THE EAR AND NOSESAPKOTA RAJITA

Anatomy and Physiology

The ear has three compartments:

a) External ear,

b) The middle ear, and

c) The inner ear.

The External Ear• Consists of:

▫ Auricle (pinna) Made of elastic cartilage

Helix

Antihelix

Lobule (ear lobe)

Tragus

▫ External auditory canal Lies within temporal bone

& connects to ear drum (tympanic membrane)

Approximately 24 mm long.

Contains ceruminous glands which secrete ear wax

At the end of the ear canal lies the tympanic membrane (marking the lateral limit of middle ear)

The Middle EarThe middle ear is an air-filled

cavity that transmits sound by way of three tiny bones, the ossicles.

• Ossicles (smallest bones in body)▫ Malleus

Attaches to ear drum

two chief landmarks- the handle and the short process.

Articulates with incus

▫ Incus Articulates with stapes

▫ Stapes (stirrup) Footplate of stapes fits into

oval window

• Opening to Eustachian tube

• The cone of light-a light reflection where the eardrum meets the tip of the malleus.

• Above the short process lies a small portion of the eardrum called the pars flaccida.

• The remainder of the drum is the pars tensa.

• Anterior and posterior malleolar folds- extend obliquely upward from the short process, separate the pars flaccida from the pars tensa but are usually invisible unless the eardrum is retracted.

The Inner Ear (Labyrinth)• Bony labyrinth

▫ Contains perilymph

▫ Semicircular canals Anterior, posterior, and

lateral

Lie right angles to each other

▫ Vestibule Oval portion

▫ Cochlea Looks like a snail

Converts mechanical energy into electrical energy

• Membranous labyrinth▫ Contains endolymph, high in

K+ ions

Pathways of Hearing

• Vibrations of sound pass through the air of the external ear and are transmitted through the eardrum and ossicles of the middle ear to the cochlea, a part of the inner ear.

• The cochlea senses and codes the vibrations, and nerve impulses are sent to the brain through the cochlear nerve.

Conductive phase (The first part of this pathway)

• From the external ear through the middle ear.

• Disorder here causes conductive hearing loss.

Sensorineural phase (The second part of the

pathway)

• Involving the cochlea and the cochlear nerve.

• Disorder here causes sensorineural hearing loss.

The Nose

• The nose consists of the external nose and the nasal cavity,

• Both are divided by a septum into right and left halves.

• Upper one third – supported by Bone.

• Lower two third- supported by cartilage

External Nose

• The external nose has two elliptical orifices called the naris (nostrils), which are separated from each other by the nasal septum.

• The lateral margin, the ala nasi, is rounded and mobile.

• Air enters the nasal cavity by way of the anterior naris on either side, then passes into a widened area known as the vestibule and on through the narrow nasal passage to the nasopharynx.

The Medial Wall of Nasal Cavity • The medial wall of each nasal

cavity is formed by Nasal Septum.

• Divides the nasal cavity into right and left halves

• Supported by both bone and cartilage.

• Nasal septum consists of the perpendicular plate of the ethmoid bone (superior), the vomer (inferior) and septial cartilage (anterior)

The Lateral Walls of Nasal Cavity

Marked by 3 projections:

▫ Superior turbinate

▫ Middle turbinate

▫ Inferior turbinate

• The space below each concha or turbinate is called a meatus, each named according to the turbinate above it.

The Paranasal Sinuses• The paranasal sinuses are

cavities found in the interior of the maxilla, frontal, sphenoid, and ethmoid bones .

• They are lined with mucos membrane and filled with air.

• They communicate with the nasal cavity through relatively small apertures.

• Only the frontal and maxillary sinuses are readily accessible to clinical examination.