.
What are the main nerves of the skin of the ear?
The main nerves to the skin of the auricle are the great auricular and auriculotemporal nerves (Fig. 7.69D), with minor contributions from the facial (CN VII) and vagus (CN X) nerves.
Cone of light. What is its clinical significance?
From the inferior end of the handle of the malleus, a bright cone of light is reflected from the otoscope's illuminator. This light reflex is visible, radiating antero-inferiorly in a healthy ear.
Viewed through an otoscope (an instrument used for examining the tympanic membrane), the tympanic membrane is normally translucent and pearly gray. It has a concavity toward the external acoustic meatus with a shallow, cone-like central depression, the peak of which is the umbo. The handle of the malleus (one of the small ear bones, or auditory ossicles, of the middle ear) is usually visible near the umbo.
Define Pars Flaccida.
Superior to the attachment of the lateral process of the malleus, the membrane is thin and is called the flaccid part (L. pars flaccida).
Define Pars Tensa.
the radial and circular fibers present in the tympanic membrane, called the tense part (L. pars tensa).
Idenitfy the Manubrium of the Malleus.
Identify Posterior and Anterior Malleolar Folds.
Describe the difference in innervation between the external and internal surfaces of the tympanic membrane.
The external surface of the tympanic membrane is supplied mainly by the auriculotemporal nerve, a branch of CN V3 (Fig. 7.69D). Some innervation is supplied by a small auricular branch of the vagus nerve (CN X). The internal surface of the tympanic membrane is supplied by the glossopharyngeal nerve (CN IX).
What does the innervation of the tympanic membrane suggest suggest about the embryonic origin of the tympanic membrane?
suggest the that it received contribution from the first (trigeminal), third (glossopharyngeal), and fourth (Vagus) pharyngeal arches.