Question

Trace the path of blood through the heart, including chambers, valves, and vessels the blood travels through. (pages \(96-97\) )

Short answer

The blood flows through the heart as follows: Deoxygenated blood enters the right atrium through the superior and inferior vena cava, passes through the right atrioventricular (tricuspid) valve into the right ventricle, and is then pumped through the pulmonary valve into the pulmonary artery. After getting oxygenated in the lungs, the blood flows through the pulmonary veins into the left atrium, passes through the left atrioventricular (bicuspid or mitral) valve into the left ventricle, and is finally pumped through the aortic valve into the aorta to be distributed throughout the body.

Step-by-step solution

Right atrium

The blood, which is low in oxygen and high in carbon dioxide after delivering oxygen to the body, returns to the heart through two large veins called the superior and inferior vena cava. These veins carry the deoxygenated blood into the right atrium, which is the first chamber of the heart in this journey. Step 2: Flow through the right atrioventricular (tricuspid) valve

Right atrioventricular (tricuspid) valve

When the right atrium contracts, the blood is pushed through the right atrioventricular (tricuspid) valve. This valve prevents blood from flowing back into the atrium once it moves into the next chamber - the right ventricle. Step 3: Flow into the right ventricle

Right ventricle

After passing through the right atrioventricular valve, the blood flows into the right ventricle. The right ventricle is responsible for pumping the blood to the lungs, where it will receive oxygen and exchange carbon dioxide. Step 4: Flow through the pulmonary valve

Pulmonary valve

When the right ventricle contracts, it pushes the deoxygenated blood through the pulmonary valve. This valve prevents blood from flowing back into the ventricle once it moves into the pulmonary artery. Step 5: Flow into the pulmonary artery

Pulmonary artery

The deoxygenated blood leaves the heart for the first time through the pulmonary artery. This is the only artery carrying deoxygenated blood. The blood in the pulmonary artery will travel to the lungs and exchange carbon dioxide for oxygen. Step 6: Flow into the pulmonary veins

Pulmonary veins

Once the blood is oxygenated in the lungs, it returns to the heart through the pulmonary veins. These veins carry the oxygenated blood into the left atrium, which is the third chamber of the heart in this journey. Step 7: Flow through the left atrioventricular (bicuspid or mitral) valve

Left atrioventricular (bicuspid or mitral) valve

When the left atrium contracts, the oxygen-rich blood is pushed through the left atrioventricular (bicuspid or mitral) valve. This valve prevents the backflow of blood into the atrium once it moves into the left ventricle. Step 8: Flow into the left ventricle

Left ventricle

After passing through the left atrioventricular valve, the blood flows into the left ventricle, which is the last chamber the blood will be in before leaving the heart again. Step 9: Flow through the aortic valve

Aortic valve

When the left ventricle contracts, it pushes the oxygen-rich blood through the aortic valve into the aorta. This valve ensures that blood doesn't flow back into the left ventricle once it moves into the aorta. Step 10: Flow into the aorta

Aorta

The oxygenated blood flows into the aorta, which is the largest artery in the body. The aorta branches into various arteries that carry the oxygen-rich blood throughout the body, providing oxygen and nutrients to cells and tissues. The given steps provide a detailed explanation of blood flow through the heart, including the chambers, valves, and vessels involved in the process.

Key concepts

Right Atrium

The right atrium is a crucial component in the circulatory pathway of the heart and serves as the initial receiving chamber for deoxygenated blood coming from the body. Once the oxygen has been used by body tissues, the now deoxygenated blood is carried back to the heart via the superior and inferior vena cava. The right atrium acts as a reservoir; when it is filled with blood, it contracts, pushing blood through the tricuspid valve into the next chamber.

Understanding the right atrium's role is essential as it is the gateway for deoxygenated blood to enter the heart's circuit, ensuring a seamless flow towards the lungs for oxygenation. It's also worth noting that the right atrium not only receives blood from the systemic circuit but also from the heart itself, through the coronary sinus.

Heart Valves

Heart valves play a pivotal role in maintaining the one-way flow of blood through the heart. They open and close with each heartbeat, ensuring that blood moves forward through the chambers of the heart and preventing backflow. There are four main valves in the heart: the tricuspid, pulmonary, mitral, and aortic valves. Each of these valves corresponds to a transition point between different areas of the heart.

For example, the tricuspid valve stands between the right atrium and right ventricle, and the pulmonary valve leads to the pulmonary artery from the right ventricle. The mitral valve, on the other hand, is the gateway from the left atrium to the left ventricle, and the aortic valve controls the exit of oxygen-rich blood from the left ventricle into the aorta. It's important to stress that the proper functioning of these valves is essential for efficient blood circulation and overall cardiac health.

Pulmonary Circulation

Pulmonary circulation is the passage of blood from the heart to the lungs and back to the heart again. This circuit is particularly important for oxygenating the blood. Once the right ventricle contracts, deoxygenated blood is pushed through the pulmonary valve into the pulmonary artery, the only artery that carries deoxygenated blood, and travels to the lungs. Here, carbon dioxide is exchanged for oxygen.

After the blood is oxygenated, it returns to the heart through the pulmonary veins - the only veins that carry oxygenated blood - and enters the left atrium. This freshly oxygenated blood is then prepared to be distributed throughout the body via systemic circulation. The pulmonary circuit is critical because it recharges the blood with oxygen, which is vital for survival and function of all body tissues.