huid

Huid, commonly referred to as skin, is the largest organ of the human body and a primary component of the integumentary system. It forms a barrier between the body and the environment, helps regulate temperature, enables the sense of touch, and participates in immune defense and metabolism, including vitamin D synthesis in response to sunlight.

Structure: The huid has three main layers: the epidermis, the dermis, and the hypodermis (subcutaneous tissue). The epidermis is mainly keratinocytes and contains melanocytes, Langerhans cells, and Merkel cells. The dermis houses connective tissue, blood vessels, nerves, hair follicles, and glands (sweat and sebaceous). The hypodermis consists largely of fat and connective tissue that insulates and cushions the body.

Functions: It acts as a waterproof barrier, reduces water loss, and defends against pathogens. Sensation is provided by cutaneous nerves and receptors for touch, pressure, temperature, and pain. It regulates body temperature through sweating and vasomotor changes, and it participates in immune responses and vitamin D production.

Turnover and repair: Epidermal cells renew roughly every 2–4 weeks. Wound healing proceeds through stages of hemostasis, inflammation, proliferation, and remodeling, with scar formation possible depending on injury and factors.

Variation and health: Melanin provides coloration and some UV protection. Aging leads to thinner, drier skin with reduced elasticity. Common conditions include dermatitis, acne, psoriasis, and skin cancers (basal cell, squamous cell, melanoma).

Care: Protection from UV exposure is essential, alongside hydration, moisturizers, and proper hygiene. Regular skin examinations help detect early signs of disease.