![]() Thoracic cavity, and allow inhalation to occur. (costal) breathing: The rib cages changes shape, altering thoracic volume.Ĭontractions of the external intercostal muscles raise the ribs, enlarge the When it relaxes, air is passively exhaled. Thoracic volume change,with air drawn into the lungs as the diaphragmĬontracts. (diaphragmatic) breathing: Diaphragm contrac tion provides the required There are variations in the actions of these muscles: Usually includes contraction of the diaphragm and external internal intercostal Required for inhalation, while exhalation is done passively. In this type of breathing, muscular contractions are TheseĬlassifications are made based on pat-terns of muscle activity within a single ![]() Respiratory movements are usually classified as either quiet breathing or forced breathing. Respiratory system influences different combinations of respiratory muscleĪctions. The volume of air required to be move in or out of the Oblique, transversus abdominis, and rectus abdominis. The abdominal muscles include the external oblique, internal Internal intercostal muscles by compressing the abdomen, which forces theĭiaphragm upward. Width and depth of the thoracic cavity is reduced. Internal intercostal and transversus thoracic muscles. Musclesīased on the level of respiratory activity, expiration Muscle contraction: This assists the exter-nal intercostal muscles inĮlevation of the ribs the speed and mount of rib movement is increased. Intercostal muscle contraction: This raises the ribs, contributing about About 75% of air movement in normalĪt-rest breathing results from this contraction. The active process of inhalation involves one or more ofĬontraction: This flattens the thoracic cavity floor to increase its The processes of expiration and inspiration are shown in FIGURE 21-8A and B. Pectoralis minor, scalene, transverse thoracis and abdominis, external andĪbdominis muscles. Muscles include the internal intercostal, Greatly increased respiratory depth and frequency. Inward, forcing the diaphragm even higher against the lungs. The abdominal wall muscles squeeze the abdominal organs This pulls the ribs and sternum downward and inward to increase the ![]() ![]() If more forceful exhalation is required, the posterior internal or expiratory intercostal musclesĬontract. Lungs is forced out, meaning that normal resting expiration is a passive Surface tension decreases theĭiameters of the alveoli, increasing alveolar air pressure. Previous shapes to push the diaphragm upward. Return to their original shapes, and the abdominal organs move back into their The elastic tissues cause the lungs and thoracic cage to As the diaphragm low-ers, it compresses the abdominal The lungs then expand in allĮxpiration occurs because of the elastic recoil of tissuesĪnd surface tension. Pleura also moves as does the visceral pleura. Intercostal muscles move the thoracic wall upward and outward, the parietal Movements as well as those of the pleural membranes. The ribs raise and the sternum elevates,Įnlarging the thoracic cavity further. ![]() FIGURE 21-1 shows the structures of the respiratory system.Īs the diaphragm contracts, the external or inspiratory intercostal muscles between The lungs contain the bronchi, bronchioles, and alveoli. The lowerrespiratory tract includes the larynx, trachea, and lungs. The upper respiratory tract includes the nose, nasal cavity, paranasal sinuses, and pharynx. ![]()
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