Overview
This lesson explains the structure and function of the human heart, focusing on how it pumps blood in a double circulatory system to supply oxygen and nutrients to the body and remove waste.
Structure of the Heart
- The heart is a muscular organ that pumps blood around the body.
- It has four chambers: two atria (upper chambers) and two ventricles (lower chambers).
- Blood enters the heart through the atria and exits via the ventricles.
- The right atrium receives deoxygenated blood from the body through the vena cavae.
- The left atrium receives oxygenated blood from the lungs through the pulmonary veins.
- Heart valves prevent blood from flowing backward into the atria.
Pathway of Blood Through the Heart
- Deoxygenated blood enters the right atrium from the body.
- Blood moves from the right atrium to the right ventricle, which pumps it to the lungs via the pulmonary artery.
- Oxygenated blood returns from the lungs to the left atrium.
- Blood passes from the left atrium to the left ventricle, which pumps it to the body through the aorta.
Double Circulatory System
- The heart pumps blood through two circuits: pulmonary (to the lungs) and systemic (to the body).
- Pulmonary circulation transfers blood to the lungs for oxygenation and removal of carbon dioxide.
- Systemic circulation delivers oxygen and nutrients to tissues and removes wastes.
- Blood passes through the heart twice per full body circuit, once through each side.
- Systemic circulation is under high pressure to reach the whole body; pulmonary circulation is lower pressure for efficient gas exchange.
Key Terms & Definitions
- Atrium — Upper heart chamber receiving blood from veins.
- Ventricle — Lower heart chamber pumping blood into arteries.
- Vena cava — Large vein carrying deoxygenated blood to the right atrium.
- Pulmonary vein — Vein carrying oxygenated blood from lungs to left atrium.
- Aorta — Main artery carrying oxygenated blood from heart to body.
- Pulmonary artery — Artery carrying deoxygenated blood from heart to lungs.
- Double circulatory system — Blood passes through the heart twice in each complete body circuit.
- Pulmonary circulation — Right side of heart, lungs, and connecting vessels.
- Systemic circulation — Left side of heart, body (except lungs), and connecting vessels.
Action Items / Next Steps
- Review diagrams showing the flow of blood through the heart and the double circulatory system.
- Study the functions of each heart chamber and the associated blood vessels.