Block 5 Anat, Ear,Nasal,Cavity

The inferior meatus receives the nasolacrimal duct which conducts tears from the orbit. So, this is the place where you should be looking to see the opening of the nasolacrimal duct. The semilunar hiatus is found in the middle meatus--it receives drainage from the frontonasal duct (draining the frontal sinus), the anterior ethmoidal air cells, and the maxillary sinus. The sphenoethmoid recess is the opening for the sphenoethmoidal sinus. The superior meatus is the opening for the posterior ethmoidal air cells.

The inferior meatus receives the nasolacrimal duct which conducts tears from the orbit. The semilunar hiatus is found in the middle meatus--it receives drainage from the frontonasal duct (draining the frontal sinus), the anterior ethmoidal air cells, and the maxillary sinus. The sphenoethmoid recess is the opening for the sphenoethmoidal sinus. The vestibule of the nose is the opening of the nose that is covered with skin and stiff hairs.

The middle meatus contains the semilunar hiatus, which receives drainage from the maxillary sinus, the frontonasal duct (draining the frontal sinus), and the anterior ethmoidal air cells. The maxillary sinus is draining into the middle meatus, so it would be easiest to approach the maxillary sinus through this space. The choana is the space where the nasal cavity opens into the nasopharynx--it is found at the very posterior border of the nasal cavity. The inferior meatus receives the nasolacrimal duct which conducts tears from the orbit. The sphenoethmoidal recess is the opening for the sphenoethmoidal sinus. Finally, the superior meatus receives drainage from the posterior ethmoidal air cells.

The handle of the malleus is attached to the center of the tympanic membrane. The head of the malleus then articulates with the body of incus, and the long process of incus articulates with the head of stapes. The foot plate of stapes sits in the oval window. Take a look at Netter Plate 88 for a better idea of how these ossicles connect!
The tragus is a cartilagenous structure of the external ear, located anterior to the external auditory meatus. It is hard to describe the tragus; it is labeled in the upper left picture of Netter Plate 88. The utricle is a part of the balancing apparatus of the ear--like the saccule, it is a fluid filled sac in the vestibule.

The superior and middle nasal conchae are part of the ethmoid bone. The maxillary bone is the bone that forms the midface. It forms the inferior orbital margin and contains the teeth and maxillary sinus. The palatine bone forms the posterior part of the hard palate. The sphenoid bone is an irregularly shaped bone forming the central portion of the skull. It has many parts, including a body, greater wing, lesser wing and pterygoid plates. The vomer is a thin plate of bone forming the posteroinferior part of the nasal septum.

Stapedius is a small muscle in the ear innervated by the facial nerve. It dampens large vibrations of the stapes and the tympanic membrane; this allows the ear to diminish loud noises. If the facial nerve is paralyzed (as seen with Bell's palsy), the nerve to stapedius is lost, and the ear cannot lessen the vibrations of stapedius. This causes hyperacusis.
The digastric muscle elevates the hyoid bone and depresses the mandible. Its posterior belly is innervated by the facial nerve, so this muscle would be paralyzed if the facial nerve was damaged. However, the posterior belly of the digastric is not involved with the ear. Tensor tympani is a muscle in the ear with a similar function to stapedius--it dampens vibrations of the tympanic membrane. This muscle is innervated by the mandibular branch of the trigeminal nerve (V3)--not the facial nerve. Stylohyoid elevates and retracts the hyoid bone. It's innervated by the facial nerve, but it does not have any effect on the ear.

The middle meatus contains the semilunar hiatus, which receives drainage from the frontonasal duct (draining the frontal sinus), the anterior ethmoidal air cells, and the maxillary sinus. So, it's draining most of the paranasal sinuses. The inferior meatus receives the nasolacrimal duct which conducts tears from the orbit. The superior meatus receives drainage from the posterior ethmoidal air cells. The nasal vestibule is the opening of the nose--none of the sinuses drain directly into this area. The sphenoethmoidal recess is the opening for the sphenoethmoidal sinus.

The auditory (nasopharyngeal) tube is a connection between the nasal portion of the pharynx and the tympanic cavity that allows pressure to equalize on either side of the tympanic membrane. It is located in the anterior wall of the middle ear and is comprised of bone at the tympanic end and cartilage on the pharyngeal end. The pharyngeal mucosa is continuous with the lining of the tympanic cavity and mastoid air cells. This allows infectious material to pass to the middle ear and mastoid area.
The cochlea is the organ of hearing that receives, interprets, and transmits sound via the vestibulocochlear nerve (CN VIII). The external acoustic meatus is the opening in the temporal bone that allows sound waves to reach the tympanic membrane. The internal acoustic meatus is the foramen in the temporal bone that allows the vestibulocochlear nerve and the facial nerve to pass into the skull at the base of the brain. Finally, the sacculus is a fluid filled sac that is part of the balancing apparatus of the ear - it is located in the vestibule of the ear.

The oval window is a fossa in the medial wall of the middle ear--it is found just above the promontory. It leads into the vestibule of the bony labyrinth. In life, this fossa is completely covered by the footplate of the stapes. So, if there was otosclerosis of the stapes to the surrounding bone, there would be damage to the oval window. The round window is also a fossa in the medial wall of the middle ear, but it is located below the promontory. The round window is covered by a thin membrane.
The aditus ad antrum is an opening on the posterior wall of the middle ear. It is the opening to the mastoid antrum and mastoid air cells. The cochlear duct is the spiral tube suspended in the cochlear canal--it is part of the membranous labyrinth. Finally, the internal acoustic meatus is a foramen in the base of the skull. The facial nerve (CN VII) and the vestibulocochlear nerve (CN VIII) enter the petrous temporal bone through this foramen.

When this girl ruptured her eardrum, she damaged the tympanic membrane. So, you need to think about the nerve and structures that are associated with the tympanic membrane (ie, on the lateral wall of the middle ear). Chorda tympani lies across the tympanic membrane, so it's possible that this nerve was injured by the pencil.
The auricular branch of the vagus nerve is a small branch of the vagus that supplies afferent sensory innervation to the external acoustic meatus. This nerve is not close to the tympanic membrane The glossopharyngeal nerve and lesser petrosal nerve are associated with the promontory of the ear, which is on the medial wall of the middle ear. The trigeminal nerve is not close to the ear and would not be damaged by the injury.
What might happen if chorda tympani was injured? No taste sensation to the anterior 2/3 of the tongue and no secretomotor innervation to the sublingual and submandibular glands!

The tympanic plexus is formed by the tympanic nerve, a branch of the glossopharyngeal nerve (CN IX). The tympanic plexus provides sensory innervation to the mucosal lining of the middle ear. The lesser petrosal nerve also comes out of the tympanic plexus. This nerve carries preganglionic parasympathetic fibers from the tympanic plexus - these fibers eventually synapse in the otic ganglion. The postsynaptic fibers that leave the otic ganglion provide parasympathetic secretomotor innervation to the parotid gland. So, if the tympanic plexus was destroyed, the lesser petrosal nerve would be destroyed and the parotid gland would not secrete saliva.
Mucosal secretions in the nasal cavity and the soft palate and tear secretions by the lacrimal gland are all mediated by the postganglionic fibers of the pterygopalatine ganglion. This ganglion receives preganglionic fibers from the greater petrosal nerve, a branch of the facial nerve (CN VII). The submandibular and sublingual glands receive their preganglionic fibers from the chorda tympani - another branch of the facial nerve.

The alar cartilage is found on the inferolateral side of the nose. This is probably the cartilage that was injured in this laceration. The septal cartilage creates the septum of the nose. The lateral cartilage is a specialization of the septal cartilage that is superior to the alar cartilage, also on the lateral side of the nose. The accessory cartilage is a small piece of cartilage between the alar cartilage and the lateral cartilage

The mandibular division of the trigeminal nerve is not associated with the middle ear. So, chronic ear infections should have no effect on this structure. All of the other answers refer to structures that are closely associated with the middle ear--a chronic infection in this area could cause any of the other listed complications. The chorda tympani nerve travels along the lateral wall of the middle ear, running across the tympanic membrane. It could be damaged by chronic infection and inflammation. Remember--chorda tympani provides secretomotor innervation to the submandibular and sublingual glands and taste sensation to the anterior 2/3 of the tongue. Mastoiditis is an infection of the mastoid air cells. Since these air cells connect to the middle ear through the aditus ad antrum on the posterior wall, an infection in the middle ear could easily spread to the mastoid air cells. The facial nerve is also located on the posterior wall of the middle ear, so it could also be damaged by the chronic infection. Finally, a chronic infection can damage the three ossicles and lead to deafness.

The tonsillar fossa is the place where you find the palatine tonsil - it is a space found between the palatoglossal and palatopharyngeal folds. Torus tubaris is a mucosal fold covering the anteromedial end of the auditory tube cartilage - it projects toward the midline from the lateral wall of the nasopharynx. The salpingopharyngeal fold is a vertical fold of mucous membrane that extends from the medial end of the auditory tube - it covers the salpingopharyngeus muscle. The lateral glossoepiglottic fold is a small fold extending from the tongue to the epiglottis - it is found posterior to the tonsillar fossa. Finally, the medial pterygoid plate is a part of the sphenoid bone in the skull - it is the attachment of the superior pharyngeal constrictor muscle and the pharyngobasilar fascia.

The greater petrosal nerve is a branch of the facial nerve that arises adjacent to the geniculate ganglion. It carries preganglionic parasympathetic fibers to the pterygopalatine ganglion. The fibers synapse in this ganglion, and the postsynaptic parasympathetic fibers go on to innervate the lacrimal gland, mucous glands of the palate, and the mucous glands of the nasal cavity. So, if the greater petrosal nerve was damaged, the presynaptic parasympathetic fibers would be lost, and the lacrimal gland would not function properly.
The sublingual and submandibular glands are innervated by the chorda tympani, which brings preganglionic parasympathetic fibers to the submandibular ganglion. The chorda tympani also provides taste sensation to the anterior 2/3 of the tongue. Although the chorda tympani, like the greater petrosal nerve, is a branch of the facial nerve, the chorda tympani never runs with the greater petrosal nerve. So, injuring the greater petrosal nerve would not harm the chorda tympani. The parotid gland is innervated by the lesser petrosal nerve, a branch of the glossopharyngeal nerve (CN IX). The fibers from this nerve go to the otic ganglion, synapse there, and then continue on to the parotid gland via the auriculotemporal nerve. Finally, general sensation to the anterior 2/3 of the tongue is carried by the lingual nerve, a branch of V3.

The otic ganglion is in the infratemporal fossa, just inferior to the foramen ovale, medial to the mandibular nerve and posterior to the medial pterygoid muscle. It is the ganglion where fibers from the lesser petrosal nerve synape. The postsynaptic parasympathetic fibers from the otic ganglion are secretory to the parotid gland--they reach the parotid gland by the auriculotemporal nerve. The pterygopalatine fossa is a small pyramidal space inferior to the apex of the orbit. It lies between the pterygoid process of the sphenoid bone posteriorly and the posterior aspect of the maxilla anteriorly. It contains the terminal part of the maxillary artery, the maxillary nerve, and the pterygopalatine ganglion. The internal ear is buried in the petrous part of the temporal bone--it contains the vestibulocochlear organ which allows for the reception of sound and maintaining balance.
Finally, the middle cranial fossa is the large depression in the cranial base, formed by the greater wings of the sphenoid and squamous parts of the temporal bones laterally and the petrous parts of the temporal bones posteriorly. It contains four important foramina: the superior orbital fissure, which transmits the ophthalmic veins and the nerves entering the orbit (CN III, CN IV, CN V1 and CN VI); the foramen rotundum which transmits CN V2; the foramen ovale, which transmits CN V3, and the foramen spinosum, which transmits the middle meningeal vessels.

The soft palate is the movable posterior 1/3 of the palate, which is suspended from the posterior border of the hard palate. When a person swallows, the soft palate is initially tensed to allow the tongue to press against it, squeezing the bolus of food to the back of the mouth. The soft palate is elevated posteriorly and superiorly against the wall of the pharynx, thereby preventing the passage of food into the nasal cavity. The soft palate functions similarly to prevent the bolus of food from passing into the nasal cavity while chewing and to prevent expectorated material from entering the nasal cavity while coughing. The soft palate also elevates when yawning. The soft palate does not elevate during breathing--if it did rise during breathing, the air inspired through the nose might be blocked from entering the trachea.

The pharyngeal tonsil is located on the roof of the nasopharynx. The pharyngeal recess is a space located posterior to the torus tubarius in nasopharynx. The tonsillar fossa is the space where the palatine tonsil is located--it is found between the palatoglossal fold and the palatopharyngeal fold. The piriform recess is a shallow depression located lateral to the aryepiglottic fold in the laryngopharynx. This is a common place where food can get stuck. The piriform recess is also significant because the internal branch of the superior laryngeal nerve is located immediately deep to the mucosa of this region--so, an injury here may damage this nerve! Finally, the lingual tonsil is found on the dorsal surface of the tongue.

To answer this question, you first need to identify the component of the glossopharyngeal nerve that innervates parotid gland. Remember--preganglionic parasympathetic fibers from CN IX are arriving at the otic ganglion via the lesser petrosal nerve and synapsing in the ganglion; the postganglionic fibers then travel on the auriculotemporal nerve (V3) and innervate the parotid gland. So, the lesser petrosal nerve, or fibers that create the lesser petrosal nerve, must have been injured. Now, you just need to think about where these fibers are in the ear.
These fibers from the glossopharyngeal nerve are covering the promontory on the medial wall of the ear. The tympanic nerve is a branch of the glossopharyngeal nerve that carries the preganglionic parasympathetic fibers that will eventually travel to the otic ganglion. The tympanic nerve lies on the promontory and creates the tympanic plexus, which gives rise to the lesser petrosal nerve. Given the clinical presentation, the patient must have an infection in the tympanic nerve, tympanic plexus or lesser petrosal nerve. And, all of these nerves are associated with the medial wall of the middle ear.
What are the important associations with the other walls of the ear? The lateral wall is formed by the tympanic membrane, and the chorda tympani courses across this membrane. The anterior wall contains the opening of the auditory tube and a semicanal for tensor tympani. The posterior wall of the ear has the aditus ad antrum, which is the entrance to the mastoid antrum and air cells. The facial nerve (VII) and a small branch of the facial nerve which innervates stapedius are found on the posterior wall.

The facial nerve passes in a canal situated in the posterior and medial walls of the middle ear. It is not associated with the anterior wall. The other 4 statements are true. The ossicles articulate with each other at synovial joints. The chorda tympani is a branch of the facial nerve that is related to the lateral wall of the middle ear, near the tympanic membrane. It passes between the malleus and incus. The auditory tube is found in the anterior wall--it is a path of communication between the nasal portion of the pharynx and the tympanic cavity that allows pressure to equalize on either side of the tympanic membrane. Finally, the mucous membrane of the middle ear is supplied by branches of the tympanic plexus, which is formed by the tympanic branch of the glossopharyngeal nerve.

The geniculate ganglion is the sensory ganglion of the facial nerve. These fibers travel as part of the chorda tympani to provide taste sensation to the anterior 2/3 of the tongue. The glossopharyngeal nerve has superior and inferior ganglia, located near the jugular foramen. These ganglia contain the cell bodies for the afferent components of this nerve. The trigeminal nerve has a trigeminal ganglion which contains the cell bodies of neurons composing the sensory root of this nerve. The vagus nerve also has a superior and inferior ganglion, which are located near the ganglia of the glossopharyngeal nerve. The superior ganglion is concerned with the general sensory component of the nerve, and the inferior ganglion is concerned with the visceral sensory component of the nerve. Finally, the vestibulocochlear nerve has a vestibular ganglion, which houses the neurons for balance, and the cochlear ganglion, which houses the neurons concerned with hearing.

The choanae are the opening at the posterior border of the nasal cavity that allow the nasal cavity to communicate with the nasopharynx. The aditus is the laryngeal inlet - this is the space that is covered by the epiglottis when swallowing. The auditory tube is a tube that connects the nasopharynx with the middle ear, allowing for pressure to equalize on both sides of the tympanic membrane. The fauces is the passage from the mouth to the oropharynx, including the lumen and its boundaries. Finally, the piriform recess is a shallow depression located lateral to the aryepiglottic fold in the laryngopharynx. This is a place where food is commonly lodged.