THE CARDIOVASCULAR SYSTEM: BLOOD

THE CARDIOVASCULAR SYSTEM: BLOOD

1. FUNCTIONS

   • 1. TRANSPORT
     • OXYGEN
       •  Carried by haemoglobin in rbc’s   
     • C02
       • Formed by tissues, carried to the lungs   
     • NUTRIENTS
       • Carried from SI to (via hepatic portal vein) liver and other tissues   
     • H20
       • to the tissues   
     • WASTE
       • resulting from metabolism, carried to point of excretion (kidneys, liver)   
     • HORMONES & ENZYMES
       • Carried to target organs   
   • 2. HOMEOSTASIS
     • Homeostatsis is a condition in which the body’s internal environment remains within certain physiological limits (Tortara, 1990)   
     • DEFENCE
       • including WBC’s and immunoglobulins   
     • TEMPERATURE
       • Blood conducts heat around the body   
     • ACID-BASE BALANCE
       • buffers maintain pH   
     • OSMOTIC CONCENTRATION
       • volume of body fluids – plasma proteins and electrolytes   
     • BLOOD CLOTTING
       • stop haemorrhage, maintain normal levels of blood, limit blood loss.   

2. COMPOSITION

   • 60% PLASMA
     •  Aqueous solution containing a variety of dissolved substances   
     • H20
     • ELECTROLYTES
       • e.g. sodium, chloride, potassium   
     • PLASMA PROTEINS
       •    –e.g. albumin, globulin, (antibodies), fibrinogen, prothrombin (big molecules)   
       • LARGE MOLECULES
       • REGULATE OSMOTIC PRESSURE
         • Plasma proteins keep osmotic pressure constant by regulating fluid exchange between plasma and extracellular fluid (can move in and out of blood) If the number of plasma proteins fall, because of either reduced production or loss from blood vessels, osmotic pressure is reduced and plasma fluid moves into the tissues (oedema) and body cavities   
     • NUTRIENTS
       •  e.g. amino acids, fatty acids, glucose   
     • GASES
       • e.g. oxygen, carbon dioxide   
     • WASTE
       • e.g. urea, creatinine   
     • HORMONES
       •  adrenaline, insulin, thyroxin, oestrogens   
     • ENZYMES
       • alanine aminotransferase (ALT), amylase, lipase   
   • 40% VARIOUS CELLS

3. BLOOD CELLS

   • CREATED THROUGH HAEMOPOIESIS
     • the process by which mature blood cells develop from precursor or stem cells   
   • MADE IN..
     • Production of blood cells occurs in the liver, spleen, bone marrow and lymph nodes   
   • TYPES..
     • 1. ERYTHROCYTES/ RBC
       • MADE IN BONE MARROW
       • NO NUCLEUS
       • FILLED WITH HAEMOGLOBIN
       • FUNCTION: CARRIES O
         • carry oxygen as oxyhaemaglobin from the lungs to the tissues   
       • ERTHROPOIESIS
         • Production of RBC Controlled by hormone erythropoietin, secreted by the kidney, which stimulates the bone marrow to produce more erythrocytes   
         • ERYTHROBLASTS
           • Cells that form RBC these form normoblasts when they take up haemoglobin
     • 2. LEUCOCYTES/ WBC
       • GRANULOCYTES (70%)
         • GRANULATED CYTOPLASM
         • MULTILOBED NUCLEUS
         • TYPES...
           • NEUTROPHILS
             • Phagocytic cells (cell eating) – do not stain/clear cytoplasm– 90% of granulocytes   
           • EOSINOPHILS
             • Involved in inflammatory reaction – stain red   
           • BASOPHILS
             • Produce heparin and histamine – stain blue   
         • MADE IN THE BONE MARROW
           • From the myeloid tissue
       • AGRANULOCYTES (30%)
         • CLEAR CYTOPLASM
         • TYPES..
           • LYMPTHCYTES (80%)
             • large, round nucleus – support immune system, classified as B lymphocytes and T lymphocytes 
           • MONOCYTES
             • largest white cell, horseshoe shaped nucleus – function is phagocytosis – migrate into connective tissues where they play an important role in immunity   
     • 3. THROMBOCYTES
       • Commonly known as platelets 
       • SMALL
       • IRREGULAR
       • NO NUCLEUS
       • MADE IN THE BONE MARROW
         • Made by the break up of megakaryocytes cells
       • INVOLVED IN BLOOD CLOTTING
         • –Clump together to plug small defects in small blood vessels –Release serotonin that  reduces blood flow to the area by constriction of the vessel   
     • 4. RETICULOCYTES
       • IMMATURE RBC
         • Partly still has a nucleus
       • LOADS= ANAEMIA

4. BLOODCLOTTING

   • 1. PLATELETS STICK TO VESSELS
     • 1.Platelets stick to the damaged wall of the vessel   
   • 2. BROKEN PLATELETS RELEASE THROMBOPLASTIN
     • 2..Broken platelets release an enzyme when they break down – thromboplastin   
   • 3. PROTHROMBIN- THROMBIN
     • 3. The protein prothrombin is converted to thrombin in the presence of thromboplastin   
   • 4. THROMBIN CAUSES FIBRINOGEN TO MAKE FIBRIN FIBRES
     • 4. Thrombin is an active enzyme that causes fibrinogen to produce fibrin fibres   
   • 5. FIBRES STICK TO PLATELETS = CLOTS
     • 5. The fibrin sticks to the platelets to form a clot   
   • 6. CLOTS SHRINK + SERUM IS RELASED
     •  6. After some time the clot shrinks and serum is released   
     • 7. VITAMIN K IS NEEDED!
       • 7.Vitamin K is required for the manufacture of prothrombin- without this the process cant occur!   
       • 8. HEPARIN STOPS UNWANTED BLOOD CLOTS
         • 8. The anticoagulant heparin is present in the blood to form unwanted clots forming in the heart/brain (balance out the levels of clotting)