Let's Get Pumping! (Lesson 7.01)

Overview of Blood

  • Blood is not merely a liquid; it is a specialized tissue composed of cells and dissolved chemicals that serve critical functions in the body.

  • Blood maintains homeostasis through the circulation of its components in relation to the heart and lungs.

Blood Tissue

  • Blood consists of:

    • Fluid: Plasma

    • Cells: Red blood cells (RBCs), white blood cells (WBCs), platelets, and cell fragments.

  • Plasma:

    • Described as a straw-colored fluid, consisting of 90% water and 10% solutes.

    • Solutes in plasma include:

    • Proteins (e.g., albumin, fibrinogen, globulins, prothrombin)

    • Nutrients, waste products, gases, and substances that help in homeostasis.

    • Makes up 55% of blood volume.

Functions of Plasma Proteins

  • Clotting: Essential for hemostasis (the process of blood clotting).

  • Immune System: Essential for mounting an immune response.

  • Viscosity and Volume: Maintain the consistency of blood viscosity and overall blood volume.

  • Osmotic Pressure: Regulates fluid balance within and outside of cells, facilitating homeostasis across body systems.

Impact of Liver Disease on Blood

  • Liver disorder leads to:

    • Impaired immunity due to reduced plasma protein production.

    • Impaired blood clotting functions.

    • Potential disruptions in electrolyte and fluid balance.

Percentages in Blood Composition

  • Plasma and other solutes account for 55% of blood, while the remaining 45% is made up of formed elements.

  • In a typical drop of blood:

    • Approximately 5 million RBCs.

    • 7,500 WBCs.

    • 300,000 platelets.

Formed Elements: Types of Blood Cells

  • Hematopoiesis: The process of creating new blood cells, predominantly occurring in the red bone marrow (myeloid tissue).

  • Lymphocytes: Produced in lymphoid tissues such as lymph nodes, spleen, and thymus gland.

Red Blood Cells (Erythrocytes)

  • Lifespan: 105 to 120 days.

  • Characteristics:

    • Concave disc shape and lack a nucleus.

    • Packed with hemoglobin, crucial for oxygen transport and acid-base homeostasis.

  • Functions:

    • Transport inhaled oxygen from lungs to tissues.

    • Carry about 24% of carbon dioxide waste back to lungs for exhalation.

    • Flexible structure aids in navigating narrow capillaries.

Platelets

  • Description: Small, non-nucleated cell fragments.

  • Lifespan: 8 to 11 days.

  • Functions: Key role in blood clotting (hemostasis).

  • Synthesis stimulated by thrombopoietin, released by kidneys.

  • Approx. one-third stored in the spleen for emergencies.

White Blood Cells (Leukocytes)

  • Comprise 1% of formed elements yet are critical for immune response.

  • Characteristics: Sphere-shaped with variably shaped nuclei; color differentiation when stained.

Types of Leukocytes

  1. Neutrophils

    • Function: Protect against bacterial and viral infections through phagocytosis.

    • Lifespan: From hours to 3 days.

    • Appearance: Pink-purple when stained.

  2. Lymphocytes

    • Structure: Single-lobed nucleus, minimal cytoplasm.

    • Function: Secretion of antibodies; involved in immune response against antigens (viruses, pollen, bacteria).

    • Lifespan: Days to years; stained appearance is purple.

  3. Monocytes

    • Characteristics: Kidney bean-shaped nucleus; large cytoplasm.

    • Function: Perform phagocytosis; destroy bacteria and waste products.

    • Lifespan: Months; stained appearance is steel blue.

  4. Eosinophils

    • Structure: Single-lobed nucleus, abundant cytoplasm.

    • Function: Regulate allergic reactions, perform phagocytosis, combat parasitic infections.

    • Lifespan: 10 to 12 days; orange-red appearance when stained.

  5. Basophils

    • Function: Secretion of heparin (anticoagulant) and histamine (inflammatory response).

    • Lifespan: Hours to 3 days; stained light purple.

Hemostasis: The Process of Blood Clotting

  • Hemostasis comprises several stages:

    • Vasoconstriction: Smooth muscle spasms in damaged vessel walls reduce blood loss.

    • Platelet Plug Formation: Platelets adhere to damaged areas, forming a temporary plug, akin to sealing a leak.

    • Coagulation (Clotting Phase): Sequential chemical reactions (clotting cascade) release substances (thrombin and fibrin) to promote optimized clotting mechanisms.

Hemostasis and Tissue Repair

  • The hemostatic process also involves tissue repair through a structured sequence:

    1. Hemostasis: Initial bleeding and clot formation.

    2. Inflammation: Immune cells target foreign materials and bacteria at the injury site.

    3. Proliferation: New cells support epidermis growth; new blood vessels form.

    4. Remodeling: Post-healing adjustments where excess cells break down and skin normalizes.

Neutrophils