B2: Circulatory System

B2: Circulatory System

1. Components of Blood

   • Plasma (55%)
     • Function
       • Carries Co2, hormones, glucose etc. 
     • Structure
       • Straw coloured liquid Contains dissolved substances and suspended cells.
   • Red Blood Cells
     • Function
       • Carry oxygen to cells.
     • Structure
       • Biconcave disc shape - large surface area for absorbing O2 by diffusion.  No nucleus - makes more room for oxygen.  - cells die after 30 days Contain haemoglobin proten (iron) - allows O2 to bing to it, creating oxyhaemoglobin Flexible - can fit through small blood vessels
   • White Blood Cells
     • Function
       • Fight infection/defend against microbes
     • Structure
       • Lobed nucleus 2 mechanisms: - some engulf microbes - some produce antibodies to stick to microbes.
   • Platelets
     • Function
       • Form clots which become scabs. - stops excess bleeding - prevents microbe infections
     • Structure
       • No nucleus Cell fragments Form mesh with blood platelets at site of cut.

2. Heart

   • Vena Cava
     • Right Atrium
       • Valve
         • Right Ventricle
           • Pulmonary Artery
             • Lungs
               • Pulmonary Vein
                 • Left Ventricle
                   • Valve
                     • Left Atrium
                       • Aorta

3. Transportation

   • Arteries
     • Carry blood away from heart High pressure Thick wall
   • Veins
     • Carry blood to heart Low pressure Valve to prevent backflow
   • Capilliaries
     • Site of exchange between cells and blood. Thin walls for diffusion - lots of surface area Tiny holes for tissue fluid to leak