Chapter 20: Blood

Introduction to the Cardiovascular System

• Cardiovascular System Function: Enables rapid transport of nutrients, waste, and cells over long distances, throghout the body.

Functions and Composition of the Blood

• Blood: Specialized connective tissue with various vital functions:

  • Transport: Dissolved gases (O2 & CO2), nutrients, metabolic wastes to kidneys, specialized cells that defened against disease (WBCs), enzymes, and hormones.

  • Homeostasis: Stabilizes pH and electrolyte composition (ion composition) of interstitial fluids.

  • Fluid Loss Prevention: Clotting reaction restricts fluid loss from damaged vessels.

• Blood Components: Whole blood is broken down into 2 primary components

  1. Plasma: Liquid matrix (~55% of blood volume— 92% water 7% plasma protein). Plasma contains dissolved proteins

  2. Formed Elements: Includes RBCs, WBCs, and platelets.

• Blood Volume: Average adult has 4-6 liters; terms. Whole blood is very viscous and resistant to flow. Blood levels are calssified as

  1. Hypovolemic (low),

  2. Normovolemic (normal)

  3. Hypervolemic (excessive).

• Blood pH: 7.35-7.45 (Slightly Basic)

• Blood Temperature: 100.4 ferinheight

Plasma (~55% of blood volume)

• Plasma vs. Interstitial Fluid:

• Plasma contains higher dissolved oxygen and more proteins.

• Types of Plasma Proteins:

  1. Albumins: 60% of plasma proteins, important for maintaining osmotic pressure.

  2. Globulins: 35% of plasma proteins, including immunoglobulins (antibodies) and transport globulins (bind ions and hormones).

  3. Fibrinogen: 4% of plasma proteinsEssential for blood clotting; forms fibrin.

• Other Solutions: Make up less than 1% of plasma

  • Electrolytes: Includes ions that are essential for various physiological processes, such as maintaining fluid balance, nerve transmission, and muscle contraction.

  • Organic Nutrients: Includes FAs, CH, glycerides, carbohydrates, and AAs essential for ATP production

  • Organic Wastes: Carried to sites for breakdown or excretion, includes: Uric Acid, urea, creatinine, bilirubin, ammonium ions

• Differences between plasma and interstitial fluid (fluid that surrounds cells in tissue beds)

Formed Elements (~45% of blood volume)

Erythrocytes— Red Blood Cells (RBCs)

• Hematocrit: used to measure the percentage of whole blood occupied by the formed elements

  • Also referred to as VPRC (volume packed red cells) or PCV (packed cell volume) indicates volume occupied by cellular elements.

• Erythrocytes: Transport oxygen and carbon dioxide.

  • Accounts for approximately 99.9% of whole blood

  • Biconcave Disc Shape: Increases surface area allowing for rapid exchange of gasses and passage through vessels.

  • Contain no nucleus or organelles

    • Rely fully on anaerobic metabolism of blood glucose due to lack of mitochondria

    • Cannot repair themselves due to lack of ribosomes

  • Lifespan: Approximately 120 days; lack organelles limits repair/maintenance.

  • Recycled by phagocytes after damage.

• Hemoglobin: The most common protein in RBCs that binds to oxygen and carries it throughout the body.

  • Composed of four subunits, each containing heme with an iron ion that binds oxygen.

    • Each heme group can bind one molecule of Oxygen

    • One Hb can reversibly bind 4 O2 molecules at a time

    • Gas exchange occurs at lungs and tissues, involving the diffusion of O2 and CO2.

  • Anemia: A condition characterized by an abnormally low O2 carrying capacity— blood O2 levels cannot support normal metabolism

    • Low Hb affects O2 transportation

    • Iron-deficiency anemia does not have many normal-sized RBCs— meaning the PVC is lower bc they are not able to make adequate Hb to fill the RBCs

• Blood Type Determination:

  • Blood types are determined by the presence of specific surface antigens (Agglutinogens) on the surface of RBCs

    • Agglutinogens A: Circular immunoglobulin structures

      • Contain anti-B antibodies

    • Agglutinogens B: Triangle shaped immunoglobulin structures Triangle-shaped

      • Contain anti-A antibodies.

    • Agglutinogens AB: Combination of both circular and triangle-shaped immunoglobulin structures

      • Contain no anti-A or anti-B antibodies.

      • Universal recipient (no AB)

    • Neither A nor B agglutinogens are present (blood type O)

      • Anti-A & anti-B antibodies

      • Universal donor (surface Ag)

  • Rh is an antigen either present or absent on the RBC membrane

    • Rh +/-

White Blood Cells (WBCs): (Comprise less than .1% of formed elements)

• Leukocytes (WBCs): Defend against invading agents, defending the body against pathogens, remove toxins, wastes, and abnormal/damaged cells.

• Most WBCs have a short life span of a few days

  1. Granular Leukocytes: Neutrophils, eosinophils, and basophils.

     1. Neutrophils: Most common, contain chemicals that kill bacteria via phagocytosis (general infection)

        • (50-70% of WBCs).

     2. Eosinophils: Attack foreign compounds by releasing enzymes that reduce inflammation and attack foreign substances reacting to circulating Ab (parasitic/allergy)

        • (2-4% of WBCs).

     3. Basophils: Release histamine, aid in inflammation reactions (autoimmune or allergic)

        • (<1% of WBCs).

  2. Agranular Leukocytes: Monocytes and lymphocytes.

     1. Monocytes: Differentiate into macrophages in tissues.

        • (2-8% of WBCs).

     2. Lymphocytes: For specific immunity— Include T cells (attack foreign cells), B cells (produce antibodies), and NK cells (destroy abnormal tissue).

        • (20-30% of WBCs).

Platelets

• Characteristics: Not whole cells; packets of cytoplasm from megakaryocytes in bone marrow.

• Functions:

• Transport chemicals for clotting.

• Form temporary patches in damaged vessels.

• Contraction post-clot formation to reduce vessel wall break size.

Hemopoiesis

Blood Cell Formation

• Definition: Process of blood cell formation from hematopoietic stem cells.

Erythropoiesis (RBC Formation)

• Occurs in red bone marrow under erythropoietin (EPO) influence.

• Stages include erythroblasts and reticulocytes.

Leukopoiesis (WBC Formation)

• Begins in red bone marrow; stem cells produce granular leukocytes and monocytes.

• Lymphocyte production (lymphopoiesis) also starts in red bone marrow, with many migrating to lymphatic tissues.

• Colony-stimulating factors (CSFs) regulate WBC populations.