Overview
This lecture explains the anatomy and function of the human heart, focusing on the flow of blood through its chambers, valves, and vessels.
Structure and Function of the Heart
- The heart is a muscular organ that acts as a pump for blood circulation.
- It begins beating around eight weeks of fetal development and continues until death.
- Blood returns to the heart from the body through veins and is pumped out via arteries.
Blood Flow Pathway Through the Heart
- Blood from the upper body (arms, head) enters the heart through the superior vena cava.
- Blood from the lower body (legs, abdomen) enters via the inferior vena cava.
- Both these major veins deliver blood into the right atrium (first heart chamber).
- Blood flows from the right atrium through the tricuspid valve into the right ventricle (second chamber).
- The right ventricle pumps blood through the pulmonary valve into the pulmonary arteries, leading to the lungs.
Oxygenation in the Lungs
- Blood in the pulmonary arteries is low in oxygen (deoxygenated) and high in carbon dioxide.
- In the lungs, blood releases carbon dioxide and picks up oxygen.
Return to the Heart and Systemic Circulation
- Oxygen-rich blood returns to the left atrium (third chamber) via pulmonary veins.
- Blood passes through the mitral valve into the left ventricle (fourth chamber).
- The left ventricle pumps blood through the aortic valve into the aorta.
- The aorta distributes oxygenated blood to the rest of the body.
Heart Valves and Their Functions
- Valves ensure blood flows in only one direction and prevent backflow:
- Tricuspid valve (right atrium to right ventricle)
- Pulmonary valve (right ventricle to pulmonary arteries)
- Mitral valve (left atrium to left ventricle)
- Aortic valve (left ventricle to aorta)
Key Terms & Definitions
- Vein — blood vessel carrying blood toward the heart.
- Artery — blood vessel carrying blood away from the heart.
- Atrium — one of the two upper chambers of the heart.
- Ventricle — one of the two lower chambers of the heart.
- Tricuspid valve — valve between right atrium and right ventricle.
- Pulmonary valve — valve between right ventricle and pulmonary artery.
- Mitral valve — valve between left atrium and left ventricle.
- Aortic valve — valve between left ventricle and aorta.
- Aorta — main artery carrying blood from the heart to the body.
- Pulmonary artery — artery carrying blood from the heart to the lungs.
Action Items / Next Steps
- Review diagrams of heart chambers, valves, and major vessels.
- Practice tracing the path of blood through the heart and lungs.