a. Nose. There is an external nose, the part projecting from the face, and an
internal nose, the portion that is inside the skull.
(1) External portion of the nose. A supporting framework of bone and
cartilage covered with skin and lined with mucous membrane makes up the external
nose. Nasal bones form the bridge of the nose and hold it in a fixed position. The rest
of the external nose is flexible because it has a framework of pliable cartilage. The
midline divider of the external nose is called the nasal septum. Two openings called the
nostrils or external nares are on the underside of the external nose. These nostrils lead
to paired spaces (vestibules).
(2) Internal portion of the nose. Behind each vestibule of the external nose
is a nasal chamber. The two chambers together form the internal nose. These
chambers are separated by the nasal septum.
(a) Mucoperiosteum. The walls of the nasal chambers are lined with a
thick mucous-type membrane known as the mucoperiosteum. This lining is moist and
full of blood vessels. As air is inhaled and passes over this lining, several changes
happen to the inhaled air. Blood in the lining's blood vessels warms the air. The air
picks up moisture from the lining. Dust sticks to the mucous of the lining resulting in
relatively dust-free air.
(b) Conchae. The lateral wall of each nasal chamber has three scroll-
like extensions into the chamber, which help increase the surface area exposed to
inflowing air. These scroll-like extensions are known as conchae.
CONCHA = sea shell
CONCHA (singular), Conchae (plural)
(c) Olfactory epithelium (membrane). The olfactory epithelium is a
membrane that lines the upper nasal chambers. The olfactory receptors (nerve endings
responsible for the sense of smell) are located in this membrane.
(d) Paranasal sinuses. Paranasal sinuses (figure 1-5) are air "cells" or
cavities in the skull. They are connected with the nasal chambers and are lined with the
same ciliated mucoperiosteum. These sinuses are extensions of the nasal chambers
into the skull bones. For this reason, they are known as paranasal sinuses.