3. Anatomy and Physiology
The ear has three compartments:
a) External ear,
b) The middle ear, and
c) The inner ear.
4.
5. 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)
6. The Middle Ear
The 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
7. • 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.
8. 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
9. 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.
10. 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.
11.
12. 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
13. 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.
14. 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)
15. 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.
16. 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.
17. • Only the frontal and maxillary sinuses are
readily accessible to clinical examination.
Editor's Notes
Helix -prominent curved outer ridge
Anithelix-Parallel and anterior to the helix is another curved prominence
lObule- Inferiorly lies the fleshy projection of the earlobe
Tragus- the nodular eminence that points backward over the entrance to the canal.
The maxillary sinus opens into the middle meatus of the nose.
Frontal sinus also Opens into the middle meatus .