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Human Blood


•    Human blood is the fluid circulated by the heart through the human vascular system.

•    There are three cellular components of human blood: red blood cells (r.b.c.), white blood cells (w.b.c.), and platelets.


•    Red blood cells transport oxygen to other cells of the body. Packed with hemoglobin (an iron-bearing protein) and shaped like plump disks with indented centers, red bloods cells are produced in bone marrow and have a life span of about 120 days.

•    White blood cells (purple) protect the body from infection, attacking and destroying foreign particles like dust, pollen, and viruses. Platelets defend the body against excessive blood loss.

•    Platelets (blue) flow freely in the blood in an inactive state; but when an injury is sustained, platelets become sticky to plug the injured area.


Functions of Human Blood


Blood performs many important functions within the body including:

•    Supply of oxygen to tissues (bound to hemoglobin, which is carried in red cells)
•    Supply of nutrients such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins (e.g., blood lipids))
•    Removal of waste such as carbon dioxide, urea, and lactic acid
•    Immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies
•    Coagulation, which is one part of the body's self-repair mechanism (blood clotting after an open wound in order to stop bleeding)
•    Messenger functions, including the transport of hormones and the signaling of tissue damage
•    Regulation of body pH
•    Regulation of core body temperature
•    Hydraulic functions


Constitution of normal blood


Parameter
Value
Hematocrit
45 ± 7 (38–52%) for males
42 ± 5 (37–47%) for females
pH
7.35–7.45
base excess
−3 to +3
PO2
10–13 kPa (80–100 mm Hg)
PCO2
4.8–5.8 kPa (35–45 mm Hg)
HCO3
21–27 mM
Oxygen saturation
Oxygenated: 98–99%
Deoxygenated: 75%














The discovery of blood groups


•    Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 blood group (in 1901) and Rh blood group (in 1937).
•    Karl Landsteiner's work made it possible to determine blood groups and thus paved the way for blood transfusions to be carried out safely.
•    For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.

AB0 blood grouping system


According to the AB0 blood group system there are four different kinds of blood groups: A, B, AB or 0 (null).
   

•    Blood group A - If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma.
•    Blood group B - If you belong to the blood group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma.
•    Blood group AB - If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma.
•    Blood group 0 - If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma.

Rh factor blood grouping system


Many people also have a so called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.


Blood group notation


According to above blood grouping systems, you can belong to either of following 8 blood groups:


A Rh+
B Rh+
AB Rh+
0 Rh+
A Rh-
B Rh-
AB Rh-
0 Rh-


People with blood group 0 Rh - are called "universal donors" and people with blood group AB Rh+ are called "universal receivers."

Rh+ blood can never be given to someone with Rh - blood, but the other way around works. For example, 0 Rh+ blood can not be given to someone with the blood type AB Rh -.


Blood Group
Antigens
Antibodies
Can give blood to
Can receive blood from
AB Rh+
A, B and Rh
None
AB Rh+
AB Rh+
AB Rh -
A Rh+
A Rh -
B Rh+
B Rh -
0 Rh+
0 Rh -
AB Rh -
A and B
None
(Can develop Rh antibodies)
AB Rh -
AB Rh+
AB Rh -
A Rh -
B Rh -
0 Rh -
A Rh+
A and Rh
B
A Rh+
AB Rh+
A Rh+
A Rh -
0 Rh+
0 Rh -
A Rh -
A
B
(Can develop Rh antibodies)
A Rh -
A Rh+
AB Rh -
AB Rh+
A Rh -
0 Rh -
B Rh+
B and Rh
A
B Rh+
AB Rh+
B Rh+
B Rh -
0 Rh+
0 Rh-
B Rh -
B
A
(Can develop Rh antibodies)
B Rh-
B Rh+
AB Rh-
AB Rh+
B Rh -
0 Rh -
0 Rh+
Rh
A and B
0 Rh+
A Rh+
B Rh+
AB Rh+





0 Rh+
0 Rh -
0 Rh -
None
A and B (Can develop Rh antibodies)
AB Rh+
AB Rh -
A Rh+
A Rh -
B Rh+
B Rh -
0 Rh+
0 Rh -
0 Rh -