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The terminal bronchioles are the most distal segment of the conducting zone. They branch off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple ciliated cuboidal epithelium containing club cells. Club cells are non ...
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]
Bronchial anatomy showing terminal bronchioles (BT) leading to respiratory bronchioles (BR) and alveolar ducts (DA) that open into alveolar sacs containing out pockets of alveoli (A) separated by alveolar septa (AS) The alveoli are first located in the respiratory bronchioles as scattered outpockets, extending from their lumens.
Instead of hard cartilage, the bronchi and bronchioles are composed of elastic tissue. The lungs are made up of thirteen different kinds of cells, eleven types of epithelial cell and two types of mesenchymal cell. [13] The epithelial cells form the lining of the tracheal, and bronchial tubes, while the mesenchymal cells line the lungs.
In humans and other mammals, the anatomy of a typical respiratory system is the respiratory tract.The tract is divided into an upper and a lower respiratory tract.The upper tract includes the nose, nasal cavities, sinuses, pharynx and the part of the larynx above the vocal folds.
The end of the terminal bronchioles in the lungs mark the beginning of a pulmonary acinus that includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. [ 4 ] See also
The cells in the respiratory epithelium are of five main types: a) ciliated cells, b) goblet cells, c) brush cells, d) airway basal cells, and e) small granule cells (NDES) [6] Goblet cells become increasingly fewer further down the respiratory tree until they are absent in the terminal bronchioles; club cells take over their role to some extent here. [7]
A bronchopulmonary segment is a portion of lung supplied by a specific segmental bronchus and its vessels. [1] [2] These arteries branch from the pulmonary and bronchial arteries, and run together through the center of the segment.