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Chapter 11
The Blood and Body Defenses
Blood •
•
•
Represents about 8% of total body weight
Average volume
– 5 liters in women
– 5.5 liters in men
Consists of 3 types of specialized cellular elements suspended in plasma (liquid portion of blood)
– Erythrocytes
◊
–
◊
–
Red blood cells for O2 & CO2 transport
Leukocytes
White blood cells
◘
Immune system’s mobile defense units
Platelets ◊
Cell fragments
◘
Important in hemostasis
♦
the process of keeping blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage)
Plasma
55% of whole blood
Packed cell
volume, or
hematocrit
Buffy coat:
platelets and
leukocytes
(<1% of
whole blood)
Erythrocytes
(45% of whole
Blood)
Platelets
Leukocytes
(white blood
cells)
Erythrocytes
(red blood
cells)
Fig. 11-1, p. 298
Plasma
• Plasma proteins
– Compose 6% to 8% of plasma’s total weight
– 3 groups of plasma proteins
◊ Albumins
◘ Most abundant plasma proteins (60%, 3.5‐5g/dl)
♦ Osmotic pressure (oncotic pressure)
♦ Transport of hormone, bile salts, bilirubin, fatty acids, calcium, transferrin, etc
♦ Tranport of many drugs – competition = drug interactions
◊ Globulins (2‐3.5g/dl)
◘ 3 subclasses
♦ Alpha1, Alpha2 (α) transport
♦ Beta (β) transport
♦ Gamma (γ) immune
◊ Fibrinogen ◘ Key factor in blood clotting
Erythrocytes •
Red blood cells (RBCs)
– 2‐3 x 1013
◊
4‐5million per cc female ◊
5‐6million per cc male
– 120 day life span ….. 2 million new RBC/sec
– Contain no nucleus, organelles, or ribosomes
– Structure is well suited to main function of O2 transport in blood
– Biconcave discs
◊
Provides larger surface area for diffusion of O2 across the membrane
◊
Thinness = short diffusion distance from exterior to innermost regions of the cell
– Flexible membrane
◊
Allows RBCs to travel through narrow capillaries without rupturing in the process
Hemoglobin
• Found only in red blood cells
• 15g/dl male 13g/dl female
• Pigment containing iron
– Appears reddish when oxygenated
– Appears bluish when deoxygenated
• Molecule consists of 2 parts
– Globin portion
◊ Protein composed of four highly folded polypeptide chains
– Heme groups
◊ Four iron‐containing nonprotein groups
◊ Each is bound to one of the polypeptides
•Binding
sites for
O2
CO2
H+
•Binding
of one
effects
affinity for
the other
Hemoglobin • Primary role is to carry O2
• Also combines with
– Carbon dioxide
– Acidic hydrogen‐ion portion (H+) of ionized carbonic acid
– Carbon monoxide
– Nitric oxide
Erythropoiesis
•
•
•
•
•
Erythrocyte production
RBCs survive about 120 days
Spleen removes most of old erythrocytes from circulation
Must be replaced at rate of 2 million to 3 million cells/second
Erythropoiesis occurs in bone marrow
– Pluripotent stem cells in red bone marrow differentiate into the different types of blood cells
Kidney
2
1
Normal
Erythropoietin 3
normal oxygencarrying capacity
keeps
Normally
Developing
erythrocytes
in red bone
marrow
5
4
Normal oxygencarrying capacity
Erythrocytes
Fig. 11-3, p. 301
Homeostasis: response to low O2 carrying capacity