Date post: | 11-May-2015 |
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Introduction to blood
Fluid component of blood“Formed elements”
Function of blood
Maintenance of blood volume
Total volume of blood is ~5.5 liters
About 55% is plasma; rest is cells
Most are red cells (RBCs)
Cells are specialized to carry oxygenfull of hemoglobin; no organelles
4-6 million RBCs per cc for males; 4-5 millionfor females
What factors affect RBC count and activity?
Insufficient red cell production and/oroxygen delivery- anemia
Causes:iron deficiency (most common)vitamin B12, folic acid (pernicious anemia)
hemolytic anemia sickle cell anemia
blood lossbone marrow diseaseinfections
All blood cells are formed in the bone marrow
Red blood cells
White blood cells (leukocytes)neutrophilslymphocytesmonocyteseosinophilsbasophils
Platelets (megakaryocytes)
Leukocytes help fight infection
Phagocytesneutrophilsmonocytes/macrophagesphagocytes
Inflammationneutrophils infiltrate sitemonocytes/mactrophages help control
immune reactionsbasophils release chemicals involved
in inflammation, allergy
White cell counts is normally 5000-10000/cc
Leukocytosis- elevated cell count
Leukopenia- count is depressed
Differential- neutrophils 50-75%lymphocytes 20-40%monocytes 5-10%eosinophils 1-3%basophils 0-1%
Hemostasis (clotting; stoppage of blood loss)
Platelets- plug formation; can repair smallwounds
Clotting factors (coagulation)
A cascade
What’s in plasma?waternutrientsplasma proteins
albuminsalpha and beta globulingamma globulin (antibodies)all except gamma globulins areformed in the liver
maintain osmotic pressure (and thusblood volume)
gases; wastes
Red blood cell antigens and blood typing
Antigen: a molecule that is recognized as foreignby the immune system
Lots of these: several different types of antigensfound on red blood cells (RBCs)
ABO system especially important
Four blood types: A, B, AB, O
A and B are dominant, O is recessive
People with type A blood can tolerate type Ablood from other individuals
But type A people make antibodies to type Bantigens
People with type AB can tolerate all blood types:universal recipient (of CELLS)
People with type O blood can donate to all buthave antibodies to both A and B antigens:universal donor (of CELLS)
Rh antigen is also important
People either have the antigen or do not
Rh-negative people will develop antibodies tothe Rh antigen if they are exposed to theRh-positive blood
If a Rh-negative woman becomes pregnantwith a Rh-positive fetus she may makeantibodies to the fetus’ RBCs
This can be prevented with RhoGAM
Implications for:blood transfusions
Blood type antigen antibody
A A anti-B B B anti-AAB A, B neither O neither anti-A and B
Transfusions are preferred between people ofthe same blood type
If blood is properly processed and administered:
A can receive from A and OB from B and OAB from AB, A, B and OO only from type O- but can donate to everyone
else
Rh-positive can receive from negative and positiveRh-negative only from negative
Blood types are inheritedIn some parts of the world some blood types are
more common than others
In U.S.:~45% are O, ~40% are A, 12% are B, andabout 3% are AB
about 85% are Rh-positive
Roles of blood
oxygen transportnutrient transportwaste transporttransport of other essential molecules
(antibodies, hormones, etc.)
regulation (temperature, metabolism, etc.)
fighting infection