Download Anatomy and physiology of the nose and paranasal sinuses 1

Anatomy and physiology of the nose and paranasal sinuses
The nose is an important part of the face; it gives the individual his characteristic
appearance.
The nose is divided into 2 parts:
1- The external nose.
2- The internal nose (nasal cavities)
1-The external nose:
It is the prominent part of the face, pyramidal in shape .the apex is the tip of the
nose; the base is the attached area to the forehead. The external nose projecting
downwards and is perforated by two apertures called the nostrils separated by the
columella.
The lateral surfaces joined along the dorsum of the nose where it meets the forehead.
The external nose has a skeleton made up of bony and cartilaginous parts .
The bony part is the two nasal bones, the nasal processes of the frontal and maxillary
bones .
Clinical point(1): the nasal bones commonly get fractured by facial trauma.
The cartilaginous part is made up of 2 pairs of lateral cartilages (upper lateral
cartilages and lower lateral cartilages ) these cartilages are connected by fibrous
tissue. The lower lateral cartilages help in shaping the nostrils.
The outer surface is covered by skin which is thin and mobile above and thick and
adherent to the subcutaneous structures near the tip.
Clinical point(2): surgical refashioning of the lower lateral cartilages is an important point in nasal
tip surgery (part of rhinoplasty)
2-The internal nose (the nasal cavity )
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The nasal cavity is divided by midline partition (the nasal septum) into right and left
chambers,. It extends from the nostrils in front into the choanae behind (where it opens into
the nasopharynx)
The entrance to the nasal cavity is called the nasal vestibule which ends at the
mucocutaneous junction, it is lined by skin and contains skin appendages.
Clinical point(3) : the vestibule is a common site of boil development because it is hair bearing area
The rest of nasal cavity lined by respiratory mucosa ( pseudo- stratified columnar ciliated
epithelium ), and small area lined by olfactory epithelium.
Each cavity has a roof ,floor, medial and lateral walls .The floor is formed by the
palatine process of the maxilla and the horizontal process of palatine bone. The roof
is narrow and is formed (from behind forward) by the body of the sphenoid
,cribriform plate of the ethmoid and the frontal bone.
Clinical point(4): cribriform plate is a thin plate of bone and easily to be fractured in head injury
and may associated with CSF leak through the nose.
The medial wall (the nasal septum) is an osteocartilaginous partition covered by
adherent mucoperichondrium and mucoperiostium .The upper part is formed by the
perpendicular plate of the ethmoid bone ,the posterior part by the vomer and the
anterior portion is formed by septal cartilage.
The lateral wall is the most complex, it contains 3 shelf –like projections into the
nasal cavity called the turbinates ( the superior, middle and the inferior turbinates )
The groove below each turbinate is referred to as a meatus.There are 3 meati called
the superior ,middle and the inferior meatus) into these meati the paranasal sinuses
open and join the nasal cavity.The area above the superior turbinate is called the
sphenoethmoial recess.
The inferior meatus contain the opening of nasolacrimal duct.
The middle meatus contains the ostia (openings) of the frontal ,maxillary and the
anterior ethmoid sinuses.
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The superior meatus receives the opening of the posterior ethmoid sinus.
The sphenoethmoidal recees receives the opening of the sphenoid sinus.
Blood supply of the nasal cavity
It supplied by branches of internal and external carotid arteries.
i branches of the internal carotid artery that supply the nose are the anterior and
posterior ethmoidal arteries.
While the external carotid artery supplies the nose through it`s maxillary branch and
small contribution of the facial artery.
The internal carotid artery and external carotid artery branches anastomose
freely in the nose ,the common site of anastmosis is in the antero-inferior part of the
nasal septum (little`s area) ,the arteries that share in this anastmosis are the
sphenopalatine artery ,greater palatine artery, superior labial artery and branch from
the anterior ethmoidal artery .
The venous drainage
The nose characterized by rich submucosal plexus of venous sinusoids ,these drained
by veins that accompany the arteries.
Nerve supply of the nasal cavity
1- Olfactory nerves: they arise from a specialized olfactory epithelium in the olfactory
mucosa .they ascend through the cribriform plate to reach the olfactory bulb.
2- Nerves of ordinary sensation: They are from the ophthalmic and maxillary
divisions of the trigeminal nerve.
3-vasomotor nerve supply (the autonomic nerve supply):
A-Parasympathetic when it is simulated it causes vasodilatation. And stimulate
glandular secretion
B- Sympathetic nerves it causes vasoconstriction when stimulated and inhibit
glandular secretion
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lymphatic drainage
The nose drained to the submandibular lymph nodes and the upper deep cervical
lymph nodes .
paranasal sinuses :
These are air filled cavities within the bones of the skull .They are 4 pairs of
sinuses divided into anterior and posterior groups . The anterior group contains the
frontal sinus ,maxillary sinus and the anterior ethmoid sinus .The posterior group
includes the sphenoid sinus and posterior ethmoid sinus.
The anterior group drain into the middle meatus of the nose and posterior ethmoid air
cells drain into the superior meatus and the sphenoid sinus drain into the
sphenoethmoidal recess.
maxillary sinus
It is pyramidal in shape and lies within the maxilla on each side of the nose. The roof
of the sinus is formed by the floor of the orbit and the floor is related to the roots of
the second premolar and first molar teeth .,medialy it is related to the nose,and
posteriorily to the pterygopalatine fossaThe maxillary sinus open into the middle
meatus.
frontal sinus :
The two frontal sinuses are contained within the frontal bone. A bony septum
separates the two commonly unequal frontal sinuses. It is related anteriorly to the
forehead, posteriorly to the anterior cranial fossa and inferiorly to the nose and orbit.
each sinus opens into the middle meatus
sphenoid sinus :
The two sinuses lie within the body of the sphenoid, each sinus opens into the
sphenoethoidal recess above the superior turbinate. It is related laterally to the
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cavernous sinus, optic nerve and internal carotid artery. It is related superiorly to the
pituitary gland, and inferiorly to the nasopharynx.
Ethmoid sinus
The ethmoid sinuses divided into anterior and posterior air cells and contained within
the ethmoid bone on each side between the orbit laterally and the nose medially. A
thin sheet of bone ‘lamina papyracea’ separates these sinuses from the orbit. Their
roof is directly related to the anterior nasal fossa. The anterior ethmoid air cells open
into the middle meatus and the posterior ethmoid air cells open into the superior
meatus.
The physiology of the nose
The nose has several functions
1- Respiratory function
a- It provides an airway for respiration.
b- Filtration of the inspired air.
c- Humidification of the inspired air.
d- Adjusts the temperature of he inspired air.
2- Olfactory function.
3- Phonatory function. It provides the voice with a resonant quality.
Investigations:
Approach to patient with nasal disease start from
1-Adequate history
2-Examination of the nose by anterior rhinoscopy using nasal speculum and
posterior rhinoscopy by post nasal mirror,and by edoscopic examination which can be
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done under local anaesthesia by using either fibro-optic endoscope(flexible)or rigid
endoscope
3- Investigations:
A- Radiology
1-plain radiography
the nasal bones usually demostated by plain lateral radiograph.
Radiography of the paranasal sinuses; there are several standard views of the sinuses
1-Occipitomental mental view it the most commonly requested view to demonstrate
the maxillary ,frontal and sphenoid sinuses
2-other views are occipittofrontal view, the lateral view and submentovertical view
2-Computerizd axial tomography (ct scan )
Advantages it delineates fine bony outline and soft tissue and is the preferred imaging
technique for detailed anatomy especially in relation to the skull base and the orbit
Disadvantage Is the ionizing radiation .
3-Magnaic resonanane imaging (MRI)
It delineate soft tissue better than ct scan and can distinguish between retained
secretion and soft tissue .It is an important investigation where the disease extends
outside the nose and sinuses for example into the anterior cranial fossa .
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