Download 14-Nasal cavity

Nose
 Only externally visible part of
the respiratory system
 Has a free tip and is attached
to the forehead by the root or
the bridge
 Has two openings, the
anterior (external) nares or
nostrils, which lead to the
nasal cavity
 Each nostril is bounded
laterally by the ala and
medially by the nasal septum
root
tip
ala
septum
external nares
Nose: Structure
 Nose consists of bony &
cartilaginous framework
 Formed above by the:
• Nasal bones
• Frontal processes of
maxillae
• Nasal part of frontal bone
 Formed below by plates of
hyaline cartilage, which
include upper & lower nasal
cartilages and the septal
cartilage
Nasal part of
Frontal bone
Nasal Cavity
 Extends from the
external (anterior)
nares to the posterior
nares (choanae)
 Divided into right & left
halves by the nasal
septum
 Each half has a:
 Floor
 Roof
 Lateral wall
 Medial wall (septum)
 Roof
 Is narrow & formed (from behind
forward) by the:
• Body of sphenoid
• Cribriform plate of ethmoid bone
• Frontal bone
• Nasal bone & cartilage
 Floor
• Separates it from the oral cavity
• Formed by the hard (bony)
palate
 Medial Wall (Nasal Septum)
 Osteocartilaginous partition, only
rarely lying in the midline
 Covered by the mucoperiosteum
 Formed:
• Superiorly by the vertical
(perpendicular) plate of ethmoid
bone
• Posteriorly by the vomer bone
• Anteriorly by the septal cartilage
 Lateral Wall
 Shows three horizontal bony
projections, covered by mucous
membrane, the superior, middle &
inferior conchae (turbinates)
 The superior and middle conchae
are parts of the ethmoid bone,
whereas the inferior concha is a
separate bone
 The cavity below each concha is
called a meatus and are named as
superior, middle & inferior
corresponding to the conchae
 The small space above the superior
concha is called the
sphenoethmoidal recess
• The middle meatus is continuous in
front with a depression called the
atrium
• Atrium is limited bove by a ridge
called agar nasi
• Below and in front of atrium, and
just within the nostril lies the
vestibule
 The conchae
increase the surface
area of the nasal
cavity
 The recess & meati
receive the
openings of the:
 Paranasal
sinuses
 Nasolacrimal duct
 Sphenoethmoidal recess:
Receives the opening of the
sphenoidal sinus
 Superior meatus: Receives the
opening of the posterior ethmoidal
sinus
 Inferior meatus: Receives the
opening of the nasolacrimal duct.
The opening is guarded by a
valve, a fold of mucous
membraneMiddle meatus:
• Shows a rounded eminence, the
ethmoidal bulla, caused by the
bulging of the underlying middle
ethmoidal sinus, which opens on
its upper border.
• A curved groove, hiatus
semilunaris, lies below the bulla.
Hiatus receives the opening of the
maxillary sinus
• Anterior end of hiatus leads to
funnel-shaped infundibulum,
which receives the openings of the
frontal & the anterior ethmoidal
sinuses
Lining of the Nasal Cavity
 Vestibule is lined by
modified skin, and has
short, curved hair called
vibrissae
 The roof, upper part of the
septum, upper surface of
the superior concha, and
the sphenoethmoidal recess
are lined by the olfactory
mucosa
 The rest of the cavity is
lined by the respiratory
mucosa
A
V
V
Olfactory Mucosa
 Contains olfactory cells (bipolar sensory
ganglion cells), which serve as receptors for
olfactory stimuli.
 Distinct smells are far more numerous than
tastes
 The sense of smell plays a major role in the
flavor of foods and it is common for
individuals who lose their sense of smell to
report that food loses its taste. (food seems
somewhat tasteless when a person has
cold)
 Most air breathed in normally flows through
the nose but only a small part reaches the
olfactory mucosa, enough to get a response
to an odor. Sniffing, however, increases the
flow of air over the smell receptor cells,
greatly increasing their exposure to odors.
Respiratory Mucosa
 Pseudostratified ciliated columnar epithelium with
goblet cells
 Rests on thick network of thin walled veins that
warms the air as it flows through the cavity
 Glands produce ‘mucus’, which:
 moisten the air
 cleans the air by trapping the incoming bacteria
and foreign debris
 Cilia help in moving the contaminated mucus
posteriorly towards the throat, where it is
swallowed and digested by the stomach juices

Nasal cavity receives sensory & visceral
innervation
Sensory innervation


Olfactory mucosa supplied by olfactory nerves
Nerves of general sensation are derived from
opthalmic & maxillary nerves
 Anterior part supplied by the anterior
ethmoidal nerve (branch of opthalmic
nerve)
 Posterior part supplied by nasal,
nasopalatine and palatine branches (of
maxillary nerve)
Visceral Innervation
 Sympathetic fibers arise from neurons of
superior cervical ganglion and are
distributed through plexuses around the
arteries, supply mainly vascular smooth
muscle
 Parasympathetic fibers arise from neurons
of the pterygopalatine ganglion that
course in the nasopalatine nerve (branch
of maxillary) and its branches, supply the
mucosal glands.
Nerve Supply
 Sphenopalatine artery (branch of the
maxillary artery) is the main supply
 Alar and septal branches of superior labial
artery (branch of the facial artery)
 Anterior & posterior ethmoidal arteries
(branches of the ophthalmic artery)
 The arteries make a rich anastomosis in
the region of the vestibule, and anterior
portion of the septum
Venous Drainage:
 Veins begin as a rich plexus in the
submucosa, accompany the corresponding
arteries, and drain into the facial,
ophthalmic, and sphenopalatine veins.
Lymphatic Drainage:
 The lymphatics from the:
 Vestibule drain into the submandibular
lymph nodes
 Rest of the cavity drains into the upper
deep cervical lymph nodes
Arterial Supply
Functions of Nose & Nasal Cavities
 Air conditioning: warming, cleaning and
humidifying the inhaled air
 Add resonance to the voice
 Vocal sounds are also produced in the nasal
cavity thus aiding in vocalisation
 Involved in the special sense of smell
 Central role of the nose in facial appearance
 ??
Paranasal Sinuses
 Air filled cavities located in the
bones around the nasal cavity:
ethmoid, sphenoid, frontal bones
& maxillae
 Lined by respiratory mucosa
which is continuous with the
mucosa of the nasal cavity
 Drain into the nasal cavity
through relatively small apertures
 Drainage of the sinuses mainly
depends on the movement of the
cilia, which propel the mucus
toward their openings in the
nasal cavity
 The development of sinuses begins in
3-4 month, but only maxillary &
ethmoid sinuses are present in
rudimentary form at birth. The frontal &
sphenoidal sinuses are not clinically
perceptible at birth and can rarely be
demonstrated on plain x-ray before two
years of age.
 Continue to grow postnatally
 Enlarge appreciably after 8th year &
become fully formed at adolescence
Functions:
 Lighten the skull
 Act as resonant chambers for speech
 The respiratory mucosal lining helps in
warming, cleaning and moistening the
incoming air
E
M
From a 3 months old fetus,
showing ethmoid & maxillary
sinuses
Maxillary Sinuses
• Located within the body of the
maxilla
• Pyramidal in shape with the base
forming the lateral wall of nose &
the apex lies in the zygomatic
process of the maxilla
• Roof: formed by the floor of the
orbit
• Floor: formed by the alveolar
border. Roots of 1st and 2nd
premolars and the 3rd molar
(sometimes canines) project into
the sinus
• Opens into the middle meatus
through the hiatus semilunaris
• Supplied by superior alveolar &
infraorbital nerves
M
Frontal Sinuses
 Two in number
 Located within the frontal
bone, separated from
each other by a bony
septum
 Triangular in shape,
extending backward into
the roof of the orbit
 Opens into the middle
meatus through the
infundibulum
 Supplied by the
supraorbital nerve
 Located within the ethmoid bone,
between the nose and the orbit
 Divided into three groups:
anterior, middle & posterior
 Anterior group opens into the
infundibulum, middle opens on
the bulla, and posterior into the
superior meatus
 Supplied by the anterior &
posterior ethmoidal nerves
Sphenoidal Sinuses
 2 in number
 Located within the body of
sphenoid
 Open into the sphenoethmoidal
recess
 Supplied by the posterior
ethmoidal nerve
Ethmoidal
Sinuses
 Epistaxis: Little’s area, common site of
bleeding from nose
 Inflammation of the nasal mucosa, Rhinitis,
results in nasal congestion and excessive
production of mucus leading to ‘postnasal
drip’
 Infections of the nasal cavity can extend to
the:
 Paranasal sinuses
 Nasolacrimal duct & lacrimal sac
 Inflammation of mucosa of the sinuses,
Sinusitis, causes excessive production of
mucus leading to obstruction of the drainage
of sinuses. This results in headache and
change in the voice
 Infection of frontal & anterior ethmoidal
sinus can easily spread to maxillary sinus
because of the location of their openings
 Infection of upper teeth can lead to
inflammation of the maxillary sinus
 Extraction of an infected upper tooth may
result in a fistula
Clinical
Notes
 The maxillary sinus is most
commonly the site of infection
 The inflamed mucosa results
in excessive production of
mucus as well as narrowing of
its opening in the nasal cavity
 The position of the drain
causes problems in that
mucus can collect in the sinus
below the drain. In this
situation, the sinus will only
drain if the patient lies on
their opposite side.
 Pressure from the trapped
fluid/mucus causes sinus pain