3 : The Ear ππΌ Flashcards
What is the sensory nerve supply to the auricle of the external ear
The outer aspect of the auricle is supplied by:
a) auriculotemporal nerve(Viii)
b) greater auricular nerve (C2 & C3 of the cervical plexus).
What is the sensory nerve supply to the tympanic membrane?
It has two surfaces, Internal & External with separate nerve supplies
The External Surface
a)Auriculotemporal nerve, a branch of the mandibular division of the fifth nerve
b) Small branch of the Vagus (CN X)
Internal Surface
Supplied by the Glossopharyngeal nerve (CN IX).
What is the important posterior relation of the mastoid antrum and explain your answer?
The mastoid antrum is a cavity in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear. Lying in front of this assembly is the sigmoid venous sinus (a dural sinus) and the cerebellum. Infection in the region of the mastoid may spread to involve these structures.
Name three branches from the facial nerve (VII CN) given off in the petrous temporal bone and what is their functional significance?
The three branches are the greater petrosal nerve, nerve to stapedius and the chorda tympani.
The greater petrosal nerve contains preganglionic parasympathetic fibres that are destined for the sphenopalatine ganglion(*); from here the postganglonic fibres are distributed to the lacrimal gland and glands of the nose.
The nerve to stapedius is motor to the stapedius muscle which damps down movements of the stapes and prevents damage to the inner ear should it be subjected to loud noises.
The chorda tympani contains special taste fibres from the anterior 2/3rd of the tongue and preganglionic parasympathetic secretomotor fibres to the submandibular ganglion(**) from where they are distributed to the sublingual and submandibular salivary glands
Explain why you are given hard-boiled sweets to eat at take-off and landing during air travel.
Swallowing opens up the auditory tube that allows equalisation of pressure from the middle ear to the βoutside worldβ. During take-off and landing, the pressure changes are quite noticeable and unless the tube is opened, the increased air pressure inside the middle ear may cause considerable pain.
When clearing the ears with a cotton-wool bud stick, why do some people start coughing and a few people even vomit?
The nerve supply of the auditory canal and tympanic membrane is via the auricular branch of the vagus nerve. This nerve may also carry glossopharyngeal and facial nerve fibres and some people who are sensitive to stimulation of these nerves may well develop an ear-cough reflex or occasional vomiting which may be associated with vagal and glossopharyngeal innervation. Sometimes a persistent lump of wax against the tympanic membrane may cause of unexplained cough. Foreign bodies lodged in the external auditory meatus may lead to unexplained persistent coughs in such people susceptible to the ear-cough reflex
Why might an infection deep in the pterygoid region (the infratemporal fossa) be of danger to the eye?
The pterygoid venous plexus, which lies deep within the temporal fossa, is connected with both the ophthalmic and anterior facial veins. Thus the plexus drains into the cavernous sinus and so pus within the venous plexus may cause direct increased ophthalmic venous pressure or may even lead to a cavernous sinus thrombosis with resultant paralysis of extraocular muscles.
Explain why does the skin, mucous membrane of the lower lip together with the labial alveolar mucosa and the gum are also anesthetised during the inferior alveolar nerve block?
The inferior alveolar nerve sends dental branches to all the mandibular teeth.
The mental nerve, which is a branch of the inferior alveolar nerve, passes through and out of the mental foramen of the mandible and supplies the skin and the mucous membrane of the lower lip, the skin of the chin and the vestibular gingival(gum).
Why does the tongue become numb during inferior alveolar nerve block?
The anaesthetic solution may spread to the side of the tongue and involve the lingual nerve (that carries nerve fibres of general sensation from the anterior 2/3 rd of the tongue) that lies immediately in front of the inferior alveolar nerve.
On clenching the jaw tight, what structure can you palpate lying on the contracted masseter muscle?
The parotid duct lies about ΒΎ of an inch below and parallel to the zygomatic arch; on clenching the jaw, the duct can be rolled on the tensed masseter muscle, particularly along its anterior border before it pierces the buccinator.
Why might a dislocation of the TMJ sometimes occurs during yawning or taking very large bites of food?
The lateral pterygoid muscles protrude and depress the jaw. If the other muscles of mastication are relaxed, excessive contraction of the lateral pterygoids may cause the head of the mandible may βclickβ over the articular tubercle and dislocate anteriorly to lie just alongside the zygomatic arch. In this position the mandible remains wide open.
Following trauma, prominent bulge in the upper auricle due to a haematoma - between what anatomical layers/structures has this bleed occurred?
The auricle consists of cartilage overlaid by perichondrium which has blood vessels within it. The haematoma is likely to have developed between these layers.
What are the implications of the haematoma to the cartilage of the auricle?
The cartilage is avascular and relies on diffusion of gases and nutrients from the perichondrium. As the perichondrium has been prised away because of the haematoma, that part of the cartilage is deprived of gases and nutrients. It will thus undergo necrosis.
What would the ENT specialists most likely to do to treat an auricular haematoma?
Drain the haematoma.
Without treatment, what complications will this patient develop over time?
Necrosis of the underlying cartilage will lead to what is described as a βcauliflower earβ.
