Midterm anatomy Flashcards
Cartilage frame, helps funnel and localize sound, amplifies sound as it enters EAC
Pinna
Concavities of Pinna
Concha-Tragus
Triangular fossa
Scaphoid fossa
Convexities of Pinna
Helix
Antihelix
Length of external auditory canal
2.5 cm
What part of external auditory canal is cartilage?
Lateral 1/3
What part of external auditory canal is bony?
Medial 2/3
Skin of external auditory canal
Cartilaginous portion- hair follicles, sebaceous glands, and ceruminous glands
Bony- thinner with no other structures
Neural innervation of external auditory canal
Trigeminal nerve
Greater auriculnar nerve
Auricular branch of Vegus
Facial nerve & chordo tympani
Tympanic membrane characteristics
Approx 9mm diameter, approx 140 degrees, attached to canal wall & malleus
Layers of pars Tensa
Lateral epidermal- continuous with EAC skin
Medial mucosal
Intermedial fibrous
Ossicular chain bones
Malleus
Incus
Stapes
Parts of malleus
Manubrium-attaches to TM at umbo due to encircling by pars propria
Head & neck
Lateral process-adheres to pars propria of TM
Anterior process
Parts of incus
Body- articulates with head of malleus
Short process- anchors to posterior ligament
Long process- parallels manubrium
Lenticular process- articulates with stapes
Parts of stapes
Head- attaches to incus
Footplate- attaches to oval window by the annular ligament
2 crura- support the footplate to head
Middle ear tegmen
Serves as roof & floor to middle cranial fossa
Floor of middle ear contains
Jugular bulb & root of styloid process
Anterior part of middle ear contains
Internal carotid, ET orifice, tensor tympani
Posterior part of middle ear contains
Pyramidal eminence (Stapedius tendon)
Medial part of middle ear contains
Sinus tympani, oval & round window niches
Eustacian tube
Mucosal lined tube for ventilation of the ME
Composition of ET
Cartilaginous portion- anteromedial 2/3
Bony portion- lateral 1/3
Oval window
Membrane covering entry to cochlea
Areal ratio
With area of TM larger than that of the oval window there is at least a 20:1 ratio of pressure amplification
Transduction in audition
Sound pressure–> mechanical pressure–> hydromechanical pressure –> generation of electrical potential
Scala vasculara of organ of Corti
Provides nutrition
How the organ of Corti works
Reissner s membrane moves and displaces fluid
What are the 2 types of hair cells
Type 1 is globular, IHC
Type 2 is cylindrical, OHC
What are the 2 types of afferents
- Thicker, mylinated, IHC
2. Thinner, unmylinated, OHC
Connections that join the HCs
Cross row, between row, tip links
Type 1 afferents
Make up 95% of auditory system Multiple neurons innervate single HC Mylinated Thickens after it leaves habenula perforata Dendrites thin as they approach soma
Small opening in the spiral lamina throug which dendrites of primary auditory system pass
Habenula perforata
Type 2 afferents
Make up 5% of auditory system Single neuron innervates multiple HCs Most innervate first row of OHCs Unmylinated Thickens as it leaves habenula perforata Dendrites thicken as they approach soma
Tonotopic arrangement
The basilar membrane is arranged from HF to LF, narrow and thinner to wider and thicker
Movement of basilar membrane
Envelope- traveling wave
Ascending auditory pathway
C SLIM C Cochlea Superior Olivary complex Lateral Lemniscus Inferior Colliculus Medial Geniculate body Auditory cortex
