Chapter 11: Blood

Introduction to Blood

• Focuses on blood as a part of the cardiovascular system (heart, arteries, veins).
• Importance of blood and its unique functions.

Functions of Blood

• Transport Functions:
  • Carries oxygen and carbon dioxide to tissues.
  • Transports nutrients, waste products, ions, and regulatory molecules.
• Regulatory Functions:
  • Regulates pH levels.
  • Helps with osmosis and maintains body temperature.
• Protection Functions:
  • Provides defense against foreign substances via white blood cells (immune system).
  • Platelets assist in forming clots to stop bleeding.

Composition of Blood

• Plasma: 55% of blood volume, mostly water with proteins and solutes.
  • Key Proteins:
    • Albumin: Maintains blood volume balance.
    • Globulins: Involved in immune response.
    • Fibrinogen: Essential for clot formation.
• Formed Elements: 45% of blood volume.
  • Includes:
    • Erythrocytes (Red Blood Cells): Carry oxygen.
    • Leukocytes (White Blood Cells): Fight infection.
    • Thrombocytes (Platelets): Assist in clotting.

Blood Sample Analysis

• Blood samples are taken via venipuncture and centrifuged to separate components:
  • Plasma: Top layer (mostly water and proteins).
  • Buffy Coat: Middle layer (contains white blood cells and platelets).
  • Erythrocytes: Bottom layer (denser red blood cells).
• Blood tests can assess cell counts and diagnose diseases.

Hematopoiesis

• Formation of blood cells from hemocytoblasts (stem cells).
• Occurs in:
  • Fetus: Liver, spleen, thymus, lymph nodes.
  • After birth: Mostly in red bone marrow.
• Differentiation into various blood cell types (myeloid/lymphoid lines).

Erythrocytes (Red Blood Cells)

• Structure: Disc-shaped, no nucleus, lifespan ~120 days.
• Function: Primary role in oxygen transport via hemoglobin.
• Hemoglobin binding:
  • Oxyhemoglobin: Hemoglobin with oxygen.
  • Deoxyhemoglobin: Hemoglobin without oxygen.

Erythropoiesis Regulation

• Increased erythrocyte production in response to low oxygen levels (via erythropoietin hormone).
• Importance for athletes training at high altitudes.

Breakdown of Old Erythrocytes

• Process involves macrophages in spleen/liver breaking down RBCs.
• Iron recycled, heme converted to bilirubin (used in bile production).

Leukocytes (White Blood Cells)

• Function: Fight infections and clear debris.
• Types:
  • Granulocytes: Neutrophils, eosinophils, basophils.
  • Agranulocytes: Monocytes, lymphocytes.
• Each type has specific roles in immune response.

Thrombocytes (Platelets)

• Small cell fragments involved in clotting processes.
• Formed via megakaryocytes in red bone marrow.

Blood Clotting Mechanism

• Vascular Spasm: Constriction of damaged blood vessels.
• Platelet Plug Formation: Platelets adhere to injury site and aggregate.
• Clot Formation: Fibrinogen converts to fibrin, forming a stable clot.

Blood Grouping and Compatibility

• Blood types determined by antigens on RBC surfaces (A, B, AB, O).
• Universal Donor: Type O (no antigens).
• Universal Recipient: Type AB (no antibodies against A or B antigens).
• Rh factor (+ or -) indicates presence of additional antigen.

Hemolytic Disease of the Newborn

• Occurs when an Rh-negative mother has an Rh-positive baby, leading to antibody production in the mother.
• Risk for subsequent pregnancies if antibodies cross the placenta.

Diagnostic Blood Tests

• Complete Blood Count (CBC): Counts RBCs, WBCs, hemoglobin, and hematocrit levels.
• Prothrombin Time: Measures clotting time; normal range is 9-12 seconds.
• White Blood Cell Count: Elevated counts indicate infections or disorders (leukopenia/leukocytosis).

Conclusion

• Blood is vital for transporting substances, regulating the body, and protecting against diseases. Understanding blood components and functions is essential for diagnosing health conditions.