chapter 8

• reasons for specialised transport systems

  metabolic demands are high, SA:V ratio decreases as organisms get bigger, food that has been digested needs to be transported, waste needs to be removed
• features of common circulatory systems

  liquid transport medium e.g blood, vessels, pumping mechanism to move fluid around
• mass transport system

  a transport system where substances are transported in a mass of fluid
• open circulatory system


  a circulatory system with a heart but few vessels to contain the transport medium
• open body cavity

  haemocoel, where transport medium is under low pressure
• organisms with open ended circulatory systems

  invertebrates because their transport medium does not carry oxygen or carbon dioxide, only food and waste
• insect blood

  hemolymph
• insects body cavity

  split by membrane and heart is length of thorax and abdomen, where hemolymph circulates but there is no diffusion gradient, and amount cannot be varied with demand
• closed circulatory system


  a circulatory system where the blood is enclosed in blood vessels and does not come into direct contact with the cells of the body beyond the blood vessels
• method substances leave blood in closed circulatory systems

  diffusion through the walls of the blood vessels
• how is blood amount adjusted in vessels

  widening or narrowing of blood vessels adjusts amount of blood to a particular vessel
• animals where there are closed circulatory systems

  echinoderms, cephalopod molluscs, common earthworm, all vertebrates and mammals
• single closed circulatory system

  a circulatory system where blood flows through heart and is pumped out to travel all around the body before returning to the heart
• organisms with single closed circulatory systems

  fish and annelid worms
• single closed circulation pathway

  blood passes through microscopic blood vessels where oxygen and carbon dioxide exchanged, then in second set of capillaries it is exchanged between blood and cells
• efficiency of single closed circulatory systems

  as they pass through two sets, blood pressure drops so blood returns to heart slowly, which limits efficiency of exchange so activity levels of these are low
• fish specialised single closed circulatory system

  countercurrent gaseous exchange system where gills allow oxygen to be taken in, as water supports weight, they do not need to regulate temp either, so they can be active
• double closed circulatory systems

  where blood travels twice through the heart for each complete circulation of the body
• pulmonary circulation


  heart to lungs
• systemic circulation


  back to heart from lungs then to the brain and rest of the body
• elastin fibres


  composed of elastin and can stretch and recoil providing vessel walls with flexibility
• smooth muscle

  contracts or relaxes which changes the size pf the lumen
• collagen


  provides structural support to maintain the shape and volume of the vessel
• arteries


  carry oxygenated blood away from the heart to the body apart from the pulmonary artery that carries deoxygenated blood to the lungs
• pressure in arteries

  very high pressure, and elastic fibres help withstand this and they can stretch to take the larger blood volume, the fibres recoil in between contractions
• lining of the artery

  endothelium, smooth so blood flows easily over it
• arterioles

  link arteries and capillaries, and have more smooth muscle and less elastin, because of little pulse
• vasoconstriction

  narrowing of blood vessels preventing blood flow
• vasodilation


  widening of blood vessels to allow blood through to the capillary bed
• capillaries


  microscopic blood vessels that connect arterioles with venules, forming an extensive network through tissues
• capillary structure


  small lumen that only fits one rbc, endothelium one cell thick for efficient diffusion, large SA:V, slow movement allows exchange
• veins


  carry blood to the heart at a low pressure and carry deoxygenated blood apart from the pulmonary vein that carries oxygenated blood back to the heart
• veins structure

  have valves to prevent back flow of blood, do not have a pulse, contain lots of collagen as they have a wide lumen and lots of endothelium
• venules


  small veins that link capillaries with veins with little smooth muscle
• veins adaptations to move against gravity

  one way valve interval that open and close, big veins run through muscles so they can surge the blood upwards, breathing movements act as a pump to squeeze the blood
• plasma

  main component of blood, yellow fluid containing dissolved substances and carrying blood cells
• plasma dissovled subtacnes

  glucose, mineral ions, hormones, large plasma proteins, platelets
• platelets

  fragments of large cells called megakaryocytes found in red bone marrow and are involved in blood clotting
• blood transports


  oxygen, carbon dioxide, nutrients, wastes, antibodies and hormones
• how does blood act as a buffer

  maintenance of steady body temperature, minimising pH changes