How Does Human Blood Circulation Work?

Origins of the blood

Deep inside the bones, a soft tissue, known as the bone marrow acts as a factory to produce blood. Blood has three main components: red cells, white cells and platelets. Red cells carry oxygen through the blood and the white cells fight off invading organisms such as viruses and bacteria. The platelets aid the blood in clotting by gathering at the site of a cut with other platelets and tissues, forming a covering over the cut. This later hardens into a scab.

Pulmonary Circulation

Blood transports oxygen from the lungs to the other parts of the body and it brings carbon dioxide to the lungs for removal through exhalation. As carbon dioxide rich blood moves through the veins into the heart via the vena cavae; it flows into the right atrium where it waits until full. The valve separating the right atrium from the right ventricle then opens, letting the blood move through. The right ventricle pumps the blood into the lungs with a strong contraction.

Once in the lungs, the blood moves into the lung's capillaries where it trades its carbon dioxide for oxygen. It returns to the heart through the pulmonary vein and into the left atrium. It waits in the atrium until the valve opens, allowing it to move into the left ventricle. Like the right ventricle the left contracts to push the blood out. Since, leaving the left ventricle the blood must travel throughout the body, the contraction needs to be stronger than that of the right. This pushes the blood out of the ventricle into the aorta, where it moves throughout the body.

Coronary Circulation

As the main mover of blood throughout the body, the heart requires the freshest supply of blood. Coronary arteries surround the heart, like a crown. These arteries branch directly off the aorta and remove carbon dioxide waste from the cells and replace it with oxygen. Damage to the coronary arteries could lead to death to portions of the heart muscle, reducing its function.

Systemic Circulation

Blood exiting the heart from through the aorta moves throughout all of the organ systems. As the largest artery, the aorta resembles the trunk of a tree, all of the smaller arteries and capillaries branch off of it. The heart pumps the blood through these arteries and their smaller branches, the capillaries. Oxygen carried by the red blood cells is traded for carbon dioxide from the body in the capillaries. This blood with carbon dioxide returns to the heart through the veins. Other stops along this path enable the blood to assist in filtering wastes from the body and moving sugar and nutrients. These occur during renal and portal circulation.

As the blood delivers oxygen, it also must carry other wastes from the cells. Known as renal circulation, the blood flows through the kidneys, which filter the waste and excess salt from the blood, producing urea, which the body excretes through urination. Nutrients from food consumes become absorbed by the walls of the small intestine. During portal circulation, the blood takes sugar to the portal vein where it flows into the liver which pulls the sugar from the blood to provide the body with an energy source.

References

• Pulmonary Circulation
• Coronary Circulation
• Systematic Circulation

Resources

• Red Gold, Blood Journey
• Circulatory System