Overview
This lecture explains the pathway of blood through the heart and circulatory system, focusing on the pulmonary and systemic circuits and how specific tissues receive oxygenated blood.
Heart Structure & Blood Flow
- The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle.
- Blood enters the right atrium, flows to the right ventricle, and is pumped to the lungs.
- Oxygenated blood returns to the left atrium, moves to the left ventricle, and is pumped to the body.
Pulmonary Circulation
- Starts at the right ventricle and sends deoxygenated blood to the lungs via the pulmonary trunk and arteries.
- Pulmonary arteries carry blood away from the heart to the lungs.
- Blood becomes oxygenated in lung capillaries and returns to the left atrium via pulmonary veins.
- There are usually several pulmonary veins from each lung.
Systemic Circulation
- Begins in the left ventricle and sends oxygenated blood through the aorta to the rest of the body.
- Blood delivers oxygen to organs and tissues like the brain, liver, bones, and muscles.
- Deoxygenated blood returns to the right atrium via the superior and inferior vena cava.
Oxygen Supply to Specific Tissues
- Red blood cells (RBCs) do not use oxygen they transport because they lack mitochondria and nuclei.
- The heart receives oxygenated blood from the coronary arteries, which branch off the aorta.
- Coronary veins return deoxygenated blood directly to the right atrium, not the vena cava.
Oxygenation of the Lungs Themselves
- The lungs receive oxygenated blood via bronchial arteries from systemic circulation.
- Bronchial veins return blood to systemic veins, but most blood in lungs mixes at capillaries with pulmonary circulation.
- Mixed blood from the lungs mostly returns via pulmonary veins to the heart.
Key Terms & Definitions
- Pulmonary Circulation — Blood flow from the heart to lungs and back.
- Systemic Circulation — Blood flow from the heart to the body and back.
- Pulmonary Arteries — Vessels carrying deoxygenated blood from heart to lungs.
- Pulmonary Veins — Vessels carrying oxygenated blood from lungs to heart.
- Aorta — Largest artery distributing blood from left ventricle to body.
- Vena Cava — Large veins returning deoxygenated blood to right atrium.
- Coronary Vessels — Arteries and veins supplying blood to the heart muscle.
- Bronchial Vessels — Arteries and veins supplying lung tissue itself.
- Red Blood Cell (RBC) — Cell specialized for oxygen transport, without mitochondria or nucleus.
Action Items / Next Steps
- Review the pathways and functions of pulmonary and systemic circulation.
- Study diagrams of heart structure and blood vessel routes.
- Prepare questions about mixed circulation in the lungs for the next lecture.