Physiology of Blood

Physiology of Blood

• Blood is crucial for life, performing vital functions like transporting oxygen and nutrients, regulating processes, and protecting against diseases.

Functions of Blood

• Transport:
  • Carries oxygen from lungs to tissues, and carbon dioxide from tissues to lungs.
  • Transports nutrients (glucose, amino acids, fatty acids) and removes waste products.
  • Delivers hormones to target organs.
• Regulation:
  • Maintains body temperature by absorbing and distributing heat.
  • Regulates pH (7.35-7.45) through buffer systems.
  • Regulates electrolyte and water content.
• Protection:
  • Contains white blood cells (leukocytes) and antibodies that fight infections.
  • Has a clotting mechanism to stop excessive blood loss.

Components of Blood

• Plasma: Liquid portion (about 55% of blood volume), primarily water, dissolved proteins, electrolytes, nutrients, and waste.
• Red Blood Cells (Erythrocytes): Carry oxygen using hemoglobin; essential for oxygen transport.
• White Blood Cells (Leukocytes): Protect against infection via various types, each with a specialized function.
• Platelets (Thrombocytes): Crucial for blood clotting when vessels are damaged.

pH and Temperature

• Blood pH ranges from 7.35 to 7.45 (slightly alkaline).
• Blood temperature is slightly higher than body temperature (~38°C), assisting in maintaining homeostasis.

Haematopoiesis

• Blood cell production occurs primarily in bone marrow.
• This process constantly maintains the supply of red blood cells, white blood cells, and platelets.

Erythropoiesis

• The process of red blood cell production.
• Regulated by erythropoietin (EPO), primarily produced by kidneys, stimulating red blood cell production, especially in hypoxia (low oxygen).

Leukopoiesis

• The process of white blood cell production.
• Regulated by cytokines like interleukins and colony-stimulating factors, promoting differentiation and proliferation of specific leukocyte types.

Thrombopoiesis

• Platelet production, involving the differentiation of hematopoietic stem cells into megakaryocytes in bone marrow.
• Regulated by thrombopoietin, produced by the liver and kidneys.

Cytokines

• Signaling molecules that regulate immunity, inflammation, and haematopoiesis.
• They function as messengers, coordinating the immune response and influencing blood cell production.

Red Blood Cells (Erythrocytes)

• Contain hemoglobin, a protein responsible for oxygen transport.
• Types include HbA, HbA2, and HbF (important during fetal development).

White Blood Cells (Leukocytes)

• Crucial for the body's immune response.
• Different types include neutrophils (most abundant), eosinophils (involved in allergies/parasites), basophils (allergic reactions), and others.

Blood Types

• ABO and Rh blood group systems are crucial for compatibility during blood transfusions.
• Incompatibility can result in life-threatening reactions.
• O RhD negative is considered the universal blood donor.

Blood Tests

• ESR (Erythrocyte Sedimentation Rate): Measures the rate at which red blood cells settle, indicating inflammation or infection.
• CRP (C-Reactive Protein): Measures inflammation in the bloodstream, useful for diagnosing various conditions.
• Troponin: Cardiac muscle protein raised in the blood during a heart attack, used as diagnostic marker.
• Lipid Profile: Measures cholesterol and triglyceride levels in blood; useful for assessing cardiovascular disease risk.
• Urea and Electrolytes: Evaluate kidney function by assessing waste products and electrolyte levels.
• Full Blood Count (FBC): Comprehensive blood test providing information on various blood cells, crucial in diagnosing conditions like anemia, infections, and leukemia.
• HbA1c: Measures average blood glucose over the past two to three months; used to monitor diabetes.

Clinical Cases

• Anaemia: Explanation of possible causes (iron deficiency, chronic disease), tests to determine the cause.
• Heart Attack: Significance of elevated troponin levels, other tests to confirm the diagnosis, and to assess damage extent.