Nose

 

• The nose performs two functions.
  
• It is a respiratory passage.
  
• It is also the organ of smell.
  
• The receptors for smell are placed in the upper one-third of the nasal cavity. This part is lined by olfactory mucosa.
  
• The rest of the nasal cavity is lined by respiratory mucosa.
  
• The respiratory mucosa is highly vascular and warms the inspired air.
  
• The secretions of numerous serous glands make the air moist; while the secretions of mucous glands trap dust and
  other particles.
  
• Thus the nose acts as an air conditioner where the inspired air is warmed, moistened and cleansed before it is passed
  on to the delicate lungs.
  
• The olfactory mucosa lines the upper one-third of the nasal cavity including the roof formed by cribriform plate and the
  medial and lateral walls up to the level of the superior concha.
  
• It is thin and less vascular than the respiratory mucosa.
  
• It contains receptors called olfactory cells.
  For descriptive purposes, the nose is divided into two main parts, the external nose and nasal cavity. 

EXTERNAL NOSE 

The external nose has a skeletal framework that is partly bony and partly cartilaginous. 

The bones are the nasal bones, which form the bridge of the nose, and the frontal processes of the maxillae. 

The cartilages are the superior and inferior nasal cartilages, the septal cartilage, and small alar cartilages.
The skin over the external nose is supplied by the external nasal, infratrochlear and infraorbital nerves 

Nasal Cavity 

The nasal cavity extends from the external nares or nostrils to the posterior nasal apertures, and 

is subdivided into right and left halves by the nasal septum.
Each half has a roof, a floor, and medial and lateral walls. 

Each half measures about 5 cm in height, 5-7 cm in length, and 1.5 cm in width near the floor.
The width near the roof is only 1-2 mm.
The roof is about 7 cm long and 2 mm wide. 

It slopes downwards, both in front and behind.
The middle horizontal part is formed by the cribriform plate of the ethmoid.
The anterior slope is formed by the nasal part of the frontal bone, nasal bone, and the nasal cartilages. 

The posterior slope is formed by the inferior surface of the body of the sphenoid bone 

The floor is about 5 cm long and 1.5 cm wide.
It is formed by the palatine process of the maxilla and the horizontal plate of the palatine bone.
It is concave from side to side and is slightly higher anteriorly than posteriorly

Clinical Anatomy 

• Common cold or rhinitis is the commonest infection of the nose. It may be infective of allergic or both.
• It commonly occurs during change of the seasons.
• The paranasal air sinuses may get infected from the nose. Maxillary sinusitis is the commonest of such infections. 
• The relations of the nose to the anterior cranial fossa through the cribriform plate and to the lacrimal apparatus through the nasolacrimal duct are important in the spread of infection 
• Fracture of cribriform plate of ethmoid with tearing off of the meninges may tear the olfactory nerve rootlets.
• In such cases, CSF may drip from the nasal cavity. It is called CSF rhinorrhoea 

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External Nose & Nasal Cavity | Boundaries | Blood supply & Nerve Supply