Capillary walls in aging individuals tend to do which of the following?

• A. Speed up exchange
• B. Slow the exchange process
• C. No effect
• D. Decrease capillary density

Answer: (B)

As people age, capillary walls often thicken and the overall capillary network can shrink (less capillary density). Diffusion and exchange between blood and tissues depend on how easily substances can cross a thin barrier and how much surface area is available. A thicker capillary wall increases the distance substances must travel, and fewer capillaries reduce the surface area for exchange. Both changes slow the rate at which oxygen, nutrients, and waste products move between blood and tissues. So capillary exchange tends to slow in aging individuals. This can contribute to slower tissue perfusion and healing under stress.