Circulatory System Organs

circulatory systemOur body is in constant homeostasis, which is pumping the blood through circulatory system from the heart to the vessels and back. This is a circle which happens non-stop and keeps the organs healthy by getting its needed nutrients and oxygen and filtering the blood. The blood carries all the ingredients inside and flows rapidly through our system. It keeps our temperature constant as well as the blood pH. Let’s talk about the circulatory organs and its parts.

Circulatory System Organs

The circulatory or cardiovascular system is made out of the heart and the vessels which include the veins and the arteries. The fluid which runs down the hollow space of this system is blood. Another important part which has a crucial role in circulation and oxidation are lungs. They are the place where the oxygen goes in and the carbon dioxide goes out of the system. This keeps our pH and gets the necessary oxygen to the organs.

The Heart

The main organ which is a muscle pump is located inside our chest, in the part called mediastinum. It stands a bit to the left behind the sternum and it is surrounded by the lungs and the rib cage. It has 4 different chambers which are left ventricle, left atrium and right ventricle and right atrium. This is often referred to as the left and the right heart where the division comes from the properties of the blood where the right heart has deoxygenated blood and the left side has oxygenated blood. The blood from the body comes to the right atrium, goes into the right ventricle and into the lungs where it gets its oxygen. This is called the small circulation. The big circulation goes from the left atrium into the left ventricle and onto aorta which leads the blood to the system via arteries. The veins gather the blood and the system goes again into the right atrium. This happens every single second of our life.

The Vessels

As we mentioned above, there are two types of blood vessels, arteries and veins and also one add-on which are lymph vessels that are together with the lymphatic system which filters the blood and gets the immune cells and protection. The arteries and veins go from the biggest ones to the smaller ones such as venule and capillaries. The oxygen happens on the level of capillaries where the membrane is thin and the nutrients easily transfer from one chamber to another. The blood vessels are crucial since they carry all the blood from one space to another. If there is a barrier in a form of thrombus or something gets in the way of the blood flow inside of the lumen, it gets harder for the blood to get to its destination and this often leads to diseases such as infarct and stroke. The size of the lumen of the blood vessels turns when going through the body, starting at the heart with aorta to the smallest ones at the periphery. The vessels are built out of several layers where the inner layer is made out of squamous epithelium which is lined with a muscular layer at the outer part. This type of layer prevents the clot from happening inside of the vessels.

The Blood

The third part of the circulatory system is certainly the blood. This is the thick fluid which goes to every single part of our body and has a network of vessels which carries it. It is made out of cells, hormones, water, nutrients, oxygen, other gasses and waste metabolites. The standard quantity of blood in a human body is 5 liters and a young person can have about a gallon of blood.  The blood gets its color from the red blood cells which have hemoglobin. Each of these molecules of hemoglobin has subunits called hemes which give the blood that red color. Inside, there is the iron molecule together tied with oxygen. This carries the blood through the system. Hemochrome is the protein which gives the color and it is responsible for oxygen transport.

Blood Structure. It is made out of cells and plasma.

  • Red Blood Cells. They are responsible for oxygen transport and carbon dioxide release.
  • White Blood Cells. These cells are responsible for the immune system and the body protection which fight the microorganisms and other germs from affecting the body.
  • Platelets. These cells are responsible for blood clotting. This keeps you from bleeding out when you cut yourself or bleed from any other reason. It creates a cork at the location of the injury and helps accumulation of the cells which form a network with fibers and they create a scab.
  • Plasma. This is the fluid where all the cells flow. It makes about a half of blood and it is made inside the liver. It carries all the ingredients and keeps the body warm.

Circulatory System Facts

  • If you would lay all the vessels on the surface, they would take up to 60,000 miles. Which is more surprising is, the capillaries, which are the smallest of all the vessels, would take up to 80% of the length. The Earth is about 25,000 in the scope, so that means that we could wrap 2.5 times around the Earth!
  • The smallest vessels are capillaries which are approximately 8 microns in diameter. The red blood cells are about the same size so they have to move one by one through capillaries and the vessels force the cells to distort their shape in order to get through.
  • Although you might think this is odd, but bigger bodies have a slower heart rate. The human heart has a rate approximately 75 per minute. The whales which are much larger than human have only 5 beats per minute.


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