Nose, Nasal cavity

&

Paranasal Sinuses

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 ornostrils, which lead to the nasal cavity

Each nostril is bounded laterally by the ala and medially by the nasal septum

root

tip

external naresseptum

ala

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)

Osteocartilaginouspartition, only rarely lying in the midline

Covered by the mucoperiosteum

Formed:

• Superiorly by the vertical (perpendicular) plate of ethmoid bone

• Posteriorly by the vomerbone

• Anteriorly by the septal cartilage

Lateral Wall

Shows three horizontal bony projections, covered by mucous membrane, the superior, middle & inferiorconchae (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 meatusand are named as superior, middle & inferiorcorresponding 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 theatrium

• Atrium is limited bove by a ridge called agar nasi

• Below and in front of atrium, and just within the nostril lies thevestibule

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 membrane

Middle 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

V

V

A

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

Nerve Supply 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.

Arterial 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

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

M

E

From a 3 months old fetus, showing ethmoid & maxillary sinuses

Functions

Lighten the skull

Act as resonant chambers for speech

The respiratory mucosal lining helps in warming, cleaning and moistening the incoming air

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

Ethmoidal Sinuses

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 anteriorand posterior ethmoidal nerves

Sphenoidal Sinuses

Two in number

Located within the body of sphenoid

Open into the sphenoethmoidal recess

Supplied by the posterior ethmoidal nerve

Clinical Notes

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

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

Thank You & Good Luck