The given table shows some of the functions of different components of the blood. State the correct component for each function. Component one, clotting blood; component two, targeting and destroying pathogens; component three, carrying oxygen; and component four, transporting waste substances and nutrients.
Let’s start with an overview of the blood and its components. Here you can see a blood vessel and all the key components of the blood: platelets; red blood cells, or erythrocytes; plasma; and white blood cells. Now, let’s study each component in more detail, starting with platelets.
Platelets are fragments of cells around two to three micrometers in diameter. When a blood vessel wall is damaged, platelets adhere to the exposed collagen and become activated. They release clotting factors and other substances that make nearby platelets sticky. The platelets form a plug to prevent blood loss. Platelets also activate further proteins leading to blood clotting. We now have enough information to identify component one with the function of clotting blood. Component one is platelets.
Let’s move on to the next component in our blood vessel, the red blood cell, or erythrocyte. Red blood cells are the most numerous type of cell in the body. There are around five billion per millimeter of blood. Red blood cells are highly specialized for their role of carrying oxygen around the body. They are shaped like a biconcave disc. The prefix bi- means two, and concave means curved inwards. As you can see from the diagram, the upper and lower surface of the red blood cell are curved inwards. This provides a large surface-area-to-volume ratio, making it easier for oxygen to diffuse into the cell.
Red blood cells are packed with a protein called hemoglobin. Hemoglobin contains iron, which binds to oxygen so that it can be transported around the body and delivered to cells for use in respiration. We can now identify component three with the function of carrying oxygen as red blood cells.
Let’s move on to the next component, plasma. Plasma makes up more than half of the volume of the blood. It is a yellow liquid, 90 percent of which is made up of water. The function of the plasma is to carry blood cells, nutrients like glucose, waste products like urea, hormones, and other essential materials like enzymes and antibodies throughout the body within the blood vessels. We can now identify component four. Plasma transports waste substances and nutrients.
The final component in our blood vessel is the white blood cell. White blood cells have the important role of protecting us from infection. Harmful microorganisms and other biological agents are called pathogens, and white blood cells protect us by targeting pathogens in different ways. Phagocytes are white blood cells which surround and engulf pathogens. Then, they digest them. Another type of white blood cell is called a lymphocyte. One specific type of lymphocyte produces antibodies. Antibodies are specific for particular pathogens, which they target and destroy. We can now identify our final component. We have just seen how white blood cells target and destroy pathogens, so component two is white blood cells.
We have now identified each of the four components. Component one is platelets with the function of clotting blood; component two, white blood cells with the function of targeting and destroying pathogens; component three, red blood cells with the function of carrying oxygen; and component four is plasma with the function of transporting waste substances and nutrients.