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The trachea begins at the lower edge of the cricoid cartilage of the larynx [3] at the level of sixth cervical vertebra (C6) [2] and ends at the carina, the point where the trachea branches into left and right main bronchi., [2] at the level of the fourth thoracic vertebra (T4), [2] although its position may change with breathing. [3]
The trachea is the largest tube in the respiratory tract and consists of tracheal rings of hyaline cartilage. It branches off into two bronchial tubes, a left and a right main bronchus. The bronchi branch off into smaller sections inside the lungs, called bronchioles. These bronchioles give rise to the air sacs in the lungs called the alveoli. [10]
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 lung bud branches into two lateral outgrowths known as the bronchial buds, one on each side of the trachea. The right and left bronchial buds branch into main (primary), lobar (secondary), segmental (tertiary), and subsegmental bronchi and lead to the development of the lungs . [ 2 ]
These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood. [2] These air sacs communicate with the external environment via a system of airways, or hollow tubes, of which the largest is the trachea, which branches in the middle of the chest into the two main bronchi.
The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, which receive air breathed in via the conducting zone. These divide until air reaches microscopic alveoli, where gas exchange takes ...
The carina is a cartilaginous ridge separating the left and right main bronchi that is formed by the inferior-ward and posterior-ward prolongation of the inferior-most tracheal cartilage. [2] The carina occurs at the lower end of the trachea - usually at the level of the 4th to 5th thoracic vertebra.
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 ]