Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Doctrine of Viscera (Splanchnology)
Respiratory System
Nasal Cavity

The Nasal cavity performs a dual function: it serves as the beginning of the respiratory tract and, at the same time, as the Organ of Smell. As inhaled air passes through the nasal cavity, it is filtered of foreign particles, warmed, and moistened. Odorous substances in the inhaled air stimulate sensitive olfactory Cells and nerve endings—receptors—which generate Olfactory nerve impulses.

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Fig. 54. Respiratory system:

1 — Oral Cavity; 2 — nasal part of the Pharynx (nasopharynx); 3 — soft palate; 4 — Tongue; 5 — oral part of the pharynx (oropharynx); 6 — epiglottis; 7 — laryngeal part of the pharynx (laryngopharynx); 8 — Larynx; 9 — Esophagus; 10 — Trachea; 11 — apex of the lung; 12 — superior lobe of the left lung; 13 — left main bronchus; 14 — inferior lobe of the left lung; 15 — alveoli; 16 — right main bronchus; 17 — right lung; 18 — Hyoid bone; 19 — Mandible; 20 — Vestibule of the oral cavity; 21 — oral fissure; 22 — hard palate; 23 — nasal cavity

Antterior to the nasal cavity lies the External Nose. The external nose features a dorsum of the nose, which has a bony framework. Inferiorly, the dorsum of the nose transitions into the apex. The alae of the nose (the lateral PARTS OF THE external nose) contain cartilaginous plates in their walls known as the nasal alar cartilages.

The nasal cavity is divided into right and left halves by a sagittally oriented septum. The nasal septum is formed by the perpendicular plate of the Ethmoid bone and the Vomer. Posteriorly, the nasal cavity communicates with the upper part of the pharynx—the nasopharynx—through openings called choanae. On the lateral walls of the nasal cavity, three nasal conchae (superior, middle, and inferior) are visible, hanging into the nasal cavity. Between the conchae lie the nasal meatuses: superior, middle, and inferior (Fig. 55).

The mucous membrane lining the upper Regions of the nasal cavity walls (the superior nasal conchae and the upper part of the nasal septum) contains olfactory receptor cells that perceive various odors. This part of the nasal cavity is called the olfactory region. The zone of the inferior and middle nasal conchae, where olfactory receptors are absent in the mucous membrane, is termed the respiratory region.

The mucous membrane of the nasal cavity is rich in Blood Vessels, particularly small Veins, whose function is to warm the inhaled air. When the mucous membrane is irritated or damaged, nosebleeds (epistaxis) easily occur here.

The paranasal air sinuses open into the nasal cavity: the frontal, maxillary (highmore), sphenoid, and ethmoid labyrinths. These air-filled Paranasal Sinuses not only reduce the weight (mass) of the Skull, but also serve as acoustic resonators for sound and voice.

Fig. 55. Lateral wall of the nasal cavity:

1 — frontal sinus; 2 — middle nasal concha; 3 — superior nasal concha; 4 — Inferior nasal concha; 5 — sphenoid sinus; 6 — pharyngeal tonsil; 7 — pharyngeal opening of the auditory tube; 8 — hard palate

From the nasal cavity, the inhaled air passes through the choanae into the nasopharynx. Then, after passing through the oral part of the pharynx, where the respiratory and digestive pathways intersect, the air enters the larynx.