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Blood
Chapter 8
Functions of Blood
• Transports oxygen and nutrients to cells
• Carries carbon dioxide and wastes away
from cells
• Helps stabilize internal pH
• Carries infection-fighting cells
• Helps equalize temperature
Blood Volume and
Composition
• Plasma
– 50-60 percent of volume
– Water, plasma proteins, dissolved ions
and molecules
• Cellular portion
– 40-50 percent of volume
– Red cells, white cells, and platelets
Plasma
• Mostly water
• Main plasma protein is albumin
• Other proteins, including hormones
• Ions, glucose and other simple sugars,
amino acids, various communication
molecules, and dissolved gases
Erythrocytes (Red Cells)
• Most numerous cells in the blood
• Transport oxygen and carbon
dioxide
• Colored red by oxygen-binding
pigment (hemoglobin)
• Have no nucleus when mature
Leukocytes (White Cells)
• Function in housekeeping and defense
• Cell types
Basophils
Eosinophils
B lymphocytes
Neutrophils
T lymphocytes
Macrophages
NK cells
Dendritic cells
Mast cells
Platelets
• Membrane-bound cell fragments
• Derived from megakaryocytes, which
arise from stem cells
• Release substances that initiate blood
clotting
Oxygen Transport
• Oxygen binds to heme group of
hemoglobin
• Forms oxyhemoglobin
• Binding affected by
– Oxygen concentration
– Temperature
– pH
heme group
Life Cycle of Red Blood Cells
• Stem cell gives rise to nucleated
“pre-erythrocyte” that synthesizes
hemoglobin
• Once filled with hemoglobin, nucleus is
expelled
• Cell is now an erythrocyte and will
function for about 120 days
ABO Blood Type
• Type A red cells have one type of
marker at surface
• Type B red cells have a different type
of marker
• Type AB cells have both markers
• Type O cells have neither marker
Blood Type in Transfusions
• Require that donor and recipient have
same blood type
• If bloods of incompatible types are mixed,
recipient’s immune system will attack and
destroy donor cells
• Agglutination reaction
ABO and Transfusions
Rh Blood Type
• Based on presence or absence of Rh
factor on red cells
• Can cause problems during pregnancy
– if mother is Rh negative
– has previously carried Rh positive child
– is carrying fetus that is Rh positive
• Mother’s antibodies can attack fetal cells
Hemostasis
• Blood vessel
spasm
• Platelet plug
formation
• Blood
coagulation
Enzymes activate factor X, forming
prothrombinase
Prothrombinase converts enzyme
precursor to thrombin
Thrombin converts fibrinogen
to insoluble threads (fibrin)
Fibrin forms net that entangles
blood cells, platelets
Blood Clot
Intrinsic and Extrinsic Triggers
• Intrinsic clotting mechanism gets under
way when a protein in the blood plasma
is activated
• Extrinsic clotting mechanism is triggered
by the release of enzymes and other
substances by damaged blood vessels
or from the surrounding tissues
Blood Disorders
Anemias
Leukemias
Mononucleosis