Circulatory System

Blood can be broken down into two parts, solid and liquid. The liquid portion of the blood is a straw-colored fluid called plasma and is composed of water and dissolved materials. The dissolved materials fall into several groups: proteins, minerals, foods, and wastes. The proteins include such things as clotting factors, antibodies, and albumin, a protein that is identical to the one that takes up the white of an egg.

The solid portion of the blood can be broken into three groups: Red blood cells, or erythrocytes (erythor = red , cyte-cell); white blood cells, or leukocytes (leuko =white, cyte=cell) and platelets.

Erythrocytes are specialized red cells made to carry oxygen from the lungs to the cells of the body and to return carbon dioxide to be exhaled. Red blood cells are produced in the red bone marrow found at the ends of some of the bones in the body. When red cells are first produced they have a nucleus. This nucleus soon disintegrates causing the erythrocytes to be concave on each side. Since mature red blood cells do not contain a nucleus, more room is available for the red pigment called hemoglobin. Hemoglobin is composed of a protein with iron and is able to pick up oxygen because of the iron atom. The oxygen released at the cells in exchange for the waste product carbon dioxide.

Sometimes people get a condition called anemia in which the amount of erythrocytes in their blood is decreased, thus making it more difficult for the body to supply the cells with enough oxygen. Anemia is sometimes caused by an iron deficiency in the person's diet.

Another condition which has the same effect is a genetic condition called sickle cell anemia and is found predominately in African-Americans. With sickle cell anemia the erythrocytes of the afflicted person can "sickle," or become curve shaped, in such a way as to decrease the ability of the cell to carry oxygen to the body.

Leukocytes, or white blood cells, is the second solid part of the blood. The primary function of these cells is to defend the body against disease. When a particle of materiel foreign to your body enters, the leukocytes can leave the capillaries and "eat" the bacteria or some other particle by a process call phagocytosis. Sometimes so many bacteria are eaten that the leukocytes dies. Many dead leukocytes mixed with plasma and bacteria form pus.

In two other ways white blood cells differ from the red blood cells: (1) leukocytes have a nucleus, sometimes with several lobes, and (2) leukocytes do not contain hemoglobin.

Leukocytes are produced in the lymph glands and the red bone marrow. When cancer cells form in the tissues that grow the leukocytes, a condition called Leukemia develops. Leukemia is most common in children.

Platelets are the third solid component of the blood which contain materials responsible for blood clotting. Platelets are bits of protoplasm broken from large cells made in the bone marrow. The platelets burst open when a cut ruptures a blood vessel. When platelets burst, a substance call thromboplastin is released which, in the presence of calcium, reacts with another substance call prothrombin to form thrombin.


thromboplastin +prothrombin + calcium = thrombin

Thrombin then reacts with a protein called fibrinogen, already in the blood stream and changes fibrinogen into fibrin, a substance which is made up of many tiny threads.

thrombin + fibrinogen = fibrin (which forms the clot)

Blood cells get caught in this maze of fibers formed by the fibrin and form what we call a "clot." A bruise is an example of a clot where blood vessels were broken from an impact against the tissue without cutting the skin If blood did not clot, one could bleed to death when he was cut. A condition in which people are unable to form blood clots when cut is called hemophilia, or bleeder's disease. Hemophilia is inherited and was common in Queen Victoria's family in England.

Organs which serve as blood reservoirs or storage areas are the liver and the spleen. When one bleeds internally or exercises strenuously, these organs contribute more blood to the circulation system. The Bible tells us in Leviticus 17:11 and 14 "life of all flesh" is identified with it's blood. Jesus had to shed His blood for our sins because sin brings forth death. If He had not died in our place, we would have to bear the penalty of death ourselves, and the penalty is eternal separation from God.



-Taken from my Science book by Alpha Omega Publications.

I hope I haven't bored you to tears. :) I found this interesting though. :)