3.13 circulatory system of a mammal

• Why is a transport system required in large organisms?


  to take materials from cells to exchange surfaces and from exchange surfaces to cells. between exchange surfaces and the environment. between different parts of the organism
• Why may there be or may there not be a specialised transport medium, and whether or not it is circulated by a pump, in an animal?

  • the surface area to volume ratio
  • how active the organism is

  low SA:V and more active animal = the greater the need for a specialised transport system with a pump
• Features of transport systems:


  • suitable medium in which to carry materials, for example blood.
  • a form of mass transport in which the transport medium is moved around in bulk over large distances
  • a closed system of tubular vessels that contain the transport medium, and form a branching network to distribute it to all parts of the organism
  • a mechanism for moving the transport medium within vessels. requires a pressure difference between one part of the system and another
• A mechanism for moving the transport medium is achieved by:


  1. animals using muscular contraction either of the body muscles of a specialised pumping organ, such as the heart
  2. plants rely on natural, passive process such as the evaporation of water.
• Features of transport systems pt.2 :

  • a mechanism to maintain the mass flow movement in one direction (valves)
  • a means of controlling the flow of the transport medium to suit the changing needs of different parts of the organism
  • a mechanism for the mass flow of water or gases, for example, the intercostal muscles and diaphragm during breathing in mammals.
• What type of circulatory system do mammals have?


  a closed, double circulatory system
• Why is the mammals circulatory system a double system?


  due to the fact that the when blood is passed through the lungs, the pressure is reduced. if this blood did not pass again through the heart, the low pressure would make the circulation very slow
• why do mammals have a high body temperature and a high rate of metabolism?


  due to the double circulatory system allowing substances to be delivered to the rest of the body quickly
• Plan of mammalian circulatory system: