Download HOW THE HUMAN BODY PRODUCES BLOOD CELLS

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HOW THE HUMAN BODY PRODUCES BLOOD CELLS
The human body consists of a number of complex systems, including the circulatory
system. Also known as the cardiovascular system, the circulatory system employs a fluid known
as blood to carry nutrients and oxygen throughout the body and take waste away from other
cells. The human body produces its blood, a substance needed for survival, through
hematopoiesis, which literally means “to make blood.”
Main Components of Blood. The main components of blood are plasma, red blood
cells, white blood cells, and platelets. (See Figure 1).
Plasma, which is mostly water, carries the red blood
cells, white blood cells, platelets, and many other
substances throughout the body. Red blood cells
(“RBCs”) distribute oxygen from the lungs to the rest
of the body. White blood cells (“WBCs”) fight
Figure 1. Main Components of Blood.
infection. Lastly, platelets help blood to clot after an
injury.
Formation of Blood Cells. Blood cells form in bone marrow, although other parts of the
body contribute to the blood-making process.
The human body contains both red and yellow marrow, a jelly-like substance found in
bones. RBCs, WBCs, and platelets form from pluripotential hematopoietic stem cells located in
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red bone marrow. (See Figure 2.) During emergencies involving sudden blood loss, yellow bone
marrow also creates blood cells to meet the body’s needs.
In children, the red bone
marrow in all bones forms blood cells.
As human beings age, however, red
bone marrow decreases and only
certain bones produce blood cells.
Under conditions like low
oxygen content, loss of blood or
anemia, sudden loss of RBCs, the
Figure 2. Cells Produced By Bone Marrow.
kidneys secrete erythropoietin, a
hormone important to blood production. This hormone stimulates the red bone marrow to
produce more RBCs and causes the RBCs to mature more quickly to meet the body’s demands.
The human body alters the blood-making process in response to emergencies. When
faced with infection or bacteria, red bone marrow begins to produce more WBCs. Platelet
creation increases when sudden blood loss occurs.
Once blood cells are formed, they enter the bloodstream by passing from the bone
marrow to the blood that is traveling through the bones. The cells then circulate through the
body, performing their specific duties.
Blood cells eventually die. (See
Figure 3.) A healthy human body assesses
its need for blood cells and stimulates cell
production to meet demand.
Figure 3. Life Span of Blood Cells
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SOURCES:
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“Circulatory System.” IHW 2005. n.p. March 2005. Web.
<http://www.biologymad.com/resources/Circulatory%20System%20Revision.pdf>
Panchbhavi, Vinod K. M.D., FRCS, FACS. “Bone Marrow Anatomy.” Medscape.com. 22
August 2013. Web. <http://emedicine.medscape.com/article/1968326overview#aw2aab6b4>
“What is the difference between red bone marrow and yellow bone marrow.” n.p. Web.
http://www.preservearticles.com/201101133203/difference-between-red-bone-marrowand-yellow-bone-marrow.html
Wilson, Sue. “How is Blood Produced.” Pbs.org. The Educational Broadcasting Corporation.
2002. Web.<http://www.pbs.org/wnet/redgold/journey/phase1.html>
Wilson, Sue. “What is Blood Made Of.” Pbs.org. The Educational Broadcasting Corporation.
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