Blood

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Mariebs Human Anatomy and Physiology Marieb w
Hoehn

• Chapter 17
• Blood
• Lecture 1
• Part 1 Overview and Red Blood Cells

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Overview of Blood (Hem(o)-)
Blood is what type of tissue?
Connective tissue.

• Functions
• transports vital substances (O2, waste)
• maintains stability of interstitial fluid
• distributes heat
• hemostasis
• prevents infection

• Blood Cells (formed elements)
• form in red bone marrow
• red blood cells
• white blood cells
• platelets (cell fragments)

• Plasma (liquid portion - matrix)
• contains dissolved substances
• mostly water and proteins

• amount of blood varies with
• body size
• changes in fluid volume
• changes in electrolyte concentration
• amount of adipose tissue
• about 7-8 of body weight
• About 5.0 liters of blood in adult

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Blood Composition
Hematocrit (HCT) Percentage of red cells in
blood by volume. Also called Packed Cell Volume
(PCV). Usually about 45
What would happen to the hematocrit if someone
was dehyrated and lost plasma volume?
Figure from Saladin, Anatomy Physiology,
McGraw Hill, 2007
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Formed Elements of the Blood
45 of blood
Figure from Holes Human AP, 12th edition, 2010
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Origin of Blood Cells
All formed elements of blood arise from a common
hematopoietic pluripotent stem cell (a
hemocytoblast) in the red bone marrow
Figure from Holes Human AP, 12th edition, 2010
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Red Blood Cells

• erythrocytes
• biconcave (? surface area)
• lack nuclei and mitochondria
• one-third hemoglobin ( 280 million Hb
  molecules per RBC)
• oxyhemoglobin
• deoxyhemoglobin
• can readily squeeze through capillaries

Figure from Holes Human AP, 12th edition, 2010
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Hemoglobin
General structure - Four polypeptides chains
- A porphyrin - An iron atom
Heme
Figure From Martini, Anatomy Physiology,
Prentice Hall, 2001
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Red Blood Cell Count

• number of RBCs in a cubic millimeter (mm3) of
  blood. (1 mm3 1 microliter, µl)

• 4,600,000 6,200,000 in males

• 4,200,000 5,400,000 in adult females

• 4,500,000 5,100,000 in children

Average is about 5 x 106 RBCs / µl

• Number of RBCs reflects bloods oxygen carrying
  capacity

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Types of Anemia
Anemia deficiency of RBCs or Hb in RBCs
reduces O2-carrying capacity of blood

• aplastic anemia
• bone marrow damaged
• toxic chemicals
• radiation

• iron deficiency anemia
• hemoglobin deficient
• lack of iron

• pernicious anemia
• excess of immature RBCs
• inability to absorb B12

• hemolytic anemia
• RBCs destroyed
• toxic chemicals

• thalassemia
• hemoglobin deficient
• RBCs short-lived
• defective gene (? or ?-chain)

• sickle cell anemia
• abnormal shape of RBCs
• defective gene (?-chain)

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Red Blood Cell Production

• low blood oxygen causes kidneys and liver to
  release erythropoietin which stimulates RBC
  production (up to 30 million per second under
  maximum EPO stimulation!)
• Erythropoiesis

• vitamin B12, folic acid and iron necessary for
  RBC production

Figure from Holes Human AP, 12th edition, 2010
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Blood Viscosity and Osmolarity

• Viscosity (thickness)
• Resistance to flow of blood
• Whole blood is about 5x as viscous as water
• Changes in viscosity can put strain on the heart
• Erythrocytosis (polycythemia) ? viscosity
• Osmolarity
• Due to NUMBER of particles dissolved, not the
  type
• Na, proteins, erythrocytes
• Osmolarity determines fluid flow between blood
  and tissues

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Red Blood Cell Turnover
The average life span of an RBC is about 120 days
(4 months)
Iron is carried in the blood by transferrin to
red bone marrow, liver
Figure From Martini, Anatomy Physiology,
Prentice Hall, 2001
Porphyrin from worn out RBCs is converted into
biliverdin and bilirubin