The 'dermis' is a layer of
skin beneath the
epidermis that consists of
connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a
basement membrane. It also harbors many nerve endings that provide the sense of touch and heat. It contains the
hair follicles,
sweat glands,
sebaceous glands,
apocrine glands and
blood vessels. The blood vessels in the dermis provide nourishment and waste removal to its own cells as well as the Stratum basale of the epidermis.
Structure
The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the ''papillary region'', and a deep thicker area known as the ''reticular region''.
Papillary region
The papillary region is composed of loose
areolar connective tissue. It is named for its fingerlike projections called ''papillae'', that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin.
In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These are called ''friction ridges'', because they help the hand or foot to grasp by increasing
friction. Friction ridges occur in patterns (see
fingerprint) that are genetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of
identification.
Reticular region
The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of
collagenous,
elastic, and
reticular fibers that weave throughout it. These
protein fibers give the dermis its properties of strength, extensibility, and elasticity.
Located within the reticular region are also the
hair roots,
sebaceous glands,
sweat glands, receptors,
nails, and
blood vessels.
Tattoo ink is injected into the dermis.
Stretch marks are also located in the dermis.
Additional images
External links
★
Diagrams at cdc.gov
★
Diagram at cdc.gov
★ - "Integument: three layers, reticular dermis, papillary dermis "
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