Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 299 The trachea and primary bronchi carry air to and from the lungs. The trachea, or windpipe, is a robust, flexible tube whose epithelium is continuous with the larynx. The mucosa of the trachea resembles that of the nasal cavity and nasopharynx. The submucosa , a thick layer of connective tissue, surrounds the mucosa and communicates with the epithelial surface through many secretory ducts. The walls of the trachea are stiff and protect the airway with 15–20 tracheal cartilages. They also prevent its collapse or overexpansion as pressures change in the respiratory system. Each tracheal cartilage is C-shaped. The Primary Bronchi The trachea branches within the mediastinum and gives rise to the right and left primary. The carina separates the two bronchi with a ridge. The right primary bronchus supplies the right lung, and the left supplies the left lung. The right primary bronchus is larger in diameter than the left primary bronchus, and it descends toward the lung at a steeper slope. Therefore, most foreign objects that enter the trachea find their way into the right bronchus rather than the left. Before branching further, each primary bronchus travels to a groove along the medial surface of its lung. This groove, the hilum of the lung, also provides access for entry to pulmonary vessels, nerves, and lymphatics. of 368 22.4 Lower Respiratory System The Larynx The larynx is the organ of phonation (sound production). It is composed of cartilages, ligaments, and muscles. Inhaled air leaves the pharynx and enters the larynx through a narrow opening called the glottis. The larynx protects and surrounds the glottis. Three large, unpaired cartilages form the larynx: the epiglottis, thyroid cartilage, and the cricoid cartilage. During swallowing, to prevent the entry of both liquids and food into the respiratory tract, the larynx elevates, and the epiglottis covers the glottis. The larynx also contains three pairs of smaller hyaline cartilages: The arytenoid cartilages, the corniculate cartilages (the corniculate and arytenoid cartilages function in the opening and closing of the glottis and the production of sound), and cuneiform cartilages. The vocal ligaments and vestibule are covered by folds of laryngeal epithelium that project into the glottis. The vestibular folds house the vestibular ligaments. These folds, which are relatively inelastic, help prevent foreign objects from entering the glottis and protect the more delicate vocal folds. The entrance to the glottis is guarded by the vocal folds. The vocal folds are highly elastic because the vocal ligaments consist of elastic tissue. The vocal folds aid in phonation and produces sound; so they are also known as the vocal cords. Sound Production The glottis vibrates when air passes through the vocal folds and produces sound waves. The pitch of the sound produced depends on the vocal fold length, diameter, and tension. The diameter and length are directly related to the size of the larynx. The tension is controlled by the contraction of voluntary muscles that reposition the arytenoid cartilages relative to the thyroid cartilage. When the distance increases, the vocal folds tense and the pitch rises; when the distance decreases, the opposite occurs. With the vocal folds relax, the pitch falls. The Trachea