Epidermis is keratinized stratified squamous epithelium and is avascular. Dermis is connective tissue with vessels, nerves, follicles and glands. Hypodermis/subcutaneous tissue lies beneath skin and contains variable adipose/connective tissue; technically it is not part of the skin proper.
Deep to superficial: stratum basale → spinosum → granulosum → lucidum (thick skin only) → corneum. Keratinocytes predominate. Melanocytes produce melanin; Merkel cells participate in touch; epidermal dendritic/Langerhans cells have immune roles.
Superficial papillary layer contains loose areolar connective tissue; deeper reticular layer contains dense irregular connective tissue. Collagen contributes tensile strength and elastin contributes recoil.
Sebaceous glands produce sebum. Eccrine sweat glands are important in thermoregulation. Apocrine glands are concentrated in areas such as axilla/groin and become active around puberty. Hair follicles and nails are epidermal derivatives.
Free nerve endings contribute to pain, temperature and itch. Merkel receptors respond to sustained light touch/pressure and form. Meissner corpuscles are associated with light touch/low-frequency vibration in glabrous skin. Pacinian corpuscles respond strongly to deep pressure/high-frequency vibration. Ruffini endings respond to skin stretch.
Barrier/protection · sensation · thermoregulation · vitamin D synthesis · immune defense · limited excretion · prevention of excessive water loss.
Always inspect exposed skin for integrity and unexpected changes. Contagious infection, open wounds, active inflammation, sensory loss, fragile skin and recent procedures can alter technique or require local avoidance/referral.