Inner Ear

Question 1

Bony labyrinth

Answer 1

Filled w perilymph
Vestibule
Semicircular canals
Cochlea

Question 2

Vestibule

Answer 2

It is the central chamber of the labyrinth. Lateral walls have oval window. The inside of medial walls have 2 recesses spherical recess that has saccule
Elliptical recess that has utricle

Question 3

Elliptical recess k neechay

Answer 3

Opening of aqueduct of vestibule through which passes the endolymphatic duct, posterosuperior part are the 5 openings of semicircular canals

Question 4

Semicircular canals

Answer 4

3 in number
Lateral posterior, superior and lie in a plane at right angles to each other.
Each canal has an ampullated end that opens independently into the vestibule & a nonampullated end. The nonampullated ends of 2 canals will combine to form a crus commune. The 3 canals open into the vestibule by 5 openings.

Question 5

Cochlea

Answer 5

Bony cochlea is a coiled tube making ,2.5 to 2.75 turns round a central pyramid of bone called modiolus. Base is directed towards internal acoustic meatus,and transmits vessels and nerves to the cochlea.
Modiolus k around osseous spiral lamina

Question 6

Cochlea

Answer 6

Bony cochlea is a coiled tube making ,2.5 to 2.75 turns round a central pyramid of bone called modiolus. Base is directed towards internal acoustic meatus,and transmits vessels and nerves to the cochlea.

Question 7

Modiolus k around osseous spiral lamina

Answer 7

Bony bulge in the medial wall of middle ear,the promontory is due to the basal coil of the cochlea
Scala vestibule
Scala tympani
Scala media

Question 8

Scalas

Answer 8

Scala vestibuli and tympani
Filled w perilymp communicate w opening called helicotrema
SV is closed by footplate of stapes to separate it from the air filled middle ear
Scala tympani is closed by sec tympani membrane it is also connected by subarachnoid space through the aqueduct of cochlea

Question 9

Membranous labyrinth

Answer 9

Membranous cochlea or the Scala media
Blind coiled tube appearing triangular on cross section & it’s 3 walls are formed by
Basilar membrane—organ of corti
Reissner’s membrane seperating from Scala vestibule
Stria vascularis– vascular epithelium and is concerned w secretion of endothelium

Question 10

Cochlear duct is connected to the saccule

Answer 10

Ductus reuniens

Question 11

Length of basilar membrane

Answer 11

Inc as we move from basilar coil to the apical coil, higher freq at basal

Question 12

Utricle and connections

Answer 12

The utricle lies in the posterior part of bony vestibule. It receives the five openings of the three semicircular ducts. It is also connected to the saccule through utriculosaccular duct.

Question 13

Epithelium

Answer 13

The sensory epithelium of the utricle is called macula and is concerned with linear accelerationdeceleration. The saccule also lies in the bony vestibule, anterior to the utricle and opposite the stapes footplate. Its sensory epithelium is also called macula. Its exact function is not known. It probably also responds to linear accelera-tion and deceleration.

Question 14

Saccule in menniere’s disease

Answer 14

In Ménière’s disease, the distended saccule lies against the stapes footplate and can be surgically decompressed by perforating the footplate.

Question 15

Semicircular ducts

Answer 15

They are three in number and cor-respond exactly to the three bony canals. They open in the utricle. The ampullated end of each duct contains a thick-ened ridge of neuroepithelium called crista ampullaris.

Question 16

Perilymph

Answer 16

resembles extracellular fl uid and is rich in Na ions. It fi lls the space between the bony and the mem-branous labyrinth. It communicates with CSF through the aqueduct of cochlea which opens into the scala tympani near the round window. In fact this duct is not a direct communication but contains connective tissue resembling arachnoid through which perilymph percolates. There are two views regarding the formation of perilymph: (i) It is a fi ltrate of blood serum and is formed by capillaries of the spiral ligament and (ii) it is a direct continuation of CSF

Question 17

Endolymph

Answer 17

fi lls the entire membranous labyrinth and resembles intracellular fl uid, being rich in K ions. It is secreted by the secretory cells of the stria vascularis of the cochlea and by the dark cells (present in the utricle and also near the ampullated ends of semicircular ducts). There are two views regarding its fl ow: (i) longitudinal, i.e. endolymph from the cochlea reaches saccule, utricle and endolymphatic duct and gets absorbed through endolymphatic sac, which lies in the subdural space and (ii) radial, i.e. endolymph is secreted by stria vascularis and also gets absorbed by the stria vascularis. This view presumes that endolymphatic sac is a vestigial structure in man and plays no part in endo-lymph absorption