Mechanism of Coagulation | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Blood Clotting Mechanism: Intrinsic Pathway

• Initiation of Coagulation:
  • Intrinsic mechanism involves enzymatic reactions triggered when blood encounters a foreign surface.
  • Any surface other than the intact endothelial lining of blood vessels is recognized as "foreign" by coagulation proteins and blood cells.
  • Damage to vessel walls or exposure to air can kickstart the clotting process.
• Sequence of Enzymatic Reactions:
  • Once clotting begins, a series of chain reactions occurs.
  • Culminates in the generation of thrombin, a crucial enzyme.
  • Leads to the formation of an insoluble fibrin clot.
• Steps in the Process:
  • Recognition of a foreign surface activates clotting proteins.
  • Series of enzymatic reactions unfolds.
  • Eventually, thrombin is produced.
  • Thrombin converts soluble fibrinogen into insoluble fibrin, forming a clot.

Blood Clotting Process Simplified

(a) Contact Activation Phase: Triggering Clotting Mechanism:

• Factor XII, a plasma protein, gets activated to become Factor XIIa.
• Various substances like grass, celite, or collagen initiate this conversion.
• These substances cause a change in Factor XII, exposing an enzymatic site.

(b) Activation of Factor X: Effect on Factor IX:

• Factor XIIa activates Factor XI, which, in turn, activates Factor IX.
• Calcium ions are essential for this process.
• Platelet-supplied phospholipids and large protein molecule Factor VIII act as co-factors.
• This complex rapidly converts Factor X to Factor Xa.

(c) Formation of Thrombin: Role of Factor Xa:

• Factor Xa, a proteolytic enzyme, slowly converts prothrombin to active thrombin in the presence of calcium ions.
• Phospholipid and Factor V are required as co-factors, speeding up the reaction.

(d) Formation of Fibrin: Thrombin's Action:

• Thrombin, a specific enzyme, transforms soluble fibrinogen into soluble fibrin.
• Factor XIII enzyme, with calcium ions, catalyzes the process.
• Soluble fibrin turns into an insoluble fibrin clot, trapping platelets, white cells, and red cells.
• This clotting process stops blood flow.

Blood Clotting: Intrinsic and Extrinsic Mechanisms Simplified

• Intrinsic Mechanism:
  • Trigger: Traumatic damage to blood vessels and surrounding tissues releases tissue juices.
  • Key Component: Tissues contain a specific lipo-peptide, thromboplastin, triggering rapid fibrin formation when entering the bloodstream.
  • Role: Responds to everyday minor traumas and injuries to blood vessels.
• Extrinsic Mechanism:
  • Trigger: Major traumatic damage causing release of tissue juices.
  • Key Component: Thromboplastin from tissues initiates a faster response.
  • Role: Complementary system working with intrinsic mechanism to address significant injuries.
• Clotting Process:
  • Time Frame: Clotting times vary (2 to 11 minutes) in different species and health conditions.
  • Contraction: After hours, the formed fibrin contracts, squeezing out blood serum.
  • Vitamin K Requirement: Adequate vitamin K is necessary for prothrombin supply, influencing clotting.
  • Inhibition: Clotting can be inhibited by anticoagulants like heparin, warfarin, or in cases of diseases like hemophilia.
• Circulation of Blood:
  • Regulation: Circulatory regulation ensures coordination between heart activity and metabolic changes in response to external and internal conditions.
  • Complex Reflex Act: Heart activity adapts to changes in the environment and body activity, maintaining a balance in blood circulation.
• Haemorrhage Disorders:
  • Categories: Bleeding problems due to defective blood coagulation fall into congenital and acquired categories.
  • Importance of Cardiac Regulation: Heart adapts to pump more blood during vigorous activities, highlighting the significance of cardiac regulation.

Blood Disorders Simplified

Anticoagulants: Controlling Blood Clotting

• Chelating Agents:
  • Function: Bind calcium ions, preventing their use in coagulation reactions.
  • Examples: Sodium oxalate, EDTA (used frequently in laboratories).
• Heparin:
  • Function: Most effective anticoagulant, inhibits both thrombin generation and its activity.
  • Effect on Coagulant Proteins: Inhibits synthesis of functional coagulant proteins (II, X, VII, IX).
• Vitamin K Antagonists:
  • Mechanism: Inhibit synthesis of vitamin K-dependent coagulation proteins.
  • Result: Non-functional proteins are synthesized, preventing normal coagulation reactions.

Blood Groups: Genetic Markers

• Blood Group Systems:
  • Purpose: Determine blood types based on different antigens on red blood cells.
  • Systems Recognized: Vary across species (e.g., 12 in cattle, 15 in swine, 8 in dogs).
• Pleiotropic Effects of Genes:
  • Definition: Some genes affect multiple traits simultaneously.
  • Implications: Blood group genes with pleiotropic effects may influence economic traits.
• Genetic Applications:
  • Genetic Improvement Programs: Blood typing may aid in improving desirable traits.
  • Parentage Exclusion: Useful for excluding parentage but cannot prove it.
  • Monozygosity of Twins: Can't prove monozygosity but can detect genetic differences in dizygotic twins.

Blood Group Classification and Blood Volume Insights

Blood Group Classification: Understanding Antigenic Nature

• Basis: Blood group classification relies on the antigenic nature of erythrocytes (red blood cells).
• Pioneering Studies: Landsteiner and other researchers laid the foundation for this classification.
• Importance: Crucial for transfusion therapy and medical interventions.

Blood Volume: A Key Parameter

• Significance: Knowing an animal's blood volume is crucial for interpreting various hematological values.
• Parameters Affected: Packed cell volume, hemoglobin, red cell counts, plasma protein concentration.
• Limitations: Hematological values can be misleading; blood volume changes are not reflected.
• Estimation Methods: Indirect techniques, considering factors like dilation, are used.

Plasma Expanders: Restoring Circulating Volume

• Definition: Substances like hypertonic saline, dextran, or hetastarch used to replenish circulating volume.
• Alternatives: Crystalloids, stored plasma can also serve this purpose.

Compensatory Mechanisms After Hemorrhage

• Responses to Hemorrhage: Trigger compensatory mechanisms like vessel contraction, fluid shift, vasopressin release.
• Rapid Blood Loss: Severe stress and anemic shock can result from rapid loss exceeding 30 percent of blood volume.

Types of Plasma Expanders and Administration

• Dextrans:
  • Administered in infusion fluids (5% dextrose or 0.9% sodium chloride solution).
  • Causes slight hyperthermia.
• Hetastarch (Hydroxyethyl Starch):
  • Administered as a 5% solution in 0.9% sodium chloride solution.
  • Mimics osmotic pressure of plasma proteins.
• Hypertonic Solutions:
  • Dextrose, urea, mannitol in appropriate concentrations can be used.
• Other Options:
  • Gelatin and Polyvinyl Pyrrolidone (PVP) solutions (4-8% concentration) can also be beneficial.

Blood Buffer Systems: Maintaining pH Balance

• Main Buffer Systems: Bicarbonate, plasma protein, phosphate, and hemoglobin are key blood buffer systems.
• Key Players: Bicarbonate and hemoglobin are particularly crucial in maintaining pH balance.
• Buffer Contributions:
  • Bicarbonate: 53%
  • Hemoglobin: 35%
  • Plasma Protein: 7%
  • Phosphates: 5%
• Total Buffering Capacity: Significant, preventing drastic pH shifts even with sudden metabolic acid increases.

Biochemical Tests in Disease Diagnosis: Understanding Lab Results

• Importance: Lab tests aid clinicians in accurate disease diagnosis, prognosis, and treatment assessment.
• Test Types:
  • Haematology: Study of blood components.
  • Blood Chemistry: Analyzing blood for chemical indicators.
  • Urine Examination: Assessing urine for health indicators.
  • Mastitis Tests: Detecting inflammation in mammary glands.
  • Liver Function Tests: Evaluating liver health.
  • Cerebrospinal Fluid Examination: Analyzing fluid around the brain and spinal cord.
  • Clinical Semen Examination: Evaluating semen health.
  • Clinical Parasitology: Identifying parasites in blood and feces.
  • Cultural Examination: Identifying causative organisms and conducting sensitivity tests.
• Significance:
  • Aids in arriving at accurate diagnoses.
  • Guides prognosis of the condition.
  • Assesses the effectiveness of treatments.

Biochemical Tests: Insights into Animal Health

• Blood Sugar Examination:
  • Hyperglycemia: Indicates conditions like diabetes, convulsions, hyperthyroidism, liver disease.
  • Hypoglycemia: Suggests issues like starvation, hypopituitarism, excess insulin therapy, ketosis.
• Calcium Estimation:
  • Hypercalcemia: Found in excess vitamin D intake, parathyroid adenoma, renal disease, bone tumors.
  • Hypocalcemia: May indicate hypoparathyroidism, vitamin D deficiency, milk fever in cows, rickets.
• Phosphorus Levels:
  • Hyperphosphatemia: Seen in renal disease, hypoparathyroidism, vitamin D excess, parturient paresis.
  • Hypophosphatemia: Occurs in inadequate phosphorus intake, rickets, vitamin D deficiency.
• Magnesium Levels:
  • Hypermagnesemia: Noticed during parturition in older cows, chronic nephritis, oxalate poisoning.
  • Hypomagnesemia: Results from inadequate magnesium consumption, grazing on magnesium-deficient pastures.
• Serum Alkaline Phosphatase:
  • Increased Levels: Indicate biliary obstruction, liver diseases, bone disorders.
  • Dog-Specific: Used as a liver function test.
• Serum Cholesterol:
  • Hypercholesteremia: Found in conditions like nephritis, diabetes, pregnancy, hypothyroidism.
  • Hypocholesteremia: Associated with hyperthyroidism, low-fat diet, acute infections, liver diseases.
• Liver and Kidney Function Tests:
  • Provide insights into the actual conditions of liver and kidneys.
• Globulins in Cerebrospinal Fluid:
  • Increased levels may indicate inflammation, encephalitis, abscesses, meningitis, toxoplasmosis.
  • Also points to issues like pneumonia, convulsions, ureisis, and hemorrhages.
• Significance of Biochemical Tests:
  • Diagnosis: Helps in identifying specific conditions.
  • Prognosis: Aids in predicting the course of the condition.
  • Treatment Assessment: Evaluates the effectiveness of treatments.

Insights from Diagnostic Tests in Animal Health

• Cerebrospinal Fluid Analysis:
  • Favorable Sign: Reduced globulin content indicates subsiding inflammation.
  • Increased Levels: Suggest hyperglycemia, encephalitis, spinal cord compression, brain tumors, and abscesses.
  • Decreased Levels: Occur in hypoglycemia and acute pyogenic infections.
• Clinical Examination of Semen:
  • Essential for Fertility Assessment: Crucial for artificial insemination and management of reproductive health.
  • Coital Diseases Control: Helps in monitoring and controlling diseases related to mating.
• Other Diagnostic Tests:
  • Tuberculin Test: Detects tuberculosis.
  • Jehne's Disease Test: Identifies this specific infectious disease.
  • Glanders Test: Screens for glanders infection.
  • Di L Test: Rapid test for epizootic lymphangitis.
  • Pullorum Disease Test: Rapid test for pullorum disease in poultry.
  • Brucellosis Test: Detects brucellosis infection.
  • Negri Bodies Test: Screens for rabies.
  • Mundes Agglutination Test: Identifies bovine vibriosis.
  • Agglutination Test for Avian Mycoplasmosis: Detects mycoplasmosis in birds.
  • Surface Fixation Test for Listeriosis: Screens for listeriosis.
  • Fluorescent Antibody Technique: Advanced technique for disease confirmation.
• Diagnostic Samples:
  • Serum, Heart Blood Swabs, Pus Lesions, Blood Smears: Essential samples for diagnosing various livestock and poultry diseases.
  • Muzzle Piece of Biological Test: Specific diagnostic material for disease confirmation.
  • Dead Chick Examination: Useful in confirming diseases affecting poultry.
• Significance of Diagnostic Tests:
  • Disease Identification: Pinpoints specific illnesses in animals.
  • Confirmation: Validates disease presence through advanced testing.
  • Livestock and Poultry Health: Essential for maintaining the health and well-being of animals.