Path of Blood in the Heart and Blood Composition
The Heart is a double pump. The right side of the heart sends blood through the lungs. The left side sends blood throughout the body. Blood low in oxygen and high in carbon dioxide enters the right atrium from the largest veins in the body, the superior vena cava and the inferior vena cava. The right atrium contracts and forces the blood through the valve into the right ventricle. The right ventricle pumps the blood into the pulmonary arteries which take blood to the lungs. From the lungs, blood high in oxygen and low in carbon dioxide enters the left atrium from the pulmonary veins. The left atrium contracts and forces the blood through the valve into the left ventricle. The left ventricle pumps it into the largest artery in the body, the aorta. The aorta sends blood to all tissues in the body.
Blood Vessels
Blood enters and leaves the heart through a number of blood vessels. These vessels make up a closed transport system that carries blood throughout the body. They are the pathways through which the blood carries food and oxygen to all parts of the body. They are made up of the arteries, veins and capillaries.
Arteries are thick-walled blood vessels that carry blood away from the heart. These vessels carry blood rich in food and oxygen. Each ventricle is connected to a large artery. The aorta is the largest artery leading from the left ventricle. With each heartbeat, ventricles pump blood through the arteries. As blood surges through, the artery wall stretches, then contracts. This contraction helps move blood through the body.
The pumping of blood produces blood pressure. Blood pressure is the “push” of blood against the walls of a blood vessel.
Large arteries branch into smaller blood vessels. These vessels keep branching until they form capillaries. Capillaries are the smallest blood vessels in the body which connect an artery to a vein. Their walls are only one cell thick. One blood cell can pass through at a time on these walls. Capillaries supply the cells with food and oxygen.
Digested food, oxygen, and other kinds of matter leave the blood to pass on into the cells. At the same time, waste matter moves out from the blood into the capillaries. It is in the capillaries where distribution, absorption and assimilation of food, and excretion of waste products take place. From the capillaries, blood flows into the veins.
Veins are blood vessels that carry blood back to the heart. The largest vein is the vena cava. The thin walls of veins do not stretch like artery walls.
Veins have parts called valves that keep the blood from flowing backwards. Blood flows in only one direction in the veins.
Blood is the third main part of the circulatory system. It is the red fluid that continually flows through the blood vessels. It circulates through the heart, arteries, veins, and capillaries, carrying food and oxygen to every part of the body. It is called the “red river of life” because it transports important materials, or substances, which the body needs to maintain life and health.
Composition of Blood
Blood is a complex substance made up of different kinds of cells, particles of protein, and dissolved salts and nutrients. It contains solid particles: red blood cells, white blood cells, platelets, which make up almost one half of the blood. It also has a liquid part called plasma which make up a little more than one half of the blood.
Red Blood Cells (RBC)
· -Oxygen is carried in your body by red blood cells, the first solid part of the blood.
· -RBC contains hemoglobin, a protein that attracts and holds oxygen molecules. The hemoglobin contains iron and makes blood red.
-· -RBC looks something like a doughnut without a hole. A single drop of blood contains about five million red blood cells.
· -RBCs are made in the bone marrow. These cells live for about 120 days after they enter the bloodstream. The bone marrow continuously makes new blood cells to replace dead cells.
White Blood Cells (WBC)
· -A whole army of cells in the blood protects your body against diseases. These are the WBC, the second solid part of the blood.
· -WBCs fight harmful germs that may enter your body through a cut on your skin of through food, water, or air that is not clean.
· -Large numbers of WBCs can move quickly to a danger spot.
· -They can change shape as they move about in the blood.
· -They destroy bacteria and other harmful things inside the body.
· -They surround and digest the bacteria.
· -WBCs are much larger than red cells. There are only about one or two white cells among every thousand red cells.
· White cells began their development also in the bone marrow.
Platelets
· -Platelets are the third solid part of the blood.
· -They are smaller than the RBCs.
· -They are not whole cells. They are just part of cells that control bleeding.
· -They help you blood clot when you have a cut or wound.
o If you have accidentally cut your skin, blood flows out. This is what you call bleeding. But soon, the bleeding stops. The tiny blood platelets start to stick together. They cause the blood to thicken and clot. Without platelets, a person could bleed to death from a cut.
Plasma
· -Red and white blood cells get around in your body through the yellowish liquid part of the blood called plasma.
· -Plasma has many kinds of matter in it, but it is mostly made of water.
· -It contains important salts that help your muscles function well.
· -It also carries food that has been broken down or digested.
Category: Circulatory System
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