THE BLOOD

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THE BLOOD

• Introduction to the cardiovascular system
• Components of blood
• Formed elements
• Stages of blood cell formation
• Hematopoiesis (hemopoiesis)
• Erythrocytes
• Hemoglobin (Hb)
• Erythrocyte lifespan
• Leukocytes
• Containment of pathogens
• Thrombocytes
• Hemostasis control of bleeding
• Coagulation (clotting)
• Fibrinolysis clot dissolution)
• Blood types
• Blood donors and recipients
• Rh system of grouping

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INTRO TO THE CARDIOVASCULAR SYSTEM
The more specialized a cell becomes in order to
perform a specialized function, the less capable
it is of an independent existence.
As a result, it cannot
protect itself seek and procure food move away
from its own wastes
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COMPONENTS OF BLOOD
Formed elements 45
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FORMED ELEMENTS
Erythrocytes (red blood cells) males 4.6
6.2 million/mm3 hematocrit 45-52
females 4.2 5.4 million/mm3 hematocrit
37-48
Thrombocytes (platelets) 130,000 360,000/mm3
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STAGES OF BLOOD CELL FORMATION
Yolk sac stage (3rd week end of 2nd month)
Hepatic stage (beginning of 2nd month just
after birth) Myeloid stage (beginning of 5th
month death)
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HEMATOPOIESIS (HEMOPOIESIS)
Hemocytoblast Stem cells Growth factors
hemocytoblast
erythropoietin thrombopoietin leukopoietins (?)
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ERYTHROCYTES
7 10 µm diameter Biconcave disk Large surface
area Very flexible Not true cells Sacs of
hemoglobin
view from above
cross sectional view
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HEMOGLOBIN (Hb)
1 globin (4 protein subunits) 4 Fe-containing
heme groups 1 O2 per heme group 1 Hb can carry 4
O2 1 globin can carry 1 CO2
beta 1 subunit
beta 2 subunit
alpha 1 subunit
alpha 2 subunit
heme groups
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ERYTHROCYTE LIFESPAN
120 days in circulation Synthesis (2 million/sec)
required substances
iron (Fe3 ) globulin vitamin B12 erythropoietin
Destroyed by liver and spleen (2
million/sec)
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LEUKOCYTES
Granulocytes
neutrophils phagocytize bacteria 1st line of
defense eosinophils phagocytize Ab-Ag complexes
and allergens anti-parasitic basophils secrete
histamine and heparin
Agranulocytes
lymphocytes -- immunity monocytes become
macrophages phagocytosis Ag-presentation
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CONTAINMENT OF PATHOGENS
Chemotaxis Chemotactic factors Margination Paveme
nting Diapedesis Emigration Ameboid motion WBC
lifespan 4 5 days
wound
chemotactic factors
emigration
diapedesis
margination and pavementing
margination and pavementing
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THROMBOCYTES
AKA platelets Shed from megakaryocytes Cytoplasmi
c fragment Not a true cell Biconvex disk
2µm Clotting factors Lifespan 5 9 days
platelets
RBCs
WBCs
platelets
megakaryocyte
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HEMOSTASIS CONTROL OF BLEEDING
Three basic mechanisms go into operation after a
vascular injury
vascular spasm
coagulation
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COAGULATION (CLOTTING)
EXTRINSIC PATHWAY
INTRINSIC PATHWAY
damaged tissues
platelets
Factor XII
release
activates
release
Factor XI
thromboplastin (Factor III)
activates
Factor VII
Factor IX
activates
Factor VIII
Factor X
activates
BLOOD CLOT
prothrombinase
converts
prothrombin
thrombin
converts
fibrin polymer
platelet plug

fibrinogen
fibrin
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CLOT RETRACTION
AKA syneresis Cross-linking of fibrin causes
compaction of clot into wound site
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BLOOD TYPES
Membrane-bound agglutinogens
ABO system and Rh system
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BLOOD DONORS AND RECIPIENTS
Who can give what to whom? Blood recipient has
type A blood. Can she receive type A
plasma type A RBCs type B plasma
type B RBCs type AB plasma type AB
RBCs type O plasma type O RBCs
X
X
X
X
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Rh SYSTEM OF GROUPING
Agglutinogen Rh There is no Rh agglutinin. Hemolyt
ic disease of the newborn
A
B
Mom must be Rh negative
fetal Rh RBCs
C
end