Characteristics of capillaries

Here are the key characteristics of capillaries:

• Small Diameter: Capillaries are extremely narrow, often just wide enough for a single red blood cell to pass through in single file. This close proximity to cells facilitates efficient exchange.
• Thin Walls: Their walls are composed of a single layer of endothelial cells, making them very thin. This thinness minimizes the diffusion distance for gases, nutrients, and waste products.
• Permeable Walls: The walls are selectively permeable, allowing for the easy passage of water, dissolved gases (like oxygen and carbon dioxide), nutrients, and waste products between the blood and the surrounding tissues.
• Extensive Network: Capillaries form vast, intricate networks called capillary beds, ensuring that almost every cell in the body is close to a blood supply for efficient exchange.
• Slow Blood Flow: Blood flow through capillaries is very slow, which provides sufficient time for the exchange of substances to occur effectively.