BSC 215 Lecture Notes - Lecture 50: Nasal Concha, Lingual Tonsils, Thyroid Cartilage
11 Jun 2018
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Structure of the Respiratory System
The respiratory system is represented by the following structures, shown in Figure 1:
• The nose consists of the visible external nose and the internal nasal cavity. The
nasal septum divides the nasal cavity into right and left sides. Air enters two
openings, the external nares (nostrils; singular, naris), and passes into the
vestibule and through passages called meatuses. The bony walls of the
meatuses, called concha, are formed by facial bones (the inferior nasal concha
and the ethmoid bone). From the meatuses, air then funnels into two (left and
right) internal nares. Hair, mucus, blood capillaries, and cilia that line the nasal
cavity filter, moisten, warm, and eliminate debris from the passing air.
• The pharynx (throat) consists of the following three regions, listed in order
through which incoming air passes:
o The nasopharynx receives the incoming air from the two internal nares.
The two auditory tubes that equalize air pressure in the middle ear also
enter here. The pharyngeal tonsil (adenoid) lies at the back of the
nasopharynx.
o The oropharyrnx receives air from the nasopharynx and food from the oral
cavity. The palatine and lingual tonsils are located here.
o The laryngopharynx passes food to the esophagus and air to the larynx.
• The larynx receives air from the laryngopharynx. It consists of several pieces of
cartilage that are joined by membranes and ligaments, shown in Figure 2:
o The epiglottis, the first piece of cartilage of the larynx, is a flexible flap that
covers the glottis, the upper region of the larynx, during swallowing to
prevent the entrance of food.
o The thyroid cartilage protects the front of the larynx. A forward projection
of this cartilage appears as the Adam's apple (anatomically known as the
laryngeal prominence).
o The paired arytenoid cartilages in the rear are horizontally attached to the
thyroid cartilage in the front by folds of mucous membranes. The upper
vestibular folds (false vocal cords) contain muscle fibers that bring the
folds together and allow the breath to be held during periods of muscular
pressure on the thoracic cavity (straining while defecating or lifting a heavy
object, for example). The lower vocal folds (true vocal cords) contain
elastic ligaments that vibrate when skeletal muscles move them into the
path of outgoing air. Various sounds, including speech, are produced in
this manner.
o The cricoid cartilage, the paired cuneiform cartilages, and the paired
corniculate cartilages are the remaining cartilages supporting the larynx.
• The trachea (windpipe) is a flexible tube, 10 to 12 cm (4 inches) long and 2.5 cm
(1 inch) in diameter (Figure 2).
• The mucosa is the inner layer of the trachea. It contains mucus‐producing goblet
cells and pseudostratified ciliated epithelium. The movement of the cilia sweeps
debris away from the lungs toward the pharynx.
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Document Summary
The respiratory system is represented by the following structures, shown in figure 1: the nose consists of the visible external nose and the internal nasal cavity. The nasal septum divides the nasal cavity into right and left sides. Air enters two openings, the external nares (nostrils; singular, naris), and passes into the vestibule and through passages called meatuses. The bony walls of the meatuses, called concha, are formed by facial bones (the inferior nasal concha and the ethmoid bone). From the meatuses, air then funnels into two (left and right) internal nares. The two auditory tubes that equalize air pressure in the middle ear also enter here. The pharyngeal tonsil (adenoid) lies at the back of the nasopharynx: the oropharyrnx receives air from the nasopharynx and food from the oral cavity. The palatine and lingual tonsils are located here: the laryngopharynx passes food to the esophagus and air to the larynx, the larynx receives air from the laryngopharynx.
