Blood Chapter 11 Pgs 343-359 Overview Functions of Blood

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Blood

• Chapter 11
• Pgs 343-359

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Overview

• Functions of Blood
• Composition of Blood
• Plasma
• Plasma proteins
• Formed Elements
• Production of formed elements
• Red blood cells
• White blood cells
• Platelets

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Functions of Blood

• Transportation of dissolved gases, nutrients,
  hormones, and metabolic wastes
• Regulation of pH and electrolyte composition of
  ISF
• Restriction of fluid loss through damaged vessels
  and other injury sites
• Defense against toxins and pathogens
• Stabilization of body temperature

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Composition of Blood

• Plasma
• Formed elements
• Red blood cells (RBC) or Erythrocytes
• White blood cells (WBC) or Leukocytes
• Platelets
• Both constitute whole blood
• 5-6 L in men
• 4-5 L in women

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Plasma

• Electrolyte concentration similar to ISF
• Plasma proteins
• Lg so cannot diffuse
• 3 primary classes
• Albumins
• Globulins
• Fibrinogen
• Serum

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Formed Elements The Production

• Hemopoiesis
• Embryonic blood cells
• Stem cells
• Hemocytoblasts

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Red Blood Cells (Erythrocytes)

• Accounts for 99.9 of formed elements
• RBC count (RBCs per microliter)
• Adult male 5.4million/µl
• Hematocrit of whole blood occupied by
  cellular elements
• Determined by centrifuge
• Adult male avgs 46
• Closely approx vol of erythrocytes
• Hematocrit values often reported as
• Volume of packed red cells (VPRC)
• Packed cell volume (PCV)

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Structure of RBCs

• Specialized to transport oxygen and carbon
  dioxide
• Shape has 2 important effects on function
• Lg SAvol
• Increases rate of diffusion between cytoplasm and
  plasma
• Enables bending and flexing to fit through narrow
  capillaries
• Contains hemoglobin (Hb)

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RBC Formation (Erythropoiesis)

• Occurs in red bone marrow (myeloid tissue)
• Erythroblasts
• Very immature RBCs
• Actively synthesizing Hb
• After 4 days differentiates into
• Reticulocyte
• Enter circulation after 2 days in bone marrow
• After 24 hrs in circ, complete maturation and
  become
• Erythrocyte!

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RBCs and Blood Types

• Blood type classification determined by presence
  or absence of specific surface antigens in RBC
  membrane
• Surface antigens of RBC called agglutinogens
• Genetically determined
• 3 important antigens
• A
• B
• Rh

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RBCs and Blood Typing

• Type A antigen A only (40 US pop)
• Type B antigen B only (10)
• Type AB both A and B (4)
• Type O neither A nor B (46)
• Rh factor present in some, absent in others

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White Blood Cells (Leukocytes)

• Divided into 2 groups
• Granulocytes
• Neutrophils
• Eosinophils
• Basophils
• Agranulocytes
• Monocytes
• Lymphocytes

• Microliter typically contains 6,000-9,000 WBCs
• Most located in connective tissue proper or in
  organs of lymphatic system

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WBC Circulation and Movement

• Do not circulate for extended periods of time
• 4 characteristics of circulating WBCs
• Amoeboid movement
• Diapedesis
• Positive chemotaxis
• Phagocytosis

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WBCs General Functions

• Nonspecific defense
• Neutrophils
• Eosinophils
• Basophils
• Monocytes
• Specific defense
• Lymphocytes

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Neutrophils

• 50-70 circulating WBCs
• Dense, twisted nucleus
• 1st to arrive to injury scene
• Active phagocytes
• Specialize in attacking and digesting bacteria

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Eosinophils

• 2-4 circulating WBCs
• Similar in size to neutrophils
• Contain granules and 2-lobed nucleus
• Attracted to foreign compounds that have reacted
  with circulating antibodies

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Basophils

• Less than 1 circulating WBCs
• Numerous granules
• Migrate to injury site, cross cap wall, and accum
  w/in damaged tissue
• Discharge granules into ISF
• Contain heparin and histamine

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Monocytes

• 2-8 circulating WBCs
• Lg, oval (kidney) shaped nucleus
• Remain in circ only 24 hrs before entering tissue
• Become a free macrophage
• Very aggressive

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Lymphocytes

• 20-30 circulating WBCs
• Lg nucleus w/ thin halo of cytoplasm
• Continuously migrating from bloodstream? tissues
  ? blood stream
• Protect but do not rely on phagocytosis
• Attack foreign and abnormal cells

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Differential Count and Changes in WBC Profiles

• Differential count
• Number of circulating WBCs obtained in a blood
  sample
• Values reported indicate the of each type of
  cell encountered in a sample of 100 WBCs
• Leukopenia
• Too few WBCs
• Leukocytosis
• Too many WBCs
• Leukemia
• Extreme form of leukocytosis (WBC counts of
  100,000/µl

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White Blood Cell Formation

• Stem cells originate in red bone marrow
• All from myeloid stem cells except for
  lymphocytes
• Neutrophils, eosinophils, basophils complete dev
  in marrow
• Monocytes begin in marrow, enter circ, complete
  development when free macrophages

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WBC Formation Lymphocytes

• Lymphoid stem cells migrate from bone marrow to
  lymphoid tissues
• Process called lymphopoiesis
• Hormones involved in regulation of WBC
  populations
• Colony-stimulating factors (CSFs) regulate WBCs
  other than lymphocytes
• Thymosins promote differentiation of T-cells from
  lymphocytes

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Platelets

• Components of formed elements
• Cell fragments not individual cells
• Derived from megakaryocytes
• Shed packets of cytoplasm
• Platelets!
• Initiate clotting process and help close injured
  blood vessels
• Continuously replaced
• Thrombocytopenia abnormally low count
• Thrombocytosis abnormally high count

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