Animal Transport

• How do single celled organisms import and export everything they require?

  Through diffusion, osmosis, active transport, endocytosis, and exocytosis.
• Why do multicellular organisms require specialised transport systems?


  • High metabolic demand of oxygen, food, waste removal etc.
  • The surface area to volume ratio is too small, as diffusion distances increase, and the amount of surface area available for absorption or removal of substances reduces.
  • Molecules such as hormones and enzymes are made in one place, but required in another.
  • Food is digested in one organ system, but needed in every cell for use in respiration and other metabolic processes.
  • Waste products of metabolism need to be removed from cells and transported to excretory organs.
• What is a circulatory system?

  Transport systems that carry gases, nutrients, waste products, and hormones around the body.
• What are the key features of circulatory systems?

  • They have a liquid transport medium that circulates around the system, such as blood.
  • They have vessels that carry the transport medium.
  • They have a pumping mechanism to move fluid around the system.
• What is a mass transport system?

  When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body.
• What is an open circulatory system?

  A system where the transport medium is not contained within vessels, and is instead pumped straight from the heart into the body cavity, where it is under low pressure. It comes into direct contact with tissues and cells, allowing exchange to take place between the medium and cells, before the medium returns to the heart through an open ended vessel.
• What is the body cavity of an animal called?

  Haemocoel.
• What type of creature is an open circulatory system most commonly found in?

  Invertebrates.
• What is insect blood called?

  Hemolymph, it doesn't carry oxygen or carbon dioxide, but transports food, nitrogenous waste products, and the cells involved in defence against disease; with its flow to a particular tissue varying to meet particular demands.
• What is the structure of an insects body cavity?

  It is split by a membrane, with the heart extending along the length of the thorax and abdomen of the insect.
• What is a closed circulatory system?

  A system where the transport medium is contained within vessels and does not directly come into contact with body tissues, with the heart pumping the medium around the body under pressure and relatively quickly, before it returns back to the heart. Substances enter and exit the blood through the walls of the blood vessels, and the flow to a particular tissue is controlled by the widening or narrowing of the vessels.
• What do most closed circulatory systems contain?

  A blood pigment that carries respiratory gases.
• What type of creatures are closed circulatory systems most commonly found in?

  Vertebrates.
• What is a singular circulatory system?

  This is when the blood flows through the heart and is pumped to the rest of the body before returning to the heart, traveling through the heart once per complete circulation.
• What is the process of blood passing through a singular circulatory system?

  The blood passes through two sets of capillaries, before returning to the heart. In the first, oxygen and carbon dioxide are exchanged, and in the second, which are in different organ systems, substances are exchanged between the blood and cells.
• Why does the blood return to the heart at a slow pace?

  Due to the blood passing through narrow capillaries, the blood pressure in the system drops considerably so the blood returns to the heart slowly, making most with single circulatory systems of low activity, due to this limiting the efficiency of exchange processes.
• What are double circulatory systems?

  This is when the blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, before returning to the heart, and being pumped around the body, before returning to the heart once again; this being the most efficient system for transporting substances around the body, due to the blood passing through the heart twice per circulation.
• What is the process of blood passing through a double circulatory system?

  The blood only passes through one capillary network per circulation, and so maintains a high pressure, allowing for a fast flow of blood.
• What are the key components of blood vessels?

  Elastic fibres, smooth muscle, collagen.
• What are elastic fibres?

  These are composed of elastin and can stretch and recoil, providing vessel walls with flexibility.
• What is smooth muscle?

  This is muscle composed of sheets or strands of smooth muscle cells, that contract or relax, changing the size of the lumen (channel in vessels).
• What is collagen?


  It is a protein, fibre like structure that forms tough connective tissue, providing structural support to maintain the shape and size of the vessel.
• What are the different types of blood vessel?

  Arteries, capillaries, veins.
• What are arteries?


  These are high pressure blood vessels that carry oxygenated blood away from the heart to the rest of the body, except the pulmonary artery, which carries deoxygenated blood from the heart to lungs and the umbilical artery during pregnancy, which carries deoxygenated blood from the foetus to placenta.
• What is the structure of the arteries?

  The walls contain elastic fibres, smooth muscle, and collagen; with the elastic fibres allowing them to withstand and stretch with the force and volume of the blood pumped out of the heart, recoiling to their normal length in between contractions in order to regulate flow.
• What is the artery lined with?

  Endothelium, consisting of endothelial cells, making the walls smooth so blood can easily flow through.
• What is the layering order of the artery?

  Lumen, endothelium, elastic fibres, smooth muscle, collagen.
• What are arterioles?


  Small blood vessels that connect arteries to capillaries, containing more smooth muscle and less elastin due to the lower pressure surge, and constricting or dilating to regulate the blood flow to individual organs.
• What is vasoconstriction?

  The narrowing of blood vessels, due to the smooth muscle in arterioles contracting, constricting the vessel and preventing blood flow into the capillary bed.
• What is vasodilation?


  The expansion of blood vessels, due to the smooth muscles in arterioles relaxing, allowing blood to flow freely into the capillary bed.
• What is an (aortic) aneurysm?

  A bulge or weakness in a blood vessels, most commonly in the aorta or brain arteries, that can eventually burst; with high blood pressure increasing the risk of one.
• What are capillaries?


  These are narrow blood vessels that connect arterioles to venules, forming networks throughout the bodies tissues, with substances being exchanged through the capillary walls between the tissue cells and blood, and large gaps between endothelial cells that make up the walls being where many substances pass out of the capillaries into the fluid surrounding cells.
• Which capillary type is an exception to having large gaps in its endothelium?

  Capillaries in the central nervous system, which have very tight junctions between cells.
• What is the content of the blood being carried by the capillaries?

  The blood entering the capillaries is oxygenated, and by the time it leaves it is deoxygenated, with less oxygen and more carbon dioxide; again with the exceptions of the lungs and placenta, where deoxygenated blood enters the capillaries and oxygenated leaves.
• How are the capillaries adapted for their role?

  • They provide a large surface area for substance diffusion into and out of the blood.
  • The cross sectional area of capillaries is greater than arterioles supplying blood, so the rate of blood flow falls, and the slowed movement allows more time for the exchange of materials between the blood and cells.
  • The walls are a single endothelial cell thick, decreasing the diffusion distance for substances.
• What are venules?


  These are small blood vessels that connect capillaries to veins, with very thin walls, containing a small amount of smooth muscle; several venules joining to form a vein.
• What are veins?


  These are low pressure blood vessels that carry deoxygenated blood away from the cells of the body towards the heart, with the exceptions of the pulmonary vein that carries oxygenated blood from the lungs to the heart, and the umbilical vein that carries oxygenated blood from the placenta to the foetus during pregnancy.
• What do the walls of veins contain?

  They contain lots of collagen and little elastic fibre, with a wide lumen and smooth, thin endothelium lining for easy blood flow.
• What do the majority of veins in the venous system contain?

  Valves, preventing the backflow of blood.
• What adaptations help the veins overcome the low pressure of the blood and the moving of it against gravity?

  • Valve intervals, flaps in the vein's inner layer, open when blood must flow through, and close if the blood begins to move back.
  • Many veins run between big, active muscles, so when the muscles contract they squeeze the veins, forcing blood towards the heart, with valves preventing backflow if the muscles relax.
  • The breathing movement of the chest acts as a pump, in which the pressure changes and squeezing actions move blood in the veins of the chest and abdomen towards the heart.