Chapter 18: Blood (Hematology)

Introduction

• Focus on the study of blood (hematology).
• Functions of blood: composition, physical characteristics, plasma functions, erythrocytes and hemoglobin, leukocytes, platelets.
• Abnormalities, hemostasis, hemostatic disorders, significance of blood typing and transfusion reactions.

Physical Characteristics of Blood

• Color: Ranges from scarlet red to dark red, never blue.
• Volume: Females (4-5 liters), Males (5-6 liters), average used: 5.25 liters.
• Viscosity and Concentration: 0.9% saline concentration.
• Temperature: Approximately 38°C (98.6°F).
• pH Range: 7.35 to 7.45, normal pH is 7.4.

Composition of Blood

• Composed of formed elements and plasma.
• Plasma: 55% of blood; contains 92% water, 7% proteins, 1% other solutes.
  • Proteins: Albumin, Globulins (antibodies), Fibrinogen.
  • Solutes: Electrolytes (mainly sodium), nutrients, gases (CO2, O2), waste products.
• Formed Elements: Erythrocytes, leukocytes, platelets.
  • Erythrocytes (Red Blood Cells): 44% of blood, biconcave disks, anucleate, flexible.
  • Leukocytes (White Blood Cells): Present in Buffy coat (<1%), include neutrophils, lymphocytes, monocytes, eosinophils, basophils.
  • Platelets: Cell fragments important for hemostasis.

Function of Blood

• Distribution: Carries nutrients, gases, wastes.
• Regulation: Body temperature, pH, fluid volume.
• Protection: Blood clotting, immune defense.

Hematocrit

• Percentage of red blood cells in a blood sample.
• Normal values: Males 47% ±5, Females 42% ±5.

Erythrocytes

• Contain hemoglobin for oxygen transport.
• Hemoglobin Structure: 4 globin chains, 4 hemes, binds oxygen.
• Factors for Production: Iron, vitamin B12, folic acid.
• Lifecycle: 120 days, phagocytized by spleen.

Blood Disorders

• Anemia: Low oxygen capacity due to insufficient RBCs or hemoglobin.
  • Types: Hemorrhagic, hemolytic, aplastic, iron deficiency, pernicious, sickle cell, thalassemia.
• Polycythemia: Excess RBCs, increased blood viscosity.

Blood Typing

• ABO System: A, B antigens on RBCs, antibodies in plasma.
  • Type A: A antigen, anti-B antibody.
  • Type B: B antigen, anti-A antibody.
  • Type AB: A and B antigens, no antibodies (universal recipient).
  • Type O: No antigens, anti-A and anti-B antibodies (universal donor).
• Rh Factor: Positive or negative based on the presence of Rh antigen.

Leukocytes

• Types: Granulocytes (neutrophils, eosinophils, basophils) and Agranulocytes (lymphocytes, monocytes).
• Function in immune response, phagocytosis, and defense against parasites.

Platelets

• Cell fragments from megakaryocytes.
• Essential for blood clot formation and hemostasis.

Conclusion

• Blood is a complex connective tissue vital for transport, regulation, and protection in the body.
• Understanding its components, functions, and disorders is crucial for medical and health sciences.