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Blood
Chapter 11
Pgs 343-359
Overview
• Functions of Blood• Composition of Blood• Plasma
– Plasma proteins
• Formed Elements– Production of formed elements– Red blood cells– White blood cells– Platelets
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
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
Plasma
• Electrolyte concentration similar to ISF
• Plasma proteins– Lg so cannot diffuse– 3 primary classes
• Albumins• Globulins• Fibrinogen
• Serum
Formed Elements: The Production
• Hemopoiesis – Embryonic blood cells– Stem cells
• Hemocytoblasts
Hemocytoblasts
Myeloid stem cells Lymphoid stem cells
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)
Structure of RBCs
• Specialized to transport oxygen and carbon dioxide
• Shape has 2 important effects on function:– Lg SA:vol
• Increases rate of diffusion between cytoplasm and plasma
– Enables bending and flexing to fit through narrow capillaries
• Contains hemoglobin (Hb)
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!
Hemocytoblasts
Myeloid stem cells Lymphoid stem cells
Proerythroblast
Erythroblast
Reticulocyte
Erythrocyte
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
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
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
WBC Circulation and Movement
• Do not circulate for extended periods of time
• 4 characteristics of circulating WBCs:– Amoeboid movement– Diapedesis – Positive chemotaxis– Phagocytosis
WBCs: General Functions
• Nonspecific defense– Neutrophils– Eosinophils– Basophils– Monocytes
• Specific defense– Lymphocytes
Neutrophils
• 50-70% circulating WBCs
• Dense, twisted nucleus
• 1st to arrive to injury scene
• Active phagocytes– Specialize in attacking
and digesting bacteria
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
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
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
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
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
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
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
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
Hemocytoblasts
Myeloid Stem Cells Lymphoid Stem Cells
Erythrocytes Platelets Basophils Eosinophils Neutrophils Monocytes Lymphocytes
B cells
T cells
NK cells