The nose and paranasal sinuses are vital for breathing, filtering air, and providing resonance for speech. The nose warms, humidifies, and filters incoming air, while the paranasal sinuses lighten the skull and contribute to voice resonance. Together, they protect the respiratory system from pollutants and pathogens.

1. MDS 311.1
Nose and Paranasal sinuses

2. NOSE
The nose consists of the external nose and the nasal cavity which is
divided into right and left halves by a midline nasal septum.
External nose
It is pyramidal in shape with the apex in anterior position
The upper angle of the nose between the openings of the orbits is
continuous with the forehead at the root or bridge of the nose.

3. The external nose has a free tip. The external orifices are the two
nostrils or nares.
Each nostril is bounded laterally by the ala (nasal cartilage) and
medially by the nasal septum.
The frame work of the external nose is made up above by the nasal
bones, frontal processes of maxillae and the nasal part of frontal bone.
Below, the frame work is formed by plates of hyaline cartilage which
includes the upper and lower nasal cartilages and septal cartilage.

4. NASAL CAVITY
This extends from the nostrils (anterior nares) to the posterior end of the
nasal septum (Choanae).
The two choanae are rigid, bony apertures that provide communicating passages
between the nasal cavities and the nasopharynx.
The nasal cavity is involved in respiration, olfaction, speech and taste.
Each half of the cavity has olfactory region, a small area located inside the
skull at the apex of the cavity lined with olfactory cells.
Vestibular region found inside the anterior external opening of the nose. It
contains hair cells and
Respiratory region, the largest region lined with respiratory epithelium

6. There are twelve cranial bones that make up the structure of the nasal
cavity. They include:
Paired nasal, maxillary, palatine and lacrimal bones and
Unpaired ethmoid, sphenoid, frontal and vomer.
The ethmoid is the most important of all the nasal bones because it
makes the greatest portion of the skeletal framework by forming the roof
and walls
It also contains ethmoid cells and is one of the paranasal sinuses.

7. The nasal cavity is divided into two halves by the bony nasal septum.
Each half have a floor a roof and a lateral and medial wall.
The floor is formed by the horizontal hard palate formed from the
palatine process of maxilla and horizontal plates of palatine bone.
The roof is composed of three parts:
An anterior part whose slope corresponds to the slope of the inferior
surface of the nasal bones at the bridge.

8. An intermediate part formed by the horizontally oriented cribriform
plate of the ethmoid bone.
A posterior part of the roof formed by the anterior and inferior parts of
the body of sphenoid bone.
The lateral wall is marked by three projections called the superior,
middle and inferior nasal conchae. The area below the concha is referred
to as meatus.
The superior meatus lies below and lateral to the superior concha. It
receives the opening of the posterior ethmoid sinuses.

10. The middle meatus lies below and lateral to the concha.
On its lateral wall is the bulla ethmoidalis caused by the bulging of the
underlying middle ethmoidal air sinuses.
The maxillary sinus opens into the middle meatus thru the hiatus
semilunaris which lies immediately below the bulla.
The frontal sinus opens into the infundibulum.
The anterior ethmoidal sinuses open into the infundibulum.

11. The middle meatus is continuous in front at a depression called the
atrium.
The inferior meatus is between the floor and inferior concha.
The medial wall or nasal septum is composed of bone and cartilage and
is lined by a very thin and tightly mucous membrane.
The bony components:- the perpendicular plate of ethmoid and the
vomer form the superior and inferior portions of the septum.
They articulate in the posterior portion but widely separated anteriorly

12. The septal cartilage also forms the support for the midline ridge of the
nose, the tip, the columella and the anterior nasal spine of maxilla.
The two nasal cavities communicate with the four bony recesses called
the paranasal sinuses. Sphenoidal, ethmoidal, maxillary and frontal air
sinuses.
They are innervated by trigeminal nerve (CNV) for general sensation.
The olfactory N also supplies the nasal cavity.
BLOOD SUPPLY
The nose is supplied by branches of external and internal carotid
arteries:

13. Branches from the external carotid includes:
The maxillary artery through its sphenopalatine branch
The greater palatine, superior labial and lateral nasal arteries.
They mostly supply the vestibule and respiratory regions of the nasal
cavity, apex and dorsum of nose.
Branches from internal carotid includes:
Posterior ethmoidal arteries which supply the apex of the nasal cavity and
external nose.
Most branches from both external and internal carotid arteries
anastomose at the anterior part of the medial wall ( area of nose bleeding).

14. Venous drainage parallels the arterial supply. Veins form a rich venous plexus
in the submucosa.
Lymph vessels draining the vestibule end in the submandibular nodes, while
the rest of the nasal cavity is drained by vessels that pass to the upper deep
cervical nodes.
Clinical significance
Epistaxis: This is also referred to as nose bleeding which can be caused by-
trauma, sinus infection, rhinitis, arid environment, hypertension, hematologic
disorders and neoplasms.
Anterior epistaxis which occurs along the septum originates from kiesselbach
plexus. This is the most common type.

15. Posterior epistaxis is due to trauma on the maxillary artery in which
blood runs out of the throat.
Rhinitis: stuffy nose is an inflammation that results in nasal congestion,
sneezing, rhinorrhea/runny nose and nasal itching.
Allergic rhinitis or hay fever is the most common type.
Deviated nasal septum: this is as a result of a shift in the bony midline
from the center due to either trauma or birth defect. There will partial or
total occlusion of one side of the cavity.

16. PARANASAL AIR SINUSES
Paranasal sinuses are paired symmetrical air- filled cavities found in the
sphenoid, ethmoid, frontal and maxillary bones.
The first three are located in the neurocranium while the maxillary sinus
is located in the viscerocranium.
They are lined by respiratory epithelium and drain into the nasal cavity.
These sinuses protect the organism by mainly humidifying the inhaled
air and enhancing immune response of the respiratory epithelium.

17. SPHENOID SINUSES
The two sphenoidal air sinuses are within the body of the sphenoid bone.
They are separated from each other by a midline bony partition.
The sinus drains through an ostium in its anterior wall into the spheno-
ethmoidal recess of the nasal cavity (located supero-posterior to the
superior nasal concha).
The pituitary fossa is in the roof of the sphenoid sinuses and the sinuses
are separated from the pituitary gland by bony floor of the fossa.
The sinus is also closely related to the optic N, optic chiasma. Internal
carotid artery and cavernous sinus.

19. Nerve supply
The sinus is innervated by the posterior ethmoidal N, branches of
ophthalmic N while blood supply is from posterior ethmoidal arteries,
and sphenopalatine branches of maxillary artery.
ETHMOIDAL SINUSES
These are small spaces located within the ethmoid bone (between the
nasal cavity and the orbit).
They are divided into three groups: Anterior ,middle(bullar cells) and
post ethmoidal sinuses.
The anterior and middle ethmoidal air cells(sinuses) drain into the
middle meatus of the nasal cavity through opening on the ethmoid bulla.

21. The posterior ethmoidal air cells drain into the superior nasal meatus.
The ethmoidal cells are supplied by the anterior and posterior
ethmoidal nerves (branches of nasociliary N), supraorbital, lateral,
posterior, superior nasal and orbital nerves.
Blood supply is by branches of supraorbital, anterior and posterior
ethmoidal and sphenopalatine arteries.
Lymph drains into submandibular and retropharygeal nodes.

22. FRONTAL SINUSES
The paired frontal sinuses are triangular-shaped cavities contained within the
frontal bone.
These are the only sinuses not present at birth. They appear during the 2 year.
The sinuses invade the frontal bone above the superior margins (supercilliary
arches) of the orbits.
They are separated from each other by a bony septum.
The frontal sinus drains through the frontonasal duct into ethmoidal
infundibulum which opens into the middle nasal meatus via the hiatus
semilunaris

24. The sinus is innervated by the supraorbital and supratrochlear nerve
branches of the ophthalmic N that pierce the frontal bone.
Blood supply is from anterior ethmoidal, supraorbital and
supratrochlear arteries.
Lymph drains into submandibular nodes.
MAXILLARY SINUSES
 These are the largest sinuses situated within the maxilla and the most
inferior of the paranasal sinuses.

26. It is pyramidal in shape with the base forming the lateral wall of the
nose and the apex is the zygomatic process of the maxilla.
Its floor is at the level of the hard palate and the ostium of the maxillary
sinus is near its roof on the medial wall.
The roof is formed by the floor of the orbit.
The roots of the 1st
and 2nd
premolars and sometimes of the canine
project up into the sinus.
It is innervated by anterior, middle, posterior superior alveolar nerves,
branches of the maxillary (CNV2).
Blood supply is from the superior alveolar branch of maxillary artery.

27. End of lecture