For processing the data, I drew 2 graphs. Graph one represents the elastic recoil percentage of the aorta and the vena cava as the mass increases. Graph two shows the elasticity of the aorta and the vena cava. This is measured from the length of the artery/vein when a mass of 800g is put on. No averages and standard deviation is calculated as I only did one trial because I was unable to do another repeat as this means I will have to dissect another heart to obtain an aorta and vena cava again.
Conclusion
The aim of this experiment was to compare the recoil and elastic limit of an aorta and vena cava. This was done by hanging weights onto the aorta/vena cava and measuring the length of it when the mass was put on and afterwards to test the elasticity of it. In conclusion, I found out that the aorta has the ability to recoil and stretch a lot more than the vena cava. This can be supported from my results. The elastic recoil of the vena cava when 100g of weight is added on is 5.9% whereas for the aorta, it is 15.2%. The elasticity of the vena cava is limited. It stretched by 1.4cm from the original length to when 100g is added. 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. This proves that the aorta can recoil effectively, thus meaning that arteries are more elastic and can recoil more than veins. In my results, I did not encounter any anomalous results.
There is a biological explanation to support this hypothesis and theory that aorta has the ability to stretch and recoil more than the vena cava. The function of the aorta is to distribute oxygenated blood to all parts of the body, thus arteries carry blood away from the heart. This means that the walls of the aorta (and arteries) are thicker than the vena cava (and veins). This can be seen from the diagram below.
In the diagram, we can see the walls of the artery is thicker then the vein thus causing the lumen of the artery to be smaller than the vein. The elastic muscle fibers and smooth muscles from the tunica media that make up the walls enable the aorta to withstand high blood pressure as it is pumped from the heart. When the aorta expands as the pulse of blood passes through, the elastic recoil of the elastic fibers causes it to spring back quickly afterwards thus pushing the blood along. Also, the artery walls contain collogen fibers, which provide the arteries with firmness and strength to prevent overstretching. This reinforces that the aorta has good recoil. Therefore, veins (vena cava) will have less elastic fibers and thinner walls due to their lower pressure environment. This also proves that due to the vena cava having a larger lumen, it will not return to it’s oringal length after an applied force have been taken off, but will be permanently stretched.
Weaknesses and improvements
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