## 2.3 FLOW OF BLOOD THROUGH THE HEART This section details the pathway blood takes through the four chambers of the heart, highlighting the separation of oxygenated and deoxygenated blood and the role of the heart as a double pump for pulmonary and systemic circulation. ### 1. Pulmonary Circulation (Right Side of the Heart) This circuit carries **deoxygenated blood** from the body to the lungs to get oxygenated. * **Step 1: Blood Enters the Right Atrium** * The **Superior Vena Cava** (from the upper body) and **Inferior Vena Cava** (from the lower body) deliver deoxygenated blood into the **right atrium**. * **Step 2: Blood Enters the Right Ventricle** * The right atrium contracts, pushing blood through the **tricuspid valve** into the **right ventricle**. * **Step 3: Blood is Pumped to the Lungs** * The right ventricle contracts, sending the blood through the **pulmonary semilunar valve** into the **pulmonary trunk**, which splits into two **pulmonary arteries** leading to the lungs. ### 2. Systemic Circulation (Left Side of the Heart) This circuit carries **oxygenated blood** from the lungs to the rest of the body. * **Step 1: Blood Enters the Left Atrium** * Four **pulmonary veins** carry newly oxygenated blood from the lungs into the **left atrium**. * **Step 2: Blood Enters the Left Ventricle** * The left atrium contracts, pushing blood through the **bicuspid valve** (also known as the *mitral valve*) into the **left ventricle**. * **Step 3: Blood is Pumped to the Body** * The powerful left ventricle contracts, forcing blood through the **aortic semilunar valve** into the **aorta**, the body's largest artery, which distributes it to all body parts. ### The Heart as a Double Pump The heart is considered a *double pump* because its two sides work simultaneously but pump blood to different destinations. * **Right Side Pump:** The **right ventricle** pumps deoxygenated blood to the lungs. * **Left Side Pump:** The **left ventricle** pumps oxygenated blood to the entire body. ### Valve Function and Blood Flow Valves (Tricuspid, Pulmonary, Bicuspid, Aortic) ensure the one-way flow of blood and prevent backflow. The Atrioventricular (AV) valves are anchored by chordae tendineae to prevent them from eversion during the high pressure of ventricular contraction. | Heart Side | Blood Type | Receives Blood From | Pumps Blood To | Main Vessels Involved | | :--- | :--- | :--- | :--- | :--- | | **Right** | Deoxygenated | Body | Lungs | Vena Cavae, Pulmonary Artery | | **Left** | Oxygenated | Lungs | Body | Pulmonary Veins, Aorta | The biological significance of this double circulatory system is that it allows for high-pressure delivery of oxygenated blood to the body's tissues, supporting a higher metabolic rate than would be possible with a single-loop system. ### Related Topics