ihokerrosten

ihokerrosten is the Finnish term for the layers of the skin. In humans, the skin consists of three main structural strata: the epidermis, the dermis, and the hypodermis (subcutaneous tissue). Each layer has distinct cells, extracellular material, and functions that together protect the body, regulate temperature, and sense the environment.

The epidermis is the outermost layer and provides a barrier against pathogens and dehydration. It is a stratified epithelium mainly made of keratinocytes. These cells progress from the basal layer to the surface through stages associated with differentiation, forming the sublayers: basale, spinosum, granulosum, lucidum (present only in thick skin), and corneum. Melanocytes in the basal layer produce pigment, while Langerhans cells aid immune defense and Merkel cells contribute to touch sensation. The epidermis undergoes continuous turnover, with shed cells replacing those that are lost.

Beneath the epidermis lies the dermis, a thicker, connective tissue-rich layer that provides strength and elasticity. It contains two subregions: the papillary dermis, which has loose connective tissue and capillaries, and the reticular dermis, rich in collagen and elastin fibers. The dermis houses hair follicles, sebaceous and sweat glands, blood vessels, and nerves, supporting thermoregulation, sensation, wound healing, and nutrient delivery to the epidermis.

The hypodermis, or subcutaneous tissue, lies below the dermis and consists mainly of adipose tissue and loose connective tissue. It functions as insulation, energy storage, and cushioning, and helps anchor the skin to underlying structures.

Clinically, disruptions to any layer can affect barrier function, hydration, and sensation. Thickness and composition vary by body site and age, with thick skin on the palms and soles and thinner skin elsewhere.