Dermis

Unlike the epidermis, the dermis or lower layer of the skin is richly supplied with blood vessels and sensory nerve endings. The dermis also contains relatively few cells compared to the epidermis—instead, it is made up mainly of fibrous proteins and other large molecules.

The main structural component of the dermis is a protein called collagen. Bundles of collagen molecules pack together throughout the dermis, accounting for three-fourths of the dry weight of skin. Collagen is also responsible for the skin’s strength. Another protein in the dermis, elastin, is the main component of elastic fibers. These protein bundles give skin its elasticity—the ability to return to its original shape after stretching. Collagen and elastin are produced by cells called fibroblasts, which are found scattered throughout the dermis.

The upper part of the dermis is known as the papillary layer. It is characterized by dermal papillae, tiny, fingerlike projections of tissue that indent into the epidermis above. In the thick skin on the palms and soles, the epidermis conforms to the shape of the underlying dermal papillae, forming ridges and valleys that we know as fingerprints. These ridges provide traction that helps people grasp objects and surfaces.