húðinni

The skin, referred to in Icelandic as húð, is the body’s largest organ, forming a protective boundary between internal tissues and the external environment. It helps regulate temperature and water balance, and serves as a sense organ and immune barrier.

It consists of three main layers: the epidermis (outer), the dermis (middle), and the hypodermis or subcutaneous tissue (inner). The epidermis contains keratinocytes, melanocytes, and Langerhans cells; the dermis houses connective tissue, blood vessels, nerves, hair follicles, and glands; the hypodermis consists mainly of fat and connective tissue. The epidermis’s outermost layer is the stratum corneum.

Functions include a protective barrier against pathogens and chemicals, and prevention of water loss. Thermoregulation occurs via sweating and regulation of blood flow. Sensation is provided by cutaneous nerves. The skin participates in metabolic activities such as vitamin D synthesis, and immune defense through Langerhans cells and antimicrobial peptides. It harbors a diverse microbiome.

Variation and health considerations: Skin color is largely determined by melanin distribution. Aging leads to thinning, reduced elasticity, and slower cell turnover; sun exposure contributes to photoaging and increases skin cancer risk. Common conditions include dermatitis, psoriasis, acne, fungal infections, and skin cancers. Care includes sun protection, moisturization, and appropriate medical treatment for disorders.