Human Heart: The Incredible Pump
General Overview
- The human heart is often called the hardest working organ in the body.
- Functions as a pump that starts at approximately 8 weeks of fetal development and continues until death.
External and Internal Structure
- External View: Shows the heart with vessels entering and leaving.
- Internal View: A diagram is used to follow the path of blood through the heart.
Circulatory Pathway
Blood Entering the Heart
- Blood returns from the body to the heart via veins.
- Veins from arms and head converge into the superior vena cava entering the top of the heart.
- Veins from legs and lower body converge into the inferior vena cava joining the heart.
Heart Chambers and Valves
- Right Atrium
- Blood enters from the superior and inferior vena cavae.
- Right Ventricle
- Blood passes from the right atrium through the tricuspid valve.
- The tricuspid valve has three flaps, preventing backflow.
- Blood exits the right ventricle through the pulmonary valve.
- Lungs
- Blood travels from the heart to the lungs via the right and left pulmonary arteries.
- Blood picks up oxygen (O2) and releases carbon dioxide (CO2) in the lungs.
- Blood changes from deoxygenated (blue) to oxygenated (red).
- Left Atrium
- Oxygenated blood returns to the heart from the lungs.
- Left Ventricle
- Blood passes from the left atrium through the mitral valve.
- Exits through the aortic valve into the aorta.
Major Vessels
- Aorta: Largest artery that distributes oxygenated blood to the body.
- Pulmonary Arteries: Carry deoxygenated blood from the heart to the lungs.
Function of Valves
- Ensure unidirectional blood flow.
- Prevent backward blood flow.
- Tricuspid Valve: Between right atrium and right ventricle.
- Pulmonary Valve: Between right ventricle and pulmonary arteries.
- Mitral Valve: Between left atrium and left ventricle.
- Aortic Valve: Between left ventricle and aorta.
Summary of Blood Flow
- Blood flows from the body to the right atrium.
- Moves to the right ventricle, then to the lungs via pulmonary arteries.
- Returns oxygenated to the left atrium.
- Moves to the left ventricle, exits via aorta to the rest of the body.
This cycle occurs continuously, ensuring blood is delivered throughout the body and supporting cellular functions.