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The blood–air barrier or air–blood barrier, (alveolar–capillary barrier or membrane) exists in the gas exchanging region of the lungs. It exists to prevent air bubbles from forming in the blood , and from blood entering the alveoli .
The membrane has several layers – a layer of alveolar lining fluid that contains surfactant, the epithelial layer and its basement membrane; a thin interstitial space between the epithelial lining and the capillary membrane; a capillary basement membrane that often fuses with the alveolar basement membrane, and the capillary endothelial membrane.
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the innermost layer of an artery or vein), consisting of a thin wall of simple squamous endothelial cells. [2]
The primary purpose of the respiratory system is the equalizing of the partial pressures of the respiratory gases in the alveolar air with those in the pulmonary capillary blood (Fig. 11). This process occurs by simple diffusion , [ 22 ] across a very thin membrane (known as the blood–air barrier ), which forms the walls of the pulmonary ...
The edema contributes to the deposition of a hyaline membrane (composed of dead cells, surfactant, and proteins) along the alveolar walls. Hyaline membranes are characteristic of DAD. The edema interferes with the naturally occurring surfactant, which is critical for reducing surface tension and allowing alveoli to remain open and allow air in ...
alveolar duct. alveolar sac. alveolus; At each division point or generation, one airway branches into two smaller airways. The human respiratory tree may consist on average of 23 generations, while the respiratory tree of the mouse has up to 13 generations. Proximal divisions (those closest to the top of the tree, such as the bronchi) mainly ...
First CO crosses the alveolar capillary membrane (represented by ) and then CO combines with the hemoglobin in capillary red blood cells at a rate times the volume of capillary blood present (). [13] Since the steps are in series, the conductances add as the sum of the reciprocals:
They become alveolar dead space. Zone 2 is the part of the lungs about 3 cm above the heart. In this region blood flows in pulses. At first there is no flow because of obstruction at the venous end of the capillary bed. Pressure from the arterial side builds up until it exceeds alveolar pressure and flow resumes.