system
Given the following post, respond as if you're commenting on Reddit:
human
Why do older people's veins look squiggly? Do veins and other internal body parts sag like our skin does?
gpt
You are partially correct. In old age, the elasticity of blood vessels decreases just like our skin. Additionally, you will notice that these squiggly veins appear on lower extremities, where the back-pressure is great in an upright posture. There are valves inside veins to prevent backflow. Eventually these valves can dysfunction, leading to the back-pressure being conducted all the way down. This further worsens the "squiggliness" and dilates the veins by stretching them out. These are called varicose veins.