Ytc

Figure

Lung cancer may begin as a tiny tumor growing in an alveolus, a microscopic air sac (125x).

the tiny, conelike corniculate cartilages. These cartilages are attachments for muscles that help regulate tension on the vocal cords during speech and aid in closing the larynx during swallowing.

The cuneiform cartilages are small, cylindrical structures in the mucous membrane between the epiglot-tic and the arytenoid cartilages. They stiffen the soft tissues in this region.

Inside the larynx, two pairs of horizontal folds composed of muscle tissue and connective tissue with a covering of mucous membrane extend inward from the lateral walls. The upper folds (vestibular folds) are called false vocal cords because they do not produce sounds. Muscle fibers within these folds help close the larynx during swallowing.

The lower folds are the true vocal cords. They contain elastic fibers and are responsible for vocal sounds, which are created when air is forced between these folds, causing them to vibrate from side to side. This action generates sound waves, which can be formed into words by changing the shapes of the pharynx and oral cavity and by using the tongue and lips. Figure 19.6 shows both pairs of folds.

Changing tension on the vocal cords, by contracting or relaxing laryngeal muscles, controls pitch (musical tone) of the voice. Increasing the tension produces a higher pitch, and decreasing the tension creates a lower pitch.

The intensity (loudness) of a vocal sound depends upon the force of the air passing over the vocal cords. Stronger blasts of air result in greater vibration of the vocal cords and louder sound.

During normal breathing, the vocal cords remain relaxed, and the opening between them, called the glottis (glot'is), is a triangular slit. However, when food or liquid is swallowed, muscles close the glottis within the false

(a)

Figure 19.4

Radiograph of a skull (a) from the frontal view and (b) from the lateral view, showing air-filled sinuses (arrows) within the bones.

Figure 19.4

Radiograph of a skull (a) from the frontal view and (b) from the lateral view, showing air-filled sinuses (arrows) within the bones.

-Epiglottic cartilage

-Hyoid bone

-J--Thyroid cartilage

-J--Thyroid cartilage

Cricoid cartilage

Trachea

Cricoid cartilage

Trachea

Hyoid bone Epiglottic cartilage Corniculate cartilage Arytenoid cartilage

Trachea

Figure 19.5

(a) Anterior view and (b) posterior view of the larynx.

Hyoid bone Epiglottic cartilage Corniculate cartilage Arytenoid cartilage

Trachea

Thyroid cartilage Cricoid cartilage

Figure 19.5

(a) Anterior view and (b) posterior view of the larynx.

vocal folds. Along with closing of the epiglottis, this action helps prevent food or liquid from entering the trachea (fig. 19.7). The mucous membrane that lines the larynx continues to filter incoming air by entrapping particles and moving them toward the pharynx by ciliary action.

H What part of the respiratory tract is shared with the alimentary canal?

^9 Describe the structure of the larynx.

^9 How do the vocal cords produce sounds?

Q What is the function of the glottis? Of the epiglottis?

Trachea

The trachea (windpipe) is a flexible cylindrical tube about 2.5 centimeters in diameter and 12.5 centimeters in length. It extends downward anterior to the esophagus and into the thoracic cavity, where it splits into right and left bronchi (fig. 19.8 and reference plate 50).

The inner wall of the trachea is lined with a ciliated mucous membrane that contains many goblet cells. This membrane continues to filter the incoming air and to move entrapped particles upward into the pharynx where the mucus can be swallowed.

False vocal cord

Epiglottis Hyoid bone

Thyroid cartilage Cricoid cartilage

False vocal cord

Glottis

True vocal cord

Thyroid cartilage

Cuneiform cartilage

Corniculate cartilage

Arytenoid cartilage

True vocal cord

Epiglottis Hyoid bone

Thyroid cartilage Cricoid cartilage

Hyoid bone

Epiglottis

False vocal cord

Thyroid cartilage Cricoid cartilage

Figure 19.6

(a) Coronal section and (b) sagittal section of the larynx.

Hyoid bone

Epiglottis

False vocal cord

Thyroid cartilage Cricoid cartilage

Figure 19.6

(a) Coronal section and (b) sagittal section of the larynx.

Posterior portion of tongue

Glottis

Corniculate cartilage

Posterior portion of tongue

Glottis

Corniculate cartilage

Epiglottis

Glottis

Figure 19.7

False vocal cord

True vocal cord

Cuneiform cartilage

Epiglottis

Glottis

Inner Wall Trachea
Inner lining of trachea

Vocal cords as viewed from above (a) with the glottis closed and (b) with the glottis open. (c) A photograph of the glottis and vocal folds.

Within the tracheal wall are about twenty C-shaped pieces of hyaline cartilage, one above the other. The open ends of these incomplete rings are directed posteriorly, and the gaps between their ends are filled with smooth muscle and connective tissues (figs. 19.9 and 19.10). These cartilaginous rings prevent the trachea from collapsing and blocking the airway. At the same time, the soft tissues that complete the rings in the back allow the nearby esophagus to expand as food moves through it on the way to the stomach.

A blocked trachea can cause asphyxiation in minutes. If swollen tissues, excess secretions, or a foreign object obstruct the trachea, making a temporary, external opening in the tube so that air can bypass the obstruction is lifesaving. This procedure, shown in figure 19.11, is called a tracheostomy.

On December 13, 1799, George Washington spent the day walking on his estate in a freezing rain. The next day, he had trouble breathing and swallowing. Several doctors were called in. One suggested a tracheostomy, cutting a hole in the throat so that the president could breathe. He was voted down. The other physicians suggested bleeding the patient, plastering his throat with bran and honey, and placing beetles on his legs to produce blisters. No treatment was provided, and within a few hours, Washington's voice became muffled, breathing was more labored, and he was restless. For a short time he seemed euphoric, and then he died.

George Washington had epiglottitis, an inflammation that swells the epiglottis to ten times its normal size. A tracheostomy might have saved his life.

Tracheostomy Blood Vessels

Figure 19.8

The trachea transports air between the larynx and the bronchi.

Connective tissue

Hyaline cartilage

Connective tissue

Ciliated epithelium

Lumen of trachea

Light micrograph of a section of the tracheal wall (63x).

Connective tissue

Hyaline cartilage

Connective tissue

Ciliated epithelium

Lumen of trachea

Figure 19.8

The trachea transports air between the larynx and the bronchi.

Lumen of trachea

Hyaline cartilage

Ciliated epithelium

Lumen of trachea

Hyaline cartilage

Name Trachea Vertebra

Ciliated epithelium

Smooth muscle

Connective tissue

Figure

Cross section of the trachea. Note the C-shaped rings of hyaline cartilage in the wall.

Smooth muscle

Connective tissue

Quit Smoking For Good

Quit Smoking For Good

Quit smoking for good! Stop your bad habits for good, learn to cope with the addiction of cigarettes and how to curb cravings and begin a new life. You will never again have to leave a meeting and find a place outside to smoke, losing valuable time. This is the key to your freedom from addiction, take the first step!

Get My Free Ebook


Post a comment