Chapter 5: Integumentary System

Integument

The external protective covering of the body, consisting of skin, hair, nails, glands, and the subcutaneous tissue (hypodermis).

Epidermis

Outer skin region; stratified squamous epithelium; keratinization; 40–56 days for new cells to reach the surface.

Dermis

Second major skin region; dense connective tissue with collagen and elastic fibers; houses nerve endings, glands, hair follicles, and blood vessels; contains cleavage lines.

Hypodermis (subcutaneous tissue)

Below the dermis; foundation of skin; anchors skin to underlying tissues; contains loose and adipose tissue and about half of body fat.

Stratum corneum

Outermost epidermal layer; 20–30 layers of dead keratin-filled cells; ~75% of epidermal thickness; dandruff is flaking of this layer.

Stratum basale

Deepest epidermal layer; single row of cells attached to the dermis; source of new skin cells.

Keratinization

Process by which new cells produce keratin and push older cells toward the surface; ~40–56 days.

Dandruff

Flaking of the stratum corneum; dead keratinized skin cells.

Callus

Thickened stratum corneum caused by repeated friction or pressure.

Dermal papillae

Projections of the dermis into the epidermis; contain capillary loops and nerve endings; create fingerprints.

Papillary layer

Thin superficial dermal layer with blood vessels and dermal papillae; contributes to ridges/fingerprint patterns.

Reticular layer

Deeper dermal layer; dense connective tissue; accounts for ~80% of the dermis.

Cleavage lines

Pattern of collagen fiber orientation; incisions parallel to these lines heal with less gapping and scarring.

Hair follicle

Structure surrounding the hair root; extends from epidermis