Composition & Function of Blood

Composition & Function of Blood

Introduction

  • Blood is the ONLY fluid connective tissue in the body.

  • Consists of both solid and liquid components:

    • Solid components:

    • White blood cells and platelets

    • Red blood cells

    • Liquid component:

    • Plasma

  • Composition breakdown:

    • Plasma: 55%

    • Formed elements: 45%

10.1a Physical Characteristics & Volume

  • Description of Blood Characteristics:

    • Color:

    • Dependent on oxygen levels:

      • Scarlet (oxygen-rich)

      • Dull red/purple (oxygen-poor)

    • Taste:

    • Metallic & salty

    • Texture:

    • Viscous & sticky

    • pH:

    • Alkaline (7.35 - 7.45)

    • Temperature:

    • 100.4℉ (due to friction between blood and vessels)

    • Percentage of body weight:

    • 8%

    • Approx. 5 to 6 L in healthy adults

10.1b Components of Blood

  • Blood separation through centrifuge:

    • Upper layer:

    • Plasma

    • Non-living matrix, making up 55% of volume

    • Middle layer:

    • Buffy coat

      • Leukocytes (white blood cells)

      • Platelets

      • Less than 1% of volume

    • Lower layer:

    • Erythrocytes

      • Red blood cells

      • 45% of volume

  • Formed elements: Includes red blood cells, white blood cells, and platelets.

10.1c Plasma

  • Plasma makes up 55% of blood volume:

    • Water: 90%

    • Distributes body heat

    • Salts (electrolytes):

    • Important for osmotic balance, pH buffering, and membrane regulation

    • Key electrolytes include:

      • Sodium (Na)

      • Potassium (K)

      • Calcium (Ca)

      • Magnesium (Mg)

      • Chloride (Cl)

      • Bicarbonate (HCO3)

    • Plasma Proteins:

    • Crucial for functions making blood a connective tissue:

      • Albumin: Keeps fluid in the bloodstream

      • Fibrinogen: Involved in blood clotting (scabs)

      • Globulins: Fights infections

    • Transported substances include:

    • O₂, CO₂, glucose, urea, hormones, etc.

  • Regulation of plasma:

    • Body systems maintain plasma in the "normal" range:

    • If plasma proteins are low, the liver will produce more.

    • If pH shifts, the respiratory and urinary systems will adjust.

Questions:

  1. Which organ plays the major role in making plasma proteins?

  2. List the three major categories of formed elements.

  3. What determines the shade of red for blood?

10.1d Formed Elements (Cells)

  • Made up of 45% of blood volume:

    • Types of cells:

    • Erythrocytes:

      • Also known as red blood cells (RBCs)

      • Primary function: Transport O₂ and CO₂

    • Leukocytes:

      • Also known as white blood cells (WBCs)

      • Function: Defense and immunity

      • Types include:

      • Basophil

      • Eosinophil

      • Neutrophil

      • Lymphocyte

      • Monocyte

    • Platelets:

      • Function: Blood clotting

Visuals:

  • Human blood smear shows:

    • Erythrocytes

    • Platelets

    • Leukocytes

Erythrocytes

  • Also known as red blood cells (RBCs):

    • Function:

    • Transport oxygen

    • Structure:

    • No nucleus or organelles

    • Biconcave shape

    • Contains hemoglobin (Hb):

      • An iron-protein that binds to oxygen

      • Each hemoglobin can bind to four O₂ molecules

      • 1 RBC contains approximately 250 million Hb molecules

Homeostatic Imbalance:

  • Anemia:

    • Decreased oxygen-carrying ability due to:

    • Decreased RBCs resulting from hemorrhaging or infection

    • Decreased hemoglobin due to iron deficiency (diet-related)

Platelets

  • Not actual cells:

    • Fragments of megakaryocytes (multinucleated cells)

    • Function: Blood clotting

Leukocytes

  • White blood cells (WBCs):

    • Represent less than 1% of blood volume:

    • Normal range: 4,800 to 10,800 WBC/mm³

    • Diapedesis:

    • Process where WBCs can travel through blood vessels and exit into tissues

    • Structure:

    • Contain nuclei and other organelles

    • Categories:

    • Granulocytes:

      • Eosinophils

      • Neutrophils

      • Basophils

    • Agranulocytes:

      • Monocytes

      • Lymphocytes

    • Function: Defense against pathogens

Immune Response Mechanisms:

  1. Chemotaxis:

    • Damaged cells emit chemical signals indicating distress.

  2. Amoeboid motion:

    • WBCs travel to the location of the distress signal:

    • Increased production of WBCs in response:

      • WBC count >11,000 cells/mm³ indicates leukocytosis (typically due to infection).

      • WBC count <4,000 cells/mm³ indicates leukopenia (may be due to medications like corticosteroids or anticancer therapy).

  3. WBCs engage in phagocytosis, engulfing microorganisms and disposing of dead cells.

Leukemia:

  • Termed "White Blood" leukemia.

  • Cancer of the bone marrow characterized by:

    • Excessive increase of WBCs:

    • Immature WBCs are ineffective, increasing infection susceptibility.

    • Overcrowding of formed elements leading to anemia and bleeding problems.

10.1e Hematopoiesis (Blood Cell Formation)

  • Occurs in red bone marrow:

    • Also known as myeloid tissue.

    • Produces all types of blood cells in varying amounts according to body needs:

    • Once mature, cells exit into blood vessels.

    • Rate of production:

    • Produces approximately 100 billion cells per day.

Steps of Hematopoiesis:

  1. Hemocytoblast (stem cell):

    • Located in red bone marrow

    • Undifferentiated for all formed elements

  2. Secondary Stem Cells:

    • Lymphoid stem cells: Develop into lymphocytes.

    • Myeloid stem cells: Develop into erythrocytes, basophils, eosinophils, monocytes, neutrophils, and platelets.

Formation of RBCs:

  • Process Details:

    1. Hemocytoblast divides multiple times to produce RBCs.

    2. RBCs continue cell division, producing hemoglobin until the nucleus and organelles are ejected, producing a biconcave shape.

    3. The young RBC is termed reticulocyte (some rough ER present).

    • Circulates in bloodstream, ejecting remaining rough ER within 2 days.

      • Time to mature: 3-5 days from hemocytoblast to mature RBC.

Regulation of RBC Production:

  • Controlled by the hormone erythropoietin:

    • Produced in kidneys.

    • Stimulates red bone marrow to create more RBCs based on oxygen-carrying ability, not merely the number of RBCs.

Degradation of RBCs:

  • Lifespan of RBCs is 100-120 days:

    • Becomes rigid and begins breakdown.

    • Phagocytes eliminate RBC remains in spleen, liver, and other tissues.

    • Iron binds to a protein as ferritin; the heme group is degraded into bilirubin and exits the body as stercobilin in feces.

Formation of White Blood Cells & Platelets:

  • Hormone-dependent formation:

    • Leukocytes:

    • Controlled by colony stimulating factors (CSFs) and interleukin hormones.

    • Platelets:

    • Regulated by thrombopoietin hormone.

formed elements:

  • Eosinophil - phagocytes and anti-histamines

  • Neutrophil - Bacterial phagocyte

  • Basophil - Pro-inflammatory

  • Monocyte - Pathogen Phagocyte and old cells

  • Lymphocyte - T-cells: attack other cells. B-cells: antibodies killer cells and non-specific

  • Erythrocyte (RBC) - Oxygen transports

  • Platelet - blood clotting