2 tto
circulation
1
Section 1 – Blood cells
The blood consists of special cells in a liquid called
plasma. An adult man has 5-6 litres of blood.
Blood consists of 55 % plasma, and 45 % by
cells (see Fig. 1).
The blood performs a lot of important functions.
Hemoglobin in the erythrocytes (red blood
cells) carries oxygen to the cells and collects the
carbon dioxide (CO2). Blood also transports
Figure 1. What is blood made up of.
nutrients (e.g. amino acids, sugars, mineral salts) and waste. The blood also carries
hormones, enzymes and vitamins. It performs the defence of the organism by means of
leukocytes (white blood cells) against bacteria and viruses.
Erythrocytes (red blood cells)
The erythrocytes are the most numerous blood
cells i.e. about 4-6 millions/mm3. They are also
called red blood cells. In man and in all
mammals, erythrocytes have no nucleus and
have the shape of a car tire (see Fig. 2). The red
cells are rich in hemoglobin, a protein able to
bind to oxygen. These cells are responsible for
providing oxygen to tissues and partly for
recovering carbon dioxide produced as waste.
Figure 2. An example of red blood cells.
In the red blood cells of the mammalians, the lack of nucleus allows more room for
hemoglobin and the biconcave shape of these cells raises the surface and cytoplasmic
volume ratio. These characteristics make the diffusion of oxygen into these cells more
efficient.
Platelets (thrombocytes)
The main function of platelets, or thrombocytes, is to stop the loss of blood from
wounds. To this purpose, they aggregate (komen samen) and release factors (substances)
which promote the blood coagulation (sticking together of cells, stollen van bloed). Their
diameter is 2-3 µm about, hence they are much smaller than erythrocytes. Their density in
2
the blood is 200.000-300.000 /mm3. Like
erythrocytes, thrombocytes don’t have a
nucleus.
When a blood vessels is damaged, the wall
of the vessel and the thrombocytes release
substances that start the production of long,
sticky threads (fibrin) in which thrombocytes
and erythrocytes are caught to put a plug in
the hole (see Fig. 3).
Leukocytes (white blood cells)
Leukocytes, or white blood cells, are
responsible for the defence of the organism.
They fight bacteria, viruses and other
Figure 3. the formation of a blood clot
organisms that enter the body. In the blood,
they are much less numerous than red blood cells. The density of the leukocytes in the
blood of a healthy person is 5000-7000 /mm3. When someone has an infection the
numbers of leukocytes increase.
Some of the leukocytes fight bacteria by taking them up by phagocytosis (see Fig. 4).
3
questions:
1. What substances are present in the blood?
2. What kind of blood cells are present in our blood and in what relative numbers (per
mm3)?
3. Make a table in which you present the cell types and their functions.
4. Red blood cells have no nucleus. What does that tell you about their lifespan?
Figure 5. Many kinds of blood cells.
5. Use Figure 5 for this question. Do leukocytes have nuclei?
6. Blood is takes of a person who is ill. What do you think will be different in Fig. 6?
Figure 6. A microscopic view on a droplet
of blood of a healthy person.
7. Make a list of the events that take place when a blood vessel is damaged.
4
Section 2 – a double circulation
The function of the circulatory system is to carry
the blood throughout the body. In mammals, the
blood is pumped around by the heart in two
rounds. One round goes from the heart to the
lungs and back to the heart, this is called the
pulmonary circulation (kleine bloedsomloop).
The other one goes from the heart to the body
and then back again, called the systemic
circulation (grote bloedsomloop).
question:
8. A red blood cell present in your left leg has
just passed on its oxygen to the muscle cells
and goes to the lungs to collect more oxygen.
Figure 7. the double circulation
How many times does this erythrocyte pass
the heart minimally before it returns to the muscles in your left leg?
Section 3 – the heart
Below you will find a number of
pictures of the heart. Some are
rather schematic, others are
very realistic. You are asked to
learn all the parts of the heart
by heart (!?). What is more,
you need to know them in a
certain order; the order in
which the blood passes through
the heart twice (see Fig. 8):
The blood enters the heart for
the first time through the
Figure 8. the parts of the heart
superior and inferior vena cava.
This is the blood vessel that brings the blood from the body to the heart. The blood
5
Figure 9. Several pictures of the heart –
schematic and realistic ones.
enters the heart in the right atrium. Keep
in mind that left and right in these pictures
is that of the patient’s.
The blood then continues into the right
ventricle and leaves for the lungs through
the pulmonary artery.
It returns in the left atrium through the pulmonary vein and
via the left ventricles the blood flows towards the body
through the aorta.
The heart is a muscle that contracts and relaxes alternately
(afwisselend). When the heart muscle of the atrium contracts,
the blood that is in the atrium is squeezed into the ventricle.
Once the blood is in the ventricle, the muscle of the ventricle
contracts. The blood doesn’t flow back into the atrium
because of the tricuspid valve.
Figure 10. how do valves
function
A valve can only be opened from one side only. If pushed from the other side, the
valve shuts (see Fig. 10). There are also valves between the ventricles and the arteries
(see Fig. 9). You should learn their names and locations.
6
questions:
9. Study the heart and all its parts carefully. Now close your booklet and make a
schematic drawing of a heart with all the parts and their names in it. Afterwards check
your drawing and correct it. Make sure it is a schematic drawing, a real heart s too
difficult to draw. Don’t forget the attached blood vessels.
10. What is the advantage of the valves in the heart. What would happen in the circulation
if there were no valves in the heart?
Section 4 – one contraction of the heart
Visit this site: watch and listen to the animation:
http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html
A heart beat consists of two stages: a diastole and a systole.
Diastole
Diastole is the period of time when
the heart relaxes after contraction in
preparation for refilling with blood.
Ventricular diastole is when the
ventricles are relaxing, while atrial
diastole is when the atria are
relaxing. Together they are known
as complete cardiac diastole (stage 1
in Fig. 11).
During ventricular diastole (stage
1 + 2), the pressure in the ventricles
drops. When the pressure in the left
ventricle drops to below the pressure
in the left atrium, the mitral valve
Figure 11. the stages of a heart beat
opens, and the left ventricle fills with blood that was in the left atrium. Likewise, when the
pressure in the right ventricle drops below that in the right atrium, the tricuspid valve
opens, and the right ventricle fills with blood that was in the right atrium.
7
Systole
Atrial systole is the contraction of the heart muscle of the left and
right atria. Normally, both atria contract at the same time. The
term systole is synonymous with contraction (movement or
shortening) of a muscle.
As the atria contract, the blood pressure in each atrium
increases, pushing blood into the ventricles through the mitral and
atrial systole
tricuspid valves. 70% Of the blood flows passively down to the
ventricles during the diastole, so the atria do not have to contract a
great amount.
Ventricular systole is the contraction of the muscles of the left
and right ventricles pushing the blood, through the pulmonary and
aortic valves, into the pulmonary artery and the aorta, respectively.
from: http://en.wikipedia.org/wiki/Cardiac_cycle
ventricular systole
Figure 12.
questions:
11. What happens with the volume of a ventricle when it relaxes?
12. What happens with the pressure in a ventricle when it relaxes?
13. What effect does the relaxation of a ventricle have on what valves?
14. From where to where does the blood flow during the relaxation of a ventricle?
15. What does the atrium do after the relaxation of the ventricle?
16. Describe the blood flow following the action of the atrium.
17. The cycle of a complete heart contraction if completed by the ventricular systole.
What is a ventricular systole?
18. Describe what happens during a ventricular systole with certain valves and the blood
flow.
19. Write down exactly (step by step) what happens during one complete cycle of a heart
beat. Use a drawing of the heart.
8
Practical 1 – valves
In this experiment you will receive a balloon pump to show you how valves function. The
balloon pump functions as follows: Put end B in a beaker with water and squeeze the
pump in. Keep the pump squeezed in and remove it from the beaker.
1 - Describe what you saw. Why didn’t anything happen?
Place the pump with end A in the beaker. Squeeze the pump and then release the pump
again while holding it under water. Once the pump has resumed its normal shape remove
it from the beaker.
2 – Describe what happened in two steps.
Keep the pump above the beaker, with side B facing down and squeeze again, carefully.
3 – Describe what happens at end B.
4 - Why didn’t anything happen at end A?
Repeat this a few times to understand how the pump works.
If your examine the pump closely you can see that the pump has valves.
5 - Make two drawings of the pump with ends A and B.
In the first drawing indicate where the water enters the pump.
In the second drawing indicate where the water leaves the pump.
In your drawings point out which valves are closed and which are opened.
The pump can be compared with the ventricle of your heart. It fills and pushes blood out
just like the balloon pump does with water. The two stages of pumping in the previous
question resembles two stages of a heart contraction: the diastole and the systole of the
ventricle.
6 – Label each drawing with the correct stage of the heart contraction.
9
Section 5 – names of blood vessels
You need to know he names and locations of (see Fig. 13):
Aorta, inferior vena cava, superior vena cava, pulmonary artery / vein (longslagader,
-ader), renal artery / vein (nierslagader, -ader), iliac artery / vein (beenslagader, -ader),
hepatic vein / artery (leverslagader, -ader), hepatic portal vein, mesenteric artery
(darmslagader), jugular vein (halsader) and carotid artery (halsslagader).
Figure 13. names of all the important blood vessels
10
questions:
20. Through which blood vessels and through which parts of the heart does a glucose
molecule (that has just been absorbed into the blood in the intestine) flow when it
travels from the small intestine to muscle cells in the left leg (where it will be respired
to give energy to the muscle there)?
21. Through which organ(s) does a red blood cell always flow in 1 circulation (rondgang)?
1 – the heart
2 – the lungs
3 – the liver
4 – the head and arms
Section 6 – functions of the blood vessels
The function of most blood vessels is transporting nutrients and oxygen towards the
organs and cells and transporting waste like carbon dioxide away.
There are two exceptions: The hepatic portal vein and the pulmonary blood vessels (see
Fig. 13).
The hepatic portal vein
In the intestines (digestive tract / gut) nutrients are absorbed and put in the blood. Cells
need nutrients for growth and energy, but too much nutrients in the blood is bad for the
cells. Therefore, all the superfluous (overtollige) nutrients are stored in the liver. When the
cells have too little nutrients (te weinig voedingsstoffen) because the blood is low in
nutrients, nutrients are released by the liver and sent to the cells.
The hepatic portal vein transports the nutrients absorbed by the intestine to the liver
so that the liver can store the nutrients until they are needed. The blood in the hepatic
portal vein is low in oxygen since the intestines have used up all of it. To make sure the
liver gets it’s oxygen the liver also receives blood rich in oxygen via the hepatic artery (see
Fig 13).
The pulmonary artery and vein
The pulmonary artery is the only artery in the body that does not contain a lot of oxygen.
This artery is going to the lungs to collect oxygen and is therefore low in oxygen and high
in carbon dioxide. About the pulmonary vein the opposite can be said.
11
questions:
22. Does the hepatic portal vein transport a lot of nutrients:
1 – when someone has just eaten?
2 – when someone has not eaten for a long time?
Explain both answers.
23. Two situations:
1 – someone is sitting quietly in a chair
2 – someone is working very hard / running very hard
a When does the liver put glucose into the blood (situation 1 or 2)?
b Explain your answer.
c When the liver puts glucose in the blood; in what blood vessel is the glucose
concentration highest?:
1 – hepatic vein
2 – hepatic portal vein
3 – inferior vena cava
d Explain your answer.
24. Peter says that an artery always contains a lot of oxygen.
Explain that this is not true / not always.
25. How could you describe the function of the liver in your body (one of the functions,
because it has many more)?
12
Section 7 – types of blood vessels
Arteries
Arteries are tough, elastic tubes that carry blood away from the heart. They need to be
elastic because they have to deal with the high blood pressure caused by the pumping of
the heart.
As the arteries move away from the heart, they divide into smaller vessels. The largest
arteries are about as thick as a thumb. The smallest arteries are thinner than hair. These
thinner arteries are called arterioles. Arteries carry bright red blood! The colour comes
from the oxygen that it carries. There is one exception: the pulmonary artery.
Veins
Veins carry the blood to the heart. The smallest veins, also called venules, are very thin.
They join larger veins that open into the heart. The veins carry dark red blood that doesn't
have much oxygen. There is one exception: the pulmonary vein.
Veins have thin walls. They don't need to be as strong as the arteries because as blood
is returned to the heart, it is under less pressure.
Capillaries
Capillaries are tiny (extremely narrow) blood
vessels, of approximately 5-20 μm (micrometres - 1 μm is 1/1000 mm) diameter.
The capillary system is so extensive that
there isn’t a single cell much more than a
fraction of a millimeter from a capillary site.
Figure 14. a capillary
The total surface area of the capillaries in
your body is over 1,000 square miles.
The networks of capillaries are in all of the organs and tissues of the body. The
capillaries receive blood from arterioles and pass it on to venules (see Fig. 15). Capillary
walls are only one cell thick (see Fig. 14), which permits exchanges of material between
inside of the capillary and the cells in the tissue around it. Each of the cells in the walls of
the capillaries have openings between them so that the exchange can take place. The
plasma is squeezed out by the blood pressure and forms interstitial fluid (weefselvloeistof)
in the tissues so that the cells can bath in dissolved O2 and other nutrients (see Fig. 16).
13
The function of the interstitial
fluid is to give cells good
substances and also to remove
waste from the surrounding cells,
as opposed to simply moving the
blood around the body (this is all
arteries and veins do).
The number of capillaries in an
organ vary depending on the need
for oxygen and other nutrients.
Figure 15. capillaries connect arterioles to venules
The blood flow through the
capillaries is regulated by a
sphincter, a ring of muscle, that
contracts to control the flow of blood
through the capillaries (see Fig 16).
This is important because there
would not be enough blood to fill all
the blood vessels at one time. This is
understandable when one sees that
an individual could have between
25,000 to 60,000 miles of capillaries.
Figure 16. formation of interstitial fluid
questions:
26. Blood that flows from the heart to the kidneys and back to the heart again flows
through a number of blood vessels in random order (willekeurige volgorde):
artery, capillary, venule, arteriole and vein.
Place them in the correct following order.
27. a Which of the blood vessels in question 26 is the thinnest.
b Which of the blood vessels in question 26 contain most oxygen?
c In which of the blood vessels in question 26 is the blood pressure highest?
d From which of the blood vessels in question 26 does oxygen diffuse towards the
cells in the tissues and organs?
14
28. How far does an oxygen molecule need to travel maximally from a capillary to reach a
cell?
29. How can plasma leave the capillary to form interstitial fluid?
A it goes through the cells
B it passes between the cells
C it leaves the capillary at its open end
30. Where do we find interstitial fluid?
A between the cells
B in the blood vessels
C in the cells
D in the capillaries
31. What is the function of interstitial fluid?
32. In a well trained muscle as the calf (de kuitspier) of a athlete you will find more
capillaries than in the calf of an untrained individual.
Explain that the well trained muscle needs more capillaries.
33. When you are resting after dinner, the precapillary sphincter in arterioles leading to
your intestine relax, whereas the precapillary sphincter in the arterioles leading to your
calf contract.
Explain this step by step for both sphincters.
Veins, valves and muscles
Once the blood has passed from the arteries through the
capillaries, it is flowing at a slower rate because little
pressure remains to move the blood along. Blood flow in the
veins below the heart is helped back up to the heart by the
muscle pump. The walls of the veins are thin and
somewhat floppy. To compensate for this many veins are
located in the muscles. Movement of the leg squeezes the
veins, which pushes the blood toward the heart. When the
muscles contract the blood within the veins is squeezed up
Figure 17. valves in veins
the vein and the valves open (see Fig. 17). When the muscle is at rest, the valves close
helping to prevent the backward flow of blood. This is referred to as the muscle pump.
15
Figure 18. the muscle pump in the calf
Varicose veins
Varicose veins (spataderen) can’t prevent the
blood flowing back down. The veins are too wide so
that the valves can’t close the vein anymore. The
blood is not returned to the heart which is not good.
questions:
34. What makes the blood flow through the arteries?
35. Explain that this force can not make the blood
Figure 19. Varicose veins
flow through the veins.
36. Some veins are located in or between muscles.
What happens to the blood in these veins when the muscles contract?
Explain in at least three steps.
37. What happens when the muscles relax again?
Explain in three steps.
38. Varicose veins are found in people who have s job that requires standing up all day.
because of that the veins stretch. The valves are no longer able to close.
What is the effect of this on the blood flow through these veins?
16
Section 8 - Coronary arteries
The coronary arteries (kransslagader)
deliver blood to the heart muscle, providing
a continuous supply of oxygen and
nutrients needed for it to stay healthy and
function normally (see Fig. 20).
Coronary artery disease
Coronary artery disease is atherosclerosis of the coronary arteries.
Atherosclerosis is when arteries become
clogged (verstopt) and narrowed
(vernauwd) so that the blood can’t flow
Figure 20. the coronary artery
that easily anymore.
Coronary artery disease starts when you are very young. Before your teen years, the
blood vessel walls begin to show streaks of fat. As you get older, the fat builds up, causing
slight injury to your blood vessel walls. In an attempt to heal itself, the cells release
chemicals that make the walls even stickier.
If a coronary artery is narrowed and a blot clot flows through, it completely blocks
the coronary artery (see
Fig. 21). Without adequate
blood, the heart becomes
starved of oxygen and vital
nutrients it needs to work
properly.
This can cause chest
pain called angina. When
one or more of the
coronary arteries are
completely blocked, the
result is a heart attack
(injury to the heart
muscle).
Figure 21. coronary
artery disease
17
questions:
39. What is the function of the coronary artery?
40. From which blood vessel does the coronary artery originate (waaruit ontstaat hij)?
A the pulmonary artery
B the aorta
C the pulmonary vein
D the vena cava
41. What causes coronary arteries to become narrower when you have atherosclerosis?
42. Explain what happens during a heart attack.
43. What causes death in case of a heart attack (step by step)?
18
Section 9 – measuring blood pressure
Your blood pressure can be measured either by using a machine
called a sphygmomanometer or by using an automatic machine.
A sphygmomanometer is the older kind of equipment that
measures blood pressure using a column of mercury. The person
taking your blood pressure will put a cuff around the top of your
arm, pump up this cuff and then listen for sounds through a
stethoscope placed on your arm. The sounds heard through
the stethoscope will start and then finish at certain points on
the mercury column, and this will give the reading for your
blood pressure.
There are also automatic digital machines that can
measure blood pressure. They also use a cuff around your
arm and will give a readout of your blood pressure.
What do the numbers mean?
When you have your blood pressure
measured, it is written down as two
numbers, one over the other like a fraction.
For example:
140 / 90 mm Hg
It is said as "140 over 90," for example.
The top number, which is called the
systolic pressure, shows the pressure in
your arteries when your heart is forcing
blood through them when the ventricles
squeezes blood out of the heart. The
Figure 23. measuring the blood pressure
bottom number, called the diastolic
pressure, shows the pressure in your arteries when your heart relaxes. The top number
can be anywhere from 90 to 240 and the bottom number can be anywhere from 60 to
140. Blood pressure is measured in millimetres of mercury, which is written down as: mm
Hg.
19
A sphygmomanometer cuff is wrapped around the subject's upper arm, just above the
elbow and a stethoscope is placed on the hollow of the elbow, over the brachial artery
as shown below (see Fig. 23).
The cuff is 'pumped- up' to a pressure of 180 mm Hg, pushing on the arm artery,
causing the artery to close. The pressure in the cuff is then higher than the pressure in
the artery. The highest pressure in the artery is called the systolic pressure (the pressure
of the blood caused by the contraction of the ventricle). At the point where the pressure
of the cuff is greater then the systolic pressure, the artery has collapsed thus, there is no
flow of blood through the brachial artery. In other words, the heart can’t push the blood
Figure 24. measuring the blood pressure
underneath the cuff anymore.
The doctor slowly decreases the pressure in the sphygmomanometer cuff. Once the
systolic pressure is reached (approximately 120 mm Hg in the 'normal' case), the brachial
artery opens causing the blood to flow and closes again, which cause vibrations against
the artery walls. These noises can be heard through a stethoscope. The blood flow
through the brachial artery increases steadily, until the pressure of the
20
sphygmomanometer cuff falls below the diastolic pressure (the pressure between
successive heart beats, the low pressure), approximately 80 mmHg. This is the point when
the blood can flow through the artery is constantly. You can’t hear the closing of the
artery anymore with the stethoscope.
Watch this link:
http://www.abdn.ac.uk/medical/bhs/video/tutorial/bpmeas.mpg
questions:
44. Explain that the blood pressure in your arteries is not constant but changes during
every heart beat.
45. When is the pressure highest in your arteries?
46. When is the pressure lowest in your arteries?
47. What do you actually hear when you hold a stethoscope on the hollow of your elbow
while determining your blood pressure?
48. Explain that you don’t hear vibrations anymore when the pressure in the cuff is below
the diastolic pressure.
21
section 10 – Lymph
Blood pressure squeezes plasma out of the capillaries to form interstitial fluid as explained
in section 7. Not all of the plasma that leaves the capillaries, however, can return to
venules. The interstitial fluid is removed through an alternative route (Fig. 25).
Lymph capillaries reabsorb this small amount of water that fails to be reabsorbed by
the blood capillaries. If lymph vessels are blocked and the capillaries cannot reabsorb the
water it releases into the tissue the tissues become swollen, a condition called oedema.
Figure 25. removal of excess interstitial
fluid by lymph vessels.
The lymphatic system does not form a circulation with
a “lymph heart”. It only consists of tubes that start in the
tissues and end near the heart where it returns the
lymph to the circulatory system.
Lymph moves through lymph vessels in a similar
fashion to how blood moves through blood veins:
Skeletal muscles squeeze the lymph vessels during body
movement which moves the lymph forward. The lymph
is prevented from flowing backwards by a system of
one-way valves similar to those in blood veins.
22
Figure 26. the lymphatic system
The lymphatic system is involved in the fight against infections. Organs called lymph
nodes, are located at junctions of lymph vessels. Here the fluid coming from several
organs and tissues is tested on pathogens (ziekteverwekkers). If pathogens are found an
immune response (afweerreactie) is takes place which starts with the swelling of these
lymph nodes. Here, immune cells (leukocytes) are formed and sent to the site of
inflammation (ontsteking).
questions:
49. What would happen if the excessive (overtollige) interstitial fluid wasn’t removed by
the lymphatic system?
50. How is lymph fluid moved along the lymphatic vessels?
51. If lymph nodes in your arm pit start to swell, where would you expect to find a
inflammation?
52. Does the fluid in the lymphatic system flow around in circles?
If not, how does it flow?
23
24
Glossary on circulation:
plasma
hemoglobin
erythrocytes
red blood cells
leukocytes
white blood cells
platelets
thrombocytes
coagulation
fibrin
phagocytosis
pulmonary circulation
systemic
atrium
ventricle
25
valve
diastole
systole
intestines
hepatic portal
Arteries
Veins
venules
capillaries
interstitial fluid
muscle pump
varicose veins
coronary arteries
coronary artery disease
atherosclerosis
blot clot
26
angina
heart attack
sphygmomanometer
systolic pressure
diastolic pressure
cuff
brachial
lymph capillaries
oedema
the lymphatic system
infections
pathogens
immune response
lymph nodes
27
What lists do you need to know?

All kinds of blood cells, their characteristics, English and scientific names and their
functions.

The sequence of events taking place during a complete heart beat: following order,
names of the parts of the heart, opening and closing of valves, changes in pressure.

All the names of the blood vessels.

Following order of types of blood vessels in circulation.

Know the function of each type of blood vessel.

What are the two functions of lymph.
What do need to be able to explain?

How do valves function.

How does the beating of a heart make the blood flow.

What is special about the hepatic portal vein.
What is special about the pulmonary artery and vein.

What the relation is between capillaries and interstitial fluid.

How does a muscle pump work.

How do precapillary sphincters work.

What causes a heart attack.

How do you measure your blood pressure.

How is the lymphatic system constructed.
28