This paper compares the circulatory systems of humans and oysters, two organisms that represent the closed and open circulatory system types, respectively. It traces the path of blood through the human heart, pulmonary circuit, coronary arteries, and systemic circulation before examining the oyster's three-chambered heart, open lacunae, gill-based gas exchange, and filter-feeding digestive process. The paper also contrasts fish and mammalian heart structure and discusses shared circulatory functions such as nutrient transport, waste removal, and immune response. Despite fundamental differences in mechanism, both systems accomplish the same essential biological outcomes.
There are two main types of circulatory systems: open and closed. Some members of Phylum Mollusca have a closed circulatory system, like humans, but not all do. Molluscs live in fresh water and under the sea; this group includes oysters, octopuses, and squid. Like fish, Phylum Mollusca do not breathe air as humans do, but rather rely on a gill-type system. Humans oxygenate their blood by breathing in oxygen and passing it through the body. Molluscs oxygenate the blood through gills by direct contact with water. Molluscs also have soft bodies.
The human circulatory system is made up of the heart and pulmonary system, the coronary system, and the systemic circulation. The heart, located near the center of the chest cavity, works within the circulatory system when deoxygenated blood from the body enters the right atrium. That blood then flows through the tricuspid valve into the right ventricle. Blood flows into the pulmonary artery, which branches into both lungs. There, the blood releases carbon dioxide and takes on a fresh supply of oxygen. The capillary beds of the lungs are then drained, and four pulmonary veins carry oxygenated blood to the left atrium (Inlander, 1995).
From the left atrium, blood flows through the mitral valve into the left ventricle. Contractions cause the mitral valve to close and the aortic valve to open. Two openings lead to the right and left coronary arteries, supplying blood to the heart itself. The capillaries drain into two coronary veins, which empty into the right atrium.
At the point of maximum blood pressure in the circulatory system, the coronary arteries come into play (Weight, 2006). As the body ages, the arterial walls may lose elasticity, which can limit the amount of blood that flows through them and, consequently, the supply of oxygen to the heart. If this occurs, the condition is called arteriosclerosis. If fatty deposits accumulate on the interior surface of the coronary artery — a substance known as plaque — they can reduce the bore of the coronary arteries and limit the amount of blood they can carry. This is common in individuals with high cholesterol levels.
The final part of the human circulatory system is called the systemic circulation. In this stage, blood passes from the aorta into a branching system that leads to all parts of the body and flows into a network of capillaries. From there, blood flows into venules, which drain into the veins. Veins draining the upper portion of the body lead to the superior vena cava, while those from the lower part of the body lead to the inferior vena cava. Both empty into the right atrium.
"Open lacunae, digestive system, blood cavities"
"Filter feeding, mantle exchange, waste removal"
"Chamber counts and blood pressure comparisons"
Though there are many similarities between the human and oyster circulatory systems, there is also a vast degree of difference. The ultimate outcome of the process may be the same; however, the process itself is extremely different, and it is precisely that difference which allows oysters to live and thrive in aquatic environments while humans survive only on land.
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