NOSE

NoseIntroduction:• The nose is the part of the respiratory tract superior to the hard palate • It contains the peripheral organ of smell

Composition: • external nose • nasal cavity the nasal cavity is divided into right and left cavities by the nasal

septum

Functions:• olfaction (smelling)• respiration (breathing)• filtration of dust• humidification of inspired air• reception and elimination of secretions from the paranasal sinuses and

nasolacrimal ducts

External Nose• is the visible portion that projects from the face• its skeleton is mainly cartilaginous (small bony contributions are

present)• The part of the external nose that extends from the root of the nose

to the apex (tip) of the nose is called the dorsum• The inferior surface of the nose is pierced by two piriform

openings called nares (nostrils, anterior nasal apertures)• The nares are bounded laterally by the alae (wings) of the nose• The superior bony part of the nose, including its root, is covered by

thin skin • The skin over the cartilaginous part of the nose is covered with

thicker skin, which contains many sebaceous glands

• The skin extends into the anterior part of the nasal cavity called the vestibule of the nose

• The vestibule of the nose has a variable number of stiff hairs called vibrissae

• These hairs are usually moist and these help to filter dust particles from air entering the nasal cavity

Skeleton of the External Nose

composed of:

I. bones

II. cartilages The bony part consists of the: nasal bones frontal processes of the maxillae nasal part of the frontal bone nasal spine bony parts of the nasal septum

• The cartilaginous part of the nose consists of five main cartilages and small minor cartilages:

two lateral cartilages, two alar cartilages, and one septal cartilage 3 or 4 minor alar cartilages

The U-shaped alar cartilages are free and movable; they dilate or constrict the nares when the muscles acting on the nose contract

Nasal Septum• It divides the chamber of the nose into two nasal cavities • It has a: bony part a soft mobile cartilaginous part

The components of the nasal septum are perpendicular plate of the ethmoid bone Vomer bone

septal cartilage nasal crest of the maxillary bone nasal crest of palatine bone The perpendicular plate of ethmoid, vomer, nasal crests of maxillary

and palatine bones form the bony part of nasal septum While the septal cartilage forms the cartilagenous part

The thin perpendicular plate of the ethmoid bone:• forming the superior part of the nasal septum• descends from the cribriform plate • and is continued superior to this plate as the crista galli

The vomer: a thin flat bone, forms the posteroinferior part of the nasal septum, with some contribution from the nasal crests of the maxillary and palatine bones

The septal cartilage has a tongue-and-groove articulation with the edges of the bony septum

CLINICAL ANATOMY

Nasal Fractures• Because of the prominence of the nose, fractures of the nasal bones are

common facial fractures in automobile accidents and sports (unless face guards are worn)

• Epistaxis (nosebleed) usually occurs• In severe fractures, disruption of the bones and cartilages results in

displacement of the nose. • When the injury results from a direct blow, the cribriform plate of the

ethmoid bone may also fracture

Deviation of the Nasal Septum• The nasal septum is usually deviated to one side or the other• This could be the result of a birth injury, but more often the deviation

results during adolescence and adulthood from trauma (e.g., during a fist fight)

• Sometimes the deviation is so severe that the nasal septum is in contact with the lateral wall of the nasal cavity and often obstructs breathing or exacerbates snoring

• The deviation can be corrected surgically

Nasal Cavity• Divided into right and left halves by the nasal septum• The nasal cavity is entered anteriorly through the nares • It opens posteriorly into the nasopharynx through the choanae• Mucosa lines the nasal cavity, except for the nasal vestibule, which is

lined with skin • The superior one third of the nasal mucosa forms the olfactory area• The inferior two thirds of the nasal mucosa forms the respiratory area • The olfactory area contains the peripheral organ of smell; sniffing

draws air to the area• Air passing over the respiratory area is warmed and moistened before

it passes through the rest of the upper respiratory tract to the lungs

Boundaries of the Nasal Cavity The nasal cavity has a: roof floor medial wall lateral wall

The roof :• is curved and narrow, except at its posterior end• it is divided into 3 parts frontonasal ethmoidal sphenoidal • They are named from the bones forming each part

The floor: • is wider than the roof • is formed by the; palatine processes of the maxilla horizontal plates of the palatine bone

The medial wall :

formed by the nasal septum

The lateral walls : • are irregular owing to three bony plates, the nasal conchae, which

project inferiorly, somewhat like louvers

Features on the lateral wall of the nasal cavity• There is the presence of nasal conchae and they curve inferomedially• The nasal conchae include; Superior nasal concha middle nasal concha inferior nasal concha• The conchae or turbinates of many mammals (especially running

mammals and those existing in extreme environments) are highly convoluted, scroll-like structures that offer a vast surface area for heat exchange

• Underneath each choncha in both humans with simple nasal conchae and animals with complex turbinates is a recess or meatus {passage(s) in the nasal cavity}

• The nasal cavity is thus divided into 5 passages:

1) a posterosuperiorly placed sphenoethmoidal recess 3 laterally located nasal meatus:

II) superior

III) middle

IV) inferior

V) and a medially placed common nasal meatus into which the four lateral passages open

The inferior concha • is the longest and broadest and is formed by an independent bone (of

the same name, inferior concha) covered by a mucous membrane that contains large vascular spaces that can enlarge to control the caliber of the nasal cavity

• When infected or irritated, the mucosa may swell rapidly, blocking the nasal passage(s) on that side

The sphenoethmoidal recess :• lying superoposterior to the superior concha, • receives the opening of the sphenoidal sinus, an air-filled cavity in the

body of the sphenoid.

The superior nasal meatus :• is a narrow passage between the superior and the middle nasal

conchae • The posterior ethmoidal sinuses open into this superior nasal meatus

through one or more orifices

The middle nasal meatus:• is longer and deeper than the superior one • The anterosuperior part of this passage leads into a funnel-shaped

opening, the ethmoidal infundibulum through which it communicates with the frontal sinus through a passage known as the frontonasal duct

• the anterior ethmoidal cells opens on the ethmoidal infundibulum directly or opens indirectly on the frontonasal sinus

• The ethmoidal infundibulum leads inferiorly into a semicircular groove called the semilunar hiatus

• The maxillary sinus opens into the semilunar hiatus• superior to the semilunar hiatus is a rounded elevation called the

ethmoidal bulla • The ethmoidal bulla is only visible when the middle concha is removed• The bulla is a swelling formed by middle ethmoidal cells that form the

ethmoidal sinuses• Anterior and inferior to the semilunar hiatus is a hooklike process called

the uncinate process of the ethmoid bone• This process articulates with the inferior nasal concha

The inferior nasal meatus :• is a horizontal passage inferolateral to the inferior nasal concha • The nasolacrimal duct, which drains tears from the lacrimal sac, opens

into the anterior part of this meatus

The common nasal meatus :• is the medial part of the nasal cavity between the conchae and the nasal

septum, into which the lateral recesses and meatus open

The arterial supply

The arterial supply of the medial and lateral walls of the nasal cavity is from five sources:

• Anterior ethmoidal artery (from the ophthalmic artery)• Posterior ethmoidal artery (from the ophthalmic artery)• Sphenopalatine artery (from the maxillary artery)• Greater palatine artery (from the maxillary artery)• Septal branch of the superior labial artery (from the facial artery) The anterior part of the nasal septum is the site (Kiesselbach area) of

an anastomotic arterial plexus involving all five arteries supplying the septum

The external nose also receives blood from the 1st and 5th arteries listed above plus

• nasal branches of the infraorbital artery• lateral nasal branches of the facial artery

Venous drainage• A rich submucosal venous plexus deep to the nasal mucosa drains into

the sphenopalatine, facial, and ophthalmic veins

Innervation• olfactory nerve

• branches of the ophthalmic [V1] which include the anterior and posterior ethmoidal nerves

• maxillary [V2] nerves which include;

posterior superior lateral nasal nerves posterior superior medial nasal nerves nasopalatine nerve posterior inferior nasal nerves

CLINICAL ANATOMY

Epistaxis• Epistaxis (nosebleed) is relatively common because of the rich blood

supply to the nasal mucosa• In most cases, the cause is trauma and the bleeding is from an area in

the anterior third of the nose (Kiesselbach area) • Epistaxis is also associated with infections and hypertension• Spurting of blood from the nose results from rupture of arteries• Mild epistaxis may also result from nose picking, which tears veins in

the vestibule of the nose

Rhinitis• The nasal mucosa becomes swollen and inflamed (rhinitis) during

severe upper respiratory infections and allergic reactions (e.g., hayfever)

• Swelling of the mucosa occurs readily because of its vascularity

Infections of the nasal cavities may spread to the:• Anterior cranial fossa through the cribriform plate• Nasopharynx and retropharyngeal soft tissues• Middle ear through the pharyngotympanic tube (auditory tube), which

connects the tympanic cavity and nasopharynx• Paranasal sinuses• Lacrimal apparatus and conjunctiva