Transcript The Heart and Circulatory System

The Heart and Circulatory System
DK & PK
Declarative
Knowledge
Name the organs of
the circulatory system
and describe how
they function
Procedural
Knowledge
Label parts of the
human heart and
describe the flow of
blood through the
body
How are substances transported around the body?
The next organ system we will be considering can be
known by two names…..
Blood system
Circulatory system
The circulatory system is made of three parts:
1. The heart
2. The blood vessels
3. Blood
One of the substances that the circulatory system
transports are respiratory gases.
For example, the Oxygen that the body needs, must
be taken to the cells and the Carbon Dioxide waste
gas must be taken away from the cells.
As these gases are carried by the blood, it means that in
terms of the presence of gas, we have two types of blood.
Blood high in oxygen
Blood low in oxygen
Oxygenated
Deoxygenated
At all times these two types of blood cannot mix. Why do
you think this is?
Because of this our circulatory system is in two parts. It is in
fact called a double circulatory system.
Lungs
This section of the
system including
the right side of
the heart, deals
with the
deoxygenated
blood.
This section of the
system including
the left side of the
heart, deals with
the oxygenated
blood.
Body cells
The Human Circulatory System
The Heart
Anterior Vena
Cava
Pulmonary Artery
Aorta
Pulmonary Artery
Semilunar valves
Left Atrium
Pulmonary veins
Pulmonary Veins
Atrioventricular valve
Right Atrium
Semilunar valve
Atrioventricular valve
Left ventricle
Posterior Vena Cava
Right ventricle
Oxygenated Blood
Deoxygenated Blood
Besides the chambers there is also another very
important part of the heart – the valves. These valves
are found between the top and bottom chambers on
both sides of the heart.
These valves are
rather like doors
that only open in
one direction.
blood
valve
As the atrium fills
with blood, the
valves are
closed.
When the atrium
contracts and
squeeze the blood,
the valves are
pushed open
These valves are connected to the side wall of the heart
by tough tendons. These tendons allow the valves to
close but not invert.
The blood will
naturally
push against
the valve.
However, the
valves remain
firmly shut.
In this way, the blood can be moved from chamber to
chamber quite efficiently. The valves prevent the blood
from moving in the wrong direction.
Now that we can name all of the parts of the heart it is
time to see how they work to push blood around the body.
The heart pumps blood when its muscle contracts. As
the muscle contracts the chamber gets smaller and
squeeze the blood out.
The two sides of the heart work together. The atria
contract and relax at the same time, as do the ventricles.
The next two slides describe what occurs inside the heart
during one heart cycle.
Blood from
the body
Blood from
the lungs
1. The heart beat begins
when the heart muscles
relax and blood flows into
the atria.
2. The atria then contract and
the valves open to allow
blood into the ventricles.
3. The Ventricles contract
forcing the blood to leave the
heart. At the same time, the
atria are relaxing and once
again filling with blood.
The staged cycle then repeats itself.
Just before we finish our study, let’s take a last
look at the heart…..
Do you notice anything
different about the two
sides of the heart?
Well, the left ventricle wall is
clearly thicker than the right
ventricle wall.
Why is this?
To answer this question, think about where the blood is
going when it leaves the right and left ventricles.
Lungs
This journey is
far less
demanding. The
right ventricle
only has to pump
blood from the
heart to the
adjacent lungs.
This journey is
enormous. The
left ventricle has
to pump blood all
over the body!
Body cells
Therefore, the left ventricle needs a thicker wall to
generate a stronger ‘squeeze’ on the blood.
Now, let’s consider the blood vessels...
We can get an idea of what they could look like from
considering the job they have to do.
Let us look at a small section of the circulatory system.
There seems to be 3 types of blood vessel present
One joins the
other two
together
One takes
blood away
from the
heart
Lungs
One takes
blood to the
heart
So we have 3 types of blood vessels doing 3 different
jobs.
1.
Blood vessels that take blood away
from the heart are known as
ARTERIES.
Remember, arteries (away)
2.
Blood vessels that take blood back to
the heart are known as VEINS.
Remember, veins (into the heart)
3.
Finally, if arteries take blood away from the
heart and veins take blood back to the heart,
when does an artery turn into a vein?
Well, our third type of blood vessel links the two. In
other words, we find it present where an artery
finishes and a vein is about to begin.
This third type of blood
vessel is known as a
CAPILLARY.
Let us consider each vessel in turn to see how its
shape is related to the job it has to do.
In each case we will look at a cross-section of the vessel
ARTERY
small
lumen
thick muscle
and elastic
fibres
The blood flowing through an artery will be under high
pressure and moving extremely fast.
There is no chance that the blood will turn around and
start travelling in the opposite direction. Therefore there
are no valves present in arteries.
VEINS
large lumen
thin muscle and
elastic fibres
The veins are carrying blood back towards the heart.
Materials have been exchanged and now it is
running out of energy. It needs to return to the heart
to receive another pump.
Unfortunately, this could lead to a real
human
leg
vein
Problem..
What happens
if blood loses
so much
energy that it
stops and
turns around?
This situation could arise where blood is flowing
against gravity. However, there is a solution to this
problem. It comes in two parts.
1.
Firstly, veins have valves which act to stop the
blood from going in the wrong direction.
(These valves are similar to those found in the heart)
valves
open
blood
valves
close
CAPILLARIES
These vessels link arteries with veins.
They are found all over the body and are essential for
the exchange of materials between the blood and other
body cells.
artery
vein
capillaries
Capillaries are so small
that they can only be seen
using a microscope.
A collection of capillaries is
known as a capillary bed.
The wall of a capillary is
only one cell thick!
very narrow lumen
Substances can diffuse across the lining of the
capillary. This allows useful substances which are
dissolved within the blood to move into surrounding
cells whilst cellular waste moves in the opposite
direction.
3
1
2
The exchange of materials between the blood and the body
can only occur through capillaries.
One such exchange that occurs in the capillaries is
that of oxygen and carbon dioxide.
Summary
• The respiratory system is responsible for
providing the body with oxygen and
removing carbon dioxide.
• The circulatory system is responsible for
transporting oxygen, carbon dioxide and
other substances around the body.
• These two systems work hand-in-hand
and are crucial for life.