Blood Chapter 11 Pgs

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 Proerythroblast Erythroblast Reticulocyte Erythrocyte Lymphoid stem cells

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 1 st 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 ErythrocytesPlateletsBasophilsEosinophilsNeutrophilsMonocytes Lymphoid Stem Cells Lymphocytes B cells T cells NK cells