Layers of dermis

Dermis is one of the three layers of skin. It is composed of dense irregular connective tissue containing collagen and elastic fibers. Dermis ensures great tensile strength (resist pulling or stretching forces). It can also stretch and recoil easily. Its importance, however, lies within the structures that are embedded in the dermal layer - blood vessels, nerves, glands, and hair follicles.

The dermis can be divided into a thin superficial papillary region and thick, deeper reticular region.

The image is a cube representing a cross-section of the dermis. Two major regions can be differentiated. The top part is called the papillary layer and the bottom part is the reticular layer. Some blood and lymph capillaries are present in both layers, together with some nerve terminations. Different glands, elastic fibers, and collagen are present in the reticular region.

Figure 1. Layers of dermis showing two major regions.

The papillary region is a superficial portion of the dermis. It consists of areolar connective tissue with thin collagen and fine elastic fibers. This region contains dermal ridges that house blood capillaries, corpuscles of touch, and free nerve endings

Surface of the papillary region is greatly increased by dermal papillae - small, nipple-shaped structures that project into the undersurface of the epidermis. They contain capillary loops (blood vessels). Some also contain tactile receptors - nerve endings sensitive to touch. Other papillae also contain free nerve endings that initiate signals that correspond to the sensation of warmth, coolness, pain, tickling, and itching.

The reticular region is a deeper portion of the dermis. It consists of dense irregular connective tissue with bundles of thick collages and some coarse elastic fibers. Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands. The reticular region of the dermis is attached to the subcutaneous layer of the skin.

The collagen fibers in the reticular region are arranged in a netlike manner and have more arrangement than those in the papillary region. The collagen and elastic fibers in this region provide skin with strength, extensibility, ability to stretch, and elasticity, the ability to return to its original shape after stretching. The reticular region of the dermis is attached to the subcutaneous layer of the skin.