The circulatory system
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Describe the key structural feature that differentiates arteries from veins in transverse section.
Arteries have a thicker tunica media (middle layer) containing more smooth muscle and elastic fibers compared to veins. This allows arteries to withstand higher blood pressure.
Outline the pathway of blood in the pulmonary circulation.
Deoxygenated blood is carried from the right ventricle to the lungs via the pulmonary artery. In the lungs, blood becomes oxygenated and returns to the left atrium via the pulmonary vein.
What are the primary functions of tissue fluid?
Tissue fluid provides nutrients and oxygen to cells and removes waste products like carbon dioxide and urea. It acts as an intermediary between blood capillaries and cells.
Explain how the high specific heat capacity of water is beneficial in mammalian blood.
Water's high specific heat capacity means it can absorb or release a large amount of heat without significantly changing temperature. This helps maintain a stable body temperature in mammals and prevents drastic temperature fluctuations in blood.
Describe the structure of a capillary and how it relates to its function.
Capillaries have a single-celled layer of endothelium, creating a short diffusion pathway. This thin wall allows for efficient exchange of substances like oxygen, carbon dioxide, and nutrients between the blood and tissue fluid.
Identify two differences between elastic and muscular arteries, relating the structural differences to their specific functions.
Elastic arteries have a higher proportion of elastin in their tunica media, allowing them to stretch and recoil to maintain blood pressure. Muscular arteries have more smooth muscle, allowing them to control blood flow to different organs through vasoconstriction and vasodilation.
Describe the formation of tissue fluid from blood plasma in a capillary network.
Blood pressure at the arteriole end of capillaries forces fluid out through gaps in the capillary walls, forming tissue fluid. Most of the fluid returns to the capillary at the venule end due to oncotic pressure created by plasma proteins, while the rest drains into the lymphatic system.
State two key differences between monocytes and lymphocytes when observed under a microscope.
Monocytes are typically larger than lymphocytes and have a kidney-shaped nucleus. Lymphocytes have a large, round nucleus that occupies most of the cell, leaving only a small amount of cytoplasm visible.
Explain how the structure of veins facilitates the return of blood to the heart, particularly against gravity in the limbs.
Veins have thinner walls and wider lumens compared to arteries, reducing resistance to blood flow. They also contain valves that prevent backflow of blood, ensuring it moves towards the heart even against gravity.
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