huden

Huden, in Swedish, means the skin; in English the organ is referred to as the skin or the integumentary system. The skin is the body's largest organ, serving as a protective barrier and covering the external surface of the body. In adults, it typically covers about 1.6 to 2 square meters of area and accounts for roughly 7 to 15 percent of body weight.

Structure: The skin consists of three main layers. The epidermis is the outer layer, made mainly of keratinocytes, with the stratum corneum forming a tough outer surface and melanocytes providing pigment. The dermis lies beneath, containing connective tissue, collagen and elastin, blood vessels, nerves, hair follicles, and glands. The hypodermis, or subcutaneous tissue, consists largely of adipose tissue that helps insulate and cushion.

Functions: The skin acts as a barrier against pathogens and chemical exposures, prevents water loss, and participates in thermoregulation through sweat and blood flow. It contains sensory receptors for touch, temperature, and pain, and participates in immune defense. The epidermis is involved in vitamin D synthesis under sunlight.

Appendages and microbiome: Hair, nails, sweat glands, and sebaceous glands are associated with the skin. The surface hosts a diverse microbiome that contributes to health.

Health and care: Protection from ultraviolet radiation is important; sun exposure increases skin cancer risk. Moisturizers help maintain barrier function and skin conditions vary with age and ethnicity.

Common conditions include dermatitis, eczema, psoriasis, acne, fungal infections, and skin cancers such as basal cell carcinoma, squamous cell carcinoma, and melanoma. Wound healing proceeds through hemostasis, inflammation, proliferation, and remodeling.