Yezi Cho
A pig heart was dissected to observe the structure of a heart, learning its function and anatomy.
The posterior view of the heart
The anterior view of the heart
The right ventricle and the left ventricle can be distinguished by the middle cardiac vein and posterior interventricular sulcus. The left atrium and right atrium are located above the left ventricle and right ventricle, respectively.
The heart consists of four chambers:
Right atrium
Left atrium
Right ventricle
Left ventricle
The atria collect blood into the heart, while the ventricles expel blood from the heart.
Deoxygenated blood from the body is collected in the right atrium.
The tricuspid valve opens, allowing blood to move into the right ventricle.
Contraction pushes blood into the left and right pulmonary arteries through the semilunar valve.
Carbon dioxide-rich blood passes through the capillaries of lungs, gaining oxygen and releasing carbon dioxide.
Oxygenated blood flow into the left atrium through the pulmonary vein.
The bicuspid valve opens, allowing blood to move into the left ventricle.
Contraction pushes blood into aorta through the semilunar valve.
Coronary arteries branching from aorta supply blood to muscles. Arterioles and capillaries carry oxygen-rich blood to organs, gaining carbon dioxide and releasing oxygen.
Deoxygenated blood in capillaries converge into venules/veins, flowing into the right atrium through the inferior/superior vena cava.
Figure 1. The circulatory system (Olympiad Genius, 2020)
The heart wall is composed of three layers:
Endocardium: inner layer
Myocardium: middle layer
Epicardium: outer layer
Cutting open the left atrium and ventricle reveal the thick myocardium walls.
The left ventricle especially has thick walls, having to pump oxygen-rich blood to the whole body.
The chordae tendinae, are strings of connective tissue attached to atrioventricular (AV) valves, pull ingon the valves to open or close them.
There are four major valves in the heart that direct the blood flow in one direction. Two are atrioventricular (AV) valves which are between atria and ventricles; two are semilunar (SL) valves which open when blood flows out of ventricles.
The right AV valve known as the tricuspid valve and the left AV valve known as the biscupid (mitral) valve ensure that the blood flows from the atrium to the ventricle. When the ventricles contract (systole), the valves close. Indicated by their names, the tricuspid valve has three cusps, whle the biscupid valve has two cusps.
The pulmonary (semilunar) valve and aortic (semilunar) valve prevent blood from re-entering the heart when the ventricles relax (diastole). The pulmonary valve, situated at the pulmonary trunk, prevents carbon dioxide-rich blood from returning to the right ventricle. The aortic valve, situated at the base of the aorta, prevents oxygen-rich blood from returning to the left ventricle.
Figure 2. Heart valves (DrCiuffo, 2023)
During the dissection, the adipose tissue and coagulated blood were removed from the surface and inside of the heart.
Another cut was made through the right atrium and ventricle.
It is notable that the myocardium of the left ventricle is thicker than the that of the right ventricle.
Figure 3. The pathway of blood flow through the heart (Physiopedia, 2021)
A cut was made through the right auricle.
The auricles are upper chambers of the atria, known to function as reservoirs for blood, increasing the storage capacity of the atria.
The superior vena cava and aorta are easily identifiable.
The aorta is located behind the pulmonary trunk, connected to the left ventricle. The aorta has three vessels branching from the aorta: the brachiocephalic artery, the left common carotid artery, and the left subclavian artery.
Figure 4. Anatomy of the human heart (Physiopedia, 2021)
The cut above reveals the various arteries and veins from which blood enters or leaves the heart.
The openings for the superior and inferior vena cavae can be identified as the above. The inferior vena cava and superior vena cava both lead to the right atrium. Blood from the upper body enters the superior upper body while blood from the lower body enters the inferior vena cava into the right atrium, entering the right ventricle through the right atrioventricular valve. Then the blood flows toward the left lung through the left pulmonary artery; toward the right lung through the right pulmonary artery.
The arteries and veins can be located by following each opening into and out of the heart.
Due to the big size of the pig heart, several sections were made instead of one frontal section. A typical frontal section would look like the following:
Figure 5. Heart dissection (Carolina Biological Supply, 2023)
After observing the structures, the specimen was disposed in accordance to disposal guidelines.
References
Shook, S. (2019, April 12). Chapter 5. Heart Dissection. Hawaii.edu; Kapʻiolani Community College. https://pressbooks-dev.oer.hawaii.edu/shook/chapter/chapter-5-heart-dissection/
Clinic, C. (2021). Heart: Anatomy and Function. Cleveland Clinic. https://my.clevelandclinic.org/health/body/21704-heart
Heart Dissection. (2023). Carolina Biological Supply. https://www.carolina.com/teacher-resources/Interactive/mammalian-heart-dissection/tr10828.tr
Comments