The dermis is the part of the skin that lies between the upper layer, the epidermis, and the supportive tissue beneath the skin known as the hypodermis. The dermis mainly consists of connective tissue, various nerve endings, blood vessels and sweat and oil glands. Connective tissue is made up chiefly of protein fibres called collagen. Together with collagen, supportive tissue such as elastin and the extracellular matrix gives the skin its strength and resilience. As we age, collagen and elastic tissue lose strength, leading to loss of elasticity and the development of lines. The main cells that synthesise these structures are fibroblasts. Anti-ageing treatments aim to increase the production of new connective tissue from these fibroblasts.
The nerve endings in the dermis carry sensations such as pain and pleasure. Sweat and oil glands help maintain heat and moisture balance. Sebum (oil) forms a barrier on the skin's surface, protecting against infections such as bacteria and fungi. The dermis also contains blood and lymphatic vessels, mechanoreceptors that carry sensations such as touch, heat and vibration, hair follicles, and macrophages and mast cells that play a role in the body's defences.