Activity 4.1.1: Path of Blood in the Heart

Basic Traffic Pattern of Blood Flow

1. Oxygen-poor (deoxygenated) blood flows from the body into the right atrium. 2. Blood flows through the right atrium into the right ventricle. 3. The right ventricle pumps the blood to the lungs, where the blood releases waste gases and picks up oxygen. 4. The newly oxygen-rich (oxygenated) blood returns to the heart and enters the left atrium. 5. Blood flows through the left atrium into the left ventricle. 6. The left ventricle pumps the oxygen-rich (oxygenated) blood to all parts of the body.

Vessels: Arteries vs. Veins

A series of tubes, or vessels, serve as the highways for the transportation of blood. Generally, arteries are responsible for carrying blood away from the heart and veins are responsible for returning blood to the heart.

Conclusion Question #1: Which chamber of the heart do you think is the most muscular? Explain your reasoning.

After blood flows through the left atrium into the left ventricle, the left ventricle pumps the oxygen-rich blood to all parts of the body. The heart is a relatively small organ, roughly the size of a fist. In general, an adult human is over five feet tall and at least one-hundred pounds. Considering the force it must require for the left ventricle to pump and distribute 5.6 liters of blood every twenty seconds throughout the body, from head to toe, against the pull of gravity, the left ventricle stands out to me as the most muscular chamber of the heart.

Anna Garcia's Cardiovascular Health

At the time of her death, Anna's heart stopped beating. The body's pump was no longer able to propel oxygen-rich blood to her tissues and cells.

Conclusion Question #2: A growing fetus has a vessel, the ductus arteriosus, in the heart that connects the pulmonary artery with the aorta and conducts blood directly from the right ventricle to the aorta. Why do you think this vessel closes soon after birth?

During pregnancy, an expectant mother shares a blood supply with the developing fetus. This shared blood supply enables the fetus to uptake nutrients, regulate its temperature, eliminate waste, and to engage in gas exchange. The ductus arteriosus is a structure involved in this process. After birth, the baby has emerged from the mother's womb and ceases to rely upon its mother's body to survive. Because the mother has completed her pregnancy, her body is no longer required to nourish a developing fetus through a shared supply of blood. Therefore, the ductus arteriosus will close quickly after birth.

Conclusion Question #3: In most of the body, the arteries carry oxygenated blood and the veins carry deoxygenated blood. The exception to this pattern is the heart. Explain how and why specific arteries and veins of the heart are different from the pattern seen in the rest of the body.

In most of the body, the arteries carry oxygenated blood and the veins carry deoxygenated blood. Specific arteries and veins of the heart are different from the pattern seen in the rest of the body because the heart must carry out certain functions under higher mechanical pressure. Veins are membranous tubes that have thin walls. Their structure generally makes them unable to withstand the pressure it takes to rapidly pump oxygenated blood throughout the body against the force of gravity. In contrast, arteries are stronger and more durable than veins because they are thick with muscular walls that enable them to flexible enough to cope with the differing force of blood flow by heart contraction. This is why arteries are responsible for distributing oxygenated blood to most of the body. However, inside the heart, the arteries also carry deoxygenated blood as well as oxygenated blood. An artery that carries deoxygenated blood in the heart is the pulmonary artery. This is because a lot of pressure is exerted on the right ventricle in order to circulate deoxygenated blood to the lungs. Only the structure of an artery could withstand the immense pressure put upon it.

Model Representation of Blood Flow

On models, red is traditionally used to represent oxygenated blood and blue is used to represent blood that is oxygen deficient. However, blood is never blue. Deoxygenated blood is dark red which appears blue when viewed under the skin.

The Importance of the Heart

The blood pumped by the heart carries many of the resources necessary for life, including nutrients, oxygen, and water, to the cells. The body's cells must carry out many reactions in order to survive, grow, repair, or replicate. All of these processes require energy, and oxygen is required for cells to obtain energy. Therefore, all cells need a constant supply of oxygenated blood.

The Human Heart

The human heart is an amazing pump. Each beat correlates with the pumping action of the heart as it moves blood through the entire body. The human heart has to pump 5.6 liters (about six quarts) of blood every 20 seconds.

Sides of the Heart: Right Side vs. Left Side

The right side of the heart is involved in pulmonary circulation, which means it moves blood to the lungs to pick up oxygen and brings newly oxygenated blood back to the heart. The left side of the heart is involved in systemic circulation, which means it pumps oxygenated blood to the body and returns deoxygenated blood back to the heart to be pumped back to the lungs for refueling.

Cardiovascular System

The system of the heart and the associated blood vessels.

Conclusion Question #4: Describe the mechanisms in place to prevent the blood from flowing in the wrong direction through the heart.

Throughout the heart, there is a system of valves that prevent blood from flowing in the wrong direction. The valves constitute of subunits called cusps, which are pushed open to allow blood flow and which then close together to seal and prevent backflow. Valves are opened or closed depending on the difference of pressure between specific chambers of the heart.

Conclusion Question #5: Explain what happens to tissues, such as the heart, or the brain, if oxygenated blood is not delivered in a timely manner.

When oxygenated blood is not delivered in a timely manner, metabolism begins to slow down and cease. When metabolism is inhibited due to oxygen depletion, the cells do not generate enough energy to eliminate toxic wastes. As waste products continuously accumulate, cells begin to die from lethal toxicity, damaging tissues.