Plasma Proteins and Erythrocytes Quiz

Plasma Proteins

• Synthesis
  • Liver produces albumin, globulins, and 50% of fibrinogen
  • Gamma globulins are formed by plasma cells
• Functions
  • Include clotting factors
  • Globulins are mainly formed in the liver
  • Albumin has the lowest molecular weight
  • Prevent the loss of iron and vitamin B12 in urine
  • Are sources of tissue proteins
• Deficiency
  • Produces edema
  • Can be caused by liver or kidney disease

Red Blood Cells (Erythrocytes)

• Characteristics
  • No nuclei or mitochondria
  • Biconcave shape for increased surface area and flexibility
  • Males: 5.4 million/mm3
  • Females: 4.8 million/mm3
• Lifespan and Fate
  • 120 days
  • Site of Hemolysis: Spleen
  • Iron is stored as ferritin
• Factors Affecting Erythropoiesis
  • Oxygen supply and erythropoietin (EPO)
  • Healthy organs: bone marrow, liver, kidney
  • Hormones & Diet

Erythropoiesis

• Definition
  • Formation of new red blood cells
• Site
  • Fetus: liver & spleen
  • Children: red marrow of all bones
  • Adults: flat and axial bones (vertebrae, skull, ribs, clavicle, scapula, and pelvis)
• Factors Affecting Erythropoiesis
  • Oxygen supply & erythropoietin (EPO)
    • Hypoxia (high altitudes, athletes, newborns, hemorrhage, lung & heart diseases) stimulates EPO release from kidney and liver, leading to increased erythropoiesis.
  • Healthy organs: bone marrow, liver, kidney
    • Bone marrow destruction or depression (X-ray, irradiation, toxins, infections, malignancy) can lead to aplastic anemia.
    • Liver produces 15% of EPO and participates in globin protein synthesis.
    • Kidney forms 85% of EPO and stores Iron and Vitamin B12.
  • Hormones & Diet
    • Hormones: erythropoietin, thyroxin, androgens, glucocorticoids
    • Diet: proteins, iron, vitamins (C, B12, folic acid), and trace elements (copper, zinc, cobalt, selenium)

Iron Absorption

• Process
  • Ferric (Fe+3) is converted to ferrous (Fe+2) by HCl in the enterocytes of the upper small intestine.

Vitamin B12 (Cyanocobalamin, Maturation Factor, Extrinsic Factor)

• Sources
  • Animal products
• Absorption
  • Requires intrinsic factor from the stomach
  • Occurs in the lower ileum
  • Stored in the liver
• Deficiency
  • Causes: Failure of absorption, dietary deficiency (vegetarians)
  • Leads to: Macrocytic anemia and neurological manifestations
• Importance
  • Synthesis of DNA
  • Myelination of nerves

Folate Acid (Folic Acid)

• Sources
  • Fresh food
• Deficiency
  • Causes: Deficient diet, pregnancy, malabsorption, antifolate cytotoxic drugs
  • Leads to: Macrocytic anemia

Types of Anemia

• Microcytic Hypochromic Anemia
  • Iron deficiency anemia
  • Causes: Decreased dietary intake, increased demand (pregnancy & children), decreased absorption
• Normocytic Normochromic Anemia
  • Causes: Acute blood loss (hemorrhage), hemolysis, aplastic anemia
• Macrocytic (Megaloblastic) Anemia
  • Causes: Vitamin B12 deficiency (gastrectomy, absence of intrinsic factor, pernicious anemia, distal small intestine diseases), folate deficiency (deficient diet, pregnancy, malabsorption, antifolate cytotoxic drugs).

Hemolytic Anemia

• Intrinsic Disorders
  • Hereditary spherocytosis
  • Sickle cell anemia (Hb S)
  • G-6-PD enzyme deficiency (Favism)
  • Thalassemia
• Extrinsic Disorders
  • Incompatible blood transfusion
  • Erythroblastosis fetalis (Rh incompatibility)
  • Bacterial toxins, chemicals, or poisons
  • Drugs

Hemolytic Jaundice

• Occurs due to the breakdown of red blood cells.

Platelets (Thrombocytes)

• Characteristics
  • Small, non-nucleated, granulated bodies
  • 300,000/mm3
  • Thrombocytopenia (low platelet count) and thrombocytosis (high platelet count)
  • Source: Bone marrow

Hemostasis

• Definition
  • The process of stopping bleeding from an injured blood vessel.
• Steps
  • Vasoconstriction
  • Platelet plug formation
  • Clotting (fibrin threads)

Platelet Plug Formation

• Mechanism
  • Platelets adhere to injured endothelium, becoming activated.

Blood Clotting

• Clotting Factors
  • Inactive plasma proteins synthesized in the liver.
  • Some require vitamin K.
• Mechanisms
  • Intrinsic pathway (slow, 1-6 minutes, vivo & vitro)
    • Factors VIII, IX, XI, XII, Ca++
  • Extrinsic pathway (rapid, 15 seconds, vivo only)
    • Factors III, VII, Ca++
  • Both pathways activate factor X, leading to thrombin and fibrin formation.

Anticlotting Mechanisms

• General Factors
  • Smooth endothelium
  • Rapid blood flow
  • Heparin
• Specific Factors
  • Prostacyclin (PGI2): secreted from normal endothelium, decreases platelet reactions.
  • Antithrombin III: Inhibits factors 9, 10, 11, 12. Facilitated by heparin.
  • Fibrinolysis: Breakdown of fibrin by plasmin and other proteins.

In Vitro Anticoagulants

• Mechanism
  • Inhibit coagulation by removing or inactivating calcium ions.
• Examples
  • Sodium citrate
  • Sodium oxalate
  • Silicon tubes
  • Heparin
  • EDTA

In Vivo Anticoagulants

• Heparin
  • Origin: Mast cells and basophils
  • Action: Helps antithrombin III to inactivate clotting factors, especially thrombin.
  • Site of action: Both in vivo and in vitro.
• Dicumarol
  • Origin: Plants
  • Action: Competitively inhibits vitamin K.
  • Site of action: Only in vivo.