ENT 1- ear anatomy Flashcards
when are visceral arches visible on lateral surface of neck?
3rd week of development
where does auricle develop from?
6 tubercles around margins of 1st visceral cleft
what comprises the external ear?
auricle/ pinna
external auditory canal
what is auricle formed of?
elastic cartilage (except lobule made of adipose)
composition of outer 2/3 of external ear
cartilaginous skeleton + subcutaneous layer + sebaceous apocrine glands + squamous epithelial layer
- subcutaneous layer contains hair follicles
- cerumen is produced here ( slightly acidic )
where does the osseous portion of the external ear begin?
narrow isthmus
components of the middle ear
tympanic membrane
bony ossicles- malleus, incus, stapes ( lateral to medial )
nerve supply of the ear
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 )
vascular supply of the ear
- auriculotemporal branch
- temporal artery
- posterior auricular division of carotid artery
lymphatic drainage of ear
parotid lymph nodes
post auricular
external jugular
function of eustachian tube
permits equalization of pressure on each side of the eardrum
lateral 1/3 vs medial 2/3 of eustachian tube
medial 2/3 is cartilaginous, lateral 1/3 is bony
clinical importance of smaller size of euTube in infants
feed can enter the ear in infants as they have a shorter, more horizontal and wider euTube. this causes otitis media
parts of the tympanic cavity
epitympanum- lies medial to outer attic wall above tympanic membrane
mesotympanum
hypotympanum- lies below drum head
histology of tympanic membrane
outer epithelia, middle fibrous layer and inner mucous layer
pars tensa vs pars flaccida
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
contents of outer 2/3 of EAC
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 )
where does osseous portion of EAC begin
at narrow isthmus
nerve supply of external ear
- auriculotemporal nerve- mandibular branch of CN V
- auricular branch CN X
- greater auricular nerve
- lesser occipital nerve
CN II, III, V, X
vascular supply of external ear
auriculotemporal branch
temporal artery
posterior auricular division of carotid
lymphatic drainage
parotid ( pre auricular )
post auricular
external jugular
euTube function
permits equalization of pressure on both sides of eardrum [when open]
euTube lateral 1/3 vs medial 2/3
medial 2/3 is cartilaginous, lateral 1/3 is bony
when is euTube closed/open?
closed at rest, opens during swallowing and yawning
