Circulatory System In Vertebrates

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All organisms, vertebrates and invertebrates, must have necessary nutrients to maintain life. In invertebrates, either a transport system or diffusion provides nutrients to the body. For vertebrates, a closed transport is used to transport blood away from the heart. Both of these scenarios are key to an organism 's health. Some invertebrates do not require a circulatory system. While these organisms do not require a circulatory system, they require certain nutrients to be readily available. Because of this, another mechanism takes place, whether it is the movements of coelomic fluid or the exchange of gases and wastes by each cell being exposed to water. In the case of flatworms, a thin body wall replaces the circulatory system. Diffusion …show more content…
The three kinds of blood vessels are arteries which carry blood from the heart, capillaries which contain the exchange of tissue fluid, and veins which carry blood back to the heart. Arteries have thick walls and are able to expand to adapt to heart contractions. Capillaries are narrow passageways that contain gas, waste, and nutrient exchange. Veins are thinner than arteries and have a lower pressure than the arteries. Three different kinds of circulatory pathways are present in vertebrates. Fish have a one-circuit system where the heart pumps blood to the gills, the blood returns to the dorsal aorta, and the blood is transported to the rest of the body. A two-circuit system is used for breathing air on land. The systemic circuit transports blood to tissues, and the pulmonary circuit pumps blood to the lungs. Amphibians and most reptiles the heart contains two atria and one ventricle. This feature allows for proper blood pressure for both circuits. The human cardiovascular system relies on the …show more content…
The pulmonary circuit transports blood from the right ventricle to the pulmonary trunk to the lungs to the left atrium. This oxygenates the blood. The systemic circuit transports blood from the left ventricle through the aorta to the body’s tissues. Coronary arteries are used by the heart to collect oxygen-poor blood from the capillaries and deposit it into the right atrium. Toxins and bacteria are removed from the blood by the liver. The path of blood goes through the artery to the arterioles into branching capillaries or venules which form into veins. From here, the vein enter the vena cava. Blood pressure is the force pushing against an artery wall. Blood pressure rises and falls as blood travels through the body. When blood goes from the aorta to the arteries, blood pressure falls. In the capillaries, a slow, even blood flow takes place. Blood pressure in veins is very low, so the blood cannot travel back to the heart without another mechanism. Blood flows through veins because of muscle contraction on the outside of veins by skeletal muscles. A variety of diseases can affect the cardiovascular system; some of which affect blood

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