The most prominent part of the human face is the nose. It is both the first organ of the respiratory system and the main organ in the olfactory system. The shape of the nose is defined by cartilage and bone. Male human noses tend to be larger than female ones.
The respiratory function of the nose is shown in its anatomy. Two openings, nostrils or nares, are separated by the septum, which is a long piece of cartilage. The frontal bone nasal part ends in a serrated nasal notch, articulating with paired nasal bones at the front and with the small lacrimal bones at the sides. The floor of the nasal cavity is made of incisive bone and the horizontal plates of the palatine bones. This forms the hard palate of the roof of the mouth. The posterior nasal spine is a bony process which enables the musculus uvulae in the uvula to be attached, is formed by the joining of the two horizontal plates. This is a cephalometric landmark, which can be used in radiographs or living people for measurements or orientation of the head. It is used particularly in orthodontic planning.
The nasal cavity internal ceiling is made from cribriform plate formed from the ethmoid bone. Sensory fibres from the olfactory nerve pass through it. The face of the sphenoid bone can be found below and behind the cribriform plate, at a sloping angle. At the base of the nose, two maxilla bones (or upper jaw) join together, at both the lower nasal midline between the nostrils and at the top of the philtrum. This forms the anterior nasal spine, a small projection of bone, which is also a cephalometric landmark.
As the nose is used for respiration, there is nasal mucosa lining the cavity. It both warms air and manufactures the sticky mucus that traps small particles. The paranasal sinuses are four pairs of air-filled spaces, surrounding the nasal cavity. They are used to both warm air and moisten it before it reaches the lungs. The four types of sinuses are: maxillary which are under the eyes, the frontal which are above eyes in the centre, the ethmoidal between the eyes and sphenoidal behind the eyes.
Nasal hair in the nostrils helps to keep large particles away from the lungs. Shell-like bones also known as conchae or turbinates also help to filter the air. There are three of these bones; they are in the corresponding order, of superior, middle and inferior nasal conchae.
A sneeze is a reflexive way for the body to eject unwanted foreign objects from the airways. The particles irritate the mucosal lining, leading to the sneeze. Sneezing droplets can harbour bacteria and transmit germs to other people. In recent years, the nose has been used for the administration of drugs, for example, the flu spray administered to school children in the UK.
The other main function of the nose is the sense of smell or olfaction. The organ uses the olfactory epithelium which can be found in the upper nasal cavity. It contains olfactory cells which are used for this function.
The nose is also used for the production of speech. The nasal cavity is an effective place to produce vocal sounds and some vowels and consonants are produced using the nose.
Blood Vessels of the Nose
Blood vessels supplying the nose include the interior carotid from which branch the anterior ethmoidal artery and the posterior ethmoidal artery, both of which come from the ophthalmic artery. The dorsal nasal artery also comes from the ophthalmic artery and it divides into two: the angular artery at the root of the nose and the lateral nasal branch of facial artery which supplies the nasal ridge.
The external carotid supplies branches with blood vessels, including the sphenopalatine artery, the greater palatine artery, the angular artery and the superior labial artery. These mostly supply the lateral walls of the nasal cavity and the septum.
Blood vessels carrying blood away from the nose, include the angular vein. The vein joins with the superior labial vein. In the posterior of the cavity is a venous plexus or Woodruff’s plexus. It consists of large, thin-walled veins that do not have a lot of soft tissue. Most nosebleeds occur from Kiesselbach’s plexus in the lower front part of the septum where four arteries meet. Nosebleeds from Woodruff’s plexus are much rarer.
Nerves of the Nose
The nasociliary nerve supplies sense to the skin of the nose and the mucous membrane. The anterior ethmoidal nerve is a branch of the nasociliary nerve, bringing feeling to the anterior half of the nasal cavity and the posterior ethmoidal nerve supplies sensation to the upper half of the nasal cavity, the sphenoids and the ethmoids.
The maxillary nerve supplies feeling to the face, the nostrils and the upper jaw, the internal nasal branches of the infraorbital nerve brings feeling to the septum. The sphenopalatine nerve divides and supplies sensation to the rear and central nasal cavity. The infratrochlear nerve supplies the superior part of the nose.
Parasympathetic nerves begin life as the greater superficial petrosal branch of cranial nerve VII or the facial nerve. The parasympathetic nerves link to nose glands and the palate through the upper jaw (or maxillary) branch of cranial nerve V.