transport in animals

• cells of all organisms need to be supplied with O2, glucose and other nutrients and to have waste product such as urea and carbon dioxide removed, they require a transport system for larger multicellular organism

  • small single celled organisms can rely on diffusion, active transport, exo and endocytosis
• what are the 3 main factors that influence that need for a transport system

  • as size increases surface area to volume ratio decreases
  • increased metabolic activity increases the demands for O2 and glucose and larger volumes of wastes need to be excreted
  • increased complexity means materials made in one location need to be transported to others
• what are the features of transport systems

  • liquid medium (blood)
  • have vessels to carry the medium
  • have a pump to move the medium
• what are the types of transport system

  • open circulatory: transport medium is not always in vessels, can be pumped to the body cavity and directly bathes tissue and cells where gas exchange occurs
  • mainly found in insects and their blood id called haemolymph = inefficient system
  • closed circulatory : blood stays within the vessels and is pumped to and from a heart, exchange occurs by diffusion across the walls of the vessels
• single -circulatory system : these are found in fish and annelid worm

  • conduct blood in one circuit
  • heart - gills-body- heart
  • quite inefficient - only of use to organisms with relatively low exchange requirements
• doubled circulatory system

  • found in birds and mammals, blood is conducted around 2 circuits
  • this is more efficient system and is required by animals that maintain their own body temperature as they have very high demand for energy
• advantages of a double circulation

  • will deliver oxygen and nutrients quickly to the parts of the body
  • blood can be made to flow quickly increasing the blood pressure
• • fish are not metabolically active as mammals, as they do not need to maintain their body temp
  • therefore needs less energy
  • single circulatory system delivers sufficient oxygen and nutrients for their needs
• • mammals are active animals and maintain their body temp
  • supplying the energy for activity and the heat needed to keep the body warm requires energy from food
  • the energy is released from food in the process of respiration
  • to release a lot of energy , the cells need a good supply of both nutrients and oxygen as well as the removal of waste prodcuts
• lumen, endothelium, elastic fibre, smooth muscle, collagen fibres
• artery

  • carries blood away from the heart
  • very high pressure
  • small lumen
  • very thick walls
  • semi-lunar valves present
• arteriole

  • connect arteries to capillaries
  • high pressure
  • thick walls
  • no semi-lunar valves present
• capillary

  • exchanges substances
  • low pressure
  • very small lumen
  • 1 cell thick
  • no semi-lunar valves present
• venules

  • connect capillary to the vein
  • low pressure
  • medium lumen
  • thin wall
  • semi-lunar valve present
• veins

  • carries blood back to the heart
  • low pressure
  • large lumen
  • thick wall
  • semi-lunar valve present
• the walls of the artery and veins are made up of 3 layers and lumen which is lined with endothelium

  1. inner layer (tunica intima) - elastic layer
  2. middle layer (tunica media)- smooth muscle
  3. outer layer(tunica adventitia) - collagen fibres
• arteries have elastic fibres:

  -thick layer allows wall to stretch, recoil and maintain pressure

  smooth muscle:

  -thick layer to withstand pressure

  collagen:

  -quite thick and also withstand pressure
• arterioles- thinner than arteries but same function

  smooth muscle:

  -more smooth muscle than elastin, can contract and relax changing size of lumen redirecting blood flow

  collagen is thinner
• venules have no elastic fibre, very little smooth muscle and majority of the wall is made out of collagen
• veins have thin layer of elastin fibres , medium smooth muscle and quite thick collagen
• blood is a transport medium 45% is composed of erythrocytes (RBCs) platelets and leucocytes (WBCs) the remaining 55% is plasma

  • plasma is a yellow liquid mainly composed of water with many dissolved components such as amino acids, glucose, minerals, CO2 etc
• functions of blood

  • transport of oxygen and carbon dioxide
  • digest food (amino acids/glucose) from intestines
  • urea to the kidney
  • hormones around the body
  • platelets to damaged area
  • WBC and antibodies to sites of infection
  • stored food to respiring cells
• how is tissue fluid formed

  • tissue fluid is formed when plasma through fenestrations (gaps in the capillary)
  • does not contain large proteins or RBC as they are too large to fit
  • lymph: 90% of the tissue fluid returns to the capillary, the remaining 10% drains into the lymphatic system, network of vessels containing valves which carry the lymph back to the blood via subclavical vein
  • lymph is similar to tissue fluid but contains less O2 and glucose but more fatty acids
• what is tissue fluid

  • the fluid in which that surrounds cells and tissues
• oncotic pressure

  • the pressure created by the osmotic effects of the solutes
  • always -3.3kpa
• positive pressure : move out of blood

  negative pressure: move into blood
• hydrostatic pressure

  • the pressure that a fluid exerts when pushing against the sides of a vessel or container
• what is the flow of blood

  • vena cava - right atrium - right ventricle - pulmonary artery - lungs - pulmonary vein - left atrium -left ventricle - aorta
• atrium


  pumps blood into ventricled
• ventricles

  • pumps blood into arteries
• bicuspid (left AV valve)

  • prevents back flow from left ventricle to left atrium
• tricuspid (right AV valve)

  • prevents back flow from right ventricle to right atrium
• septum

  • walls separate the 2 sides of the heart
• aorta

  • carries oxygenated blood around the body
• vena cava

  • carried deoxygenated blood back to the heart
• pulmonary artery

  • carries deoxygenated blood back to the lungs
• pulmonary vein

  • carries oxygenated blood back to the heart
• atrioventricular valves

  • prevent back flow of blood from arteries into ventricles
• tendons

  • hold valves into place
• coronary arteries

  • supply cardiac muscle with oxygen and glucose