Consists of

• Cutaneous membrane
• Epidermis and Dermis
• Accessory structures
• Subcutaneous layer

Functions of the skin

1. Protection
2. Excretion – sweat and sebum
3. Temperature maintenance – sweating and shivering
4. Nutrient storage –
5. Vitamin D3 synthesis – from the sun
6. Sensory detection – sensations from the outside world

Integumentary System Components.

Epidermis – composed of layers of keratinocytes

• Thin skin – four layers (strata)
• Thick skin – five layers

Layers of the Epidermis

• Stratum Corneum
• Stratum lucidum
• Stratun granulosum
• Stratum Spinosum
• Stratum germinativum – basale

The structure of the Epidermis

• Keratinocyte , Cells accumulate keratin and eventually are she
• Epidermal ridges are interlocked with dermal papillae
• Fingerprints and improves gripping ability
• Langerhans cells (immunity) in s. spinosum
• Merkel cells (sensitivity) is s. germinativum (basale)

Skin color depends on

• Blood supply
• Carotene (from fruits) and melanin
• Melanocytes produce melanin and protect from UV radiation.
• Epidermal pigmentation
• Interrupted blood supply leads to cyanosis

Stretch Marks

• Caused by excessive stretching of the dermis
• Patterns of collagen and elastic fibers from lines of cleavage