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Flashcards in Ear Anatomy Deck (29)
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1
Q

What is the pterion?

A

This is the thinnest part of the skull formed by an H-shaped suture between the frontal, parietal, temporal and sphenoid bone. FUN FACT: it has been referred to as ‘gods joke’ as the middle meningeal artery runs right behind this and damage will result in epidural haematoma.

2
Q

What are the 2 parts to the temporal bone?

A

squamous (smooth) part

Petrous (rocky) part.

3
Q

This is a diagram of the base of the skull, what are the 3 regions called and which bones are contained within each?

A

Anterior cranial fossa - frontal bone, ethmoidal and sphenoid

Middle cranial fossa - sphenoid and temporal (squamous and petrous)

Posterior cranial fossa - temporal (petrous) and occipital

4
Q

Where does each cranial nerve exit the skull?

A

CN 1 = cribiform plate of ethmoid bone

CN 2 = optic canal

CN 3 = superior orbital fissure (SOF)

CN 4 = SOF

CN 5 (opthalmic) = SOF

CN 5 (maxillary) = foramen rotundum

CN 5 (mandibular) = foramen ovale

CN 6 = SOF

CN 7 and 8 = internal acoustic meatus

CN 9, 10 and 11 = jugular foramen (along with internal juglar vein)

CN 12 = hypoglassal canal

5
Q

These are the areas of the ear, describe their boundaries.

A

External = auricle to tympanic membrane via the external acoustic meatus

Middle = Tympanic membrane to oval window (also contains the eustachian tube)

Internal = oval window to internal acoustic meatus.

6
Q

What are the functions of the 3 areas of the ear?

A

External - collects and conveys sound waves to the tympanic membrane

Middle - amplifies and conducts the sound waves to the inner ear

Internal - converts the sensory information into fluid waves, then APs then sent to brain.

7
Q

Where do cranial nerve 2 and 3 supply?

A

the external ear (auricle)

8
Q

What does CN V3 supply on the external ear?

A

supplies the superior aspect of the external auditory meatus and superior 2/3 of the tympanic membrane

9
Q

What does CN X supply on the external ear?

A

Inferior parts of the external auditory meatus and inferior part of the tympanic membrane.

10
Q

What is the lyphatic drainage of the auricle?

A

Lateral part of superior = partotid nodes

Cranial surface of superior = mastoid

Rest of auricle = superficial cervical nodes

these all eventually drain to deep cervical and to the venous angle.

11
Q

What produces earwax and where do these reside?

A

ceruminous glands in the ear canal

12
Q

What is the skelton of the ear?

A

Elastic cartilage (avascular) and petrous part of the temporal bone

13
Q

What does the glossopharyngeal nerve innervate?

A

Middle ear, eustachian tube, nasopharynx, oropharynx and tonsils.

14
Q

What are the three auditory ossicles are where are they?

A

These are the 3 bones in the middle ear:

Malleus

Incus

Stapes

All three articulate via synovial joints and help to conduct sound waves to the internal ear.

15
Q

What is the umbo and how is it formed?

A

This is the most inward pulled part of the tympanic membrane and is formed by the horn of the malleus pulling it inward.

16
Q

How is sound amplified and conducted to the internal ear?

A

Sound waves cause vibration of the tympanic membrane which will cause vibration of the malleus. As all three bones articulate, the vibration is passed along. At the vibration reaches the stapes bone it causes tapping against the bony surface of the ‘oval window’

17
Q

What is the eustachian tube and what is its function?

A

This is a tube that connects the middle ear to the nasopharynx.

It is thought to be there to help equalise air pressures.

18
Q

What is important clinically about the eustachian tube?

A

It is not uncommon for bacteria and viruses to spread via this tube to result in pain and hearing loss.

19
Q

What are the functions of the facial nerve?

A

Special sensory - taste (supplies first 2/3rds of tongue)

Sensory - Face

Motor - muscles of facial expression

Parasympathetic - supplies the submandibular and sublingual salivary glands (as well as lacrimal)

20
Q

Which nerve runs through the internal auditory canal?

A

CN 7

21
Q

What is the function of the stapedius muscle?

A

this is the smallest skeltal muscle that controls the stapes in times of loud noise so as not to cause damage to the inner ear.

22
Q

How would you test for a facial nerve palsy?

A

ask the patient to frown, smile, close eyes tightly and puff out cheeks.

23
Q

Where is the internal ear located and what is its function?

A

in the petrous part of the temporal bone and its function is to convert vibrations to special sensory information

24
Q

How is the vestibulocochlear nerve split (CN 8)?

A

Vestibular branch - balance

Cochlear branch - hearing

25
Q

What is the otic capsule?

A

This is a capsule of bone that is denser than the surrounding petrous temporal bone. It contains the bony labyrinths (spaces in the bone that are fluid filled - with perilymph)

26
Q

What is suspended within the perilymph of a labyrinth?

A

sacs and ducts which make up the membranous labyrinth and is filled with endolymph.

27
Q

What is the function of the fluid?

A

The movement of the fluid helps with hearing (cochlea) and balance (in the semi-circular canals)

28
Q

How are these fluid movements transported to the brain?

A

Via the cochlear and vestibular branches of CN 8 (which joins to become one in the internal acoustic meatus).

29
Q

What would some symptoms associated with internal acoustic meatus pathology be?

A

CN 7 = facial nerve palsy, dry mouth and eyes, loss of taste, loss of sensation to facial muscles

CN 8 = loss of hearing and balance