Blood and Blood Components

THE BLOOD

COMPONENTS OF BLOOD

  • Erythrocyte (Red Blood Cells)

  • Platelet

  • Leukocyte (White Blood Cells)

FLUIDS OF THE BODY (START OF LECTURE VIDEO #1)

  • The two primary fluids servicing cells of the body are:

    • Blood

    • Composed of plasma and a variety of cells.

    • Transports nutrients and wastes.

    • Interstitial Fluid

    • Bathes the cells of the body.

    • Nutrients and oxygen diffuse from the blood into the interstitial fluid and subsequently into the cells.

    • Wastes move in the reverse direction.

FUNCTIONS OF BLOOD

  • Transportation

    • Carries:

    • Oxygen (O₂)

    • Carbon Dioxide (CO₂)

    • Metabolic wastes

    • Nutrients

    • Heat

    • Hormones

  • Regulation

    • Regulates pH through buffers.

    • Maintains body temperature:

    • Utilizes vasodilation of surface vessels to dump heat.

    • Regulates water content of cells by interacting with dissolved ions and proteins.

  • Protection

    • Protects from disease.

    • Protects against loss of blood.

PHYSICAL CHARACTERISTICS OF BLOOD (END OF LECTURE VIDEO #1)

  • Blood is thicker (more viscous) than water and flows more slowly.

  • Temperature: 100.4 degrees F.

  • pH: 7.4 (normal range 7.35-7.45).

  • Accounts for approximately 8% of total body weight.

  • Blood Volume (average):

    • Male: 5 to 6 liters

    • Female: 4 to 5 liters

  • Color Differences:

    • Arterial Blood: Bright red due to hemoglobin; supplies organs with nutrients.

    • Venous Blood: Darker red due to lack of oxygen after delivering it to organs.

COMPONENTS OF BLOOD (START OF LECTURE VIDEO #2)

  • Blood Composition:

    • 55% Plasma

    • 45% Formed Elements

    • Formed elements primarily include:

      • Red Blood Cells (RBCs)

      • White Blood Cells (WBCs)

      • Platelets

  • Blood Plasma Composition:

    • 91.5% Water

    • 8.5% Solutes:

    • Principal solutes include:

      • Proteins (albumins, globulins, fibrinogen)

      • Nutrients

      • Enzymes

      • Hormones

      • Respiratory gases

      • Electrolytes

      • Waste products.

HEMATOCRIT

  • Definition: The percentage of total blood volume occupied by RBCs.

  • Typical Composition:

    • Plasma: 55%

    • Cells: 45%

    • RBCs: 99%

    • WBCs and Platelets: < 1%.

BLOOD PLASMA

  • Composition:

    • Over 90% water

    • 7% plasma proteins (produced in the liver).

    • Albumin: Maintains blood osmotic pressure, blood thickness, and acts as a pH buffer.

    • Globulins: Include immunoglobulins which function as antibodies binding to foreign substances (antigens), forming antigen-antibody complexes.

    • Fibrinogen: Crucial for blood clotting.

    • 2% Other substances (e.g., electrolytes, nutrients, hormones, gases, waste products).

FORMED ELEMENTS OF BLOOD (END OF LECTURE VIDEO #2)

  • Erythrocytes (Red Blood Cells):

    • Function: Transport oxygen and carbon dioxide.

  • Leukocytes (White Blood Cells):

    • Granular Leukocytes:

    • Neutrophils: Phagocytize microorganisms.

    • Eosinophils: Involved in inflammatory responses.

    • Basophils: Release histamine and participate in inflammatory response.

    • Agranular Leukocytes:

    • Lymphocytes: T cells, B cells, and natural killer cells.

    • Monocytes: Differentiate into macrophages.

  • Platelets: Special cell fragments involved in blood clotting mechanism.

CELL TYPE

  • Illustration:

  • Red Blood Cell:

    • Description: Biconcave disc, no nucleus, contains hemoglobin (gives red color).

    • Size: 7.5 μm in diameter.

    • Function: Transports O₂ and CO₂.

  • Platelet:

    • Description: Cell fragment surrounded by plasma membrane containing granules.

    • Size: 2-4 μm in diameter.

    • Function: Forms platelet plugs; releases clotting chemicals.

  • White Blood Cells:

    • Description: Spherical cells with a nucleus.

    • Contains five types, each with specific functions.

QUICK SUMMARY TABLE

  • Blood Plasma:

  • Plasma Proteins:

  • Other:

  • Formed Elements:

    • Erythrocytes

    • Thrombocytes

    • Leukocytes:

    • Granulocytes: Basophil, Eosinophil, Neutrophil.

    • Agranulocytes: Monocytes and Lymphocytes (B and T).

FORMATION OF BLOOD CELLS (START OF LECTURE VIDEO #3)

  • Hematopoiesis: The process of blood cell production.

  • Occurs in various organs during different life stages:

    • Embryonic Development: Yolk sac, liver, thymus, spleen, lymph nodes.

    • Postnatal (Adult): Primarily in red bone marrow of flat bones (sternum, ribs, skull, pelvis) and ends of long bones.

  • Originates from pluripotent stem cells leading to myeloid and lymphoid stem cells, which are intermediate stem cells.

    • Myeloid stem cells develop into RBCs, WBCs, and platelets.

    • Lymphocytes (specific WBCs) are formed from lymphoid stem cells.

CONTINUED: FORMATION OF BLOOD CELLS

  • Most blood cell types require continuous replacement, dying within hours, days, or weeks.

  • Hematopoiesis Process:

    • In the embryo, occurs in yolk sac, liver, spleen, lymph nodes, and red bone marrow.

    • In adults, it occurs in red marrow of flat bones and ends of long bones.

BLOOD CELLS (END OF LECTURE VIDEO #3)

  • Myeloid Stem Cells:

    • Give rise to RBCs, platelets, and all WBCs except for lymphocytes.

  • Lymphoid Stem Cells:

    • Give rise to lymphocytes.

  • Myeloid stem cells differentiate into progenitor cells (blast cells).

  • Various cells develop from myeloid stem cells, including neutrophils, eosinophils, basophils, and monocytes.

    • Lymphoid stem cells differentiate into B cell lymphoblasts, T lymphoblasts, and NK cells.

OVERVIEW TABLE

  • Hematopoiesis:

    • Lymphoid Stem Cells:

    • B-lymphoblast ➔ B-lymphocyte

    • T-lymphoblast ➔ T-lymphocyte

    • Natural Killer Cells (NKC)

    • Myeloid Stem Cells:

    • Granulocytes: Neutrophils, basophils, eosinophils

    • Monocyte ➔ Macrophage

    • Erythrocytes ➔ Red blood cells

    • Megakaryocyte ➔ Platelets

RED BLOOD CELLS OR ERYTHROCYTES (START OF LECTURE VIDEO #4)

  • Contain hemoglobin, the oxygen-carrying protein that gives blood its red color.

  • Composition: 1/3 of cell's weight is hemoglobin.

  • Shape: Biconcave disk, 8 microns in diameter.

  • Advantages:

    • Increased surface area/volume ratio

    • Flexible shape for narrow passages.

  • Characteristics:

    • No nucleus or organelles.

    • No cell division or mitochondrial ATP formation.

  • Normal RBC Count:

    • Male: 5.4 million/drop (cubic mm)

    • Female: 4.8 million/drop.

    • New RBCs enter circulation at a rate of 2 million/second.

HEMOGLOBIN

  • Structure: Globin protein consists of 4 polypeptide chains:

    • 2 alpha chains (each with 141 amino acids).

    • 2 beta chains (each with 146 amino acids).

  • Each RBC contains over 280 million hemoglobin molecules.

  • Each polypeptide chain has a heme pigment attached.

    • Each heme contains an iron ion (Fe²⁺) that can combine reversibly with one oxygen molecule.

TRANSPORT OF O₂, CO₂, AND NITRIC OXIDE

  • Each hemoglobin molecule can carry 4 oxygen molecules from lungs to tissue cells.

  • Hemoglobin also transports 23% of total CO₂ waste from tissue cells back to lungs for release.

RED BLOOD CELLS ISSUES

  • Production of abnormal hemoglobin (Hgb) may result in blood disorders like thalassemia and sickle cell anemia.

  • Sickle Cell Anemia:

    • Abnormal Hgb results from mutation at position 6 of the beta chains:

    • Glumatic in sickle cell vs. valine in normal Hgb.

    • Causes RBCs to be narrow and short-lived affecting their ability to navigate small capillaries.

    • May lead to backflow issues and tissue hypoxia.

RBC LIFE CYCLE (END OF LECTURE VIDEO #4)

  • RBCs typically live for 120 days.

  • They wear out due to bending to fit through capillaries.

  • Lack of organelles means no repair is possible.

  • Approximately 8 out of 10 blood cells are RBCs.

  • Worn out cells are removed by fixed macrophages located in spleen and liver.

  • Breakdown products are recycled.

  • Doctors often measure RBC count through blood work.

  • Typical hemoglobin levels:

    • Male: 12.5-17.5 grams

    • Female: 12-15.5 grams.

ERYTHROPOIESIS: PRODUCTION OF RBCS (START/END OF LECTURE VIDEO #5)

  • Erythrocyte Formation: Known as erythropoiesis, occurs in adult red bone marrow of certain bones.

  • Develops from hemocytoblast (pluripotent stem cells) into myeloid progenitor cells.

  • Maturation into functional blood cells typically takes approximately one week.

  • Regulation:

    • Controlled by the hormone erythropoietin produced by the kidneys in response to hypoxia (low oxygen levels).

    • Increases erythropoiesis when oxygen levels decrease.

    • Opposite occurs when oxygen blood levels rise – less erythropoietin is released, thus decreasing RBC production.

ERYTHROPOIESIS STEPS

  1. Detection of Hypoxia:

    • Low oxygen supply to tissue (caused by anemia, blood loss, high altitudes).

  2. Nutrient Absorption: Essential elements for RBC production are absorbed by the digestive system, including iron, B12, folic acid, carbohydrates, fats, and amino acids.

  3. Kidney Function: The stomach, liver, and kidneys need to secrete erythropoietin (EPO).

  4. Stem Cell Differentiation:

    • Stem cells (hemocytoblast) alter upon hypoxia detection.

  5. Production Process:

    • Myeloid stem cells differentiate through various stages:

      • Proerythroblast ➔ Basophilic erythroblast ➔ Polychromatic erythroblast ➔ Orthochromatic erythroblast ➔ Reticulocyte (immature RBC) ➔ Erythrocyte.

WHITE BLOOD CELLS (START OF LECTURE VIDEO #6)

  • Leukocytes (WBCs):

    • Nucleated cells that do not contain hemoglobin.

    • Main function: Protect the body from infections and invaders.

    • Larger than RBCs and comprise less than 1% of total blood volume.

    • Normal count: 5000 to 10,000 cells per drop of blood.

  • Groups of WBCs:

    • Granulocytes: Neutrophils, Eosinophils, Basophils.

    • Agranulocytes: Monocytes, Lymphocytes.

    • Only 2% of total WBC population circulates at any given time; the rest is located in lymphatic fluid, skin, lungs, lymph nodes, and spleen.

FUNCTION OF WBCs

  • Various WBC types combat inflammation and infections in distinct ways:

    • Neutrophils and fixed/wandering macrophages (derived from monocytes): Act through phagocytosis.

    • Eosinophils: Combat histamine effects during allergic reactions, phagocytize antigen-antibody complexes, and target parasitic worms.

    • Basophils: Develop into mast cells releasing heparin, histamine, and serotonin during allergic reactions enhancing inflammation.

    • B Lymphocytes: Differentiate into plasma cells producing antibodies in response to antigens.

    • T Lymphocytes: Directly destroy foreign invaders.

    • Chemotaxis: The process by which WBCs are chemically attracted to sites of disease or injury.

COMPLETE BLOOD COUNT (END OF LECTURE VIDEO #6)

  • Purpose: Screens for anemia and infection.

  • Tests include:

    • Total RBC, WBC & platelet counts.

    • Differential WBC count.

    • Hematocrit and hemoglobin measurements.

  • Normal Hemoglobin Range:

    • Infants: 14 to 20 g/100mL of blood.

    • Adult Females: 12 to 16 g/100mL of blood.

    • Adult Males: 13.5 to 18 g/100mL of blood.

PLATELETS (START/END OF LECTURE VIDEO #7)

  • Thrombopoietin: Stimulates myeloid stem cells to produce platelets.

  • Development Process:

    • Myeloid stem cells develop into megakaryocyte-colony-forming cells, which then transform into megakaryoblasts.

    • Megakaryoblasts become megakaryocytes and fragment to form platelets.

  • Normal Count: Ranges from 250,000 to 400,000 platelets/mm³.

  • Platelets have a lifespan of only 5 to 9 days; aged and dead platelets are removed by fixed macrophages in the spleen and liver.

ABO BLOOD GROUP (START OF LECTURE VIDEO #8)

  • Agglutinogens (antigens) A and B determine blood types:

    • Plasma contains agglutinins (antibodies) designated as anti-A and anti-B.

    • These react with foreign agglutinogens.

BLOOD GROUPS AND BLOOD TYPES

  • Type A:

    • Red blood cells with type A surface antigens.

    • Plasma containing anti-B antibodies.

  • Type B:

    • Red blood cells with type B surface antigens.

    • Plasma containing anti-A antibodies.

  • Type AB:

    • Red blood cells with both type A and B surface antigens.

    • Plasma contains neither anti-A nor anti-B antibodies.

  • Type O:

    • Red blood cells with neither type A nor type B surface antigens.

    • Plasma contains both anti-A and anti-B antibodies.

UNIVERSAL DONORS AND RECIPIENTS

  • Type AB Blood: Considered universal recipients as they have no antibodies in plasma (true if cross-matched for other antigens).

  • Type O Blood: Considered universal donors since they have no antigens on their cells and can be given to anyone theoretically.

RH BLOOD GROUPS (END OF LECTURE VIDEO #8)

  • The Rh antigen was first discovered in the blood of Rhesus monkeys.

  • Individuals with Rh agglutinogens on their RBC surface are classified as Rh+.

    • Normal plasma contains no anti-Rh antibodies.

  • Anti-Rh antibodies develop in Rh- individuals only with exposure to the antigen:

    • Through transfusion of Rh+ blood or during pregnancy with an Rh+ fetus.

  • A transfusion reaction upon second exposure leads to hemolysis of the RBCs from the donated blood (the fetus).