What Is the Dermis?
The dermis is the middle layer of skin, located beneath the epidermis and above the subcutaneous fat layer (hypodermis). It is the thickest skin layer — approximately 1–4mm depending on body location — and is primarily composed of connective tissue: collagen fibres (75–80%), elastin fibres, and ground substance (proteoglycans and glycosaminoglycans including hyaluronic acid). The dermis gives skin its strength, elasticity, and resilience.
Structure and Components
The dermis contains two sublayers. The papillary dermis is the upper portion, thin, and filled with small capillaries that nourish the avascular epidermis. The reticular dermis is the deeper, denser layer containing thick collagen bundles, elastin networks, hair follicles, sweat glands, sebaceous glands, and nerve endings. Fibroblasts — the primary cell type — produce and maintain the extracellular matrix.
Role in Skin Ageing
The visible signs of skin ageing (wrinkles, sagging, thinning) are primarily a dermis story. Collagen synthesis slows approximately 1% per year from the late twenties. Elastin fibres fragment and lose elasticity. UV radiation causes direct collagen degradation via MMP activation. The papillary dermis flattens, reducing the dermal-epidermal junction complexity and compromising nutrient exchange.
Ageing note: Approximately 20% of dermal collagen is lost in the first five years after menopause, correlating with the rapid skin thinning and wrinkling seen in this period.
See Skin Layers and Collagen.