What is the function of the skin?

Functions of the Skin

The skin serves as a vital protective barrier that encases the body's organs, preventing penetration of external xenobiotics, substances, allergens, and microorganisms while maintaining homeostasis. 1

Primary Functions

The skin performs multiple essential functions that are critical for survival and quality of life:

1. Protective Barrier

• Provides physical protection against mechanical trauma and abrasion 1
• Creates a waterproof sheath that prevents excessive water loss 1
• Blocks penetration of harmful microorganisms 1
• Shields against UV radiation 1, 2
• Prevents entry of chemicals and toxins 1

2. Homeostatic Regulation

• Temperature regulation: Controls body temperature through sweat glands and blood vessels 1, 3
• Water balance: Prevents dehydration by limiting transepidermal water loss 1
• Electrolyte balance: Helps maintain proper electrolyte levels 1

3. Sensory Function

• Contains various receptors that detect:
  • Pressure changes 1
  • Pain 1
  • Temperature 1
  • Itching 1
• Facilitates proper interaction with the environment through these sensory inputs 1

4. Metabolic Functions

• Synthesizes vitamin D when exposed to sunlight 2
• Participates in biochemical and metabolic processes 3

5. Immune Functions

• Houses Langerhans cells that participate in immune surveillance 1, 4
• Mounts defense measures in response to invading pathogens 4
• Contains immune cells that help protect against infections 4

Structural Components Supporting Functions

The skin's functions are enabled by its complex structure consisting of three main layers:

Epidermis (0.05-0.1 mm thick)

• Outermost layer with 4-5 distinct strata 1:
  • Stratum corneum: Dead, flattened cells forming the primary barrier 1
  • Stratum lucidum: Thin transparent layer (in thick skin only) 1
  • Stratum granulosum: Contains keratohyalin granules 1
  • Stratum spinosum: Cells connected by desmosomes 1
  • Stratum basale: Contains dividing stem cells for regeneration 1, 5
• Contains keratinocytes (95%), melanocytes (pigment production), Langerhans cells (immune function), and Merkel cells (sensory) 1, 5

Dermis (1-2 mm thick)

• Middle layer composed of collagen and elastin network 1
• Contains blood vessels that supply nutrients and remove waste 1
• Houses lymph vessels that help eliminate pathogens 1
• Contains nerve endings for sensory function 1
• Includes hair follicles, sweat glands, and sebaceous glands 1

Hypodermis/Subcutaneous Tissue (1-2 mm thick)

• Deepest layer primarily composed of adipose tissue 1
• Provides insulation and energy storage 1

Clinical Significance

Understanding skin functions is crucial for:

• Evaluating barrier integrity in conditions like burns or toxic epidermal necrolysis 5
• Assessing potential for healing following injury or disease 6
• Recognizing how aging affects skin function, which can lead to increased susceptibility to breakdown and infection 7
• Developing appropriate interventions for skin conditions that compromise barrier function 5

The skin's complex structure and multifunctional nature make it an essential organ for survival, providing protection while facilitating interaction with the environment through its sensory, regulatory, and immune functions.