Investigating the Stretch and Recoil of Arteries and Veins Essay
Investigating arteries and veins Methodology 1. Suspend a ring of artery from a hook on a clamp stand. 2. Use a metre rule to record the length of the ring once the mass carrier has been attached to the free end of the ring. 3. Attach a 10 g mass and record the length of the ring after the mass is added.
4. Remove the mass and record the length of the ring. 5. Repeat steps 2 and 3 using 20, 30, 40 and 50 g masses. Record the length with and without the masses each time.
When comparing the arteries and veins, the results show that the percentage change gradually increases as the amount of weights increases.The vein with mass started off with a small percentage increase of 4%, and then rose to 9%, which was maintained. The artery with mass varied from 10-29%. The artery walls contain collagen and elastic tissues which allow it to stretch and recoil, where as the veins do not have as much connective tissue containing collagen fibres. This is not a problem as the arteries, being closer to the heart, have to withstand a much higher pressure than the veins do.
When returning to the original length, the vein without mass increased by 4% then ultimately grew to 9% and the artery without mass varied from 0-10% then back to 0% again.The artery went back to 0% at the end because of its ability to recoil to its original size. This proves that the arteries have more collagen in the muscle walls which allows them to stretch and recoil. The elastic fibres allow the arteries to dilate and constrict.
The main properties of the artery are the connective tissue with collagen fibres which make up the outer coat, the smooth muscle and the elastic tissue. This elastic tissue gives the blood vessels their much needed flexibility. Furthermore the artery walls contain a fibre named collagen.Collagen works well with elastic fibres to provide the arteries with firmness and strength. It has a special network structure which gives the protein its unique characteristics.
Collagen is a fibrous protein; it has several polypeptide chains which are cross-linked for additional strength. Hydroxyproline is a one of three components of collagen. Hydroxyproline and proline play key roles for collagen stability. They permit the sharp twisting of the collagen helix. The proline residue increases the stability of the collagen triple helix.The amino acid Glycine only accounts for 35% of the sequence.
The large amount of smooth muscle in the artery provides it with more elastic tissue for recoiling. There has to be more elasticity in the artery for it to withstand the pressure from the heart. There is a big difference between the arteries with mass to recoil. i. e.
21cm stretched to 27cm, therefore increasing by 6 cm. The recoil is from 27cm to 21 cm, therefore there is 6cm of recoil. Whereas in the vein, the highest stretch was 23cm to 25cm, giving a stretch of 2 cm and its recoil was 0cm.If the vein was put under the same pressure as the artery, it would not be able to tolerate the amount of pressure because it cannot stretch then recoil. The small lumen in the artery means that there is a higher amount of pressure in the lumen compared to the vein. There is a smaller space for the blood to flow through, which increases the pressure.
The veins are put under less pressure by the large lumen and the fact that they are situated quite far from the heart. They contain valves to prevent backflow and are surrounded by skeletal muscles to keep the blood moving in the same direction.Capillaries are only one epithelial cell thick. They are tubes of endothelium, freely permeable to small molecules and extremely good at diffusing molecules like oxygen e.
g. in the lungs. The exchange of oxygen and carbon dioxide takes place through the thin capillary wall. Capillaries are also involved in releasing heat.
For example, during exercise, the body’s temperature rises, the blood delivers the heat to the capillaries which then rapidly release it to the tissue. Unlike arteries and veins, they do not transport blood around the body; they also remove waste products by a process called diffusion.Smooth muscle contracts slowly and may maintain the contraction for prolonged periods in the blood vessel walls without our conscious control. There are several different types of smooth muscle, but the type found in blood vessels is called ‘Vascular smooth muscle’. This muscle is responsible for transporting fluids around the body; it can change the volume of blood vessels and the blood pressure. It controls all of the mechanical activity in the blood vessels.
It is the tissue that allows the blood vessels to constrict or dilate. Elasticity is an essential attribute of smooth muscle.Smooth muscle cells may secrete a complex extra cellular matrix containing collagen. These fibers are spindle-shaped. When performing the experiment, the biologist should be aware of some safety implications. Eye protection should be worn at all times.
This is because sharp instruments are used e. g. forceps and scissors. Also, at any time the vein or artery may break, and come into contact with some one’s eyes, this may result in long term damage to the eye. There is a possibility that the arteries and veins may fall onto the bench, in which case the benches need to be disinfected with 1% Virkon or another suitable disinfectant.It is advised that students wash their hands before and after the experiment even if they are wearing plastic gloves due to germs and bacteria that may In this experiment the independent variable was the mass (g) added on.
Therefore the dependant variable was the length of the vein or artery once it had been stretched. The independent variable is the factor that is varied and the dependant variable depends on the independent variable. Any other factors which may affect the dependant variable but are controlled are called confounding variables. Some modifications could be made to ensure the results were reliable and valid.The experiment could be repeated, to compare the results and check for any outliers amongst the data. If the test was repeated, the experimenter would need to make sure the experiment was carried out in exactly the same way to make the test fair.
If the same people were used to repeat the experiment, this would ensure that the results would be reliable. Reliability also depends on the equipment being exactly the same, to produce the same outcome as before. To make the test precise, the equipment should be checked thoroughly encase it is faulty; also an incorrectly used piece of equipment would make the experiment inaccurate too.Another variable could be the width of the arteries and veins used, which could vary from animal to animal. However the percentage change would be accurate still as it shows the amount it stretched and recoiled, therefore it does not matter what size the vessel was to start with.
Validity was taken account for when choosing what test to carry out. The results show that the arteries contain more elastic fibres and collagen which allow the blood vessels to broaden and shrink back extremely well, where as the veins do not have this structure so they cannot recoil as well as the arteries.