Dermal

Dermal refers to the dermis, the thick layer of connective tissue beneath the epidermis in the skin of vertebrates. In medical usage, the term describes structures or processes relating to this inner, supportive layer of the skin.

The dermis consists of two sublayers: the superficial papillary dermis and the deeper reticular dermis. The papillary layer is composed of loose connective tissue with a rich capillary network and sensory nerve endings. The reticular layer contains dense irregular connective tissue rich in collagen and elastin fibers, and it houses hair follicles, sweat glands, sebaceous glands, larger blood vessels, and nerve fibers.

Functions include providing mechanical support and elasticity to the skin, supplying nutrients to the epidermis through its vascular network, and housing sensory receptors for touch, temperature, and pain. The dermis also plays a key role in wound healing and immune defense, containing various immune cells such as mast cells and macrophages. It serves as a site for adnexal structures and participates in inflammatory responses.

Clinical and cosmetic relevance is broad. Transdermal drug delivery targets compounds through the dermis for systemic absorption. Dermal fillers are injectable materials placed in the dermal layer to restore facial volume and smooth lines. Dermal aging involves gradual loss of collagen and elastin, leading to wrinkles and sagging. In severe injuries, damage to the dermis may require skin grafts or dermal substitutes.

The term dermal is distinct from epidermal, which refers to the outer skin layer, and from subcutaneous tissue, which lies beneath the dermis.