Long Answers

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Chapter: 06. Human Circulatory System

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Explain the primary functions and main components of the human circulatory system.

The human circulatory system acts as the body’s vital transport system. Its primary functions involve delivering essential substances like food and oxygen to all body cells, while simultaneously collecting and removing waste products from these cells, transporting them to organs like the kidneys for elimination. This complex system effectively connects all cells, tissues, and organs within the body. The three main components that enable this continuous transport are blood, blood vessels, and the heart.

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Describe the various components of blood and their specific roles in the body.

Blood is a red-coloured viscous fluid composed of two main parts: plasma and blood corpuscles. Plasma is the yellowish liquid portion that carries dissolved nutrients, oxygen, hormones, enzymes, and waste products. The blood corpuscles include Red Blood Corpuscles (RBCs), which transport oxygen using haemoglobin; White Blood Corpuscles (WBCs), which fight infections and provide immunity as the “soldiers of the body”; and blood platelets, which are essential for clotting blood at injury sites to stop bleeding. Each component plays a vital role in maintaining overall body health and function.

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Elaborate on the structural and functional differences between arteries, veins, and capillaries.

Arteries are muscular, thick-walled vessels that distribute blood away from the heart, typically carrying oxygenated blood under high pressure, leading to a jerky flow. Veins are thin-walled collecting vessels that bring deoxygenated blood back to the heart, featuring valves to prevent backflow due to lower pressure, resulting in a non-jerky flow. Capillaries are the finest blood vessels, with walls only one cell thick, forming networks that connect arteries and veins. Their thin walls are crucial for the efficient exchange of gases, nutrients, and waste products between blood and body cells.

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Describe the structure of the human heart and briefly explain its working in circulating blood.

The human heart is a four-chambered muscular organ, located in the chest cavity, consisting of two upper receiving chambers called auricles (or atria) and two lower distributing chambers called ventricles. A muscular wall separates the left and right sides to prevent mixing of oxygenated and deoxygenated blood. Four valves (tricuspid, bicuspid, and two semilunar) ensure unidirectional blood flow. Deoxygenated blood enters the right auricle and moves to the right ventricle, which pumps it to the lungs for oxygenation. Oxygenated blood returns to the left auricle, then enters the left ventricle, which powerfully pumps it to the entire body.

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Define the terms heartbeat, cardiac cycle, and explain blood pressure, including its measurement.

Heartbeat refers to the rhythmic contraction and relaxation of the heart’s auricles and ventricles, occurring approximately 72 times per minute in a normal adult. A cardiac cycle is the complete sequence of events, including systole (contraction) and diastole (relaxation), that occurs during one single heartbeat, lasting about 0.8 seconds. Blood pressure is the force exerted by the blood against the walls of the arteries. It is measured using a sphygmomanometer and has two values: systolic pressure (highest during contraction, ~120 mm Hg) and diastolic pressure (lowest during relaxation, ~80 mm Hg).

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Explain the ABO blood group system and the concepts of universal donor and universal recipient.

The ABO blood group system classifies human blood into four main types (A, B, AB, O) based on the presence or absence of specific antigens (A and B) on the surface of red blood cells and corresponding antibodies (anti-A and anti-B) in the plasma. This interaction is crucial for safe blood transfusions, as incompatible mixing leads to clumping. Blood group O is considered the universal donor because its RBCs lack both A and B antigens, preventing adverse reactions in most recipients. Conversely, blood group AB is the universal recipient, as its plasma lacks both anti-A and anti-B antibodies, allowing it to safely receive blood from any ABO type.

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Suggest various lifestyle practices and dietary habits that contribute to maintaining a healthy heart.

Maintaining a healthy heart requires a combination of good lifestyle and dietary habits. Key practices include giving up smoking and alcohol, which are detrimental to cardiovascular health. Diet-wise, it’s important to cut down on sugary and fried foods, prioritize fruits and vegetables for their fiber content, and manage weight through a balanced diet. Regular physical activity, such as brisk walking or a consistent exercise regime, is also vital. Additionally, reducing salt intake helps maintain normal blood pressure, consuming fish rich in omega-3 fatty acids is beneficial, and avoiding high-cholesterol foods and staying hydrated by drinking plenty of water contribute significantly to a strong and healthy heart.

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