Your body requires oxygen to be able to perform the correct functions. The lungs help with the distribution of this important gas. However, how does the oxygen get to the rest of the body from the aleoli of the lungs? That is one of the roles blood has in our body.

What is Blood?

Blood cells of the body system: Erythrocytes, leukocytes, & platelets
Blood is a bodily fluid that transports oxygen to body cells and removes waste from the same cells. It also helps maintain body temperature and fights invaders to the body. Also, blood can carry other nutrients besides oxygen. This is collected by the small intestine, where the absorption of nutrients occurs. Nutrients diffuse through the villi of the small intestine and into the blood stream.

Blood is produced in the bone marrow of the body. As babies, all of the bone marrow produces blood, but as you get older, blood production is restricted to specific areas of the body, like the spinal vertebrae, ribs, humerus, etc.

The Lymphatic System

Blood flows throughout the body through the lymphatic system, which is a network of blood vessels. These vessels are what transports blood to any area from the body. Blood carries oxygen, but it will run out of the oxygen it carries. To replenish its oxygen supply, veins (a blood vessel with thin tissue walls and valves) transports oxygen-poor blood to the heart. Once the oxygen-poor blood flows through the heart, transported to the lungs to regain oxygen, and flows back to the heart, arteries (blood vessel with thick tissue walls and no valves) takes oxygen-rich blood from the heart to the rest of the body. A third vessel, capillaries, allows nutrients to be absorbed from the blood or to it. This is how blood gains oxygen in the lungs through gas exchange in the respiratory system.

Parts of Blood

Blood is composed of 4 different parts. Each one has a specific function including those listed above. The 4 parts of blood are...

  • Erythrocyte (Red Blood Cell)
  • Leukocyte (White Blood Cell)
  • Platelet
    Photo Graphic of centrifuged blood, which shows the contents of blood seperated.
    Photo Graphic of centrifuged blood, which shows the contents of blood seperated.
  • Plasma

Erythrocyte- This blood cell carries important gases, like oxygen, to other parts of the body. They contain the protein hemoglobin, which allows the cells to be able to carry oxygen. When gas exchange occurs in the lungs between the alveoli and capillaries, the oxygen diffuses into the blood stream and is taken by the erythrocytes. Erythrocytes take up about 44% of blood.

Leukocyte- This is the cell that fights pathogens that invade the body. They can be compared to the cops of the human body. These cells also protect the immune system from any invasion by engulfing any pathogens. When you're sick, there are more white blood cells in your system, mainly because they are fighting pathogens. This battle causes many cold symptoms, like fever and congestion. There aren't many white blood cells in the body, 1 white blood cell per 1,000 red blood cells, and takes up only about 1% of blood.

Platelet- This is a fragment of bone marrow cells that helps with blood clotting. Platelets are the reason a small cut eventually stops bleeding. When a cut is created, platelets gather together around the wound. Gradually, they block the gap and becomes part of the skin or vessel. Without platelets, you will continue to bleed, and eventually bleed to death, which is a condition called exsanguination. Platelets make up the 1% of blood with leukocytes.

Plasma- This is the liquid portion of blood that has multiple functions. It is 90% water and 10% trace gases. Functions of plasma include: helping blood cells flow through the body, transport nutrients, maintain body temperature, and regulate blood volume. Plasma takes up most of the blood content by 55%.

When blood is centrifuged, it splits it's contents into different groupings based on density. This is how doctors can tell if there's anything wrong with the blood and be able to treat the problem. In a vial, you will find the erythrocytes at the bottom; the leukocytes and the platelets are found together in the "buffy coat" layer, and on top is the plasma, which should be the most plentiful of the contents in blood.

Blood Parts and Functions Tree Web


Blood Tutorial Quiz

After you read this tutorial, try your skills at this quiz below. Good Luck!!!