Circulatory system of a mammal
- Created by: Laura
- Created on: 02-05-14 16:08
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- Circulatory System of a mammal
- Diffusion is adequate for transport over short distances. The efficient supply of materials over large distances requires a mass transport system
- Why large organisms need a transport system
- All organisms need to exchange materials between themselves and their environment. However with increasing size, the surface area to volume ratio decreases to a point where gas can not be exchanged over body surface alone
- Specialist exchange surface are located in specific regions of the organisms
- A transport system is required to take materials from cells to exchange surfaces and the environment. They also need to be transported between different parts of the orhganism
- Whether there is a transport system depends on two things; the surface area to volume ratio and how active the organism is.
- Features of transport systems
- A suitable medium in which to carry materials e.g 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 contains the transport medium within vessels. This requires a pressure difference between one part of the system and the other.
- A mechanism to maintain a mass flow
- A means of controlling the flow of the transport medium to suit the changing needs of different parts of the organism
- Transport systems in mammals
- Mammals have a closed blood system in which blood is confined to vessels. Heart circulates blood around the body.
- Mammals have a double circulatory system which means that the blood passes through the heart twice in one cycle
- It passes twice through the heart because blood loses pressure when it passes through the lungs
- Vessels that make up the circulatory system are divided into three types; arteries, veins and capillaries.
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