You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Which structure enters into the lungs? and explain in detail?
ANSWER: (B) Left principle bronchusREF: Gray's anatomy 40th ed ch: 57The right main bronchus gives rise to its first branch, the superior lobar bronchus, then enters the right lung opposite the fifth thoracic vertebra.The left principal bronchus, which is narrower and less vertical than the right, is 5 cm long. Passing to the left inferior to the aortic arch, it crosses anterior to the oesophagus, thoracic duct and descending aorta; the left pulmonary artery is at first anterior and then superior to it. Itenters the hilum of the Is ft lung at the level of the sixth thoracic vertebra and divides into a superior and an inferior lobar bronchus.