What are the tightly bound parts of digits, palms, wrists, and elbows called?

The tightly bound parts of digits, palms, wrists, and elbows are referred to as flexion lines. These lines are formed by the skin being folded and stretched during movements such as bending and flexing. When the joints are moved, the skin around them must accommodate by folding, which creates these distinct lines.

Flexion lines are important as they help to maintain the functionality of the skin in areas that undergo frequent movement. They also contribute to the overall appearance of the skin and can aid in the grip and ease of movement of the fingers. In contrast, friction ridges, which are found on the fingertips and are responsible for our unique fingerprints, serve a different function related to grip and touch sensation. Hair follicles are structures from which hair grows, and Meissner's corpuscles are specialized nerve endings that are sensitive to light touch, and do not describe the binding of skin around joints.