The Ear Flashcards
Name the 3 divisions of the ear
- External ear
- Middle ear
- Internal ear
In what bony space does the internal ear sit
Between the middle and posterior cranial fossae
What is the external ear called
Auricle
Name the 5 different sections of the auricle
- Helix
- Antihelix
- Tragus
- Antitragus
- Pinna (earlobe)
What is the auricle composed of
Elastic cartilage
Where does lymph from the auricle travel to
Parotid and cervical lymph nodes
What is the function of the auricle
To catch sound waves and funnel them towards the external auditory meatus
Name the main artery that supplies the auricle
External carotid artery; superficial temporal artery
Name the branches of the superficial temporal artery that supply the auricle
Anterior and posterior auricular arteries; and their perforating branches
Where does blood drain into from the auricle
The corresponding veins (of the arteries) and into both the internal and external jugular veins
Name the different nerves that supply the auricle with sensory innervation
- Auriculotemporal nerve (CNV3)
- CN IX
- CN X
- CN VII
- Lesser occipital and greater auricular nerves (cervical plexus)
Describe the structure of the lateral third of the external auditory meatus
Elastic cartilage, hair follicles, and sweat and sebaceous glands
Describe the structure of the medial two-thirds of the external auditory meatus
Bone lined with stratified squamous epithelium
Describe the arterial supply to the external auditory meatus
Branches of the external carotid (auricular)
Describe the innervation of the external auditory meatus
- Mainly auriculo-temporal from CNV3
2. Auricular branches from CN VII and CN X
Describe the surfaces of the tympanic membrane
Outer = stratified squamous epithelium Inner = covered by mucous membrane
Name the three ossicles
- Malleus
- Stapes
- Incus
Name the ossicle that attaches to the medial surface of the tympanic membrane
Malleus
Describe the innervation to the outer surface of the tympanic membrane
- Auriculotemporal nerve (CNV3)
2. Auricular branch of vagus nerve (CN X)
Describe the innervation to the inner surface of the tympanic membrane
Tympanic branches of the glossopharyngeal nerve (CN IX)
What space houses the ossicle bones
Tympanic cavity
Name the joint that exists between the ossicle bones
Synovial plane joint
What ossicle articulates with the oval window
Stapes
Describe the sensory nerve innervation to the tympanic cavity
From CN IX
What arteries do the tympanic branches originate from
- Posterior auricular
- Ascending pharyngeal
- Maxillary
Name the two muscles within the tympanic cavity; describe their combined function
Tensor tympani and stapedius; reduce vibration passing to the delicate inner ear
Describe the attachments of tensor tympani
Wall of the auditory tube to the handle of the malleus
What is the action of the tensor tympani muscle
Tenses the tympanic membrane
What is the innervation of the tensor tympani
CNV3
Describe the attachments of the stapedius muscle
Pyramid of the middle ear to the neck of the stapes
What is the action of the stapedius
Pulls the ‘footplate’ of the stapes laterally
What is the innervation of the stapedius
CN VII
Describe the pathway of the facial nerve
Temporal bone through the internal auditory meatus; exits the temporal bone at the stylomastoid foramen; enters parotid gland and divides
What does the chorda tympani cross, and what nerve does it join
Crosses the medial surface of the tympanic membrane, and joins the lingual nerve
What does the auditory tube connect
Connects the nasopharynx with the tympanic cavity
Describe the structure of the lateral and medial portions of the auditory tube
Lateral = bony canal lined with mucosa Medial = cartilaginous and membranous tube
What is the function of the auditory tube
Equalises pressure on either side of the tympanic membrane
Describe the sensory innervation to the auditory tube
Via the CN IX
What arteries supply the middle ear
- Anterior tympanic (1st part of the maxillary artery)
- Ascending pharyngeal (inferior tympanic)
- Middle meningeal (superior tympanic)
- Posterior auricular (stylomastoid, posterior tympanic)
- Artery of pterygoid canal
- Carticotympanic branch of internal carotid
What does the inner ear house
The delicate vibration-sensitive cells of hearing and balance
Name the liquids that conduct sound vibrations and respond to mechanical forces
- Endolymph
2. Perilymph
Describe the pathway of the wave produced by sound through the cochlea
Oval window; perilymph of the scala vestibuli; helicotrema (top of the cochlea); down the scala tympani; the round window
What is the function of the cells within the organ of Corti
They detect movement and transform it into electrical energy (a nerve impulse), which is then passed to the cochlear nerve (CN VIII)
Describe the shape of each of the semicircular canals
Two-thirds of a circle and 1.5mm in diameter
Name the semicircular canals
- Anterior
- Posterior
- Lateral
What do the semicircular canals contain; name the swelling at the end
The semicircular ducts; at the end of each duct is a swelling = ampullae
What do the ampullae house; what do they respond to
Equilibrium receptor called crista ampullaris; responds to angular (rotational) movements of the head
Name the two membranous sacs within the vestibule
- Utricle
2. Saccule
What do the utricle and saccule house; what do they respond to
Equilibrium receptors called maculae; respond to the pull of gravity and changes in head position
Name the minute pieces of bone that sit on the receptor cells of the utricle and saccule
Otoliths
Where do the nerve impulses pass to from the equilibrium receptor cells in the semicircular canals
To the vestibular nerve (CNVIII)
Describe the arterial supply of the inner ear
Main supply from internal auditory forming:
- Common cochlear
- Vestibular