Transport System

The transport system refers to the transport of blood around the body. The blood can be transported by circulation, which is divided in three groups: Coronary Circulation, Systematic Circulation, and Pulmonary Circulation. Coronary Circulation is the one people give more emphasis to because it describes how the blood is pumped to the rest of the body by the heart. The heart as we might know is a myogenic muscle, which means it's a muscle that contracts. So, what happens is that the blood from the body enters the vena cava and goes to the right atrium. Once the blood fills up the atrium, a valve called the atrio-ventricular valve opens and lets the blood flow to the right ventricle. Then, after there is no more space for blood in the ventricle, another valve called the semi-lunar valve opens and lets the blood flow through the pulmonary artery, which is an artery that will lead the blood to pass through the lungs. After going through the lungs, the blood will enter the heart again through the pulmonary veins. Then, it will go through the left atrium, the left atrio-ventricular valve, through the left ventricle, and then through the left semi-lunar valve. Finally, the blood will again go to the rest of the body exiting through the aorta.

Every time blood travels through the heart, it creates a heartbeat. The heartbeat can be influenced by chemicals, such as adrenaline. When you are exercising and there is little oxygen and a lot of CO2 in your body, the medulla (part of brain) sends a signal to the SA Node, or the peacemaker to increase heartbeat so that blood with oxygen can travel to your lungs faster. The SA Node then sends a signal to the AV Node and it results in the contraction of the muscle.

So, we have the transport of the blood through our body, and we have a heartbeat. But why is it important to have blood in our body? Well, first of all, the blood carries the oxygen and nutrients necessary for our body. Blood is made out of plasma, which is a fluid that contains water, hormones, and CO2. There are two different types of blood cells: white blood cells and red blood cells. The white blood cells are for body defense, which is why they contain platelets and antibodies. The red blood cells, on the other hand, contain hemoglobin. Hemoglobin is rich in iron, which not only gives the red color to the blood but also helps to carry oxygen through the body.

Finally, we should be able to understand how blood vessels help to carry the blood in all of the processes mentioned above. The most important vessels are arteries, veins, and capillaries. Arteries have a thick muscle layer to ensure high blood pressure and they transport mainly oxygen. Veins have thin flexible walls to ensure low blood pressure and they carry mainly CO2. Valves are also a type of vein which prevent the back flow of blood. We saw two examples of valves in the heart: the atrio-ventricular and the semi-lunar valves. And lastly, the capillaries have a one-cell-thick wall and their job is to connect veins and arteries.