Anatomy of Skin: Layers and Composition

Layers of the Skin

The skin is composed of three main layers:

1. Epidermis: The outermost layer, responsible for protecting the body from external factors such as water loss, UV radiation, and infection.
   • Thickness: 0.05-1.5 mm
   • Composed of stratified squamous epithelium, melanocytes, Langerhans cells, and Merkel cells
2. Dermis: The middle layer, responsible for providing strength, elasticity, and nourishment to the skin.
   • Thickness: 1-4 mm
   • Composed of connective tissue, blood vessels, nerve endings, and hair follicles
3. Hypodermis: The innermost layer, responsible for attaching the skin to underlying tissues and storing energy.
   • Thickness: 1-4 cm
   • Composed of subcutaneous fat, connective tissue, and adipose tissue

Skin Appendages

• Hair follicles: Produces hair, anchored to the dermis by a sebaceous gland
• Sweat glands: Produces sweat, regulated by the nervous system
• Sebaceous glands: Produces sebum, an oily substance that helps to moisturize the skin
• Nail plates: Composed of dead keratin cells, grows from the nail matrix

Skin Functions

• Barrier function: Prevents water loss and entry of pathogens
• Thermoregulation: Regulates body temperature through sweating and vasodilation
• Sensation: Detects and transmits sensory information to the brain
• Immune function: Provides an immune response to pathogens and foreign substances
• Wound healing: Initiates and coordinates the wound healing process

Layers of the Skin

• Epidermis is the outermost layer, 0.05-1.5 mm thick, responsible for protecting the body from external factors like water loss, UV radiation, and infection.
• It is composed of stratified squamous epithelium, melanocytes, Langerhans cells, and Merkel cells.
• Dermis is the middle layer, 1-4 mm thick, providing strength, elasticity, and nourishment to the skin.
• It is composed of connective tissue, blood vessels, nerve endings, and hair follicles.
• Hypodermis is the innermost layer, 1-4 cm thick, attaching the skin to underlying tissues and storing energy.
• It is composed of subcutaneous fat, connective tissue, and adipose tissue.

Skin Appendages

• Hair follicles produce hair, anchored to the dermis by a sebaceous gland.
• Sweat glands produce sweat, regulated by the nervous system.
• Sebaceous glands produce sebum, an oily substance that helps to moisturize the skin.
• Nail plates are composed of dead keratin cells, growing from the nail matrix.

Skin Functions

• The skin's barrier function prevents water loss and entry of pathogens.
• Thermoregulation regulates body temperature through sweating and vasodilation.
• The skin detects and transmits sensory information to the brain through sensation.
• The skin provides an immune response to pathogens and foreign substances through immune function.
• The skin initiates and coordinates the wound healing process through wound healing.