The purposes for this experiment is observe and describe the external and internal anatomy of a mammalian (pig) heart, and draw and label the structure by hand.
Introduction
The heart is an important pump organ that all animals possess in some forms. Mammalian heart consisted of four chambers, left atrium, left ventricle, right atrium and right ventricle, however, Lane, R. (2010a) stated that the amphibian only contains one ventricle and two atriums; so that its ability to transport oxygen will be weaker than human beings. Furthermore, there is no connection between the left and right chamber, because of the muscular wall septum that separates them into two halves. Valve can be found between ventricles and atria, they are one-way, and their function is controlling blood flow. Moreover, the function of heart is to move blood around, and provide abundant oxygenated blood supply to each organ and tissue, in order to offers oxygen exchange for carbon dioxide and nutrition, and take away the waste metabolic products, such as, carbon dioxide (CO2).
The coronary artery is a blood vessel that occurs in the groove on the front of the heart, its branches spread across the front and back side of the heart, their function is to provide oxygenated blood and nutrition to the muscle of the heart (Lane, 2010a), the myocardium.
The pulmonary artery is a blood vessel that leads from the right ventricle, and carries blood to the lungs to receive oxygen (Lane, 2010a). Pulmonary veins are used to transport the oxygenated blood back to the left atrium, which is then pumped, via the Aorta around the body (Lane, 2010a).
Lane, R. (2010a) stated that, aorta, is the major vessel located near the right atria and at the back of the pulmonary arteries to the lung. According to Losos, et al (2008), the aorta and it is branches carry blood to every part of the body, carrying oxygenated blood from the left ventricle.
The inferior and superior Vena Cava, are veins located on the left side off the heart, these two functions by connecting to the right atrium, and the deoxygenated blood can get back to the lungs via the right ventricle (Lane, 2010a), and this is called circulatory system, shown in Figure 1 (Lane, 2010b).
Figure 1 The Circulatory System (Lane, 2010b)
The bicuspid valve, is located between the left atrium and the left ventricle, and controls blood to flow one way only, from the left atrium to the left ventricle preventing back flow (Medterms, 2010). However, another valve, which called tricuspid valve, located between the right atrium and the right ventricle, the function of it is to prevent blood backflow from the right ventricle back into the right atrium (The Free Dictionary, 2010).
Method
Materials
Fresh pig heart, dissectiontray, forceps, scalpel, scissors, cutting board
Required
A4 papers, HB pencils, ruler, pens, eraser
Procedure – External Structure & Observations
The heart was placed in a dissecting pan and examined; a thin membrane located at the lower two ventricles of the heart is called pericardium.
The colour of heart was light red, covered by a few of blood and white material (lipid), about 0.25kg weight; and the size was about 13 x 10 x 7cm.
The pericardium could not be removed; it was about 1mm thick.
The apex is the lower tip of heart, and the left ventricle, was extended all the way to the apex.
The apex was red colour and located on the lower side of the heart.
The left ventricle couldn’t see at the surface of the heart.
The heart was placed in the dissecting pan, with the major blood vessels on the top and the apex down. The groove was observed in front of the heart and was extended from the right side of the broad end of the heart diagonally to a point above and to the left of the apex.
The texture of heart was elastic and smooth.
Compared with the surface of the heart, the groove was slightly protruding.
The groove consisted of several red and purple vessels.
The chambers were located and observed:
The left atrium was located on the upper chamber to student’s right.
The left ventricle was on the lower chamber to student’s right side.
The right atrium was located as the upper chamber to the student’s left.
The right ventricle was the lower chamber to the student’s left side.
The blood vessels were observed at the broad end of the heart.
The blood vessels were about 3cm wide.
The external structure of heart was drawn.
The structure of external was shown in figure 2 (Cao, 2010).
Procedure – Internal Anatomy & Observations
The side of the pulmonary artery was cut using scissors, an incision was continued down into the right ventricle. The cutting line was enough to go through the wall of the heart chamber, and was above and parallel to the groove.
The pulmonary artery was smooth and thin, it was easy to cut.
Compared with the pulmonary artery, the muscular wall was thicker and difficult to cut.
The heart was opened at the cut with fingers, and the internal structure was examined.
The internal of the heart was light red color and fattiness, containing fibers and muscular walls inside.
There were several pieces of dark red dried blood inside the heart, almost black jelly; these were rinsed by the tap running.
The thinner muscular wall of receiving chamber was located as the right atrium.
The thinner muscular wall was about 1cm, and the texture of it was smooth.
The inferior and superior cava enter this chamber and located, and the valves were noticed.
The superior cava located on the upper right atrium, and the inferior cava located on the lower right atrium. The superior cava is connecting to the right atrium.
The tricuspid valve was located between the right atrium and right ventricle.
It consisted of three leaflets and had long fibers of connective tissue (chordae tendinae) that was attached it to the papillary muscles of the heart (Lane, 2010).
The thickness of the right ventricle and it is smooth lining was felt by fingers. The net work of irregular muscular cords on the inner wall of this chamber was noted.
The thickness of the right ventricle was about 3cm.
The muscular cords occur between the upper muscle and the lower muscle inside the right ventricle.
The septum was found on the right side of the right ventricle, and this muscular wall was separated the left and right pumping ventricles from each other.
The septum was red colour, and about 1.5cm.
The pulmonary artery was located on the inside of the right ventricle. The one-way valve – pulmonary valve was found.
The pulmonary valve located between the right ventricle and the pulmonary artery, and consisted of three leaflets.
The internal structure of heart was drawn.
The heart was then cut on the outside of the left atrium downward to the left ventricle; cutting from the apex to the septum at the center groove, using scissors. The heart was pushed open.
Compared with the right atrium, the thickness of left atrium was thicker and it was about 2.5cm, and the left ventricle was about 1.5cm.
There were several pieces of dried blood inside the heart, and was rinsed by the tap running.
The left atrium was examined, and the opening of the pulmonary veins from the lung was identified, the semi-lunar valves at entrance to these veins were observed.
The semi-lunar valves consisted of two valves, and a half-lunar hole was found between them.
The colour of semi-lunar valves was red, and about 1mm thick.
The valve, located between the left atrium and the left atrium, is called bicuspid.
The two parts of the valve were seen, it was red colour and had smooth surface, and the diameter of it was about 3cm.
The left ventricle was examined. The thickness of the ventricular wall was noticed.
The thickness of the ventricular wall was about 3cm, and had smooth surface.
The left ventricle was cut toward the aorta and the valve was exposed used a scissors.
Three flaps or leaflets on this valve leading from the left ventricle into the aorta were counted, and their half-moon shape was noted, this is called aortic valve, which was red colour, about 1mm thick.
The structure of internal was shown in figure 3 (Cao, 2010).
Results
All labeled diagrams can be seen in the extra paper.
Discussion
At the beginning of this experiment, a fully labeled diagram was downloaded from the Internet (Hbaike, 2009). However, the arteries, such as, the coronary artery and pulmonary artery were easily to seen, so that it was difficult to confirm the front side. Moreover, the number of muscular cords inside was less than the other students. This may be caused by careless dissection of cutting the right ventricle, severing them by accident. Additionally, the heart which used to observe was not fresh enough, so that it may influenced the colour or the states of muscles.
A fully labeled diagram and a detailed translation of the procedure were prepared before the experiment, so that a clear understanding and the processes and the heart’s structure, was achieved.
Conclusion
In conclusion, this dissection illustrated the external and the internal structures of a pig heart, the functions of every important part were mentioned in the introduction, and the labeled diagrams are shown in the results.