|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
|of the lip and the ala of the nose; the duct ends opposite the second upper molar tooth and measures about 5 cm. in length.|
The Nose.The outlines of the nasal bones and the cartilages forming the external nose can be easily felt. The mobile portion of the nasal septum, formed by the medial crura of the greater alar cartilages and the skin, is easily distinguished between the nares. When the head is tilted back and a speculum introduced through the naris, the floor of the nasal cavity, the lower part of the nasal septum, and the anterior ends of the middle and inferior nasal conchæ can be examined. The opening of the nasolacrimal duct, which lies under cover of the front of the inferior nasal concha, is situated about 2.5 cm. behind the naris and 2 cm. above the level of the floor of the nasal cavity.
FIG. 1201 The mouth cavity. The cheeks have been slit transversely and the tongue pulled forward. (See enlarged image)
The Mouth.The orifice of the mouth is bounded by the lips, which are covered externally by the whitish skin and internally by the red mucous membrane. The size of the orifice varies considerably in different individuals, but seems to bear a close relationship to the size and prominence of the teeth; its angles usually correspond to the lateral borders of the canine teeth. Running down the center of the outer surface of the upper lip is a shallow groovethe philtrum. If the lips be everted there can be seen, in the middle line of each, a small fold of mucous membranethe frenulumpassing from the lip to the gum. By pulling the angle of the