Ear Flashcards
What are the 3 structure levels of the ear?
External ear
Middle ear
Inner ear
What makes up the external ear?
Pinna and external ear canal (external auditory meatus) down to the tympanic membrane
What makes up the middle ear?
Tympanic cavity in the tympanic bulla
Contains auditory ossicles
Connected to the nasopharynx?
Where is the inner ear?
Contained within the petrous temporal bone
What are the external ear elastic cartilages.
Auricular cartilage
Annular cartilage
Scutiform cartilage
All for suppport
Auricular cartilage
Flattened distally
Ridges = forms anthelix medially and the tragus laterally
Cone-> tube shape proximally
Annular cartilage
Fits within the base of the conchal tube of the auricular cartliage
Ligamentous attachments to internal auditory meatus of the temporal bonw
Scutiform cartilage
Not part of the ear canal
Within the muscles rostromedial to the canal to provide extra support
What innervates the external ear?
Auriculopalpebral branch of CN 7= Motor nerves to the auricular muscles
Sensory innervation from branch of CN V and cervical segment 2
What is the vascular supply to the external ear?
Auricular arteries from internal carotid
Venous drainage=> internal maxillary vein
What are the adjacent structures to the external ear?
Parotid salivary gland
Blood vessels
Nerves (CN VII and CN V)
Where is henris pocket found
On the caudal pinna
Describe the epidermis of the external ear?
Thin stratified squamous keratinising epidermis (including over the tympanic membrane)
Describe the dermis of the external ear?
Thin contains adnexal structures
Hair follicles in variable density on the concave pinna and down the ear canal
Dermis has glands - sebaceous= distally
Apocrine= proximally
Where has this histology slide been taken from?
Can mainly see sebaceous glands meaning it is most likely the distal portion of the external ear
What can be seen in this slide?
Apocrine gland from the external ear
Ceruminous gland (external ear)
What can be seen in the slides?
Compound hair follicles
What is found in the secretions of the ear canal?
Exfoliated cells
Sebaceous secretions
Ceruminous gland secretions
Imunoglobulins IgA IgG and IgM
Compare sebaceous and cermunious secretions?
Sebaceous= high lipid content and various classes of lipids
Ceruminous secretions = more aqueous in nature
What is the most common immunoglobulin in the ear canal secretions?
IgG
What is the average lipid content of the ear canal secretions?
50%
What is the role of the ear canal excretions?
Protection and antimicrobial layer
How is exudate in the ear carried to the surface?
Via epithelial cell migration
Epi cells move laterally from centre of tympanic membrane to periphery
Desquamate = cerumen
Epi migration transports cerumen to superficial portion of each canal
What are the properties of the tympanic membrane?
- Epithelial structure
- Boundary between the external and middle ear
- Made of stratified squamous keratinising epithelium laterally
- Has thin lamina propria
- Made of simple squamous/cuboidal mucosal epithelium medially