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Composition and Characterisitcs of Blood
The blood is composed of formed elements suspended in a liquid plasma.
Blood cells are produced in the bone marrow of skeletal bones through a process called hematopoiesis the process in which blood cells are formed and matured .
The blood makes up about 8% of the total adult weight and has a pH of 7.35-7.45.
Red blood cells (RBCs) or erythrocytes make up 41% of the total blood.
They are biconcave in shape, without a nucleus, have a life span of 100-120 days, and contain the molecule, hemoglobin the protein molecule in red blood cells that carries oxygen (see RBC image below)
The hemoglobin (Hgb) molecule is a protein molecule with 4 iron (Fe) atoms. Oxygen (O) binds to these Fe atoms. (see Hgb Image on next slide showing Fe atoms in yellow). Interesting FactEach RBC has 250 million of Hgb molecules with each molecule carrying 4 oxygen atoms for a total of 1 billion oxygen atoms per RBC. Pretty amazing! !
White blood cells (WBs) or leukocytes make up about 4% of the total blood. They are grouped into 5 main types with each type having a specific role in the body’s defense.
Platelets, or thrombocytes, are cellular fragments and make up a very small percentage (0.01%) of the blood, but are crucial in stopping bleeding at damaged sites.
Plasma makes up 55% of the blood and is the liquid portion that the formed elements are suspended within as blood circulates through the body. Plasma is 92% water, yellow in color, and contains dissolved proteins such as antibodiesblood protein produced in response to a specific antigen/part of immunity and albumin most abundant plasma protein, made in the liver, important factor in regulating the exchange of water between the plasma and the space between the cells .
Check your understanding:
Which of the following statements about blood is true?
a. Blood is about 92 percent water.
b. Blood is maintained at a pH of 7.55.
c. Blood is composed of only red blood cells.
d. Hemoglobin is found in white blood cells.
Answer: Blood is about 92 percent water.
What molecule is found inside RBCs that is composed of Fe and carries oxygen?
Answer: Hemoglobin
What is the process of blood cell formation occurring in the bone marrow?
Answer: Hematopoiesis
