circulatory system

• what is the human circulatory system

  A double circulatory system. The blood must pass through the heart twice before completing one whole circuit of the body
• what vessels does blood move away from the heart through

  arteries
• what vessels does blood move back to the heart through

  veins
• what does blood leave the heart through

  aorta
• what does blood enter the liver through


  hepatic portal vein (from gut) and hepatic artery
• what does blood enter the kidneys through

  renal artery
• what does blood leave the kidney through

  renal vein
• what does blood leave the liver through

  hepatic vein
• what does blood enter the heart through

  vena cava
• what does blood enter the leave the heart through and enter the lungs through

  pulmonary artery
• what does blood leave the lungs through and re enter the heart through

  pulmenary vein
• draw and label circulatory system

  
• How is the heart muscle supplied with blood?

  coronary arteries
• why do arteries have thick muscular walls and elastic tissue that stretches and recoils as the heart beats

  maintains high pressure
• why is the endothelium (inner membrane) folded

  allows artery to stretch - maintains high pressure
• what type of blood do all arteries carry except for pulmonary artery

  oxygenated
• arteries divide into smaller vessels called...

  arterioles
• what do arterioles do


  direct blood into areas of demand by muscle inside the arterioles contracting to restrict blood flow and relaxing to allow blood flow
• compare the lumen and the wall of the veins to that of the arteries


  - larger lumen

  - very little elastic or muscle tissue
• why do veins contain valves


  prevents back flow of blood due to low pressure
• how is blood through through the vins helped

  by muscle contraction of nearby muscles
• what type of blood do all veins carry other than pulmonary vein

  deoxygenated
• arterioles branch into smaller vessels called...

  capillaries
• how are capillaries adapted for efficient diffusion

  -found very close to cells in exchange systems = short diffusion pathway

  - walls are one cell thick - shortens diffusion pathway

  - large number of capillaries to increase SA for exchange
• what is tissue fluid


  The fluid that surrounds cells in tissues.
• what is tissue fluid used for


  Cells take in oxygen and nutrients from the tissue fluid, and release metabolic waste into it
• How is tissue fluid formed

  As blood is pumped through increasingly small vessels, this creates hydrostatic pressure which forces fluid out of the arteriole end of the capillary.
• what is able to leave the cappilary to form tissue fluid


  water

  disolved minerals and salts

  glucose

  small proteins and amino acids

  fatty acids

  oxygen
• what substances remain in the capillary

  red blood cells

  platelets

  large plasma proteins
• why does water move back into venule end of capillary


  due to large molecules remaining in capillary and the fluid moving out the capillary has a more negative water potential than the tissue fluid so water moves back into capillary through osmosis.
• what else is reabsorbed into capillary in water

  dissolved waste products from cells e.g carbon dioxide, urea
• why does execs tissue fluid form

  not all the liquid is reabsorbed into capillary as equilibrium will be reached
• how is excess tissue fluid removed from the body

  drained into the lymphatic system which transports it from tissues to circulatory system