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The lower respiratory tract is also called the respiratory tree or tracheobronchial tree, to describe the branching structure of airways supplying air to the lungs, and includes the trachea, bronchi and bronchioles. [8] trachea. main bronchus (diameter approximately 1 – 1.4 cm in adults) [9] lobar bronchus (diameter approximately 1 cm)
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.
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
Anatomy photo:19:st-1001 at the SUNY Downstate Medical Center - "Pleural Cavities and Lungs: Bronchopulmonary segments" Illustration at uams.edu; Sealy W, Connally S, Dalton M (1993). "Naming the bronchopulmonary segments and the development of pulmonary surgery". Ann Thorac Surg. 55 (1): 184–8. doi: 10.1016/0003-4975(93)90507-E. PMID 8417676.
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]
After the lung buds have formed, they begin to grow and branch forming a primitive version of the bronchial tree, determining how the lobes of the lung will be arranged in the mature organ. [2] The first stage of alveolar development, spanning between the fifth and the 16th week of development, is called the pseudoglandular stage. [5]
Narrowing of the proximal bronchial tree is described as “type 4” and is associated with malignancy. “Type 5” is a bronchus compressed and flattened by the nodule with intact smooth wall. This type is mainly seen in benign nodules.
At the end of the fourth week, the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea. [56] [57] During the fifth week, the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds. These give rise to the lobes of the lungs, three on the right ...