The Cardiovascular
System
Assessment Criteria
P5 – Describe the structure and function of the cardiovascular
system
M2 – Explain the function of the cardiovascular system
Structure of the cardiovascular system: heart
(atria, ventricles, bicuspid valve, tricuspid valve, aortic
valve, pulmonary valve, aorta, vena cava – superior
and inferior, pulmonary vein, pulmonary artery); blood
vessels (arteries, arterioles, capillaries, veins,
venuoles)
Function of the cardiovascular system: delivery of
oxygen and nutrients; removal of waste products;
thermoregulation (vasodilation and vasoconstriction of
vessels); function of blood (oxygen transport,
clotting, fighting infection)
Structure of the Heart
BLOOD VESSELS
OF THE HEART
Several blood
vessels are attached
to the heart. They
bring either
oxygenated or
deoxygenated blood
to the heart and take
it away. This can be
highlighted by the
simplified diagram.
Chambers of the Heart
• The heart is divided into two parts by a muscular
wall called the septum; each part contains an
atrium and a ventricle.
• The atria are smaller than the ventricles as all
they do is push the blood down into the
ventricles. This does not require much force so
they have thinner muscular walls.
• The ventricles have much thicker muscular walls
because they need to contract with greater
forces in order to push blood out of the heart.
• The left side of the heart is larger because it
needs to pump blood all around the body,
whereas the right side pumps deoxygenated
blood to the lungs, which are in close proximity
to the heart.
Valves of the Heart
There are 4 main valves in the
heart that regulate blood flow
ensuring it moves in only one
directions. They open to allow
blood to pass through and then
close to prevent back-flow. The
tricuspid valve is located between
the right atrium and right ventricle
and the bicuspid valve lies
between the left atrium and left
ventricle. The semilunar valves
can be found between the right
and left ventricles and the
pulmonary artery and aorta
respectively
The Heart Wall
• The pericardium surrounds and protects the heart due to the
strong fibrous tissue it contains. It is covered in pericardial
fluid to prevent friction caused by movement from the
pumping action of the heart. The heart wall is made up of
three different layers:
• Endocardium – this is the inner layer and consists of very
smooth tissue to enable the blood to flow freely through the
heart.
• Myocardium – this is the middle layer and consists of
cardiac muscle tissue. Cardiac muscle cells only respire
aerobically (using oxygen) and are connected by intercalated
discs in order to allow a co-ordinated wave of contraction.
• Epicardium – this is the outer layer of the heart, but at the
same time forms the inner layer of the pericardium.
Blood Vessels
• 5 different types of Blood Vessel
• These carry blood from the heart, distribute it
around the body and then return it back to the
heart.
• Arteries carry blood away from the heart. The
heart beat pushes blood through the arteries by
surges of pressue and the elastic artery walls
expand with each surge, which can be felt as a
pulse in the arteries near the surface of the skin
• Arteries branch off into smaller vessels called
arterioles, which in turn divide into microscopic
vessels called capillaries.
• Capillaries have a single-cell layer of
endothelium cells and are only wide enough to
allow on red blood cell to pass through at a given
time.
• This slows the blood flow, which allows time for
exchange of substances with the tissues to take
place by diffusion
• Blood the flows from the capillaries to the venules, which
increase in size and eventually form veins, which return the
blood under low pressure to the heart.
Heart>Arteries>Arterioles>Capillaries>Venules>Veins>Heart
Structure of Blood Vessels
Arteries, arterioles, venules and beins all have a similar structure.
Their walls consist of three layers:
The tunica externa is the outer layer, which contains collagen fibres.
This layer needs to be elastic in order to stretch and withstand large
fluctuations in blood volume.
The tunica media is the middle layer, which is made up of elastic
fibres and smooth muscle. The elastic fibres stretch when blood is
forced into the arteries. The smooth muscle can contract in the walls
of the small arteries and arterioles, which ensures that the amount of
blood flowing to various organs varies according to demand
The tunica interna is made up of thin epithelial cells which are
smooth and reduce friction between the blood and the vessel walls
Functions
of
the
CV
System
• Delivering Oxygen + Nutrients
•
Removal of Waste
•
Thermoregulation
•
Vasodilation/Constriction
•
Oxygen Transport
•
Clotting
•
Fighting Infection
Thermoregulation
• Increased Energy used during
exercise
• CV System controls distribution
and redistribution of body heat
Vasodilation/Vasoconstriction
• Vasodilation = Increased diameter
of blood vessels /Expand
• Resistance Decreases
• Increased Blood Flow
• Vasoconstriction = Decreased
diameter
• Blood flow shut down
• Decreased blood flow
Delivering
2
O
/ Removing Waste
• Delivering Oxygen
• Increased O2 delivered
to muscles
• Nutrients delivered
• Removing Waste
• Transported to: Kidneys,
Liver, CO2 to Lungs
Blood
• Made from
• Plasma
• Red Blood Cells
• White Blood Cells
• Platelets
Oxygen Transport
• Demand increases
during exercise
• Blood carries the
oxygen from the
lungs to the body
• Waste is also
transported away
Clotting
• White blood cells
help to clot
• Platelets PLUG the
damage
• Coagulation factors
in plasma help to
strengthen the plug
Fighting Infection
• Antibodies and
White blood cells
defend against
viruses and bacteria