The document discusses the anatomy and function of the ears and nose as sensory organs. It describes the outer, middle and inner ear in detail, including the pinna, ear canal, eardrum, ossicles, cochlea and auditory nerve. It explains how sound is transmitted through the ear. It also discusses the nasal passages, paranasal sinuses and role of the nose in smell and breathing.

1. SENSORY ORGANS :
EARS AND NOSE

2. SENSORY ORGANS
“Sense organs are the organs that respond to external stimuli by
conveying impulses to the sensory nervous system.”
• Sense organs are specialized organs that help to perceive the world
around us. They are an integral part of our lives and it is the only way
that enables us to perceive the environment.
• Sense organs provide the required data for interpretation through
various organs and a network of nerves in response to a particular
physical phenomenon. These senses govern our association and our
interaction with the environment

3. SENSORY ORGANS
We have five sense organs, namely:
Eyes , Ears , Nose , Tongue , Skin
These five sense organs contain receptors that relay information
through the sensory neurons to the appropriate places within
the nervous system. The receptors could be classified into two parts
viz. the general and special receptors. The former is present
throughout the body while the latter includes chemoreceptor,
photoreceptors and mechanoreceptors.

4. THE EARS
• Ears are the auditory sense organs of our body. They help us to
perceive sounds.
• Our auditory system detects vibrations in the air and this is how we
hear sounds. This is known as hearing or audioception.
• The ears are divided into three sections, namely, outer ear, inner ear,
and the middle ear.
• All sounds are basically vibrations, so the outer ear transfers these
vibrations into the ear canal, where these vibrations are transformed
by the brain into meaningful sound.

5. •Apart from hearing, this sense is also
important for balancing our body or
equilibrium.
•The ear is a sensitive organ of the
human body. It is mainly concerned
with detecting, transmitting and
transducing sound. Maintaining a sense
of balance is another important
function performed by the human ear.
EARS – Hearing or Audioception

6. THE OUTER EAR
The outer ear is the external part
of the ear, which collects sound
waves and directs them into the
ear.
Parts of outer ear:
1. Pinna
2. External Auditory Canal

7. 1.THE PINNA
•The pinna is the only visible part of the ear (the auricle) with its
special helical shape.
•It is the first part of the ear that reacts with sound.
•The function of the pinna is to act as a kind of funnel which assists in
directing the sound further into the ear.
•Without this funnel the sound waves would take a more direct route
into the auditory canal. This would be both difficult and wasteful as
much of the sound would be lost making it harder to hear and
understand the sounds.

8. 1.THE PINNA
•The pinna is essential due to the difference
in pressure inside and outside the ear.
•The resistance of the air is higher inside
the ear than outside because the air inside
the ear is compressed and thus under
greater pressure.
•In order for the sound waves to enter the
ear in the best possible way the resistance
must not be too high.

9. 1.THE PINNA
•This is where the pinna helps by overcoming the difference in pressure
inside and outside the ear.
•The pinna functions as a kind of intermediate link which makes the
transition smoother and less brutal allowing more sound to pass into
the auditory canal (meatus).
•The auricle comprises a thin plate of elastic cartilage covered by a
layer of skin.
•It consists of funnel-like curves that collect sound waves and transmits
them to the middle ear. The lobule consists of adipose and fibrous
tissues supplied with blood capillaries.

10. 2. EXTERNAL AUDITORY CANAL
•Once the sound waves have passed the pinna,
they move two to three centimeters into the
auditory canal before hitting the eardrum, also
known as the tympanic membrane.
•The function of the ear canal is to transmit
sound from the pinna to the eardrum.
•It is a slightly curved canal supported by bone in
its interior part and cartilage in the exterior part.
•The meatus or the canal is lined with stratified
epithelium and wax glands.

11. THE MIDDLE EAR
•The middle ear is the part of the ear between the eardrum and the
oval window. The middle ear transmits sound from the outer ear to the
inner ear. The middle ear consists of three bones or ossicles:
The Hammer (Malleus) , The Anvil (Incus) , The Stirrup (Stapes)
• Parts of inner ear :
1. The Ear Drum
2. The Oval Window
3. The Round Window
4. The Eustachian Tube.

12. EAR OSSICLES OR BONES
•These are responsible for transmitting sound waves from the eardrum
to the middle ear.
•There are three ear ossicles in the human ear:
1. Malleus: A hammer-shaped part that is attached to the tympanic
membrane through the handle and incus through the head. It is the
largest ear ossicle.
2. Incus: An anvil-shaped ear ossicle connected with the stapes.
3. Stapes: It is the smallest ossicle and also the smallest bone in
the human body.

13. 1. THE EARDRUM
•The eardrum (tympanic membrane), is a membrane at the end of the
auditory canal and marks the beginning of the middle ear.
•The eardrum is extremely sensitive and pressure from sound waves
makes the eardrum vibrate.
•In order to protect the eardrum, the auditory canal is slightly curved
making it more difficult for insects, for example, to reach the
eardrum.
•At the same time, earwax (cerumen) in the auditory canal also helps
to keep unwanted materials like dirt, dust and insects out of the ear.

14. 1. THE EARDRUM

15. 1. THE EARDRUM
•This membrane separates the middle ear and the external ear. This
part receives and amplifies the sound waves. Its central part is known
as the umbo.
•In addition to protecting the eardrum, the auditory canal also
functions as a natural hearing aid which automatically amplifies low
and less penetrating sounds of the human voice.
•In this way the ear compensates for some of the weaknesses of the
human voice, and makes it easier to hear and understand ordinary
conversation.

16. 2. THE OVAL WINDOW
•The oval window is a membrane covering the entrance to the cochlea
in the inner ear.
•When the eardrum vibrates, the sound waves travel via the hammer
and anvil to the stirrup and then on to the oval window.
•When the sound waves are transmitted from the eardrum to the oval
window, the middle ear is functioning as an acoustic transformer
amplifying the sound waves before they move on into the inner ear.
•The pressure of the sound waves on the oval window is some 20 times
higher than on the eardrum.

17. 2. THE OVAL WINDOW
•The pressure is increased due to the
difference in size between the relatively
large surface of the eardrum and the
smaller surface of the oval window.
•The same principle applies when a person
wearing a shoe with a sharp stiletto heel
steps on your foot: The small surface of the
heel causes much more pain than a flat
shoe with a larger surface would.

18. 3. THE ROUND WINDOW
•The round window in the middle ear
vibrates in opposite phase to vibrations
entering the inner ear through the oval
window. In doing so, it allows fluid in the
cochlea to move.
•The oval window, also known as the
fenestra ovalis, is a connective tissue
membrane located at the end of the
middle ear and the beginning of the inner
ear.

19. 4. THE EUSTACHIAN TUBE.
•The Eustachian tube is also found in the middle ear, and connects the
ear with the rearmost part of the palate.
•The Eustachian tube’s function is to equalize the air pressure on both
sides of the eardrum, ensuring that pressure does not build up in the
ear.
•The tube opens when you swallow, thus equalizing the air pressure
inside and outside the ear.
•In most cases the pressure is equalized automatically, but if this does
not occur, it can be brought about by making an energetic swallowing
action.

20. 4. THE EUSTACHIAN TUBE
•The swallowing action will force the tube connecting the palate with
the ear to open, thus equalizing the pressure.
•Built-up pressure in the ear may occur in situations where the
pressure on the inside of the eardrum is different from that on the
outside of the eardrum.
•If the pressure is not equalized, a pressure will build up on the
eardrum, preventing it from vibrating properly.
•The limited vibration results in a slight reduction in hearing ability. A
large difference in pressure will cause discomfort and even slight pain.

21. 4. THE EUSTACHIAN TUBE
•Built-up pressure in the ear will often
occur in situations where the pressure
keeps changing, for example when
flying or driving in mountainous areas.
•The Eustachian tube is a 4cm long
tube that equalizes air pressure on
either side of the tympanic membrane.
It connects the tympanic cavity with
the nasopharynx.

22. THE INNER EAR
The inner ear is the
innermost part of the
ear , which consist of
three parts :
1. Cochlea
2. The Vestibular Or
Balance Mechanism
3. The Auditory Nerve.

23. 1. COCHLEA
•The cochlea resembles a snail shell or a wound-up hose and is filled
with a fluid called perilymph and contains two closely positioned
membranes.
•These membranes form a type of partition wall in the cochlea.
However, in order for the fluid to move freely in the cochlea from one
side of the partition wall to the other, the wall has a little hole in it (the
helicotrema).
•This hole is necessary, in ensuring that the vibrations from the oval
window are transmitted to all the fluid in the cochlea.

24. 1. COCHLEA
•When the fluid moves inside
the cochlea, thousands of
microscopic hair fibers inside
the partition wall are put into
motion.
•There are approximately
24,000 of these hair fibers,
arranged in four long rows.

25. 2. THE BALANCE MECHANISM OR VESTIBULAR
•The vestibular is another important part of the
inner ear. The vestibular is the organ of
equilibrium. The vestibule's function is to register
the body's movements, thus ensuring that we can
keep our balance.
•The vestibular consists of three ring-shaped
passages, oriented in three different planes.
• All three passages are filled with fluid that
moves in accordance with the body's movements.

26. •In addition to the fluid, these passages also
contain thousands of hair fibers which react to
the movement of the fluid sending little
impulses to the brain.
•The brain then decodes these impulses which
are used to help the body keep its balance.
•Disorders of the vestibular or infections in the
inner ear can cause vertigo, the spinning
sensation of dizziness.
2. THE BALANCE MECHANISM OR VESTIBULAR

27. 3. THE AUDITORY NERVE
•The auditory nerve is a bundle of nerve fibers that
carry information between the cochlea in the inner
ear and the brain.
•The function of the auditory nerve is to transmit
signals from the internal ear to the brain.
•The hair fibers in the cochlea are all connected to
the auditory nerve and, depending on the nature
of the movements in the cochlear fluid, different
hair fibers are put into motion.

28. FAHS | PALLAVI BASRA
THE NOSE
•Nose, the prominent structure
between the eyes that serves as the
entrance to the respiratory tract and
contains the olfactory organ. It
provides air for respiration, serves
the sense of smell, conditions the air
by filtering, warming, and moistening
it, and cleans itself of foreign debris
extracted from inhalations.

29. THE EXTERNAL NOSE
•The external nose is said to have a
pyramidal shape. The nasal root is
located superiorly, and is continuous
with the forehead.
•The apex of the nose ends inferiorly
in a rounded ‘tip’. Spanning between
the root and apex is the dorsum of
the nose.
•The external nose is a visible component of the face, projecting over
and allowing entrance into the nasal cavity.

30. THE EXTERNAL STRUCTURE
•Located immediately inferiorly to the apex are the nares; piriform
openings into the vestibule of the nasal cavity
•The nares are bounded medially by the nasal septum, and laterally by
the ala nasi (the lateral cartilaginous wings of the nose).
•The external is described in following parts:
1. Skeletal structure
2. Muscles
3. Blood supply
4. Innervations

31. 1. SKELETAL STRUCTURE
The skeleton of the external nose is made of
both bony and cartilaginous components:
1. Bony component – located superiorly, and
is comprised of contributions from the
nasal bones, maxillae and frontal bone.
2. Cartilaginous component – located
inferiorly, and is comprised of the two
lateral cartilages, two alar cartilages and
one septal cartilage. There are also some
smaller alar cartilages present.

32. 1. SKELETAL STRUCTURE
•Whilst the skin over the bony part
of the nose is thin, that overlying
the cartilaginous part is thicker with
many sebaceous glands.
•This skin extends into the vestibule
of the nose via the nares.
•Here there are hairs which function
to filter air as it enters the
respiratory system.

33. 2. MUSCLES
•A number of small muscles insert
into the external nose, contributing to
facial expression.
•All these muscles are innervated by
branches of the facial nerve (CN VII).
•The procerus muscle originates in the
fascia overlying the nasal bone and
lateral nasal cartilage, inserting into
the inferior forehead.

34. 2. MUSCLES
•Contraction can depress the medial eyebrows,
and wrinkles the skin of the superior dorsum.
•The transverse portion of the nasalis muscle
assists the procerus muscle in this action.
•Meanwhile the alar part of nasalis arises from
the maxilla, inserting into the major alar
cartilage.
•This allows the muscle to dilate the nares,
“flaring” them. This action is assisted by
the depressor septi nasi.

35. 3. BLOOD SUPPLY
•The skin of the external nose receives
arterial supply from branches of the
maxillary and ophthalmic arteries.
•The septum and alar cartilages receive
additional supply from
the angular artery and lateral
nasal artery.
•These are both branches of the facial
artery (derived from the external carotid
artery).

36. 3. BLOOD SUPPLY
•Venous drainage is into the facial
vein, and then in turn into the internal
jugular vein.
•Lymphatic drainage from the external
nose is via superficial lymphatic
vessels accompanying the facial vein.
•These vessels, like all lymphatic
vessels of the head and neck,
ultimately drain into the deep cervical
lymph nodes.

37. 4. INNERVATION
•The lateral aspects of the nose are supplied
by the infrorbital nerve, a branch of the
maxillary nerve (CN v2).
•Motor innervation to the nasal muscles of
facial expression is via the facial nerve (CN
VII).
•Sensory innervation of the external nose is derived from the trigeminal
nerve (CN V).
•The external nasal nerve, a branch of the ophthalmic nerve (CN V1),
supplies the skin of the dorsum of nose, nasal alae and nasal vestibule.

38. PARANASAL SINUSES
•The paranasal sinuses are air-filled extensions of the nasal cavity. Each
sinus is lined by a ciliated pseudo stratified epithelium, interspersed
with mucus-secreting goblet cells.
•There are four paired sinuses – named according to the bone in which
they are located –
1. Frontal Sinuses
2. Ethmoid Sinuses
3. Sphenoid Sinuses
4. Maxillary Sinuses

39. 1. FRONTAL SINUSES
•There are two frontal sinuses located within the
frontal bone of the skull. They are the most superior
of the paranasal sinuses, and are triangular in shape.
•Drainage is via the frontonasal duct. It opens out at
the hiatus semilunaris, within the middle meatus of
the nasal cavity.
•Sensation is supplied by the supraorbital nerve (a
branch of the ophthalmic nerve), and arterial supply
is via the anterior ethmoidal artery (a branch of the
internal carotid).

40. 2. ETHMOID SINUSES
•There are three ethmoidal sinuses located within the ethmoid bone:
1. Anterior – Opens onto the hiatus semilunaris (middle meatus)
2. Middle – Opens onto the lateral wall of the middle meatus
3. Posterior – Opens onto the lateral wall of the superior meatus
•They are innervated by the anterior and
posterior ethmoidal branches of the
nasociliary nerve and the maxillary nerve.
•The anterior and posterior ethmoidal
arteries are responsible for arterial supply

41. 3. SPHENOID SINUSES
•They are innervated by the posterior
ethmoidal nerve (a branch of the ophthalmic
nerve), and branches of the maxillary nerve.
•They receive blood supply from pharyngeal
branches of the maxillary arteries.
•The sphenoid sinuses are situated within the body of the sphenoid
bone.
•They open out into the nasal cavity in an area supero-posterior to the
superior cocha – known as the spheno-ethmoidal recess.

42. 4. MAXILLARY SINUSES
•The maxillary sinuses are the largest of
the sinuses.
•They are located laterally and
slightly inferiorly to the nasal cavities.
•They drain into the nasal cavity at the
hiatus semilunaris, underneath the frontal
sinus opening.
•This is a potential pathway for spread of
infection – fluid draining from the frontal
sinus can enter the maxillary sinus.

43. THE NASAL CAVITY
•The nose is an olfactory and respiratory organ. It consists of nasal
skeleton, which houses the nasal cavity. The nasal cavity is the most
superior part of the respiratory tract.
•It extends from the vestibule of the nose to the nasopharynx, and has
three divisions:
1. Vestibule – the area surrounding the anterior external opening to
the nasal cavity.
2. Respiratory region – lined by a ciliated psudeostratified epithelium,
interspersed with mucus-secreting goblet cells.

44. THE NASAL CAVITY
3. Olfactory region –
located at the apex of
the nasal cavity. It is
lined by olfactory cells
with olfactory
receptors

45. NASAL CONCHAE
•Projecting out of the lateral walls of the nasal cavity are curved
shelves of bone. They are called conchae (or turbinates). The are three
conchae – inferior, middle and superior.
•They project into the nasal cavity, creating four pathways for the air to
flow. These pathways are called meatuses:
1. Inferior meatus – between the inferior concha and floor of the nasal
cavity.
2. Middle meatus – between the inferior and middle concha.

46. NASAL CONCHAE
3. Superior meatus –
between the middle
and superior concha
4. Spheno-ethmoidal
recess – superiorly
and posteriorly to
the superior concha.

47. OPENING OF NASAL CAVITY
•The paranasal sinuses drain into the nasal cavity. The frontal, maxillary
and anterior ethmoidal sinuses open into the middle meatus.
•The location of this opening is marked by the semilunar hiatus, a
crescent-shaped groove on the lateral walls of the nasal cavity.
•The middle ethmoidal sinuses empty
out onto a structure called
the ethmoidal bulla.
•This is a bulge in the lateral wall
formed by the middle ethmoidal sinus
itself.

48. OPENING OF NASAL CAVITY
•The posterior ethmoidal sinuses open out at the level of the superior
meatus. The only structure not to empty out onto the lateral walls of
the nasal cavity is the sphenoid sinus. It drains onto the posterior roof.
•In addition to the paranasal sinuses, other structures open into the
nasal cavity:
1. Nasolacrimal duct – acts to drain tears from the eye. It opens into
the inferior meatus.
2. Auditory (Eustachian) tube – opens into the nasopharynx at the
level of the inferior meatus. It allows the middle ear to equalize
with the atmospheric air pressure.

49. GATEWAYS OF NASAL CAVITY
•As well as openings for the drainage of structures, nerves, vasculature
and lymphatic need to be able to access the nasal cavity.
•The cribriform plate is part of the ethmoid bone. It forms a portion of
the roof of the nasal cavity.
• It contains very small perforations, allowing fibers of the olfactory
nerve to enter and exit, At the level of the superior meatus,
the sphenopalatine foramen is located.
•This hole allows communication between the nasal cavity and
the pterygopalatine fossa.

50. GATEWAYS OF NASAL CAVITY
•The sphenopalatine artery, nasopalatine
and superior nasal nerves pass through
here.
•The incisive canal is a pathway between
the nasal cavity and the incisive fossa of
the oral cavity. It transmits the
nasopalatine nerve and greater palatine
artery.

51. VASCULATURE
•The nose has a very rich vascular supply.
The nose receives blood from both the
internal and external carotid arteries:
1. Internal carotid branches:
a. Anterior ethmoidal artery
b. Posterior ethmoidal artery
•The ethmoidal arteries are branch of
the ophthalmic artery. They descend into
the nasal cavity through the cribriform
plate.

52. VASCULATURE
2. External carotid branches:
a. Sphenopalatine artery
b. Greater palatine artery
c. Superior labial artery
d. Lateral nasal arteries
•The veins of the nose tend to follow
the arteries. They drain into the
pterygoid plexus, facial vein or
cavernous sinus.

53. INNERVATION
•Special sensory innervation refers to the ability of the nose to smell. This is
carried out by the olfactory nerves. The olfactory bulb, part of the brain, lies on
the superior surface of the cribriform plate, above the nasal cavity. Branches of
the olfactory nerve run through the cribriform plate to provide special sensory
innervation to the nose.
•General sensory innervation to the septum and lateral walls is delivered by
the nasopalatine nerve (branch of maxillary nerve) and the nasociliary
nerve (branch of the ophthalmic nerve). Innervation to the external skin of the
nose is supplied by the trigeminal nerve.
•The innervation of the nose can be functionally divided into special and general
innervation.