THE INTEGUMENT

INTEGUMENTARY SYSTEM Most visible organ system of the human body Makes about 16% of your body weight The skin is an organ system because it is composed of many different types of tissues and organs Accessory organs (Oil-, wax-, and sweat-producing glands, hair, and nails) Sensory organs for touch Blood/lymphatic vessels Seals the body in a protective barrier that is flexible yet resistant to abrasion Our first line of defense against an often hostile environment Coordination of immune response to pathogens

EPIDERMIS Superficial, stratified squamous epithelium Protects the dermis, prevents water loss and pathogen entry Synthesize vitamin D3 Sensory receptors: detect touch, pressure, pain, and temperature Immune cells – Langerhans cells Organized into many layers called strata of cells Thin skin vs. Thick skin (palms and soles of feet) Melanocytes – produce melanin / pigment Keratinocytes are cells produced deep in the epidermis Resistant to dehydration and friction Cells produce keratin, until they reach the surface of the cell and then get sloughed off Most abundant epithelial cells Production regulated by epidermal growth factor

LAYERS OF EPIDERMIS

Thick layer or irregularly arranged connective tissue Dermis Thick layer or irregularly arranged connective tissue Supports and nourishes the epidermis Papillary layer – dermal papillae Reticular layer Vascularized irregular tissue Pressure receptors Sweat glands/sebaceous glands

“Goosebumps” AND HOMEOSTASIS

What the skin can tell us

Hypodermis AKA Subcutaneous layer Composed mainly of adipose tissue and areolar tissue Important in stabilizing the position of the skin in relation to underneath tissues During early life, subcutaneous fat serves as energy reserve and shock absorber During puberty, sex hormones cause accumulation of fat Only the superficial region has large arteries and veins Deeper region have limited number of capillaries and no vital organs This makes drug administration via subcutaneous injection a useful method

Sebaceous glands & follicles

Sweat Glands

Apocrine to blame!