Overview
This lecture covers the human double circulatory system, explaining the pulmonary and systemic routes of blood flow and the process of gas exchange.
Double Circulatory System
- Humans have a double circulatory system: pulmonary (heart-lungs) and systemic (heart-body).
- Pulmonary circulation moves blood from the heart to the lungs and back.
- Systemic circulation moves blood from the heart to the rest of the body and back.
Pulmonary Circulation
- Blood enters the right atrium from the superior and inferior vena cava.
- Blood moves to the right ventricle, then to the pulmonary artery, and on to both lungs.
- Pulmonary arteries branch into capillaries surrounding alveoli (air sacs in lungs).
- Deoxygenated blood in capillaries has low oxygen, high carbon dioxide; alveoli have high oxygen, low carbon dioxide.
- Gas exchange occurs by diffusion: oxygen moves into blood, carbon dioxide moves into alveoli.
- Oxygenated blood returns to the heart via pulmonary veins to the left atrium.
- Blood moves from the left atrium to the left ventricle, then is pumped via the aorta.
Systemic Circulation
- Left ventricle pumps oxygenated blood through the aorta to all body organs, tissues, muscles, head, and arms.
- The aorta branches into arterioles and then capillaries within tissues.
- Capillaries allow diffusion: oxygen leaves the blood for the tissues, carbon dioxide enters the blood from the tissues.
- Blood returning from the body is now deoxygenated and returns to the right atrium via the vena cavae.
Gas Exchange and Energy Production
- Cells use oxygen and nutrients from the blood to produce energy, creating carbon dioxide as waste.
- Carbon dioxide diffuses from tissues into capillaries for removal via the pulmonary system.
Key Terms & Definitions
- Pulmonary Circulation — blood flow between heart and lungs.
- Systemic Circulation — blood flow between heart and the rest of the body.
- Alveoli — tiny air sacs in the lungs where gas exchange occurs.
- Capillaries — small blood vessels enabling exchange of gases and nutrients.
- Diffusion — movement of substances from high to low concentration.
- Vena cava — large vein carrying deoxygenated blood into the heart.
- Aorta — the largest artery, distributing oxygenated blood from the heart to the body.
Action Items / Next Steps
- Review diagrams of the circulatory system to visualize blood flow.
- Memorize the steps of pulmonary and systemic circulation.
- Understand the process of diffusion in alveoli and tissues.