ENT 1- ear anatomy

Question 1

when are visceral arches visible on lateral surface of neck?

Answer 1

3rd week of development

Question 2

where does auricle develop from?

Answer 2

6 tubercles around margins of 1st visceral cleft

Question 3

what comprises the external ear?

Answer 3

auricle/ pinna
external auditory canal

Question 4

what is auricle formed of?

Answer 4

elastic cartilage (except lobule made of adipose)

Question 5

composition of outer 2/3 of external ear

Answer 5

cartilaginous skeleton + subcutaneous layer + sebaceous apocrine glands + squamous epithelial layer

• subcutaneous layer contains hair follicles
• cerumen is produced here ( slightly acidic )

Question 6

where does the osseous portion of the external ear begin?

Answer 6

narrow isthmus

Question 7

components of the middle ear

Answer 7

tympanic membrane
bony ossicles- malleus, incus, stapes ( lateral to medial )

Question 8

nerve supply of the ear

Answer 8

auriculotemporal nerve from the mandibular branch of trigeminal nerve
- auricular branch of vagus
- greater auricular nerve
- lesser occipital nerve

( has innervation from CN II, III, V, X )

Question 9

vascular supply of the ear

Answer 9

• auriculotemporal branch
• temporal artery
• posterior auricular division of carotid artery

Question 10

lymphatic drainage of ear

Answer 10

parotid lymph nodes
post auricular
external jugular

Question 11

function of eustachian tube

Answer 11

permits equalization of pressure on each side of the eardrum

Question 12

lateral 1/3 vs medial 2/3 of eustachian tube

Answer 12

medial 2/3 is cartilaginous, lateral 1/3 is bony

Question 13

clinical importance of smaller size of euTube in infants

Answer 13

feed can enter the ear in infants as they have a shorter, more horizontal and wider euTube. this causes otitis media

Question 14

parts of the tympanic cavity

Answer 14

epitympanum- lies medial to outer attic wall above tympanic membrane
mesotympanum
hypotympanum- lies below drum head

Question 15

histology of tympanic membrane

Answer 15

outer epithelia, middle fibrous layer and inner mucous layer

Question 16

pars tensa vs pars flaccida

Answer 16

pars flaccida is above lateral process of malleus and is much smaller. pars flaccida does not have the middle fibrous layer
pars tensa lies below the process and has all 3 layers

Question 17

contents of outer 2/3 of EAC

Answer 17

cartilaginous skeleton + subcutaneous layer + sebaceous apocrine glands + squamous epithelial layer

• hair follicles located in subcut layer
• this is where wax is produced ( slightly acidic cerumen )

Question 18

where does osseous portion of EAC begin

Answer 18

at narrow isthmus

Question 19

nerve supply of external ear

Answer 19

• auriculotemporal nerve- mandibular branch of CN V
• auricular branch CN X
• greater auricular nerve
• lesser occipital nerve

CN II, III, V, X

Question 20

vascular supply of external ear

Answer 20

auriculotemporal branch
temporal artery
posterior auricular division of carotid

Question 21

lymphatic drainage

Answer 21

parotid ( pre auricular )
post auricular
external jugular

Question 22

euTube function

Answer 22

permits equalization of pressure on both sides of eardrum [when open]

Question 23

euTube lateral 1/3 vs medial 2/3

Answer 23

medial 2/3 is cartilaginous, lateral 1/3 is bony

Question 24

when is euTube closed/open?

Answer 24

closed at rest, opens during swallowing and yawning

Question 25

parts of tympanic cavity

Answer 25

epitympanum ( lies medial to outer attic wall above tympanic membrane ), mesotympanum, hypotympanum ( below drum head )

Question 26

pars tensa vs pars flaccida

Answer 26

pars tensa- lies below lateral process of malleus, has all 3 layers
pars flaccida- lies above same process and is much smaller; has only outer epithelial and inner mucous layers

Question 27

walls of tympanic cavity

Answer 27

lateral ( membranous ) wall
medial ( labyrinthine ) wall
anterior ( carotid ) wall
posterior ( mastoid ) wall
roof- tegmental wall
floor- jugular wall

Question 28

contents medial wall of tympanic cavity

Question 29

contents of anterior wall of tympanic cavity

Question 30

vascular supply middle ear

Answer 30

superior petrosal artery
inferior tympanic
post tympanic artery from posterior auricular

Question 31

nerve supply

Answer 31

CN IX, VII, mandibular branch of CN V