Circulatory System of a Mammal
13.5
13.5 Circulatory System of a Mammal
 Learning Objectives:
 Over large distances, efficient supply of materials is
provided by mass transport.
 The general pattern of blood circulation in a
mammal.
 (Names are required only of the coronary arteries
and of blood vessels entering and leaving the heart,
liver and kidneys).
Mass Transport – Why is it needed?
 Diffusion is adequate for transport over small distances.
 Efficient supply of materials over larger distances requires a mass
transport system.
 With increasing size, and decreasing surface area to volume ratio, the
needs of the organism cannot be met by use of the body surface alone.
 Specialised exchange surfaces are located in specific regions of the
body to allow absorption of nutrients and respiratory gases and the
excretion of waste substances.
 Materials need to then be transported from the exchange sites to other
areas of the body, and to the external environment.
Factors determining the presence of
mass transport
 The surface area to volume ratio
 The activity of the organism
 Obviously, the greater the activity and smaller the ratio, the
greater the need for mass transport and a pump.
Features of Transport Systems
 Internal Medium to carry substances (must be able to dissolve
some substances)
 A closed system of tubular vessels with a branched network
allowing supply to all areas of organism
 A mechanism for moving the internal medium within the vessels:
a pressure difference between different part of the system. This is
achieved by either :
 a pumping mechanism – muscles or organ such as heart
 A passive process, eg evaporation of water
 A mechanism to maintain mass flow in one direction eg ?
 A means of controlling the flow to suit the needs of the organism
The Heart
11
Pulmonary artery
9
Semi-lunar valve
7
Aorta
2
Pulmonary vein
Vena cava
10
8
1
3
Right atrium
4
Bicuspid
valve
Tricuspid valve
5
6
Left atrium
Right ventricle
Left ventricle
Mammalian Double Circulatory System
Mammalian Double Circulatory System
Questions
 What does a ‘double’ circulatory system mean?
 Blood passes twice through the heart for each circuit of the body.
 Why is it advantageous/necessary?
 When blood passes through the lungs, the pressure lowers. If it
didn’t go back to the heart before going off to the body, then
circulation would be very slow.
 Having a double circulation boosts pressure and helps to deliver
substances to the rest of the body quickly (which is needed due to
mammals having a high body temperature and a high metabolism)
Task
 Complete Summary Questions on page 185.
13.5 Circulatory System of a Mammal
 Learning Objectives:
 Over large distances, efficient supply of materials is
provided by mass transport.
 The general pattern of blood circulation in a
mammal.
 (Names are required only of the coronary arteries
and of blood vessels entering and leaving the heart,
liver and kidneys).
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13.5 Circulatory System of a Mammal