Circulatory system


HideShow resource information
Preview of Circulatory system

First 690 words of the document:

The heart is a muscle which needs a good supply of blood which is what the coronary artery does. The
heart works through electric impulses which make it contract and relax which allows it to pump blood
around the body.
The heart contains four chambers. It is a double circulatory system ­ the two sides are separated by the
septum. This is as the right side of the heart contains deoxygenated blood (low in oxygen) as it has been
around the body and the left side contains oxygenated blood the septum prevents the two types of blood
mixing. The right side pumps blood to the lungs whereas the left side pumps blood around the body.
Blood enters the heart from the vena cava (vein) into the right atrium at low pressure. When the right atrium
is filled up with blood the pressure of the blood here will cause the atrioventicular valves to open and
allow the blood to enter the right ventricle. The heart then contracts here which forces blood up from the
right ventricle through the semilunar valves and into the pulmonary artery and into the lungs. Here the
carbon dioxide from the blood diffuses into the alveoli and the oxygen diffuses out of the alveoli and into
the blood. The now oxygenated blood enters the left atrium and left ventricle where the left side of the heart
contracts to force the blood through the aorta and out to the rest of the body at high pressure.
The left side of the heart is thicker than the right side of the heart as the right side of the heart only pumps
blood to the lungs which is a short distance and so the right side is thinner as when it contracts it doesn't
need to be as thick as it is only forcing blood through a small distance at low pressure. However the left
side of the heart is thicker as it is responsible for pumping blood all around the body which is a longer
distance and needs a thicker muscle so when it contracts the blood is forced all around the body at high
Valves prevent the back flow of blood. They open and close to allow blood to enter and leave.
Arteries usually carry oxygenated blood away from the heart however the pulmonary vein is the exception
as it carries deoxygenated blood away from the heart instead. Veins usually carry deoxygenated blood to
the heart however the pulmonary vein is the exception as it carries oxygenated blood to the heart.
Arteries carry oxygenated blood from the heart to the body. The have small lumen, thick walls made of
elastic tissue as they carry blood at extremely high pressure so thick walls are needed to withstand this
pressure. They carry a large volume of blood. As blood is forced through the artery the walls
expand/stretch and then return back into their shape which keeps the blood moving ­ this is felt by a pulse.
Arteries can get clogged with fat which slows down blood flow and could result in a blood clot. If this
happens in the coronary artery it will cause a heart attack as this supplies blood to the heart. If this happens
in any other artery it will cause a stroke.
A stent is made out of titanium as it does not rust/unreactive. It is used to unblock arteries instead of
replacing parts of the artery. The stent is fed through where the blockage is and part of it opens like a
balloon which pushes the artery walls apart allowing blood to flow through easily.
When arteries split up into capillaries the blood pressure decreases/ slows down from high to low
Capillaries connect arteries and veins. Arteries branch out into arterioles then into capillaries which lead to
organs and then to veins. Capillaries are blood vessels responsible for exchanging/ transporting substances

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

They are adapted for this as their walls are only one cell thick so substances can easily diffuse
in and out as they have a short diffusion pathway. E.g. oxygen diffuses from the blood cells in the capillary
into the body's organs/cells, Glucose has to be transported via active transport. Waste substances such as
co2 and water diffuse out of the organs/cells into the capillary to be removed. All of these are carried in the
blood by the plasma.…read more

Page 3

Preview of page 3

Here's a taster:

Cells only have a certain amount of glucose. So if you eat too much sugar the pancreas releases insulin
which allows the liver to convert glucose into glycogen to be stored in the liver and cells. When we exercise
and you haven't enough glucose then glycogen (is a carbohydrate) stores are broken down into glucose
and released into the blood so your cells can continue to respire.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »