Question

1)Define or illustrate the following: anatomy of the ear including external-middle-and-internal ear, detail of cochlea anatomy, myopia, hyperopia, astigmatism, primary auditory cortex, myoglobin, paranasal sinus, atlas, axis,

Answer 1

1)External ear consisit of Auricle,External auditory meatus .

Auricle ( Pinna ) ---
The pinna is the only visible part of the ear (the auricle). It has special helical shape. It is the first part of the ear that reacts with sound. Pinna act as funnel which assists in directing the sound further into the ear.

External auditory meatus / External auditory canal ---It is the part of external year which connects Auricle with Tympanic membrane .Sound waves travel
For 2-3 cm in auditoy canal before striking tympanic membrane .

Tympanic membrane separate exteral ear from middle ear.   The eardrum (tympanic membrane), is a membrane at the end of the auditory canal and marks the beginning of the middle ear

2)Middle ear (Tympanic cavity )
Auditoy ossicles like
Mlaleus, incus and stapes

Auditory ossicles order is Maleus, Incus stapes from eardrum to inner ear .

*Maleus (hammer bone) is attached to tympanic membrane from where vibrational sound pressure motion is passsd .It also atriculate with Incus .

*Incus --It articulates with both maleus and stapes .

*Stapes ---The stapes ("stirrup") articulates with the incus and is also attached to fenestra ovalis, the elliptical or oval window or opening which connects the middle ear and the vestibule of the inner ear. It is the smallest bone in the body.
Dampens vibration .

*Auditory canal ( Eustachian tube ) ---It connects the middle ear to Nasopharynx .
Function is to equalise the pressure on both side of tympanic membrane .

3)Internal ear ( Labyrinth )
1. COCHLEA
2. VESTIBULE
3. SEMICIRCULAR CANALS.

INNER ear lies in Petrous part of Temporal bone .
1.Cochlea--Spiral canal which takes around 2 and 3/4 turns around central axis called Modiolus .Basal coils respond to higher frequencies and apex to lower frequencies .
Cochlea has 2 types of Labyrinth
1) Osseus labyrinth 2) Membranous Labyrinth .

Cochlea has 3 parts
a)Scala vestibuli
b)Scala media
c)Scala Tympani

*Reissner membrane separate scala vestibuli from Media
*Basilar membrane separate scala tympani from media
*Organ of corti ( sensory end organ of hearing ) present on basilar membrane .
It Contains endolymph ,hair cells ,supporting cells of Hensen ,Dieters cell ,and Claudius cells

*Outer hair cells ---Produce otoacoustic emissions ( efferent ) act as modulator and more senstive to ototoxic drugs and noise .More in number.

*Inner hair cells --Mainly for Hearing ,transmit auditory stimuli afferent and less in number.

*Stria Vascularis ( site of production of emdolymph) present on lateral side of scala media .

2)Vestibule--
The vestibule is the central part of the bony labyrinth in the inner ear, and is situated medial to the eardrum, behind the cochlea, and in front of the three semicircular canals.

3).Semicircular canal --3 semicircular canals anterior ,posterior and Lateral .All open into Utricle .
Semicircular canals are body balance organs detecting accelerations in three perpendicular planes .

Ampulla--
In human ear: Semicircular canals has an expanded part that is known as , the ampulla, which opens into the vestibule .

Auditory ( Vestibulocochlear nerve )--8 th nerve .
Vestibular part concerned with balance
Cochlear with hearing .

Auricle ----> External acoustic meatus -----> tympanic membrane ------>malleus -----> stapes ----> Oval window

---->Cochlea -----> scala vestibuli -----> Bailar membrane ------> inner hair cells ----> cochlear branch of CN VIII-----> Spiral ganglion ( spirally bound around madiolus ) -----> internal aciustic meatus ---->synapse in medulla oblongata brain stem ( Dorsal and ventral cochlear nuclei ) --- ----> synapse in Superior olivary nucleus( centre for stapdial reflex )-----> Lateral lemniscus ----> Inferior colliculus ----> Medial geniculate body -----> primary
auditory association area( Area 41 )

Primary auditory cortex loacted in temporal lobe of brain in superior temporal gyrus ( Heschls gyrus ) .Auditory sensation from organ of Corti finally reaches here then integrated through frontal and parietal lobes of brain help in hearing .

Myopia ---->>Short sightedness / Near vision
When image is formed in front of retina then it is called Myopia in which distant objects are blurred and near objects are seen clearly .Treatment is by Concave lens Divergent lens which make the light fall in Retina .

Hypermetropia ---> Farsightedness / Distant vision
When light falls beyond retina then it Is Hypermetropia .Farsightedness near objects are not visible but far objects are seen clearly .
Convex lens are used for Treatment .
It converge the light rays to fall on Retina .

Cornea and Lens
Total refractive power of eye --60 Dioptres out of which 3/4 th contributed By Cornea 45 D and 1/4 th by Lens 15 D .
So Cornea is regular structure which helps in refraction.

Astigmatism ---->Absence of point focus
When cornea become irregular then the light rays which enters the eyes through cornea is unable to focus on one part of retina instead 2 or 3 focus of image is formed on retina which result on blurred vision .
Treatment ---> Spherical and Cylindrical lenses used .

Myoglobin ---> Myo= muscles and Globin = protein
*It is iron and oxygen binding protein present in musclesIt has higher affinity for oxygen .It responds to increase oxygen demands of mucles .

*Paranasal sinuses are air-filled spaces that surround the nasal cavity. The maxillary sinuses , the frontal sinuses ,the ethmoidal sinuses and the sphenoidal sinuses
*Function is to Humidify the inhaled air ,Increase resonance of speech .

Atlas It is first Cervical vertebrae

Axis It is second cervical Vertebrae .It has dens ( Odontoid process )

Atlas and axis together form atlantoaxial joint which is responsible for greater range of motion around neck .