Dermis - Structure, Function and Diseases
The dermis is the middle layer of the skin, located between the epidermis and the subcutis. It provides structural support and contains blood vessels, nerves, and skin appendages.
Things worth knowing about "Dermis"
The dermis is the middle layer of the skin, located between the epidermis and the subcutis. It provides structural support and contains blood vessels, nerves, and skin appendages.
What is the Dermis?
The dermis (also called the corium or true skin) is the middle of the three main layers of human skin. It lies directly beneath the epidermis (outer skin) and above the subcutis (hypodermis). The dermis accounts for the majority of the skin thickness and provides the skin with its mechanical strength, elasticity, and resilience.
Structure and Composition
The dermis is composed primarily of connective tissue, rich in collagen fibers and elastic fibers. These fibers are embedded in a gel-like extracellular matrix consisting mainly of hyaluronic acid and proteoglycans. The dermis is divided into two layers:
- Stratum papillare (Papillary layer): The upper, thinner layer with finger-like projections (papillae) that extend into the epidermis. It contains fine collagen fibers, capillaries, and nerve endings.
- Stratum reticulare (Reticular layer): The lower, thicker layer with coarser collagen and elastin fibers. It forms the main structural framework of the dermis and provides tensile strength and elasticity.
Contents and Components
The dermis contains numerous important structures:
- Blood vessels: Supply the skin with nutrients and oxygen and help regulate body temperature.
- Lymphatic vessels: Drain excess tissue fluid and support immune function.
- Nerves and sensory receptors: Enable the perception of touch, pain, pressure, and temperature.
- Hair follicles: The roots of hairs are anchored deep within the dermis.
- Sebaceous and sweat glands: Produce sebum and sweat, protecting the skin and assisting in temperature regulation.
- Fibroblasts: Specialized cells that produce collagen, elastin, and the extracellular matrix, and are essential for wound healing.
Functions of the Dermis
The dermis performs many vital functions:
- Mechanical protection: Collagen and elastin protect deeper structures from pressure and injury.
- Temperature regulation: Through dilation or constriction of blood vessels and sweat production, the dermis helps regulate body temperature.
- Sensory perception: Nerve fibers and specialized receptors transmit stimuli such as touch, pain, or heat to the brain.
- Wound healing: Fibroblasts and blood vessels play a central role in repairing skin damage.
- Immune defense: Through immune cells and lymphatic vessels, the dermis participates in defending against pathogens.
Diseases of the Dermis
Various conditions can affect the dermis:
- Dermatitis (skin inflammation): An inflammatory reaction of the dermis and epidermis, for example in contact allergy or atopic eczema.
- Scleroderma: A condition characterized by excessive collagen deposition in the dermis, leading to hardening and thickening of the skin.
- Psoriasis: Primarily affects the epidermis but involves inflammatory processes in the dermis.
- Skin aging: With age, collagen and elastin production decreases, resulting in wrinkle formation and loss of skin elasticity.
- Wounds and scar formation: After injury to the dermis, fibroblasts repair the tissue, which may result in scar tissue.
Clinical Relevance
The dermis is of central importance in dermatology, plastic surgery, and wound medicine. Many diagnostic procedures, such as the skin biopsy, obtain tissue samples from the dermis to identify diseases. Cosmetic treatments such as hyaluronic acid injections or laser therapies also target the dermis to promote regeneration and slow the signs of skin aging.
References
- Bolognia, J. L., Schaffer, J. V. & Cerroni, L. - Dermatology. Elsevier, 4th Edition (2018).
- Ross, M. H. & Pawlina, W. - Histology: A Text and Atlas. Wolters Kluwer, 8th Edition (2020).
- World Health Organization (WHO) - Skin Health and Dermatological Conditions. Available at: https://www.who.int (accessed 2024).
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