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The respiratory tract can also be divided into a conducting zone and a respiratory zone, based on the distinction of transporting gases or exchanging them. The conducting zone includes structures outside of the lungs – the nose , pharynx , larynx , and trachea , and structures inside the lungs – the bronchi, bronchioles, and terminal ...
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]
The ventilation/perfusion ratio (V/Q ratio) is higher in zone #1 (the apex of lung) when a person is standing than it is in zone #3 (the base of lung) because perfusion is nearly absent. However, ventilation and perfusion are highest in base of the lung, resulting in a comparatively lower V/Q ratio.
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.
In humans, the pharynx is part of the digestive system and the conducting zone of the respiratory system. (The conducting zone—which also includes the nostrils of the nose , the larynx , trachea , bronchi , and bronchioles —filters, warms and moistens air and conducts it into the lungs ). [ 1 ]
These bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, from the sixteenth through the twenty-third division of the tract.
Anatomical dead space is the volume of the conducting airways (from the nose, mouth and trachea to the terminal bronchioles). These conduct gas to the alveoli but no gas exchange occurs here. In healthy lungs where the alveolar dead space is small, Fowler's method accurately measures the anatomic dead space using a single breath nitrogen ...
Atlas image: lung_carina at the University of Michigan Health System - "Cast of trachea and bronchi, anterior view" (#2) [dead link ] "Trachea and carina — tomogram, coronal plane" at SUNY Downstate Medical Center Archived 2016-03-03 at the Wayback Machine; Carina tracheae entry in the public domain NCI Dictionary of Cancer Terms