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However, transmural pressure across the wall of the blood vessels increases down this zone due to gravity. Consequently the vessels wall are more stretched so the caliber of the vessels increases causing an increase in flow due to lower resistance. Zone 4 can be seen at the lung bases at low lung volumes or in pulmonary edema.
The conducting zone also functions to offer a low resistance pathway for airflow. It provides a major defense role in its filtering abilities. The respiratory zone includes the respiratory bronchioles, alveolar ducts, and alveoli, and is the site of oxygen and carbon dioxide exchange with the blood. The respiratory bronchioles and the alveolar ...
The conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles. This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli. [27] An acinus measures up to 10 mm in diameter. [28]
A bronchus (/ ˈ b r ɒ ŋ k ə s / BRONG-kəs; pl.: bronchi, / ˈ b r ɒ ŋ k aɪ / BRONG-ky) is a passage or airway in the lower respiratory tract that conducts air into the lungs.The first or primary bronchi to branch from the trachea at the carina are the right main bronchus and the left main bronchus.
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 ...
But bronchial circulation supplies fully oxygenated arterial blood to the lung tissues themselves. This blood supplies the bronchi and the pleurae to meet their nutritional requirements. [citation needed] Because of the dual blood supply to the lungs from both the bronchial and the pulmonary circulation, this tissue is more resistant to infarction.
The respiratory bronchioles deliver air to the exchange surfaces of the lungs. [5] They are interrupted by alveoli which are thin walled evaginations. Alveolar ducts are side branches of the respiratory bronchioles. The respiratory bronchioles are lined by ciliated cuboidal epithelium along with some non-ciliated cells called club cells. [6]
Failure of the barrier may occur in a pulmonary barotrauma.This can be a result of several possible causes, including blast injury, swimming-induced pulmonary edema, and breathing gas entrapment or retention in the lung during depressurization, which can occur during ascent from underwater diving or loss of pressure from a pressurized vehicle, habitat or pressure suit.