Ebook West’s respiratory physiology (10/E): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook West’s respiratory physiology (10/E): Part 2
Ebook West’s respiratory physiology (10/E): Part 2
MECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2Curve Compliance Surface Tension•Cause of Regional Differences in VentilationAirway Closure•Elastic Properties of the Chest Wall•Airway ResistanceAirflow Through Tubes Measurement of AirwayResistancePressures During the Breathing CycleChief Site of Airway ResistanceFactors Determining Airway Resista Ebook West’s respiratory physiology (10/E): Part 2nceDynamic Compression of Airways•Causes of Uneven Ventilation•Tissue Resistance•Work of BreathingWork Done on the Lung Total Work of Breathing\/\/e sEbook West’s respiratory physiology (10/E): Part 2
aw in Chapter 2 that gas gets to and from the alveoli by the process of ventilation. We now turn to the forces that move the lung and chest wall, and MECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2ining the elastic properties of the lung, including the tissue elements and the air-liquid surface tension. Next, we examine the mechanism of regional differences in ventilation and also the closure ol small airways. Just as the lung is clastic, so is the chest wall, and we look al the interaction b Ebook West’s respiratory physiology (10/E): Part 2etween the two. The physical principles of airway resistance are then considered, along with its measurement, chief site in the lung, and physiologicaEbook West’s respiratory physiology (10/E): Part 2
l factors that affect it. Dynamic compression of the airways during a forced expiration is analy?ed. Finally, the work required to move the lung and cMECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2consists of a thin, dome-shaped sheet of muscle that is inserted into the lower ribs. It is supplied by the phrenic nerves from cervical segments 3, 4, and 5. When it contracts, the abdominal contents are forced downward and forward, and the vertical dimension of the chest cavity is increased. In ad Ebook West’s respiratory physiology (10/E): Part 2dition, the rib margins arc lifted and moved out, causing an increase in the transverse diameter of the thorax (Figure 7.1).In normal tidal breathing,Ebook West’s respiratory physiology (10/E): Part 2
the level of the diaphragm moves about 1 cm or so, bin on forced inspiration and expiration, a total excursion of up to 10 cm may occur. When one sidMECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2al movement and can be demonstrated at fluoroscopy when the patient sniffs.T he external intercostal muscles connect adjacent ribs and slope downward and forward (Figure 7.2). When they contract, the ribs are pulled upward and forward, causing an increase in both the lateral and the anteroposterior Ebook West’s respiratory physiology (10/E): Part 2diameters of the thorax. The lateral dimension increases because of the “bucket-handle” movement of the ribs. The intercostal muscles are supplied byEbook West’s respiratory physiology (10/E): Part 2
intercostal nerves that come off the spinal cord at the same level. Paralysis of the intercostal muscles alone does not seriously affect breathing at MECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2 sternomastoids, which raise the sternum. T here is little, if any, activity in these muscles during quiet breathing, but duringFigure 7.1. On inspiration, the dome-shaped diaphragm contracts, the abdominal contents arc forced down and forward, and the rib cage is widened. Both increase the volume o Ebook West’s respiratory physiology (10/E): Part 2f the thorax. On forced expiration, the abdominal muscles contract and push the diaphragm up.110 CHAPTER 7Figure 7.2. When the external intercostal muEbook West’s respiratory physiology (10/E): Part 2
scles contract, the ribs are pulled upward and forward, and they rotate on an axis joining the tubercle and the head of a rib. As a result, both the lMECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2. Other muscles that play a minor role include the alae nasi, which cause flaring of the nostrils, and small muscles in the neck and head.ExpirationT his is passive during quiet breathing. The lung and chest wall are elastic and tend to return to their equilibrium positions after being actively expa Ebook West’s respiratory physiology (10/E): Part 2nded during inspiration. During exercise and voluntary hyperventilation, expiration becomes active. The most important muscles of expiration are thoseEbook West’s respiratory physiology (10/E): Part 2
of the abdominal -d'all, including the rectus abdominis, internal and external oblique muscles, and transversus abdominis. W hen these muscles contraMECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume C Ebook West’s respiratory physiology (10/E): Part 2cation.The internal intercostal muscles assist active expiration by pulling the ribs downward and inward (opposite to the action of the external intercostal muscles), thus decreasing the thoracic volume. In addition, they stiffen the intercostal spaces to prevent them from bulging outward during str Ebook West’s respiratory physiology (10/E): Part 2aining. Experimental studies show that the actions of the respiratory muscles, especially the intcrcostals, arc more complicated than this brief accouEbook West’s respiratory physiology (10/E): Part 2
nt suggests.MECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume CMECHANICS OF BREATHINGHOW THE LUNG IS SUPPORTED AND MOVED•Muscles of RespirationInspiration Expiration•Elastic Properties of the LungPressure-Volume CGọi ngay
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