Blood Characteristics, Functions, and Components

  • Blood Characteristics

    • Blood is classified as connective tissue.
    • Composed of:
      • 55% plasma
      • 45% formed elements
    • Created through hematopoiesis (stem cells in bone marrow develop formed elements).

  • Average Blood Volume

    • Approximately 5-6 liters for men; 4-5 liters for women (based on body size).
    • Men have a higher quantity of red blood cells (RBCs) due to testosterone influence.
    • Blood pH ranges from 7.35 to 7.45.

  • Formed Elements of Blood

    • Erythrocytes (RBCs)
    • Leukocytes (WBCs)
    • Thrombocytes (Platelets)

  • Functions of Blood

    • Transports gases, nutrients, and hormones.
    • Regulates pH and electrolyte balance (with kidneys and lungs).
    • Defends against pathogens and toxins.
    • Prevents fluid loss from bleeding (hemostasis).
    • Aids in body temperature regulation.

  • Components of Blood: Plasma

    • Plasma is the liquid matrix that, without formed elements, is called serum.
    • Composition:
    • 92% Water
    • 7% Proteins:
      • Albumins: most abundant; maintain osmotic pressure.
      • Globulins: enzymes, transport proteins, antibodies.
      • Fibrinogen: involved in clotting.
    • 1-2% inorganic salts, carbohydrates, lipids, hormones, gases, wastes, etc.

  • Red Blood Cells (RBCs)

    • Most abundant blood cell.
    • Shape: biconcave disc (increases surface area/volume ratio).
    • Anucleate when mature; lifespan of about 120 days.

  • Hemoglobin (Hb)

    • Red pigment within RBCs.
    • Composed of four subunits (including iron) that can each bind to one oxygen molecule, allowing each hemoglobin molecule to carry four oxygen molecules.
    • Conditions affecting hemoglobin include fetal hemoglobin having a higher affinity for oxygen than adult hemoglobin.

  • Erythropoiesis

    • RBC production occurs primarily in the myeloid tissue of red bone marrow.
    • Requires amino acids, iron, vitamins B12, B6, and folic acid.

  • White Blood Cells (WBCs)

    • Function: attack invading organisms, remove toxins.
    • Types include neutrophils, eosinophils, basophils, monocytes, and lymphocytes, differing in structure and function related to immune response.

  • Platelets

    • Cell fragments involved in clotting; formed from megakaryocytes in the bone marrow.
    • Function: release clotting chemicals, patch vessel walls, and contract tissue after clotting.

  • Hemostasis

    • The stoppage of bleeding requiring Vitamin K and Ca2+.
    • Phases: vascular spasms, platelet plug formation, and coagulation.

  • ABO Blood Types

    • Example of codominance with alleles A, B dominant over O.
    • Important for transfusions, where avoiding antigen-antibody reactions (agglutination) is critical.
    • Blood type A: antigens A, antibodies B
    • Blood type B: antigens B, antibodies A
    • Blood type AB: antigens A & B, no antibodies
    • Blood type O: no antigens, antibodies A & B

  • Rh Factor

    • Determines if blood is Rh positive (with Rh factor) or Rh negative (without).
    • Rh negative individuals can produce antibodies after exposure to Rh positive blood, which can lead to complications in pregnancy (Erythroblastosis Fetalis).

  • Blood Typing Procedures

    • Involves adding antibody serum (Anti-A, Anti-B, Anti-Rh) to determine blood type based on agglutination reactions.

  • Clinical Measurements

    • Complete blood count (CBC) assesses various blood components and can indicate the presence of disorders, anemia, or infections.