Middle Ear part 2

Arteries:

From ascending pharyngeal artery: branch of external carotid artery

Carotid artery: ascending pharyngeal artery.

Maxillary artery: middle meningeal artery and artery of pterigoid canal

Veins:

Drains into the pterigoid venus plexus.

Lymphatic drainage:

To the deep cervical lymph nodes.

Nerves: from the tympanic plexus, formed from glossopharyngeal nerve fibers. Anteriorly receives fibers from the pterigopalatine ganglion.

Auditory Ossicles:

Increases the force but decreases the amplitude of vibration transmitted from the tympanic membrane to the internal ear.

Chain of small bones from the tympanic membrane to the oval window (oval opening on the labrynthine wall of the tympanic cavity leading to the vestibule of the bony labyrinth.

These ossicles are the first bones to be ossified during development and thus are mature at birth.

Lack surrounding layer of osteogenic periosteum

Covered by mucous membrane.

Malleus:

Attached to the tympanic membrane.

Head lies in the epitympanic recess.

Neck against the flaccid part of the tympanic membrane.

Tip at the umbo.

Articulates at the uncus.

Tendon of tensor tympani inserts in the handle.

The corda tympani nerve cross here.

Incus

Between malleous and stapes, articulates with them.

1 body, 2 limbs.

Body in epitympanic recess (here articulates with the head of malleus)

Long limb: interior end articulates with the stapes by the way of lenticular pross.

Short limb: connected by a ligament by the posterior wall of tympanic cavity.

Stapes:

Smallest ossicle.

1 head, 2 limbs, 1 base.

Head articulates with incus.

Bse of it in the oval window on the medial wall of tympanic cavity.

Muscles associated with auditory ossicles:

Two muscles that dampen or resist the movement of auditory ossicles.

Tensor tympani: supplied by mandibular nerve. Arises from the superior part of the cartilaginous part of the pharyngotympanic tube, the greater wing of sphenoid and the petrous part of the temporal bone. Inserts in the handle of the malleus. Pulls medially on the handle thus tensing the tympanic membrane and reducing its amplitude of the osscilation. Prevents damage to the internal ear in case of loud sounds.

Stapedius:

Tiny muscle. Inside pyramidal eminence (hollow, cup shaped prominence on the posterior wall). Arises from the pinpoint foramen in the eminence and attaches to the neck of stapes. Pulls stapes posteriorly tilting its base in the oval window, thus tightens the angular ligament and reduces the oscillatory range. Supplied by the facial nerve branch.