Pulmonary blood circulation. Pulmonary blood flow = cardiac output of the right ventricle. Key pathways: • Right atrium sends deoxygenated blood to the right ventricle, which ejects it through the pulmonary trunk and arteries. • Within the lungs, the pulmonary arteries form branching patterns that parallel the tracheobronchial tree. • Blood flow travels through the pulmonary capillary networks that surround the alveoli. • Carbon dioxide is released from the bloodstream and fresh oxygen enters it. • Oxygenated blood returns to the heart via the pulmonary veins, then drains through the left atrium to the ventricle. • Upon contraction, the left ventricle sends the oxygenated blood through the aorta to the systemic tissues. Bronchial circulation: • Blood supply to the conducting zone of the respiratory tract; thus, it is the very small portion of total blood flow that does not take part in gas exchange. Gravitational effects on pulmonary blood flow • In upright position, pulmonary blood flow is not distributed evenly throughout the lungs. • Gravitational pull results in a lower blood flow at the apex of the lung than at the base.
