The Dermis

The dermis binds the epidermis to the underlying tissues. It is composed largely of fibrous connective tissue, which includes tough white (collagenous) fibers and yellow (elastin) fibers surrounded by a gellike matrix. Networks of these fibers give the dermis its strength and elasticity. 

Since the fibers run in definite directions over the body surface, they are responsible for producing lines of tension in the skin.

Dermis

“Lines of tension produce different patterns in different regions of the skin, and their presence is of special interest to surgeons. Skin that is cut parallel to the lines tends to gape less than skin cut across the lines. Thus, a sutured parallel incision is likely to heal more rapidly and result in less scar tissue than a transverse incision”.

The structures in the dermis are

• Blood vessels
• Lymph vessels
• Nervous tissue
• Sensory (somatic) nerve endings
• Sweat glands and their ducts
• Hairs, arrector pili muscles and sebaceous glands.

Blood vessels

Blood vessels in the dermis supply nutrients to all skin cells, including those of the epidermis. Interference with the flow of blood is likely to result in the death of cells.

For example, when a person lies in one position for a prolonged time, the weight of the body pressing against the bed interferes with the skin's blood supply. As a consequence, cells may die and decubitus ulcers (bedsores) may appear. 

“Decubitus ulcers usually occur in the skin overlying bony projections, such as on the hip, heel, elbow, or shoulder. These sores can often be prevented by changing the position of the body frequently or by massaging the skin to stimulate blood flow in regions associated with bony prominences. Likewise, a diet rich in proteins and other necessary nutrients and an adequate intake of fluids to maintain blood volume help in preventing this condition”.

Dermal blood vessels also aid in regulating body temperature.

Lymph vessels

These form a network throughout the dermis.

Nerve Tissue

There are numerous nerve fibers scattered throughout the dermis. Some of them (motor fibers) carry impulses to dermal muscles and glands, causing these structures to react. Others (sensory fibers) carry impulses away from specialized sensory receptors located within the dermis. One set of dermal receptors (pacinian corpuscles) is stimulated by heavy pressure, while another set (Meissner's corpuscles) is sensitive to light touch. Still other receptors are stimulated by temperature changes or by factors that can damage tissues.