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