Cardiovascular System

• Blood


  Fluid in which materials are transported
• Vessels


  A system of passages that allows the movement of blood
• Heart


  A pump that pushes fluid through the vessels around the body
• Tissue type


  • Connective tissue
• Plasma


  Liquid component of blood
• Non-liquid


  Cells and cell fragments
• Functions of blood


  1. Transportation of oxygen & nutrients throughout the body

  2. Transportation of hormones (chemical messengers)

  3. Removal of CO2 & other waste

  4. Maintaining pH

  5. Maintaining water content

  6. Maintaining ion concentration

  7. Distributing heat (maintaining body temperature)

  8. Immune response

  9. Clotting when vessels are damaged to prevent blood loss
• Blood functions to transport materials, remove waste, maintain homeostasis, and provide protection
• Plasma


  Clear, pale yellow liquid
• Plasma


  • Very viscous (thick consistency)
  • Caused by presence of proteins
  • Comprises 55% of the whole blood
• Plasma composition


  • Water (92%)
  • Dissolved organic and inorganic solutes (e.g. glucose, sodium ions, nutrients & wastes) (1%)
  • Dissolved plasma proteins (e.g. hormones, antibodies and fibrinogen) (7%)
• Plasma functions


  • Distributing water where body needs it
  • Transporting hormones, nutrients, proteins
  • Support - blood vessels from collapsing or clogging
  • Maintains blood pressure & circulation
• Platelets


  • Fragments of cells made in the red bone marrow
  • No nucleus
  • Maintain small size
  • Improves flexibility, speed and efficiency
  • 2 µm (smallest)
• Platelet functions


  • Clotting of blood
  • Repair - release growth factor to stimulate growth of new cells when blood vessels are damaged
• White blood cells


  • Have a nucleus
  • Made in the bone marrow and lymph tissue
  • Fewer in number but larger than red blood cells (RBC)
• White blood cell types

  • Granulocytes - granular cytoplasm, lobed nucleus
  • Agranulocytes - agranular cytoplasm, spherical nucleus
• Granulocyte types


  • Lymphocytes - involved in immune response, produce antibodies
  • Monocytes - form macrophages that engulf pathogens and damaged cells
• Red blood cells (erythrocytes)

  • Biconcave disks - flattened in the middle on both sides, provides more surface area for oxygen exchange
  • No nucleus - allows more room for hemoglobin, increases flexibility, limits life span to 120 days
  • 8 µm (small)
• Red blood cell origin and lifecycle

  • Formed in bone marrow
  • Life span of about 120 days
  • Destroyed in the liver and spleen - macrophages break RBC into haeme and globin
• Red blood cell function

  Carry oxygen - on molecules called hemoglobin within each red blood cell
• Oxygen transport


  • Not very soluble in water
  • Only 3% carried in solution - the rest is carried in combination with hemoglobin molecules
• Oxygen transport


  1. Oxygen combines with hemoglobin when oxygen concentration is high

  2. Oxyhaemoglobin breaks down when oxygen concentrations are low (in tissue fluid around cells)

  3. Oxygen diffuses (passive diffusion) into the tissue fluid and then into cells
• Oxyhaemoglobin


  Bright red in colour
• Oxyhaemoglobin being bright red

  Causes arteries (that carry oxygen rich blood) to be brighter
• Ways carbon dioxide can be carried in the blood

  • 7 to 8% is dissolved in the plasma
  • 22% combines with the globin part of the haemoglobin to form carbaminohaemoglobin
  • 70% carried in the plasma as bicarbonate ions (HCO3-)
• Carbon dioxide transport


  1. Carbon dioxide diffuses (passive) out of cells, into tissue fluid and then into blood plasma

  2. Carbon dioxide diffuses (passive) out of blood to the alveoli in the lungs
• Vasoconstriction


  1. Prevent blood loss

  2. Walls of blood vessels constrict

  3. Platelet releases serotonin (causes vasoconstriction)

  4. Blood vessels contain a layer of smooth muscle within their walls in multiple layers

  5. The smooth muscle has the ability to contract
• Platelet Plugging


  1. Platelets become sticky when exposed to collagen on the exterior of the perforated blood vessel

  2. Platelets stick to the rough surface of the damaged blood vessel

  3. Sticking platelets attract other platelets to form a plug

  4. Platelets release ADP which helps additional platelets to adhere to the injury site, reinforcing and expanding the platelet plug

  5. Platelets release serotonin, maintains vasoconstriction
• Coagulation (Thrombin System)


  1. Platelets & injured cell releases thromboplastin

  2. Thrombin interacts with Ca-2 and prothrombin (inactive plasma protein) to form thrombin

  3. Thrombin converts fibrinogen (inactive plasma) to long, stretchy fibres called fibrin
• Arteries


  Carry blood away from heart. Carry oxygenated blood from the heart to the cells to the body
• Veins


  Carry blood towards the heart. Carry deoxygenated blood
• Capillaries


  Tiny vessels that carry blood between cells
• Arteries


  • Thick elastic walls, containing smooth muscle
  • Ability to withstand high pressure
  • Expand under surge of blood
  • Can constrict/dilate
  • Small lumen
• Arteries


  • Carry blood away from heart. Oxygenated blood
• Arteries


  • Thick walls of smooth muscle: allows the smooth muscle to constrict (make lumen smaller) as a response to vessel injury, temperature (cold), drugs (Nicotine, prescription medication ect.)
  • Can dilate (make larger) to handle increased pressure, temperature (body too warm)
• Veins


  • Thinner walls= less smooth muscle and elastic fibres
  • Carry blood under lower pressure
  • Valves- prevent back flow of blood
  • Veins have to fight against gravity in lower limbs
  • Have flaps that prevent the back flow of blood (valves)
• Veins


  • Take blood from venules to veins and return it to the heart
• Capillaries


  • Smallest vessels that connect arterioles
  • One cell thick- to optimise diffusion
  • No valves
  • Take blood to all cells
  • Enable exchange of substances between blood and surrounding tissues
• Pressure:

   

  •       higher at the arterial end of the capillary than the venous end.

  •       This pressure ensures materials move into the tissue fluid at the arterial end and out of the tissue fluid at the venous end

   

  Tissue Types in Blood Vessels

   

  ·      Tissue type lines blood vessels is epithelium: cell type is simple squamous cells. (single layer of cells allows for more efficient exchange of material)

  ·      Arteries/veins contain smooth muscle
• Cardiac Output: the relationship between Stroke Volume & Heart Rate

  Cardiac output (Q) = stroke volume (SR) x heart rate (HR)

  • Cardiac Output: The volume of blood ejected from heart per minute (litres ‘L’)
  • Stroke Volume: The volume of blood ejected from each ventricle (litres ‘L’)
  • Heart Rate: The number of cardiac cycles per minute (beats per minute ‘bpm’)