Chap18 PPT

Chapter 18: The Circulatory System: Blood

General Aspects of Blood

• Expected Learning Outcomes:

  • Describe the functions and major components of the circulatory system.

  • Describe the components and physical properties of blood.

  • Describe the composition of blood plasma.

  • Explain the significance of blood viscosity and osmolarity.

  • Describe in general terms how blood is produced.

Introduction

• Circulatory System:

  • Composed of the heart, blood vessels, and blood.

• Cardiovascular System:

  • Specific term referring to the heart and blood vessels.

• Hematology:

  • Field of study focused on blood.

Purposes of Blood Circulation

• Functions of the Circulatory System:

  1. Transport:

     • Carries oxygen (O2), carbon dioxide (CO2), nutrients, waste products, hormones, and stem cells.

  2. Protection:

     • Involves inflammation, limiting infection spread, destroying pathogens and cancer cells, neutralizing toxins, and initiating clotting.

  3. Regulation:

     • Maintains fluid balance, stabilizes pH, and controls body temperature.

• Composition of Blood:

  • A liquid connective tissue consisting of cells (formed elements) and extracellular matrix (plasma).

  • Types of Cells in Blood:

    • Erythrocytes (Red Blood Cells): Transport oxygen.

    • Leukocytes (White Blood Cells): Immune response.

    • Platelets: Cell fragments involved in clotting.

Blood Components and Properties

• Blood Plasma:

  • Clear, light yellow fluid that constitutes the matrix of blood.

• Formed Elements:

  • Cells and cell fragments, including:

    • Erythrocytes:

      • Red blood cells vital for oxygen transport.

    • Leukocytes:

    • White blood cells categorized as granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

    • Platelets: Small cell fragments for clotting.

• Blood Fractionation:

  • Separation of blood into components through centrifugation; density informs their order with RBCs at the bottom, plasma on top, and a buffy coat of WBCs and platelets in between.

Blood Plasma Composition

• Components of Plasma:

  • A complex mix of water, electrolytes, proteins, nutrients, waste products, hormones, and gases.

• Principal Plasma Proteins:

  1. Albumins:

     • Smallest and most abundant; crucial for transport, pH buffering, and osmotic pressure.

  2. Globulins:

     • Include alpha, beta, and gamma globulins, involved in solute transport, clotting, and immune response.

  3. Fibrinogen:

     • Precursor to fibrin, the active component in blood clotting.

Blood Viscosity and Osmolarity

• Viscosity:

  • Measure of resistance to flow; important for blood movement through vessels.

  • Whole blood viscosity is approximately 4.5 to 5.5 times greater than water.

• Osmolarity:

  • Total concentration of solute particles; regulated by sodium ions, proteins, and RBCs to maintain blood pressure.

Blood Production (Hematopoiesis)

• Hematopoiesis:

  • The process of blood cell production, occurring in various tissues including bone marrow, liver, and spleen during different life stages.

• Hematopoietic Stem Cells (HSCs):

  • Multipotent stem cells responsible for generating all formed elements in the blood.

Erythrocytes (Red Blood Cells)

• Functions:

  • Transport O2 from lungs to tissues and CO2 from tissues to lungs; a deficiency can be fatal.

• Structure:

  • Biconcave shape allows flexibility and increases surface area for gas exchange; loses organelles during development, leading to a lack of DNA, mitochondria, and protein synthesis facilitators.

• Hemoglobin Composition:

  • Contains four globin proteins and heme groups, enabling high capacity for oxygen transport.

Erythrocyte Life History

• Erythropoiesis:

  • Process of production encompassing several stages from stem cells to reticulocytes and finally mature RBCs.

• Regulation:

  • Hypoxia triggers increased erythropoietin (EPO) secretion from kidneys, stimulating RBC production as a compensatory response to low oxygen levels.

Erythrocyte Disorders

• Polycythemia:

  • Excess of RBCs; causes include cancer and environmental factors.

• Anemia:

  • Deficiency can arise from blood loss, destruction, or inadequate production of RBCs/homoglobin.

  • Specific types include iron-deficiency anemia and hemolytic anemia, each with distinct causes and effects.

• Sickle-Cell Disease:

  • A hereditary condition causing rigid, sickle-shaped RBCs that can block blood vessels, leading to severe complications.

Blood Types and Transfusion Compatibility

• ABO Blood Group:

  • Determined by presence/absence of antigens A and B; types include A, B, AB, and O.

• Rh Factor:

  • Defines if blood is Rh-positive or negative based on D antigen presence.

  • Implications during pregnancy need careful management to prevent hemolytic disease in newborns.

Leukocytes (White Blood Cells)

• Types and Functions:

  • Include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes); each has distinct roles in immunity.

• Leukopoiesis:

  • Production process from stem cells through various CFUs generating the specialized white blood cell types.

Platelets and Hemostasis

• Platelet Functions:

  • Involved in clot formation, vasoconstriction, and recruiting other immune cells to sites of injury.

• Hemostasis Mechanisms:

  1. Vascular Spasm: Immediate constriction response.

  2. Platelet Plug Formation: Adhering platelets to injury site.

  3. Coagulation (Clotting): Formation of fibrin threads to stabilize the clot.