External nose

External nose
It is a pyramidal in shape upper boney pyramid and lower cartilaginous pyramid
Boney part consists of upper 1\3 and cartilaginous part consists of lower 2\3
Boney framework consists of
Pair of nasal bone
Frontal process of maxilla
Maxillary process of frontal bone
Cartilages of external nose
Pair of upper lateral cartilages
Pair of lower lateral cartilages(greater alar cartilage)
Part of septal cartilage
Vestibule is part of the nasal cavity just within the the external nose,the vestibular skin contain hair follicles,hair and sebecious glands
Nasal cavity
Divided into two cavities by the nasal septum
It`s ant.openning called ant naris while it`s post. Opening called post.naris which open into nasopharynx
Nasal septum
Formed by
Cartilaginous part anteriorly by quadrilateral cartilage
Boney part posteriorly which formed by
Perpendicular plate of ethmoid
Vomer
Nasal crest of maxilla
Nasal crest of palatine bone
Lateral nasal wall
Within the nasal cavity there are three turbinates (superior,middle and inferior)In the inf.meatus
Opening of nasalcrimal duct
In the mid.meatus
There is bulge called bulla ethmoidalis below it there is Uncinate process between them there is a fissure formed called hiatus similunaris
The following sinuses open in the middle meatus
Ant. Ethmoid air cell and frontal sinus in the anterior part of hiatus simlunaris
Maxillary sinus ostium and sometime accessory ostia open in the posterior part of hiatus simlunaris

Superior and middle turbinate is part of ethmoid bone
Inferior turbinate is a separate bone The air space beneath each turbinate is known as
the meatus of the corresponding turbinate.
i.e each meatus named after the turbinate above it
There are various ducts and sinuses open in the meati
Each turbinate is a cigar-shaed ridges or swellings are attached to the lateral nasal wall ,each is made of bone,superior and middle is part of ethmoid bone while inferior turbinate is a separated bone,
All turbinates are coveres with vascular mucopreriostium and ciliated columnar epithelium.
The space under each turbinate is called a meatus i.e inferior meatus lies under the inferior turbinate etc…In the superior meatus
Posterior ethmoidsinus,sphenoid sinus drain in the sphenoethmoid recess which is a small depression above and behind the superior turbinate


The vascular inferior turbinate contains the second errectile tissue in the body i.e it has the ability to swell and shrink under autonomic nervous system control.Nasal resistance
The nose accounts up to half of the total airway resistance.
The resistance is made by two elements
A is essentially fixed made by bone,cartilage and attached muscle
B is variable made by mucosa
The nasal resistance is high in infants who initially are obligatory nasal breathers
Removal of nasal resistance by tracheostomy reduce the dead space but results in a degree of alveolar collapse

Factors decrease nasal resistance
Exercise
Sympathmymetic
Rebreathing
Atrophic rhinitis
Erect position
Factors increase nasal resistance
Infective rhinitis
Allergic rhinitis
Vasomotor rhinitis
Aspirin
Ingestion of alcohol
Cold air
Supine position
Hyperventilation
Sympthatic antagonists
Factors that influence nasal resistance is nasal cycle
Nasal cycle
Demonstrated in over 80% of adults but it is more difficult to demonstrate in children.
The cycle consists of alternate nasal blockage between passages.
Cyclical changes occur between 4-12 hours;they are constant for each person
Various factors may modify the nasal cycle include
Allergy
Infection
Exercise
Hormones
Pregnancy
Fear