6. The circulatory system of mammals Flashcards
The mammalian cardiovascular system is designed to
meet the oxygen needs of all the cells in the body
If body cells are deprived of oxygen, they die
The mammalian transport system is made up of
the heart and blood vessels
Unlike plants, mammals require a transport system that moves oxygen and carbon dioxide around their bodies because
mammals are much more active than plants, which means that their cells require more energy and therefore respire more rapidly.
Cells therefore need constant deliveries of oxygen and must have the carbon dioxide produced in respiration taken away.
Moreover, mammals do not have branching bodies like those of plants, so their surface area : volume ratio is usually much smaller.
Many cells in a mammal are a long way from the gas exchange surface, so diffusion would not be sufficient to supply them with their needs
what is the mass of the heart of an adult human
around 300 g and is about the size of your fist
It is a bag of muscle, filled with blood
Figure 6.2 Diagram of the external structure of a
human heart, seen from the front
chegg
The muscle of which the heart is made is called
cardiac muscle.
This muscle is able to contract and relax rhythmically, 24 hours a day, throughout your life.
The heart is the pump that
keeps blood moving through the arteries
The circulatory system of a mammal is
a closed system
a double circulation
The circulatory system of a mammal is a closed system because
blood flows inside vessels in its journey around the body.
At no point does blood flow out of these vessels except where there is a cut; and blood clots quickly to seal external and internal wounds to limit blood loss.
The heart is the pump that keeps
the blood flowing through the circulation
the three main types of blood vessel in a closed system
arteries, capillaries and veins.
blood is a
tissue composed of red and white blood cells, platelets and plasma
An artery is
a vessel that carries blood away from the heart throughout the body
A vein is
a vessel that carries blood towards the heart
what are the smallest blood vessels
Capillaries
what is primarily responsible for the movement of blood inside veins
The contraction of skeletal muscle pressing against veins
benefits of cardiac muscle
Cardiac muscle is highly resistant to fatigue and its muscle cells have very large numbers of mitochondria
Cardiac muscle fibres contract involuntarily; they branch, interconnect, relay signals to each other and help to synchronize the heartbeat
The major portion of the heart is called the
myocardium
where is the heart located
the heart is located behind the breastbone between the left and right lungs
what surrounds the heart
A thick membranous sac called the pericardium surrounds the heart
Diffusion is fast enough for transport over
short distances
The efficient supply of materials over larger distances requires a
mass transport system
All organisms exchange materials between
themselves and their environment.
Specialist exchange surfaces are required to absorb
nutrients and respiratory gases, and remove excretory products
A transport system is required to take materials from
cells to exchange surfaces and from exchange surfaces to cells
Whether or not there is a specialised transport medium, and whether or not it is circulated by a pump, depends on two factors:
the surface area to volume ratio,
and how active the organism is.
The lower the surface area Lo volume ratio, and the more active the organism, the greater is the need for
a specialised transport system with a pump
why multicellular organisms need transport systems
in multicellular organisms, oxygen obtained by the respiratory system and nutrients processed by the digestive system must be transported to cells throughout the body.
At the same time, carbon dioxide and other waste products produced within the cells must be returned to the respiratory, digestive, and urinary systems for elimination from the body
Over large distances in organisms, efficient supply of
materials is provided by
mass transport
the transport systems of many organisms have many common features:
- a suitable medium in which to carry materials (example blood)
This is normally a liquid based on water because water readily dissolves substances and can be moved around easily, but can be a gas such as air breathed in and out of the lungs. - A form of mass transport in which the transport medium is moved around in bulk over large distances - more rapid than diffusion.
- A closed system of tubular vessels that contains the transport medium and forms a branching network to distribute it to all pans of the organism.
-A mechanism for moving the transport medium within vessels.
This requires a pressure difference be tween one part of the system and another.
