Normal ear Flashcards
What is the function of the ear
Explain the structure of the mammalian ear
What are the types of cartilage in the external ear?
Auricular cartilage - forms anthelix (medially) and tragus (laterally) and conchal tube
Annular cartilage - fits within base of conchal tube ligamentous attachments to bony acoustic process of temporal bone
Scutiform cartilage - not part of ear canal, provides additional support
Label the cartilages of the inner ear
Describe the vascular supply to the external ear
Describe the innervation of the external ear
Describe the integumentary covering of the external inner
Epidermis: thin, stratified squamous keratinising epidermis (also over tympanic membrane)
Dermis: thin, contains hair follicles, sebaceous glands distally, apocrine (ceruminous) glands proximally
Label this canine ear canal
Describe the composition of cerumen/ear wax
Exfoliated cells
Sebaceous secretions (high lipid content)
Ceruminous gland secretions (more aqueous)
Immunoglobulins
What is the function of cerumen/ear wax?
provides a protective and antimicrobial layer
How do epithelial cells contribute to the cerumen/ear wax?
Epithelial cells from centre of TM travel to periphery, then desquamate
This helps transport cerumen to superficial portion of ear canal
Describe the structure of the tympanic membrane
Stratified squamous keratinising epithelium laterally
thin lamina propria (collagen bundles)
simple squamous/cuboidal mucosal epithelium medially
Label the tympanic membrane
Describe the visible parts of the tympanic membrane and their function
Pars flaccida - accomodates changes in pressure
Pars tensa - transmits sound
Manubrium of malleus
Label the tympanic membrane
What are the compartments of the middle ear?
Epitympanum - contains malleus and incus
Mesotympanum - stapes attached to oval window - round window and opening to auditory tube
Hypotympanum/fundus - tympanic cavity
What is the auditory/eustachian tube?
link between middle ear and back of throat
Label the canine middle ear
What do feline middle ears have that canines do not?
Incomplete bony septum across tympanic cavity
Label the auditory ossicles
Describe the anatomy of the eustachian tube
pseudostratified, ciliated, columnar epithelium
Scattered goblet cells
Which nerves from in/close to the wall of the tympanic bulla?
Facial nerve
Branches of facial and vagus nerves form tympanic nerve
post-ganglionic fibres of cervical sympathetic trunk
What are the sections of the inner ear?
Cochlea
Vestibule
Semicircular canals
Enceased in bony labrinth of petrous temporal bone
What are the functions of the inner ear?
Hearing
Balance
Position and rotation of head in relation to gravitational forces
What are the normal commensals found in the inner ear?
staphylococci
malassezia pachydermatis yeast
What are otitis externa, media and interna?
