Overview
This lecture introduces the circulatory (cardiovascular) system, focusing on the heart’s structure, the double circulatory system, and the main blood vessels.
The Circulatory System
- The circulatory system is an organ system made up of the heart, blood vessels, and blood.
- Its main function is to transport oxygen, nutrients, and waste products throughout the body.
- Blood acts as the transport fluid, blood vessels direct blood flow, and the heart pumps the blood.
Double Circulatory System
- Most mammals have a double circulatory system with two separate circuits: pulmonary and systemic.
- The pulmonary circuit moves blood from the heart to the lungs and back for oxygenation.
- The systemic circuit carries oxygenated blood from the heart to the body tissues and returns deoxygenated blood to the heart.
Structure of the Heart
- The heart is a muscular organ with four chambers: two atria (upper) and two ventricles (lower).
- The right atrium and right ventricle are separated by the right atrioventricular valve.
- The left atrium and left ventricle are separated by the left atrioventricular valve.
- The left ventricle has a thicker muscle wall to pump blood throughout the body, whereas the right ventricle only pumps to the lungs.
Major Blood Vessels of the Heart
- The vena cava brings deoxygenated blood from the body into the right atrium.
- Blood then moves from the right ventricle to the pulmonary artery, which carries it to the lungs.
- Oxygenated blood returns from the lungs via the pulmonary vein to the left atrium.
- The left ventricle pumps blood into the aorta, which distributes it throughout the body.
Blood Supply to the Heart
- The heart receives its own oxygen supply from coronary arteries, which branch from the aorta.
- Blockage of coronary arteries can cause coronary artery disease or a heart attack.
Key Terms & Definitions
- Circulatory (cardiovascular) system — the organ system transporting blood and substances around the body.
- Pulmonary circuit — circulation between heart and lungs.
- Systemic circuit — circulation between heart and body tissues.
- Atria (singular: atrium) — upper chambers of the heart.
- Ventricles — lower chambers of the heart.
- Atrioventricular valves — valves between atria and ventricles ensuring one-way blood flow.
- Vena cava — large vein bringing deoxygenated blood to the heart.
- Pulmonary artery — vessel carrying blood from heart to lungs.
- Pulmonary vein — vessel carrying blood from lungs to heart.
- Aorta — largest artery, carrying blood from heart to body.
- Coronary arteries — arteries supplying oxygenated blood to the heart muscle.
Action Items / Next Steps
- Review heart diagrams and practice labeling chambers and major vessels.
- Prepare for upcoming lessons on blood and blood vessels.