Externally the nose forms a prominent projection on the face, hence it is frequently injured and its construction should be studied in relation to those injuries. It forms a conspicuous portion of the features, hence deformities or disfigurements of it are very distressing, so that plastic operations are done for their relief. Internally, the nasal cavities are concerned in the sense of smell and form the passage-way to and from the lungs and the various accessory cavities for the air in respiration. It likewise serves as a receptacle for the tears as they come down the lachrymonasal duct. Interference with the flow of air by obstruction of the nasal chambers may cause affections of the pharynx, larynx, lungs, ears, or accessory sinuses - ethmoid, sphenoid, maxillary, and frontal. Catarrhal troubles may start in the nose and invade any of these parts. They may even extend up the Eustachian tube and cause deafness; or up the lachrymonasal duct and cause trouble with the lachrymal canal or conjunctiva. A knowledge of the nose is essential to all those who wish to devote themselves especially to affections of the eye, ear, and throat, because the origin of the affections of these organs may be in the nasal chambers instead of the organ in which they are most manifest.

The skin over the root of the nose is thin and lax. It is well supplied with blood by the frontal and nasal branches of the ophthalmic, and the angular branch of the facial arteries. In reconstructing a nose by means of a flap taken from the forehead, it is these branches that nourish it. The laxity of the skin allows the pedicle to be twisted around without interfering with the circulation.

The skin over the tip and alae is thick and adherent to the cartilages. It possesses a comparatively scanty blood supply, hence its liability to suffer from cold, and is a favorite site for ulcerations, as lupus, superficial epithelioma (rodent ulcer), etc. Sebaceous and sweat glands are abundant, and stiff hairs guard the inside of the nostrils. These latter are not seldom the seat of small furuncles or boils, which are extremely painful. This is due to the tension caused by the congestion and swelling, which is restricted by the tissues being so firmly bound to the cartilages beneath.

Nerves

In addition to the olfactory nerve, the nose is supplied by the nasal, infratrochlear, and infra-orbital branches of the fifth nerve, hence the eyes water when the nose is injured. In certain cases of neuralgia affecting the ophthalmic division of the fifth nerve, pain is felt along the side of the nose. As the nasal nerve enters the skull from the orbit through the anterior ethmoidal foramen, it may be involved in disease of the ethmoidal sinuses.

The nose proper consists of a bony and a cartilaginous portion. The bony portion is formed by the two nasal bones articulating with the frontal bone above, with each other in the median line, and with the nasal process of the superior maxilla on the side. They are supported on the inside by the upper anterior portion of the perpendicular plate of the ethmoid. This articulation does not extend the whole length of the nasal bones to their tip, but only about half their length.

The cartilaginous portion consists of four lateral cartilages, two on each side, upper and lower, and the triangular cartilage, or cartilaginous septum on the inside.

The external shape of the nose viewed in profile is composed of three portions: an upper of bone, a middle of cartilage - the upper lateral cartilages - and a lower, or tip, formed by the lower lateral cartilages. The bridge of the nose is formed by bone; it slopes downward and forward and where it joins the upper lateral cartilage the line changes and slopes more downward, until the tip is reached, here the lower lateral cartilages bulge forward, forming a rounded and more or less projecting tip.