Temporal Bone and Ear Flashcards by zk m

What does the petrous temporal bone house?

vestibulocochlear apparatus

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What is the direction of the petrous temporal bone?

passes obliquely anteromedially

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Where do CNIII and CNII enter the petrous temporal bone?

the internal acoustic meatus

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What is posterior to the petrous temporal bone?

groove for sigmoid venous sinus

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What passes through the stylomastiod foramen?

CNVII which emerges to supply the muscles of facial

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What are the two parts of CNIII?

vestibular (balance) cochlear (hearing).

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What is the vestibulocochlear apparatus made of and whhere is it?

CN VIII
cochlea
semicircular canals
utricle
saccule

petrous temporal bone

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What is the path of the vestibular part of CNIII?

leaves the semicircular canals, utricle & saccule of the labyrinth & lies in the internal acoustic meatus with CN VII & the cochlear part of CN VIII

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What is the path of the cochlear part of CNVIII?

derived from the organ of Corti in the cochlea & lies in the internal acoustic meatus with CN VII & the vestibular part of CN VIII

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What are symptoms of damage of the vestibular and cochlear parts?

Balance: Ataxia, vertigo, nausea, nystagmus

Hearing: Neural or conductive loss

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What is the general structure of the ear?

external
middle
internal

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What are the parts of the external ear and what is their role?

Auricle & external acoustic meatus composed of cartilage & bone leading sound waves to the tympanic membrane

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What are the parts of the middle ear and what is their role?

Ossicles mechanically transmitting sound; connected to pharynx by the auditory tube (eustachian, pharynotympanic)

contains the tympanic membrane

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What are the parts of the internal ear and what are their roles?

Semi- circular canals (motion) & cochlea (hearing) converting mechanical signals to electrical carried by CN VIII

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What is the auricle made of, what are it’s parts and what is it’s role?

elastic cartilage
helix, lobule of auricle, tragus
* Support
* ‘Catching’ & funnelling sound into the external acoustic meatus

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What is the external acoustic meatus made of?

a cartilaginous lateral 1/3rd with a bony medial 2/3rds

What is the epidermis and dermis of the EAM made of?

Epidermis: Stratified squamous epithelium
Dermis: Hair follicles, glands, ceruminous glands (modified sweat glands) that secrete ear wax, blood vessels & nerves

How is the tympanic membrane held within the temporal bone?

a fibrocartilaginous ring

What are the histological layers of the tympanic membrane?

eardrum

Skin - Outer epithelial layer consisting of stratified squamous epithelium
Fibrous core - Middle layer of connective tissue
Mucous membrane - Inner epithelial layer consisting of low simple cuboidal epithelium

What are the ossicles from lateral to medial

malleus - attached to tympanic membrane
incus
stapes

What is the role of the ossicles?

transmit vibrations from the tympanic membrane to the oval window, converting sound waves into mechanical energy that is then relayed to the inner ear.

the ossicles need to be closely connected for effective sound conduction.

What does the auditory tube connect?

middle ear with the nasopharynx

What is the role of the auditory tube?

Pressure equalisation between the middle ear & atmospheric pressure

What is a disadvantage of the audiotory tube?

Potential route of infection from the nasopharynx to the middle ear!

What is the auditory tube made of and where does it change?

Initially it is a bony canal but then it becomes cartilaginous lying between the petrous temporal bone & the greater wing of sphenoid

What is the path of CNVII in relation to middle ear?

enters IAM > forms the geniculate ganglion here. gives off the greater petrosal nerve, which supplies parasympathetic fibers to the lacrimal gland. > descends and gives off a branch called the nerve to stapedius, which innervates the stapedius muscle, helping to dampen loud sounds due to movement from the stapes > facial nerve exits the skull through the stylomastoid foramen, located just behind the ear.> it provides motor innervation to the muscles of facial expression and other branches, including the posterior auricular nerve and diagastric

What branch runs close to the ossicles and tympanic membrane?

chorda tympani any damage in this area affects taste sensation

What is a clinical consideration between middle ear and middle cranial fossa?

thin roof of bone - risk of infection spread

Why are infections in the middle ear often caused?

obstruction to auditory tube

What are middle ear infections called?

otitis media

What can chronic middle ear infections cause?

may damage the ossicles causing conductive deafness & these may even spread to the mastoid air cells or beyond

What is the bony labyrinth and what does it contain?

The bony labyrinth consists of a series of cavities (vestibule, cochlea & semicircular canals) containing a fluid known as perilymph within which the membranous labyrinth is suspended that contains endolymph

Where do the different inflows of head and neck lymphatics drain into? | and what are they?

facial, anterior/posterior auricular, superficial parotid, deep parotid, retropharyngeal > superior deep cervical nodes > inferior deep cervical nodes occipital > inferior deep cervical nodes

What can enlarged lymph nodes indicate?

current or past pathology or area of immune activity (palatine tonsils) can point to systemic (e.g.lymphoma) or local disease

How does lymphogenous cancer spread?

cancer cells travel via lymphatics, are filtered & trapped in lymph nodes, which become secondary (metastatic) cancer sites

What is the difference between malignancy and inflammation/infection in lymph nodes?

inflammation/infection = swollen,tender lymph nodes, malignancy = hard, painless lymph nodes

What do submandibular nodes drain?

oral cavity; face; nasal cavity & maxillary sinus

What do supraclavicular lymph nodes drain?

thorax and abdomen