Blood and Blood Components Notes

Blood & Blood Components

  • Prescribed textbook: chapter 4 & 5

Learning Objectives

  • Blood is one of the specialized tissue types.
  • Cellular elements of blood and their functions.
  • Plasmatic elements of blood and their functions.
  • Understand the blood clotting process (blood coagulation).
  • Understand sickle cell disease from cellular AND histological perspective.

Blood Composition and Function

  • Blood in vertebrates is a connective tissue.
  • It consists of several kinds of cells suspended in a liquid matrix called plasma.
  • Cellular elements occupy about 45% of the volume of blood.
  • Plasmatic elements occupy about 55% of the volume of blood.

Plasma (55% of Blood Volume)

  • Constituents and Major Functions:
    • Water: Solvent.
    • Ions (blood electrolytes):
      • Sodium
      • Potassium
      • Calcium
      • Magnesium
      • Chloride
      • Bicarbonate
      • Function: Osmotic balance, pH buffering, and regulation of membrane permeability.
    • Plasma proteins:
      • Albumin: Osmotic balance, pH buffering.
      • Immunoglobulins (antibodies): Defense.
      • Apolipoproteins: Lipid transport.
      • Fibrinogen: Clotting.
    • Substances transported by blood:
      • Nutrients (such as glucose, fatty acids, vitamins)
      • Waste products of metabolism
      • Respiratory gases (O2 and CO2)
      • Hormones

Cellular Elements (45% of Blood Volume)

  • Cell Types, Functions, and Number per µL (mm3) of blood:
    • Leukocytes (white blood cells):
      • Defense and immunity
      • Number: 5,000–10,000
      • Types:
        • Basophils
        • Lymphocytes
        • Eosinophils
        • Neutrophils
        • Monocytes
    • Platelets:
      • Blood clotting
      • Number: 250,000–400,000
    • Erythrocytes (red blood cells):
      • Transport of O2 and some CO2
      • Number: 5,000,000–6,000,000

Plasma Details

  • Plasma contains inorganic salts as dissolved ions, sometimes called electrolytes.
  • Plasma proteins influence blood pH and help maintain osmotic balance.
  • Particular plasma proteins function in lipid transport, immunity, and blood clotting.

Cellular Elements Details

  • Suspended in blood plasma:
    • Red blood cells (erythrocytes) transport O_2.
    • Platelets - cells that are involved in clotting.
    • White blood cells (leukocytes) function in defense.

Erythrocytes and Hemoglobin

  • Erythrocytes mainly transport oxygen molecules.
  • Each molecule of hemoglobin binds up to four molecules of O_2.
  • Hemoglobin is an iron-containing protein that transports O_2.
  • Oxygen is released to tissue cells by red blood cells.

Sickle Cell Disease

  • Understand the cellular & tissue mechanisms/process of the sickle cell disease together with protein synthesis aspects covered during Cell Biology.
    • “Point mutation in Sickle cell anaemia” (Cell Biology: Lecture 6)
    • codon table (Cell Biology: Protein Synthesis Practical)
    • IMPORTANT: https://www.youtube.com/watch?v=hRnrIpUMyZQ

Leukocytes Details

  • Neutrophils:
    • ~50% of WBC’s, first to respond against bacterial / viral invasion.
    • Alert other cells in immune system to respond as well.
  • Eosinophils:
    • Responding to parasite (e.g. worms) infections
    • Role in allergy symptoms (overreaction to mistaken invader e.g. pollen)
    • ~1% in bloodstream, but highly concentrated in digestive tract
  • Basophils:
    • ~1% of WBC’s, mount non-specific immune response to pathogens
  • Lymphocytes:
    • T-cells kills foreign invaders directly
    • B-cells humoral immunity, produce antibodies that “remember” an infection
  • Monocytes:
    • ~5% of WBC’s, important for migrating into tissues and clean up dead cells

Stem Cells and Blood Cell Production

  • Stem cells (in bone marrow):
    • Lymphoid stem cells → B cells, T cells (Lymphocytes)
    • Myeloid stem cells → Erythrocytes, Monocytes, Platelets, Neutrophils, Basophils, Eosinophils
  • Especially bones of the ribs, vertebrae, sternum, and pelvis are involved in the replacement of cellular elements.
    • White blood cells
    • Platelets
    • Red blood cells
    • Originate from Stem cells

Platelets and Blood Clotting

  • Platelets function in blood clotting.
  • Process:
    • Broken blood vessel wall
    • Platelets are activated
    • Fibrin is formed
    • Red blood cells are caught in threads of fibrin to form a clot
  • Reference: https://biology-igcse.weebly.com/
  • Video: https://www.youtube.com/watch?v=gExUCrpAKYQ