About normal expiration, TRUE/FALSE are: 1. At the end of normal expiration air in the lung is ERV 2. Chest wall has a tendency to move outward which is balanced by inward recoil of alveoli 3. In expiratory pleural pressure is equal to alveolar pressure 4. Muscle that elevates the chest cage are classified as muscle of expiration
" At the end quite of expiration, the tendency of the lung to recoil from the chest wall is just balanced by the tendency of the chest wall to recoil in the opposite direction" LUNG: INSPIRATION AND EXPIRATION. The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; this normally amounts to about 1100 mls. The compliance of the combined lung-thorax system is almost exactly one half that of the lung alone -110 milliliters of volume per centimeter of water pressure for the combined system, compared with 200 ml/cm for the lungs alone. Fuhermore, when the lungs are expanded to high volumes or compressed to low volumes, the limitation of the chest become extreme, when near these limits, the compliance of the combined lung-thorax system can be less than one fifth that of the lungs alone. All the muscles that elevate the chest cage are classified as muscles of inspiration, and those muscles that depress the chest cage are classified as muscles expiration. Note: The most impoant muscles that raise the rib cage are the external intercostals, but other that help are the (1) sternocleidomastoid muscles, which lift upward on the sternum: (2) anterior serrati, which lift many of the ribs ; and (3) scaleni, which lift the first two ribs The muscles that pull the rib cage downward during expiration are mainly the (1) abdominal recti (2) internal intercostals. The normal pleural pressure at the beginning of inspiration is about -5 centimeters of water, which is the amount of suction required to hold the lungs open to their resting level. Then, during normal inspiration, expansion of the chest cage pulls, outward on the lungs with greater force and creates more negative pressure to an averages of about -7.5 centimeters of water. To cause inward flow of air into the alveoli during inspiration, the pressure in the alveoli must fall to a value slightly below atmospheric pressure(below 0). During normal inspiration, alveolar pressure decreases to about -1 centimeter of water. This slight negative pressure is enough to pull 0.5 liter of air into the lungs in the 2 seconds required for normal quiet inspiration. During expiration, opposite pressure occur. The alveolar pressure rise to about +1 centimeter of water, and this force the 0.5 liter of inspired air out of the lungs during the 2 to 3 seconds of expiration. Transpulmonary Pressure : the difference between the alveolar pressure and the pleural pressure. This is called the transpulmonary pressure. It is the presssure difference between that in the alveoli and that on the outer surface of the lungs, and it is a measure of the elastic force in the lungs that tend to collapse the lungs at each instant of respiration, called the recoil pressure. Ref: Guyton 11/ e page 471-74 ; Ganong 23/e, page 591-92
2,3 true & 1,4 false
1,2 true & 3,4 false
1,2,3 true & 4 false
All are true