Bronchial Tree and Pulmonary Vessels
Bronchial tree and pulmonary vessels from the front. Between the 4th and 5th thoracic vertebra, the trachea splits up into the two main bronchi. The right main bronchus leads into the right lung, the left into the left lung. The left main bronchus bends a bit upwards due to being pushed away by the heart. The right main bronchus leads steeply into the lung below. The main bronchi start to split up, firstly into the lobar bronchi (that lead into the lung lobes), then into segmental bronchi. The segmental bronchi then ramify into the lobular bronchi, and those into many more and more decreasing bronchi and bronchioles (very fine branches). The smallest ramifications, called respiratory or terminal bronchioles, open up into vesicles that are grouped around the bronchiole like grapes. They are called alveoles and already belong to the lung. Here is where the exchange of oxygen and carbon dioxide happens.