The Nose

The nose has several functions: it warms, cleanses, and humidifies inhaled air; it detects odors in the airstream; and it serves as a resonating chamber that amplifies the voice. The external, protruding part of the nose is supported and shaped by a framework of bone and cartilage. Its superior half is supported by the nasal bones medially and the maxillae laterally. The inferior half is supported by the lateral and alar cartilages (fig. 22.2). Dense connective tissue shapes the flared portion called the ala nasi, which forms the lateral wall of each nostril.

The nasal cavity (fig. 22.3) extends from the anterior (external) nares (NERR-eez) (singular, naris), or nostrils, to the posterior (internal) nares, or choanae1 (co-AH-nee). The dilated chamber inside the ala nasi is called the vestibule. It is lined with stratified squamous epithelium

1 choana = funnel

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Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 22 The Respiratory System 843

Ala Nasi Philtrum

Root

Bridge

Dorsum nasi

Nasofacial angle Apex

Ala nasi

Alar nasal sulcus

Anterior naris (nostril)

Nasal septum Philtrum

Nasal bone

Lateral cartilage

Chapter 22 The Respiratory System 843

Nasal bone

Lateral cartilage

Septal cartilage

Dorsum Nasi

Septal cartilage

Lesser alar cartilages

Greater alar ■ cartilages

Dense connective tissue

Figure 22.2 Anatomy of the Nasal Region. (a) External anatomy. (b) Connective tissues that shape the nose.

and has stiff vibrissae (vy-BRISS-ee), or guard hairs, that block the inhalation of large particles.

The nasal septum divides the nasal cavity into right and left chambers called nasal fossae (FOSS-ee). The vomer forms the inferior part of the septum, the perpendicular plate of the ethmoid bone forms its superior part, and the septal cartilage forms its anterior part. The ethmoid and sphenoid bones compose the roof of the nasal cavity and the palate forms its floor. The palate separates the nasal cavity from the oral cavity and allows you to breathe while there is food in your mouth. The paranasal sinuses (see chapter 8) and the nasolacrimal ducts of the orbits drain into the nasal cavity.

The lateral wall of the fossa gives rise to three folds of tissue—the superior, middle, and inferior nasal con-chae2 (CON-kee)—that project toward the septum and occupy most of the fossa. They consist of mucous membranes supported by thin scroll-like turbinate bones. Beneath each concha is a narrow air passage called a mea-tus (me-AY-tus). The narrowness of these passages and the turbulence caused by the conchae ensure that most air contacts the mucous membrane on its way through, enabling the nose to cleanse, warm, and humidify it.

2concha = seashell

The olfactory mucosa, concerned with the sense of smell, lines the roof of the nasal fossa and extends over part of the septum and superior concha. The rest of the cavity is lined by ciliated pseudostratified respiratory mucosa. The cilia continually beat toward the posterior nares and drive debris-laden mucus into the pharynx to be swallowed and digested. The nasal mucosa has an important defensive role. Goblet cells in the epithelium and glands in the lamina propria secrete a layer of mucus that traps inhaled particles. Bacteria are destroyed by lysozyme in the mucus. Additional protection against bacteria is contributed by lymphocytes, which populate the lamina propria in large numbers, and by antibodies (IgA) secreted by plasma cells.

The lamina propria contains large blood vessels that help to warm the air. The inferior concha has an especially extensive venous plexus called the erectile tissue (swell body). Every 30 to 60 minutes, the erectile tissue on one side becomes engorged with blood and restricts airflow through that fossa. Most air is then directed through the other naris and fossa, allowing the engorged side time to recover from drying. Thus the preponderant flow of air shifts between the right and left nares once or twice each hour. The inferior concha is the most common site of spontaneous epistaxis (nosebleed), which is sometimes a sign of hypertension.

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

22. The Respiratory System I Text

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Superior Vestibule Half Head Model

Vertebral column Esophagus

Cribriform plate Auditory tube

Sites of respiratory control nuclei Pons

Medulla oblongata Nasopharynx Uvula

Oropharynx Laryngopharynx

Vertebral column Esophagus

Frontal sinus

Nasal conchae Superior

Middle

Inferior

Vestibule-

Guard hairs-

Anterior naris (nostril) Hard palate Upper lip-

-Soft palate

Tongue Lower lip

Mandible

Vocal cord Larynx

Vestibule-

Guard hairs-

Anterior naris (nostril) Hard palate Upper lip-

Anterior Nares Anatomy

-Soft palate

Glottis

Trachea

Esophagus

Figure 22.3 Anatomy of the Upper Respiratory Tract. (a) Median section of the head. (b) Internal anatomy. (c) Regions of the pharynx. Why do throat infections so easily spread to the middle ear?

Meatuses

- Middle Inferior

Sphenoid sinus

Posterior naris (choana)

Pharyngeal tonsil

Auditory tube

Uvula

Palatine tonsil

--Lingual tonsil

Epiglottis

Glottis

Trachea

Esophagus

Choanal And Tonsil

Oropharynx

-Nasopharynx

Laryngopharynx

Oropharynx

-Nasopharynx

Laryngopharynx

Figure 22.3 Anatomy of the Upper Respiratory Tract. (a) Median section of the head. (b) Internal anatomy. (c) Regions of the pharynx. Why do throat infections so easily spread to the middle ear?

Saladin: Anatomy & I 22. The Respiratory System I Text I © The McGraw-Hill

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Responses

  • ines engel
    What structure separates the laryngopharynx from the oropharynx?
    8 years ago
  • viviana derose
    Where are guard hairs located in the respiratory system,?
    6 years ago
  • kidane medhanie
    What is the anterior nare of human?
    2 years ago

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