Download Capillary Circulation in Fish

Capillary Circulation in Fish
Complete the following experiment and record your data and conclusions in your lab
notebook.
We will be looking at the fish circulatory system. Within the tail of a goldfish it is easy
to identify three types of blood vessels; arterioles that flow away from the heart,
venules that flow toward the heart, and capillaries that flow in between the other two.
Materials: Cotton, compound light microscope, petri dish, and goldfish
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Saturate a piece of cotton with aquarium water and place into a petri dish.
Place your goldfish in the petri dish and wrap it’s head with the cotton. Make sure
there is enough water in the dish to cover the bottom, but not too much.
Focus on the tail of the goldfish with low power first and then high power if needed.
You are looking for moving blood!
1. Draw an accurate picture of the blood flow and label the three different types of
blood vessels described above. Also on your diagram, label where the heart and the end
of the tail would be.
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Return your goldfish to the aquarium as quickly as possible!
Conclusion (please use complete sentences)
2. In which vessels would blood tend to throb? Why?
3. In which vessels would blood tend to flow at a uniform rate? Why?
4. Do arterioles carry blood toward or away from the tail? How do you know?
5. Which type of blood vessel has the smallest diameter? Why?
6. Which type of blood vessel has the largest diameter? Why?
7. Draw a simple diagram representing the circulatory system of a fish. Include all of
the following terms: Heart, Gills, arteries, veins, arterioles, venules, and capillaries.
8. Why would a four chambered heart be more efficient than a three or two chambered
heart?
9. Refer to your anatomy book and draw a diagram of a vein and an artery. How are they
similar? How are they different?
10. If an artery were treated with a vasodialator- a chemical which increases the
diameter of the artery- would an increase or decrease of blood flow be observed?
Explain.
11. If the artery were treated with a vasoconstrictor what would be the effects?
12. Based on your answers in 10 and 11 can an explanation be given for blushing?
Answers
Questions:
1. Why would a four chambered heart be more efficient than a three or two chambered
heart?
A four chambered heart is more efficient than a three chambered heart because it keeps
deoxygenated blood separate from oxygenated blood. A three chambered heart has only one
ventricle which allows the blood to mix. Since the ventricle pumps blood out of the heart, both
oxygenated and deoxygenated blood will be sent to both the lungs and the body meaning that
the animal will only receive half the oxygen it could. The four chambered heart allows the
maximum amount of oxygen to reach the body enabling the animal to move much faster.
A two chambered heart of a fish is also inefficient but it does not mix blood. Oxygen
enters through a fish’s gills, enters the atrium, and is pumped to the body through the ventricle.
This makes a two chambered heart more efficient than a three chambered one because it allows
the maximum amount of oxygen to reach the body. It is less efficient than the four chambered
heart however because it results in lower blood pressure and less oxygen reaching the body per
minute causing the animal to move slower.
2. Use a biology book for reference and sketch a two chambered heart and a three
chambered heart. Then sketch a four chambered heart. Label all the parts of each heart
diagram.
3. How can it be determined if an artery or vein is being observed by looking at the direction
of blood flow?
If the blood is flowing towards the heart, it usually contains deoxygenated blood and is a vein.
If the blood is flowing away from the heart, it usually contains oxygenated blood and is an
artery.
4. Refer to your anatomy book and draw a diagram of a vein and an artery. How are they
similar? How are they different?
Arteries and veins are made up of many of the same structures. These include the tunica intima,
the lumen, the tunica media, and the tunica externa. The tunica media of arteries tend to be thicker as
blood needs to be forced into them while the lumen of veins is thicker to account for lower blood
pressureand to enable the same amount of blood to be pumped to the heart as is being pumped out.
Veins also have valves to prevent backflow while arteries do not.
5. If an artery were treated with a vasodialator- a chemical which increases the diameter of
the artery- would an increase or decrease of blood flow be observed? Explain.
If an artery’s diameter was increased the blood flow through the artery would also increase but
blood pressure would be lowered.
6. If the artery were treated with a vasoconstrictor what would be the effects?
If an artery were treated with a vasoconstrictor, the artery diameter would decrease causing the
artery to narrow, blood flow to decrease, and blood pressure to increase.
7. Based on your answers in 5 and 6 can an explanation be given for blushing?
Based on the effects of changes in artery diameter, it can be concluded that when a person
exercises or gets nervous their arteries expand to allow faster blood flow to increase the amount
of oxygen reaching the body. If a person gets nervous they blush due to increased blood flow to
the head.
Conclusion:
In this lab, we were asked to observe the blood flow through the tail of a fish. We were able to
see blood flowing towards and away from the anterior end of the body suggesting that both veins and
arteries were present in the fish’s tail. Blood vessels are extremely important to the health of an
organism because they provide oxygen to the tissues and allow waste products to be carried out of the
body via the lungs in the form of carbon dioxide. If blood vessels were not specialized, the body would
be much less efficient in delivering oxygen to all of its tissues and cells. Without oxygen, the cells
would not be able to undergo cellular respiration and would be unable to produce energy for the body.
Therefore, blood vessels are some of the most important structures in the body because they allow
movement of blood and, by association, the production of energy.