The Bronchial Tree

The trachea bifurcates at about the level of the fourth thoracic vertebra into the right and left mainstem bronchi. The tracheal bifurcation at the carina is considered a major anatomical landmark where several anatomic events occur. These include the origin of the great vessels coming off the aorta and the entry of the

Coronary Tree
Fig 11.1a. Surface anatomy of the lungs, viewed anteriorly.
Carina Angle Atrium
Fig 11.1b. PA and lateral x-rays of a normal chest and line diagrams of the anatomy (SVC-superior vena cava, RA-right atrium, RV-right ventricle, LV-left ventricle, LA-left atrium, PA-pulmonary artery).

azygos vein into the superior vena cava at the level of the angle of Lewis. These occur at the level of the T4 vertebral body.

The trachea bifurcates into a right mainstem bronchus which arises in a more direct line with the trachea compared to the left bronchus which arises at a sharper angle to the trachea. Hence, aspiration pneumonia usually occurs in the right lung because the angle is more favorable for this event to occur. The right mainstem bronchus is much shorter than the left, and the origin of the right upper lobe

Intermedius Bronchus Lingular

Fig 11.2. Segmental anatomy of the lung. (RUL:

1-Apical; 2-Post; 3-Ant.) (RML: 4-Lat; 5-Med.) (RLL: 6-Sup; 7-Lat Basal; 8-Post Basal; 9-Ant Basal; 10-Med Basal.) (LUL: 1-Apical-Post;

2-Ant; [3-Sup; 4-Inf Lingula]) (LLL: 5-Sup; 6-Post Basal; 7-Ant Basal; 8-Lat Basal)

orifice is only about 1.2 cm away from the carina. Proceeding distally from the takeoff of the right upper lobe bronchus is the bronchus intermedius, i.e. that portion of the bronchus between the right upper lobe takeoff and the middle lobe takeoff. The right pulmonary artery crosses over the mainstem bronchus, hence the term "eparterial bronchus" to designate the right mainstem bronchus which is superior and posterior to the right pulmonary artery. At the level of the middle lobe bronchus is the superior segmental bronchus of the lower lobe. The middle lobe bronchus arises from the anterior surface of the bronchus intermedius, whereas the superior segmental bronchus of the lower lobe arises from the posterior wall of the bronchus intermedius only slightly distal to the middle lobe bronchus and indeed may appear to be at the same level. Thus, care must be taken in performing a lower lobectomy or a middle lobectomy so as not to injure that bronchus leading to a normal lobe. The left mainstem bronchus is longer than the right and branches about 5 cm distal to the carina. The left mainstem is "hypar-terial", i.e. inferior and anterior to the left pulmonary artery. The upper lobe bron-

chus divides into an upper lobe proper branch and a more inferior branch; this is the lingula branch. About half a centimeter distal to the left upper lobe orifice, the lower lobe bronchus gives off its first branch—the superior segmental bronchus. The lower lobe bronchus then continues down to the branch into the basal segmental bronchi. Bronchoscopic segmental anatomy is shown in Figure 11.3.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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