Skin is the largest organ of the body, forming part of the integumentary system along with hair, nails, and glands.
Functions of skin include protection against infection, temperature regulation, fluid balance, vitamin D synthesis, sensation, and communication (e.g., blushing).
Skin accounts for 3-5 kg of body weight and can cover up to 2 square meters.
Structure of Skin
Layers of Skin
Epidermis: The outermost layer, visible, composed of stratified squamous epithelial tissue.
Dermis: Below the epidermis, involved in sweating, blood circulation, and sensation.
Hypodermis (Subcutis): The innermost layer, composed mostly of adipose tissue.
Epidermal Cells
Keratinocytes: Build keratin, the protein providing structure and waterproofing.
Melanocytes: Produce melanin, responsible for skin color; the amount of melanin, not the number of melanocytes, determines skin color.
Dendritic (Langerhans) Cells: Immune cells originating from bone marrow, guarding against unwelcome invaders.
Merkel Cells: Sensory receptors for touch, located at the border between the epidermis and dermis.
Types of Skin
Thick Skin: Found on hands and feet, consisting of five layers.
Thin Skin: Covers the rest of the body with four layers.
Layers of the Epidermis (Deep to Superficial)
Stratum Basale: Single cell layer, site of most cell production.
Stratum Spinosum: Spiny layer, active in cell regeneration.
Stratum Granulosum: Granular layer, where keratin production happens.
Stratum Lucidum: Clear layer, found only in thick skin.
Stratum Corneum: Outer, horny layer, composed of dead cells.
Dermis Structure
Papillary Layer: Areolar connective tissue with dermal papillae, forming fingerprints.
Reticular Layer: Dense irregular connective tissue, houses dynamic components like nerves and blood vessels.
Hypodermis Functions
Provides insulation, energy storage, shock absorption, and anchors the skin.
Skin and Sunlight
UV radiation can damage the epidermis, affecting immune cells and DNA.
Importance of sunscreen to prevent skin damage and potential cancer.
Tattoos and Skin
Tattoos need to reach the dermis to be permanent, which can cause pain and bleeding.
Conclusion
Skin is a critical organ with complex structure and essential functions.
Further discussions will cover skincare products and hair care.
Credits: Episode written by Kathleen Yale, edited by Blake de Pastino, consulted by Dr. Brandon Jackson.