Human Anatomy - M.M. Kurepina, A.P. Ozhigova, A.A. Nikitina 2010

Internal Organs
Respiratory System
Nasal Cavity

The Nasal cavity is the initial part of the Respiratory system. In addition, it houses the olfactory receptors. The nasal cavity is divided by a septum into two nearly symmetrical halves and communicates with the external environment through openings—the nostrils. Their lateral walls, called the alae (wings of the Nose), are formed by small cartilages. Superiorly, the nostrils are bounded by a pair of major alar cartilages. The framework of the External Nose, its bridge, is formed near the ROOT of the nose by the nasal bones and paired lateral nasal cartilages (Fig. 4.28). The latter abut anteriorly against the cartilaginous nasal septum (a continuation of the bony septum formed by the perpendicular plate of the Ethmoid bone and the Vomer) and posteriorly against the nasal bones and the margins of the piriform aperture formed by the maxillae. The cartilaginous Skeleton of the nose keeps the nostrils permanently open, allowing the Upper Respiratory Tract to communicate with the external environment. The prominent nose on the face, with downward-pointing nostrils, is a distinctive feature of the human face.

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Fig. 4.28. Cartilages of the nose:

A — lateral view; B — inferior view; 1 — frontal and 2 — nasal bones; 3 — frontal process of the Maxilla; 4 — lateral cartilages; 5 — major alar cartilages; 6 — minor alar cartilages; 7 — nostril; 8 — Zygomatic bone; 9 — apex of the nose; 10 — maxilla; 11 — septal nasal Cartilage

The nasal cavity is divided by a longitudinal septum into right and left halves. They communicate with the nasopharynx through the choanae (Atl. Fig. 169). Each half is further divided by the superior, middle, and inferior nasal conchae into meatuses, into which the Paranasal Sinuses of the Skull open. The nasolacrimal duct opens into the inferior nasal meatus; the maxillary (maxillary antrum) and frontal sinuses, as well as the anterior ethmoidal Cells, open into the middle meatus; and the posterior ethmoidal cells and sphenoidal sinuses open into the superior meatus (Atl. Figs. 18, 20).

The mucous membrane of the nasal cavity is firmly adherent to the underlying bone and extends into the cranial sinuses through the corresponding openings. Posteriorly, through the choanae, it gradually transitions into the mucosa of the nasopharynx and soft palate. The mucosa is divided into respiratory and olfactory regions. The latter contains the sensory endings of olfactory Neurons. The olfactory region occupies the superior nasal concha and the adjacent PARTS OF THE middle concha and nasal septum. This part of the cavity is phylogenetically older than the respiratory region, as it is already present in gill-breathing vertebrates that lack a nasal cavity.

The remaining mucosa of the nasal cavity belongs to the respiratory region. It is richly supplied with Blood Vessels and is mostly lined with pseudostratified ciliated epithelium. The epithelial lining contains numerous goblet cells that secrete mucus, which, along with dust particles settled on the membrane, is removed by the beating of the cilia. The secretion of the lacrimal glands, draining into the nasal cavity via the nasolacrimal duct, further moistens its mucosa.

The lamina propria of the mucosa contains numerous mucous and serous glands. Lymphatic vessels and follicles are also present, being most numerous near the entrance to the nasopharynx. In the lamina propria of the middle and inferior conchae, there is A large number of thin-walled venous vessels, which are normally collapsed. However, they can dilate and engorge with blood. In this case, a sensation of nasal congestion arises.

In the nasal cavity, inhaled air is warmed (or, conversely, cooled if it is very hot), partially cleared of particulate matter (dust, smoke), and humidified. Therefore, it is crucial to breathe through the nose rather than the Mouth, as happens when nasal breathing is obstructed due to pathological overgrowths of the nasal mucosa (such as polyps).