NOSE, NASAL CAVITY AND PARANASAL SINUSES - PowerPoint Presentation

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NOSE, NASAL CAVITY AND PARANASAL SINUSES

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The Nose

Divided into

rt

& lf cavities by Nasal septum

Projects from face- mostly cartilaginous

Vary in size and shape depending on nasal cartilages

The dorsum extends from the root to the apex

Inferiorly- 2 openings-

nares

(nostrils/ ant nasal apertures), bounded lat by

alae

of nose

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Skeletal structure

The skeleton of external nose is made of

bony

and

cartilaginous components:

Bony component – located superiorly, and comprised of contributions from nasal, maxillae and frontal bones.

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Cartilaginous component –

located inferiorly, and is comprised of:

2 lateral cartilages, 2 alar cartilages

and

1 septal cartilage.

Some smaller alar cartilages are also present.

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Skin of the nose

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.

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Muscles of the Nose

The nasal group of facial muscles are associated with movements of the nose, and the skin around it.

The

muscles

in this group are all innervated by the

facial nerve.

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Nasalis:

largest of the muscles and split into 2 parts

Actions:

The two parts have opposing functions. The

transverse part

compresses the nares; the alar part opens the nares.

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Procerus:

Most superior of the nasal muscles

Actions:

Its contraction pulls the eyebrows downward to produce transverse wrinkles over nose.

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Depressor

Septi

Nasi:

Assists the alar part of the

nasali

in opening the nostrils.Actions: It pulls the nose inferiorly, opening the nares.

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NASAL CAVITY

Located above the oral cavity; separated from each other by a

cartilaginous nasal septum

Each nasal cavity communicates with the exterior via the

ant nasal aperture

(nostril) and with the nasopharynx via the post nasal aperture (choanae)

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The nasal cavity can be divided into:

Olfactory region

Respiratory region

Vestibule

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It is lined by a

mucous membrane

that is bound firmly to the

periosteum

and

perichondrium except for the vestibuleThe vestibule is lined with skin and vibrissae grow from this skinIt receives the openings of the paranasal sinuses

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The inf. 2/3 of the nasal mucosa is the respiratory area and the sup. 1/3 is the olfactory area

The olfactory area contains the peripheral organ of smell

The central processes of olfactory cells in the olfactory epithelium unite to form nerve bundles

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These nerve bundles pass thru the

cribriform

plate to enter the olfactory bulb of the brain.

Boundaries of the nasal cavity

Roof

FloorLat & med walls

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The roof: (From behind-forward)

Body of sphenoid

Cribriform

plate of

ethmoid

Frontal boneNasal bone & cartilageThe floor is formed by:The palatine process of maxillaHorizontal plate of palatine bone

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The

medial wall

is formed by the

nasal septum

The

lat wall is irregular becos of three bony projections called conchae into its wallNote: the nasal septum can be deviated to one side, if bent so far that it touches the lateral wall, can require surgery, because will affect breathing.

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The medial wall

The

nasal septum

forms the medial wall of both nasal cavities

It is an

osseocartilaginous partition btw the 2 halves and covered by mucous membrane on each side

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Bony part of the septum- formed almost entirely by;

Vomer

Perpendicular plate of

ethmoid

Cartilaginous part

Septal cartilage

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The lower margin of the septum is called

columella

The nasal septum is rarely strictly median

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The lateral wall

The lat wall is irregular owing to the presence of 3 bony projections-

conchae

The lat wall separates the nose from;

Orbit above, with

ethmoidal sinuses interveningMaxillary sinus belowLacrimal groove and nasolacrimal canal in front

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The nasal

conchae

These are scroll shaped elevations in the lat wall of the nasal cavity

They are:

superior, middle and inferior nasal

conchaeThe area below each conchae is a meatus (passage in the nasal cavity)

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Function of the nasal

concha

: is to spin the air within the nasal cavity, in order to:

to help

warm

the air,as well as aid in filtering itadd moisture to the air.

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Openings into the Nasal Cavity

One of the functions of the nose is to

drain

a variety of structures. Openings into the nasal cavity, by which drainage occurs:

The

paranasal sinuses drain into the nasal cavity- The frontal, maxillary and anterior ethmoidal sinuses open into the

middle meatus.

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In addition to the

paranasal

sinuses, other structures open into the nasal cavity.

The

nasolacrimal duct acts to drain tears from the eye – it opens into the inferior meatus. The auditory (or eustachian) tube opens into the nasopharynx at the level of the inferior meatus. The auditory tube allows the middle ear to equalize with the atmospheric air pressure.

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Sphenoethmoidal

recess:

lies sup to the sup

concha

; receives the opening of the

sphenoidal sinusSuperior meatus: lies below the sup nasal conchae and receives the openings of the post ethmoidal

sinuses

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Middle

meatus

:

Lies beneath the middle

concha

On its lat wall is a rounded elevation-the ethmoidal bulla produced by the underlying middle ethmoidal air sinusesLying below the eth. bulla is a curved groove- hiatus semilunarisAt the upper end of the

semilunar

hiatus is the opening of the

ethmoidal

infundibulum

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Occasionally, the

ethmoidal

infundibulum

ends blindly, hence the

frontal sinus opens via the frontal duct into the semilunar hiatusThe maxillary sinus opens into the lower end of the semilunar hiatus

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Inferior

meatus

:

Located

inferiorlateral

to the inf conchaThe nasolacrimal duct (drains tears from the lacrimal sac) opens into the ant part of this meatus

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Innervation

of the nasal mucosa

The

nv

supply of the

posteroinf ½-2/3 of the nasal mucosa is chiefly from the maxillary nv thru the nasopalatine, nasal & palatine branches of the

pterygopalatine

ganglion

Its

anterosup

part is supplied by

the ant & post

ethmoidal

nerves

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The olfactory

nvs

concerned with smell only, arise from the special olfactory cells in the olfactory mucous membrane

The central processes of these cells (forming the

olf

nv) pass thru the cribriform plate and end in the olfactory bulb

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Vasculature of the nasal cavity

Arterial supply to the med & lat walls of the nasal cavity arise from:

Sphenopalatine

artery

Ant & post

ethmoidal arteriesGreater palatine arterySup labial & lat nasal branches of facial art

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All arteries

anastomose

on the ant part of the nasal septum (

Kiesselbach’s

area)

[epistaxis]A rich plexus of veins in the submucosa drains into the sphenopalatine, facial & ophthalmic veins Lymphatic vessels draining the vestibule end in the submandibular

nodes

The remainder of the nasal cavity drains into

upper deep cervical lymph nodes

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Applied Anatomy

Rhinitis-

inflammation; infections may spread to;

Ant cranial

fossa

thru cribriform plateNasopharynxMiddle ear thru pharyngotympanic tubeParanasal sinusesLacrimal apparatus & conjunctiva

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Epistaxis-

(nosebleed) bleeding from the nose.

In more severe cases blood may come out of both nostrils.

Nosebleeds can have causes that aren't due to underlying disease; Examples include nasal dryness, nose picking or injury.

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Fracture of

cribriform

plate of

ethmoid

with tearing off of meninges

may lead to CSF dripping into the nasal cavity- CSF rhinorrhoeaExposing the brain to the outside environment like this increases the risks of meningitis, encephalitis and brain abscesses.The olfactory bulb lies on the cribriform plate and can be damaged irreversibly by fracture leading to anosmia (loss of smell).

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PARANASAL SINUSES

Paranasal

sinuses

are air-filled cavities produced by extension of the nasal mucous membrane into the bone around the nasal cavities

These bones are:

frontal, ethmoid, sphenoid, maxilla.

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The sinuses open into the nasal cavity thru the

lateral wall

The function of the sinuses is to make the skull lighter and add resonance to the voice

They are rudimentary or absent at birth and rapidly enlarge during 6-7 years.

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Frontal sinus

Lies btw the outer & inner tables of the frontal bone, above the

superciliary

arch and root of the nose

Appears rudimentary at birth, but is well developed by the 7

th year and reaches full size after puberty

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Drains thru the

frontonasal

duct

into the eth.

infundibulum

, which opens into the semilunar hiatus of the middle meatusAre innervated by branches of the supraorbital nerves (CN V1)

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Ethmoidal

sinuses

Comprises several cavities called

ethmoidal

cells

located in the lat mass of the ethmoid bone, btw the nasal cavity & the orbitAre usually not visible in plain radiographs before age 2

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Are divided into

ant, middle

&

post

grps

of ethmoidal cells:The ant ethm. cells open into the middle meatus thru the infundibulumThe middle

ethm

. cells

open directly into the middle

meatus

(form

ethm

. bulla)

The

post

ethm

. cells

open directly into the

sup

meatus

The

ethm

. cells are supplied by

ant & post

ethm

. branches of

nasociliary

nerve

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Sphenoidal

sinuses

Lie in the body of the sphenoid bone, making it fragile

Only thin plates of bone separate these sinuses from several important structures

(Optic

nv, optic chiasma, pituitary gland, ICAs, cavernous sinuses )

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These sinuses arise from a post

ethm

cell that begins to invade the sphenoid bone at approx 2 yrs of age

Opens into the

sphenoethmoidal

recessSupplied by post ethmoidal nerve

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Maxillary sinuses

Largest of the paranasal sinuses; located in the body of the maxilla; Have thin walls and following borders:

Superior border-

bony orbit

Inferior border-

maxillary alveolar bone and corresponding tooth rootsMedial border- nasal cavity Lateral and anterior border are limited by the cheekbones.

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Opens into the

middle

meatus

thru the

maxillary ostiumSupplied by the ant, middle & posterosup alveolar nerves (br-maxillary nv)

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Applied Anatomy

Sinusitis

Variation in the frontal sinus

Infections of the

ethm

(post) & sphenoidal sinuses may spread to vital organs like optic nv causing blindness

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Infection of the maxillary sinus more common b/c of its poor drainage, as a result of the location of the maxillary

ostia

Transillumination

impossible for the

ethm

& sphenoidal sinuses

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