The aim of this experiment was to understand the external and internal structures by dissecting a pig’s heart, drawing and labelling the structures.
Introduction
A pig’s heart is covered by the thin membrane or pericardium. Myocardium exists as the muscle located below the pericardium. Most of the myocardium in the lower two chambers of the heart called ventricles (Lane, 2010a).
A pig’s heart has four chambers which include left atrium, left ventricle, right atrium and right ventricle (Lane, 2010a). Atrium and ventricle are separated by valves. In the entrance of the left ventricle has bicuspid valve which controls the blood flows from the left atrium to the left ventricle during diastole (Lane, 2010a). While in the entrance of the right ventricle has tricuspid valve which allows blood flow from the right atrium to the right ventricle. The function of valves is to make the blood only moving from atrium to ventricle and avoid regurgitation. (Lane, 2010a).
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There are some blood vessels have a significant influence on transferring the blood (Lane, 2010a). Coronary artery which lies in the groove on the front of heart carries flesh blood to the heart muscle to receive oxygen and nutrients (Lane, 2010a). Pulmonary artery which lies out of the right ventricle supplies blood with oxygen to the lungs (Lane, 2010a). Aorta which is the major vessel located near the right atria provides blood to the upper body (Lane, 2010a). Pulmonary veins carry oxygenated blood from the lungs to the left atrium (Lane, 2010a). Inferior and Superior Vena Cava which are located on left of the heart and link to the right atrium, supplies deoxygenated blood to the right receiving chamber (Lane, 2010a).
Blood flows through the pig heart are similar with a human’s. Deoxygenated blood moving from the superior and inferior vena cava (see Figure 1) into the right atrium which has a very low pressure (Gisbornesc, 2010). During diastole which indicates the relaxation phase, the right ventricle’s pressure drops down almost zero. There is a pressure gradient between the right atrium and ventricle, leading to the blood flow into the right ventricle (Gisbornesc, 2010). When the ventricle fills, the blood goes through the tricuspid valve. During systole (the contracting phase) the ventricle begins to contract, the intraventricular pressure is increased which causes the tricuspid valve to close while the pulmonary valve open (Gisbornesc, 2010). And then blood moves out of the ventricle via the pulmonary artery to the lungs (Gisbornesc, 2010). When the ventricle relaxes, intraventricular pressure drops below the pressure in the pulmonary artery, as a result, the pulmonary valve close. In this case, blood returns to the right side of the heart and is pumped back to the lungs for gas exchange (Gisbornesc, 2010).
Figure 1(Biologymad, 2010) shows the blood flow within the heart.
Figure 1 (Biologymad, 2010): The Blood Flow within Heart
The function of a heart is to promote blood flowing to organs and tissues, providing enough blood, oxygen and various nutrients while taking away the metabolic products such as carbon dioxide, urea and uric acid. This process maintains the normal function and metabolism of the cells within the body.
Method & Observations
Material
Fresh pig heart
Scalpels
Container for heart
Scissors
Forceps
Cutting board
Equipment
Several blank A4 sheets
Pens
HB pencils
Erasers
Rulers
Sharpeners
Procedure-External Anatomy
A heart was placed in a dissecting pan.
The size of this heart was moderate; the colour of this heart was pink and it was a little smelly.
The heart was examined and the thin membrane or pericardium that still covers the heart was located. The pericardium was removed carefully.
The pericardium was too thin to remove.
The tip of the heart or the apex was located.
The left ventricle extended all the way to the apex.
The heart was placed in the dissecting pan. The major blood vessels were on the top and the apex was down.
There was a groove that extended from the right side of the board end of the heart.
The heart was in the pan in the position and faced my body. The left atrium, left ventricle, right atrium and right ventricle were located from this surface.
Four chambers were observed unclearly, but still could be identified.
While the heart was still in this position in the dissecting pan, the coronary artery, pulmonary artery, aorta, pulmonary veins and inferior & superior vena cava were located at the broad end of the heart.
Aorta, pulmonary artery and pulmonary veins inferior & superior vena cava were observed clearly, but coronary artery was not found.
A fully labelled diagram of the front heart was drawn.
Figure 2 is attached.
8. A fully labelled diagram showing the back side of heart was drew.
Figure 3 is attached.
Procedure- Internal Anatomy
The side of the pulmonary artery was cut through and continue cutting down into the wall of the right ventricle using the scissors. Cut deep enough to go through the wall of the heart chamber. (The cutting line was above & parallel to the groove of the coronary artery)
The heart was pushed open at the cut to examine the internal structure with fingers. There was a dried blood inside the chambers, the heart was rinsed out.
The right atrium was located. The thinner muscular wall of this receiving chamber was measured by ruler.
The right atrium was about 5-10 mm and very smooth.
A fully labelled diagram showing the internal of right atrium was draw.
Figure 4 is attached.
The inferior & superior vena cava enter this chamber were founded. The lack of valves was noticed.
The inferior & superior vena cava was easy to found.
The valve between the right atrium and right ventricle was located, which is called tricuspid valve.
This valve consisted of three leaflets and had long fibbers of connective tissue.
The thickness of the right ventricle and its smooth was felt by fingers. The network of irregular muscular cords was noticed on the inner wall of this chamber.
The right ventricle was about 20mm and very smooth.
The septum was found on the right side of the right ventricle.
The septum was thick which separated the right and left ventricles from each other.
The pulmonary artery was located inside the right ventricle. The one-way valve called the pulmonary valve was found.
A fully labelled diagram showing the back side of heart was drew.
Figure 3 is attached.
The heart was continued to cut open using scissors. A cut was started on the outside of the left atrium downward into the left ventricle cutting toward the apex to the septum at the centre groove. The heart was pushed open at this cut with fingers & any dried blood was rinsed out with water.
The heart was difficult to cut downward into the left ventricle because the knife was not sharp.
The left atrium was examined. The openings of the pulmonary veins were found from the lungs.
The pulmonary veins were hard to observe.
Bicuspid valve was looked for inside left atrium.
This valve consisted of two leaflets.
The left ventricle was examined. The thickness of the ventricular wall was noticed.
The left ventricle was found and the thickness of the ventricular was about 20mm.
The left ventricle was cut across the left ventricle toward the aorta & continues cutting to expose the valve using scissors.
The three flaps or leaflets were counted on this valve called aortic valve.
This valve had half-moon shape.
Notes to all the diagrams were added relating the labelled structures to their functions.
Results
Figure 2 shows the front view of heart.
In this figure, the aorta is clearly visible at the top, with left and right atrium on either side, while the ventricles are in the bottom. This figure also shows the aortic and pulmonary arteries as well as the pulmonary veins and superior vena cava.
2. Figure 3 shows the back side of heart.
In this figure, the superior vena cava and aorta can be seen.
3. Figure 4 shows the internal view of the right side.
In this figure, the tricuspid valve can be seen and the right ventricular outflow tract which includes the pulmonary artery.
4. Figure 5 shows the internal view of the left side
In this figure, the bicuspid valve and aorta can be seen.
Discussion
Possible errors may have arisen during this experiment. Firstly, the heart was cut difficultly, because the equipment given was not sharp enough. Secondly, some blood vessels can not be found such as coronary artery, because the pig’s heart was not fresh enough, may be damaged by the butcher. Thirdly, human errors may lead to the results not precise. For instance, when cut deeply to go through the wall of the heart chamber, the cutting line was not parallel to the groove of the coronary, as a result, the chamber can not observed carefully.
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A future experiment should be improved in following ways. Firstly, the equipments should be given sharp enough in order to cut the heart efficiently according to the instruction. Secondly, the pig heart should be provided fresh enough and completely. In this case, all the organs can be observed and described. Finally, when cutting line is required parallel, it is better to use the ruler to measure.
Conclusion
In conclusion, after doing the experiment, the external and internal structure was examined. A pig’s heart is four chambered pump which includes left atrium, left ventricle, right atrium and right ventricle. Valves, which separate atrium and ventricle, prevent blood from flowing backwards. A pig has double system which can make blood circulate the whole body via the vessels.
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