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Physical Properties of the Lungs

الكلية كلية طب حمورابي     القسم الكلية ذات القسم الواحد     المرحلة 2
أستاذ المادة امجد حسن عباس المنصوري       06/10/2017 17:22:00
Physical Properties of the Lungs
1.Compliance.
2.Elasticity.
3.Surface tension.

1.Compliance of the respiratory system
A. Lung Compliance
Lung compliance expresses the dispensability of the lungs, that is, how easily the lungs expand when trans-pulmonary pressure increases. It is expressed by the following equation:
C = ?V/?P
where
C = lung compliance
?V = increase in lung volume (mL)
?P = increase in trans-pulmonary pressure (mm Hg).
– Compliance is inversely related to stiffness.
– Compliance is inversely related to the elastic recoil

B. Compliance of the Lung–Chest Wall Combination
Because the lungs and chest wall expand and contract together, the overall compliance of the respiratory system is that of the lung–chest wall combination. The compliance of the lung–chest wall combination is lower than the compliance of the lungs alone or chest wall alone.
– The compliance of the lung–chest wall combination varies with lung volume. Compliance is highest at the normal resting volume and decreases at both very low and very high volumes.
– At low volumes, compression of the chest wall reduces compliance.
– At high volumes, the increased stretch of elastic tissues in the lung parenchyma causes the lungs to get stiffer (less compliant). High trans-pulmonary pressure is required to drive this increase in volume, but it is not responsible for the decrease in compliance.
Changes in lung compliance in disease states
– Lung compliance is decreased in pulmonary fibrosis because the interstitium surrounding the alveoli becomes infiltrated with inelastic collagen.
– Lung compliance is increased in emphysema because many small alveoli are replaced by fewer but larger coalesced air spaces that have less elastic recoil.
– Lung compliance is normal in asthma.


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .