Pathophysiology
Clinical meaning
The integumentary system is the body's largest organ, accounting for approximately 16% of total body weight, and serves as the primary interface between the internal body and the external environment. A comprehensive dermatological assessment is a fundamental nursing skill that enables early identification of skin disorders, systemic disease manifestations, malignancies, pressure injuries, wound healing complications, and medication adverse effects. Understanding skin anatomy, lesion morphology, and systematic assessment techniques is essential for accurate documentation, appropriate intervention, and effective communication with the healthcare team. The skin consists of three primary layers. The epidermis is the outermost avascular layer composed of stratified squamous keratinized epithelium. Its primary functions include barrier protection against pathogens, chemicals, UV radiation, and mechanical injury, as well as prevention of transepidermal water loss (TEWL). The epidermis is organized into five strata (from deepest to most superficial): stratum basale (germinativum -- single layer of stem cells and melanocytes; active mitotic layer that regenerates the epidermis every 28-45 days), stratum spinosum (multiple layers of keratinocytes connected by desmosomes; contains Langerhans cells that serve as antigen-presenting immune sentinels), stratum granulosum (keratohyalin granules...