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Heart Recoil IA. Aim To compare the recoil and subsequent elastic limit of a mammalian aorta and vena cava.

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Introduction

IA 12: Unit 6- Investigating the Properties of Blood Vessels Aim To compare the recoil and subsequent elastic limit of a mammalian aorta and vena cava. Introduction Pumped by the muscular action of the heart, the blood is propelled around the body in tubular blood vessels. Blood flows through arteries, arterioles, capillaries, venules and veins. In this investigation we shall relate some of the physical properties of arteries and veins to their functions. Data Collection and Processing Raw data table to show the elastic recoil of vena cava Mass (g) Length of vena cava (�0.1cm) Vena cava with mass Vena cava without mass Elastic recoil (�0.2%) 0 (original length) 2.2 2.2 0.0 100 3.6 3.4 5.9 200 4.2 4.0 5.0 300 4.5 4.4 2.2 400 4.6 4.5 2.2 500 4.6 4.5 2.2 600 4.6 4.6 0.0 700 4.7 4.7 0.0 800 4.7 4.7 0.0 Raw data table to show the elastic recoil of aorta Mass (g) Length of aorta (�0.1cm) Aorta with mass Aorta without mass Elastic recoil (�0.2%) 0 (original length) 3.3 3.3 0.0 100 3.8 3.3 15.2 200 4.4 3.3 33.3 300 4.6 3.3 39.4 400 4.8 3.3 45.5 500 5.0 3.3 51.5 600 5.2 3.3 57.6 700 5.3 3.3 60.6 800 5.3 3.3 60.6 Calculations Elastic recoil of the first 100g Formula Working out Answer (1 d.p) Vena cava ((length with mass-length without mass)/ length without mass) x100 ((3.6-3.4)/3.4) ...read more.

Middle

But as the mass increases, the length when the masses are added only increases by a bit (ranging from 0 to 0.6). This can be seen from the elastic recoil of the vena cava. It first increased by 5.9% but as the mass load is increased, the elastic recoil decreases and gradually reached 0, meaning the elastic limit is reached (at 4.7cm). On the other hand, for the aorta, as the mass of weights increases, the elastic recoil gradually increases till it reaches it's elastic limit (at 5.3cm) where the length wouldn't increase even though the mass increases. This is supported from the line labeled "aorta" on Graph one. In the graph, we can clearly see the line (elastic recoil) steeply rising all the way up as the mass increases till 700g to 800g when the line levels off and remains at 60.6g.This means the elastic limit of the aorta has been reached. However, even though the mass of weights increases, the aorta always return to its original length at 3.3cm, even when the 800g load is added to it. This can be seen on the results. When the 800g load is added on, the aorta stretched to 5.3cm (from 3.3cm) but when the load is taken off, it immediately returns to the original length. ...read more.

Conclusion

This will make the experiment a fair test thus my results will be reliable The preparations of the samples (vena cava and aorta) may have been damaged. For example, there were some tiny cuts on my vena cava, which can affect the elasticity and the elastic limit of it. Use scissors to prepare and cut the sample of aorta and vena cava instead of using a scalpel so the cutting is more precise. This will ensure the samples won't be damaged when the load of mass is added When measuring the length of the aorta/ vena cava both when the mass is added and after the mass, it is not precise enough. This is because sometimes the ruler may be slanted or wobbly causing the readings to be inaccurate. Use a clamp and a stand to hold the ruler vertically to ensure accuracy when measuring the length of the vena cava/aorta Using only a pig's aorta/vena cava may be insufficient to support they hypothesis Repeat the experiment using other mammalian veins and arteries in order to have further evidence to support the hypothesis thus making the results more reliable 1 Maton, Anthea (1995). Human Biology Health. Englewood Cliffs, New Jersey: Prentice Hall. ISBN 0-13-981176-1. 2 "Circulatory Systems - Biology Encyclopedia - Body, Animal, Organs, Blood, Separated, Major." Biology Reference. Web. 12 Feb. 2012. <http://www.biologyreference.com/Ce-Co/Circulatory-Systems.html>. ?? ?? ?? ?? Claudia Cheng ...read more.

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