Final answer:
Merkel cells are the unencapsulated mechanoreceptors in the skin, which respond to light touch and are abundant on the fingertips and lips.
Step-by-step explanation:
The unencapsulated mechanoreceptors in the skin are Merkel cells. These cells respond to light touch and are abundant on the fingertips and lips. Meissner's corpuscles, Pacinian corpuscles, and Ruffini endings are all encapsulated mechanoreceptors.