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Thoracic Anatomy

Thoracic Anatomy

December 14, 2021
Emily Cassidy, MD
Emily Cassidy, MD

Cardiothoracic Surgery

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So we think of thoracic anatomy as sort of an upside down tree. It’s also called the tracheobronchial tree. The trachea itself would be the trunk of your upside down tree. From the trunk, it splits off into two large branches, one that goes to the right, one that goes to the left. Those are called the main stem bronchi. From there, we have our low bar bronchi. On the right lung, you have three lobes: upper, middle and lower. And so you have three lobar bronchi: upper, middle and lower. On the left, there are only two lobes, upper and lower. So the left mainstem bronchus splits into two: upper and lower. The tracheobronchial tree is very important when we think of lymph nodes, because lymph nodes tend to reside where the branches of that tree are splitting. So lymph nodes that reside where the low bar bronchi are splitting are termed Hilar lymph nodes. Lymph nodes that are more in the central part of the chest, where the main trachea splits into right and left, those are termed mediastinal lymph nodes.