Blood Constituents | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Blood Constituents

• Blood as Connective Tissue:
  • Blood is a unique connective tissue with fluid matrix and formed elements.
  • Formed elements include cells and fragments serving various functions.
• Plasma:
  • Fluid phase of blood, straw-colored and transparent.
  • Comprises 35-50% of blood, species-dependent.
  • Approximately 90% water and 10% dissolved substances.
  • Includes inorganic ions (Na, K, Ca), plasma proteins (albumins, globulins, fibrinogen), and other organic substances.
  • Contains hormones, enzymes, pigments, vitamins, and dissolved gases.
• Formed Elements:
  • Erythrocytes: Red blood cells.
  • Leukocytes: White blood cells, further classified into agranulocytes (lymphocytes, monocytes) and granulocytes (neutrophils, eosinophils, basophils).
  • Platelets (thrombocytes): Cell fragments in mammals; in avian species, thrombocytes are complete cells.
• Chemical Composition of Blood Plasma:
  • Water: Dominates the composition.
  • Gases: Oxygen, carbon dioxide, nitrogen.
  • Proteins: Albumin, globulin, fibrinogen.
  • Carbohydrates: Glucose, lactate, pyruvate.
  • Lipids: Fat, lecithin, cholesterol.
  • Non-Protein Nitrogenous Substances: Amino acids, urea, uric acid, creatine, creatinine, ammonium salts.
  • Inorganic Substances: Sodium, potassium, calcium, magnesium, chloride, sulfate, phosphate, iron, manganese, cobalt, copper, zinc, iodine.
• Note:
  • Blood plasma composition is similar in different mammals with quantitative variations.
  • Plasma plays a crucial role in transporting nutrients, gases, and waste products throughout the body.

Functions of Blood

• Oxygen and Carbon Dioxide Transport:
  • Vital role in transporting oxygen and carbon dioxide for pulmonary and cellular respiration.
• Buffer Systems:
  • Blood contains buffer systems (carbonates, phosphates, hemoglobin, proteins) crucial for maintaining pH balance.
• Nutrient Transport:
  • Acts as a pathway for transporting all food substances, emphasizing its importance in nutrition.
• Excretory Function:
  • Removes metabolic waste products, contributing to the body's cleansing process.
• Fluid Balance Maintenance:
  • Ensures balance between blood-vascular system, tissue fluid space, intracellular fluid space, and lymphatics.
  • Important for heat regulation and transport of various materials.
• Regulatory Function:
  • Regulates body temperature through fluid content.
  • Facilitates transport of hormones, serving a regulatory role.
• Protective Device:
  • Blood provides protection through its cells and suspended materials (antibodies, antitoxins).
  • Essential for the immune system.

Plasma Protein Components

• Albumin:
  • About half of plasma protein, maintains osmotic pressure.
  • Regulates fluid balance and transports hormones, metabolites, and drugs.
• Alpha-Globulins:
  • Contribute to osmotic pressure and serve as carriers for substances like copper, hemoglobin, thyroxin.
  • Contains enzymes and factors related to blood clotting.
• Beta-Globulins:
  • Contribute to osmotic pressure.
  • Transport substances like iron, lipoproteins, and coagulation factors.
• Gamma-Globulins:
  • Include immunoglobulins for the immune system.
  • Blood group globulins.

Erythrocytes (Red Blood Cells)

• Anucleated, biconcave disk carrying oxygen as oxyhemoglobin and transporting carbon dioxide as carboxyhemoglobin.
• Primary function is oxygen delivery to tissues.
• Found as round cells in most mammals but oval in Camelidae (Camel, Llama).

Granulocytes

• Definition:
  • White blood cells (leukocytes) with specific granules and lobed nuclei.
  • Function within blood vessels and tissues for protection.
• Neutrophils:
  • Primary function: Phagocytosis of particles, bacteria, and microorganisms.
  • Crucial in immune response and defense against infections.
• Eosinophils:
  • Function not fully understood.
  • Increase during allergies, parasitic infections, and antibody/antigen reactions.
  • Phagocytic but to a lesser extent than neutrophils.
• Basophils:
  • Obscure function, possibly involved in histamine and heparin release in the bloodstream.
• B Lymphocytes (B Cells):
  • Responsible for producing antibodies (immunoglobulins) in response to antigens.
  • Form the basis for humoral antibody immunity in the blood.
• T Lymphocytes (T Cells):
  • Responsible for cell-mediated immunity.
  • May produce lymphokines.
• Monocytes:
  • Phagocytic cells that transform into macrophages in tissues.
• Platelets (Thrombocytes):
  • Essential for hemostasis (cessation of bleeding).
  • Mediate vasoconstriction due to serotonin presence.
  • Assist phagocytosis as opsonins and may interact with viral particles.

Blood Cell Formation (Hematopoiesis)

• Continuous Process:
  • Ongoing formation of blood cells.
  • Essential nutrients, including vitamins B12 and folic acid, are required for erythrocyte maturation.
• Vitamins in Hematopoiesis:
  • B12 and folic acid act as coenzymes in nucleic acid synthesis.
  • Other vitamins supporting hematopoiesis include pyridoxine, riboflavin, nicotinic acid, pantothenic acid, thiamine, biotin, and ascorbic acid.
• Nutrients and Minerals:
  • Essential for blood protein synthesis.
  • Required minerals: iron, copper, and cobalt.
• Blood Cell Replacement:
  • About 1% of red blood cells replaced daily, assuming a 120-day lifespan.
  • Adequate oxygen supply stimulates hematopoiesis.
  • Erythropoietin, released from tissues, plays a role in stimulating blood cell maturation.

Red Bone Marrow (Myeloid Tissue)

• Definition:
  • Hemopoietic tissue responsible for producing blood cells.
  • Commonly known as myeloid tissue.
• Cell Production:
  • Erythrocytes (red blood cells), granulocytes, and platelets are formed in red bone marrow.
  • Agranulocytes develop in both red bone marrow and lymphatic organs.
• Theories of Blood Cell Formation:
  • Monophyletic theory: Supports separate stem cells for agranulocytes and granulocytes/erythrocytes.
  • Polyphyletic theory: Suggests different stem cells for erythrocytes/granulocytes, lymphocytes, and monocytes.
  • Monophyletic theory widely accepted.

Hemoglobin Synthesis and Chemistry

• Hemoglobin Definition:
  • Pigment in erythrocytes composed of a protein (globin) and a pigment (heme).
  • Heme contains iron, giving hemoglobin its red color.
• Biosynthesis of Hemoglobin:
  • Begins in erythroblasts and continues in later cell development stages.
  • Reticulocytes, with RNA in their fragmented nucleus, can synthesize hemoglobin.
  • Amino acid glycine and acetate combine to form a four-carbon compound, uniting with additional glycine to create pyrrole.
  • Four pyrrole molecules form protoporphyrin, which combines with iron to produce heme.
  • Four heme molecules unite with globin to form the complete hemoglobin protein.

Hemoglobin

• Molecular Weight:
  • Hemoglobin's molecular weight ranges from 66,000 to 69,000 in most species.
  • Iron content in hemoglobin is 0.334 percent.
• Differences in Hemoglobins:
  • Fetal and adult hemoglobins vary in amino acid compositions, electrophoretic mobilities, solubilities, UV absorption spectra, and oxygen dissociation curves.

Plasma Proteins

• Production, Classification, and Properties:
  • Identified plasma proteins include albumin, globulin (α, β, γ), and fibrinogen fractions.
  • Liver produces plasma albumin, fibrinogen, and most globulins; extrahepatic globulins are formed in lymph nodes and reticuloendothelial system.
  • Severe liver damage or prolonged protein deficiency reduces plasma protein synthesis, affecting blood coagulation time.
• Equilibrium and Osmotic Pressure:
  • Plasma proteins, amino acids, and tissue proteins are in equilibrium.
  • Colloidal and non-diffusible proteins maintain colloid osmotic pressure, opposing hydrostatic blood pressure to prevent excess fluid passage and edema.
  • Albumins contribute significantly to colloid osmotic pressure.
• Functions of Plasma Proteins:
  • Maintain normal blood pressure.
  • Influence erythrocyte suspension stability.
  • Regulate blood acid-base balance.
  • Provide antibodies.
  • Affect solubility of carbohydrates and other substances.
  • Transport substances bound to plasma proteins.

Blood Coagulation

• Purpose:
  • Blood clotting is a natural process preventing excessive blood leakage from vascular wall breaks.
• Biochemical Mechanism:
  • Involves a complex sequence of protein-protein interactions.
  • Plasma proteins circulate as inactive proenzymes, activated sequentially for clot formation.
  • Blood coagulation depends on intrinsic and extrinsic mechanisms.