The nose

• External

  The external openings of the nose are called the nares (singular is naris) or the nostrils. Cartilage and bone underlie the skin, muscle and connective tissue of the external nose.

  
• External

  Cartilage associated with the midline that helps to separate the nose into 2 nostrils is described as septal cartilage. Cartilage that helps to form the shape of the nostrils is called alar cartilage. A large amount of the external nose is composed of cartilage, allowing it to have some flexibility to prevent damage to the nose.

  
• External blood and nerve supply

  •Anterior and posterior ethmoidal, (ophthalmic)

  •Sphenopalatine and greater palatine (maxillary)

  •Septal branch - superior labial and lateral nasal (facial)

  •Nerve = CN V1 (infratrochlear and external nasal branch of anterior ethmoidal)

  •Alae = nasal branches of infraorbital (CN V2)

  the bridge of the nose is supplied by the ophthalmic division of the trigeminal nerve and the alae are supplied by the maxillary division.
• Lateral wall

  The nose does have bone in the septal region (vomer and ethmoid) and at the most superior parts of the bridge (nasal bones). The lateral wall of the nasal cavity has contributions from the maxilla, the sphenoid bone, the ethmoid bone, and a small part of the frontal bone. The ethmoid bone forms the superior and middle concha but the inferior concha is an individual bone that is not part of the ethmoid.

  
• Medial wall

  The medial wall of the nasal cavities is the septal wall that separates the nasal passage into 2 cavities. A flat piece of the ethmoid bone called the perpendicular plate forms the posterior part of the septum and the vomer, palatine bones and maxilla contribute to the inferior part of the septum.

  
• Other terminology

  The nostrils lead into the ‘hallway’ or vestibule of the nose as air is carried from here towards the choanae before heading into the nasopharynx. The nasopharynx contains the openings of the auditory tube. This tube leads to the middle ear cavity and allows air to be drawn into, or expelled from, the middle ear to the nasopharynx. This helps to equalize pressure on either side of the tympanic membrane.

  
• Conchae

  There are 3 folds on each lateral wall of the nasal passages, they are called conchae. So, the superior conchae is related to the superior meatus and so on. The conchae help to swirl the air as it passes through the nasal cavity before it passes into the nasopharynx. The lining of the nasal cavity is composed of respiratory epithelium which has cilia and produces mucous to trap any fine airborne particles and thus filter the air. As the air swirls in the nose, it will pass the olfactory cells in the roof of the nasal cavity facilitating the detection of odour particles.

  
• The space above the superior concha is also given a name. It is called the sphenoethmoidal recess as it is surrounded by these bones. This recess and each meatus is related to tiny holes/passages from the paranasal sinuses.

  The CT scan shows 2 things - the way the conchae hang into the nasal cavity and disrupt the passage of air, and a large space either side of the nose. These spaces are the maxillary paranasal air sinuses.

  
• Paranasal sinuses

  The paranasal sinuses are mucous lined spaces within the frontal, (F) maxillary (M), ethmoid (E) and sphenoid bones (S).

  The paranasal sinuses are very small in children and enlarge as they reach full adulthood.

  
• Paranasal sinuses

  The frontal sinus lies within the frontal bone, it may be 2 separate cavities or just one large sinus. The sphenoid sinus lies in the body of the sphenoid bone and there is one large maxillary sinus either side of the nasal cavities. The ethmoid sinus lies within the ethmoid bone and forms a series of small sacs (or air cells) instead of one large space.

  
• Paranasal sinuses

  
• Paranasal sinuses

  Post ethmoidal air cells form the bulge of the ethmoidal bulla

  The infundibulum, semilunar hiatus, ethmoidal bulla and ostium are names given to features of the wall of the meatus.

  
• Paranasal sinuses

  The paranasal sinuses are supplied with sensory innervation by branches of the trigeminal nerve. Each membrane lining can produce mucous and this can build up in the sinus if the small channels to the nose are blocked by inflammation. This leads to an increase in pressure in the sinus and the pain associated with blocked sinuses. The photograph shows the middle meatus and the curve of the semilunar hiatus around the circular ethmoidal bulla.

  
• Lateral wall

  The nasal cavities have a rich blood supply. Blood from branches of the ophthalmic (ethmoidal), maxillary (sphenopalatine) and external carotid (facial)  arteries all supply the lateral wall.

  
• Medial wall

  Kiesselbach’s area where a large amount of the branches from these arteries anastomose with each other.

  
• Nerves – lateral wall

  The lateral walls are supplied with sensory innervation by the ophthalmic and maxillary divisions of the trigeminal nerve. The olfactory bulb communicating with the olfactory nerves can also been seen in the roof of the cavity.

  
• Nerves-medial wall

  The medial walls are also supplied by the trigeminal nerve.

  
• Veins

  The nasal cavities drain blood to the facial vein, the pterygoid venous plexus and the cavernous venous sinus. Creating yet another communication from superficial structures to deeper structures

  
• Olfactory nerve

  The nose houses the delicate olfactory nerve cells that pass processes through the cribriform plate of the ethmoid bone to reach the olfactory bulbs and form olfactory tracts. The cells detect odour and the information is passed to the brain for further processing