Components And Subdivisions Of The Human Respiratory System

See figure 7-1 for an illustration of the human respiratory system.

a. Components. The components of the human respiratory system consist of air passageways and two lungs. Air moves from the outside of the body into tiny sacs in the lungs called alveoli (pronounced al-VE-oh-lie).

b. Main Subdivisions. The main subdivisions of the respiratory system may be identified by their relationship to the voice box or larynx. Thus, the main subdivisions are as listed in table 7-1.

Figure 7-1. The human respiratory system.

SUBDIVISION

FUNCTION

(1) SUPRALARYNGEAL STRUCTURES (su-prah-lah-RIN-je-al)

Cleanse, warm, moisten, and test inflowing air

(2) LARYNX (voice box) (LARE-inks)

Controls the volume of inflowing air; produces selected pitch(vibration frequency) in the moving column of air

(3) INFRALARYNGEAL STRUCTURES (in-frah-lah-RIN-je-al)

Distribute air to the alveoli of the lung where the actual external respiration takes place

Table 7-1. The main subdivisions of the respiratory system 7-3. SUPRALARYNGEAL STRUCTURES

Table 7-1. The main subdivisions of the respiratory system 7-3. SUPRALARYNGEAL STRUCTURES

See figure 7-2.

Figure 7-2. Supralaryngeal structures.

a. External Nose. The external nose is the portion projecting from the face. It is supported primarily by cartilages. It has a midline divider called the nasal septum, which extends from the internal nose. Paired openings (nostrils) lead to paired spaces (vestibules). Guard hairs in the nostrils filter inflowing air.

b. Nasal Chambers (Internal Nose). Behind each vestibule of the external nose is a nasal chamber. The two nasal chambers together form the internal nose. These chambers too are separated by the nasal septum.

(1) Mucoperiosteum. The walls of the nasal chambers are lined with a thick mucous-type membrane known as the mucoperiosteum. It has a ciliated epithelial surface and a rich blood supply, which provides warmth and moisture. At times, it may become quite swollen.

CILIATED = provided with cilia (hairlike projections which move fluids to the rear)

(2) Conchae. The lateral wall of each chamber has three scroll- like extensions into the nasal chamber which help to increase the surface area exposed to the inflowing air. These scroll-like extensions are known as conchae.

CONCHA (pronounced KON-kah) = sea shell

CONCHA (singular), CONCHAE (plural)

(3) Olfactory epithelium. The sense of smell is due to special nerve endings located in the upper areas of the nasal chambers. The epithelium containing the sensory endings is known as the olfactory epithelium.

(4) Paranasal sinuses. There are air "cells" or cavities in the skull known as paranasal sinuses. The paranasal sinuses are connected with the nasal chambers and are lined with the same ciliated mucoperiosteum. Thus, these sinuses are extensions of the nasal chambers into the skull bones. For this reason, they are known as paranasal sinuses.

c. Pharynx. The pharynx (FAIR-inks) is the common posterior space for the respiratory and digestive systems.

(1) Nasopharynx. That portion of the pharynx specifically related to the respiratory system is the nasopharynx. It is the portion of the pharynx above the soft palate. The two posterior openings (nares) of the nasal chambers lead into the single space of the nasopharynx. The auditory (eustachian) tubes also open into the nasopharynx. The auditory tubes connect the nasopharynx with the middle ears (to equalize the pressure between the outside and inside of the eardrum). Lying in the upper posterior wall of the nasopharynx are the pharyngeal tonsils (adenoids). The soft palate floor of the nasopharynx is a trapdoor which closes off the upper respiratory passageways during swallowing.

(2) Oropharynx. The portion of the pharynx closely related to the digestive system is the oropharynx. It is the portion of the pharynx below the soft palate and above the upper edge of the epiglottis. (The epiglottis is the flap that prevents food from entering the larynx (discussed below) during swallowing.)

(3) Laryngopharynx. That portion of the pharynx which is common to the respiratory and digestive systems is the laryngopharynx. It is the portion of the pharynx below the upper edge of the epiglottis. Thus, the digestive and respiratory systems lead into it from above and lead off from it below.

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