Integumentary System 2 Regions 1 Epidermis 2 Dermis

Integumentary System 2 Regions: 1. Epidermis 2. Dermis Subcutaneous tissue: 1. below dermis 2. Also called hypodermis 3. Mainly adipose tissue

Skin regions: #1 Epidermis • Avascular • Mostly keratinized epithelium tissue Contains 4 cell types 1. 2. 3. 4. Keratinocytes Melanocytes Epidermal dendritic Tactile

Layers of the Epidermis: 4 layers Deep to superficial: 1. Stratum Basale 1. Stratum Spinosum 1. Stratum Granulosum 1. Stratum Corneum

Epidermis Layer #1: Stratum Basale • Single row of cells • Next to dermis Cell type: melanocytes or very early keratinocyte • Consistently dividing • “spidery-pigmented” • Resembles cardboard

Epidermis layer #2: Stratum Spinosum • Several cell layers thick • Cell division occurs but not as much as Basale • Basale & Spinosum only layers of epidermis to receive nutrition • Keratinocytes look “spikey”

Epidermis layer #3: Stratum Granulosum • 3 -5 cell layers thick • Keratinization starting to occur • Cells start to flatten & loss of nucleus & organelles • Accumulate granules that secrete: - glycolipid - keratin

Epidermis layer #4: Stratum Corneum • 75% of epidermis • 20 -30 cell layers thick • Cells are dead • Consistently are replaced by lower layer • Filled with keratin, flat shaped

Dermis: Layer #1 Papillary Layer • Finger like projections • Attaches to epidermis • Mainly connective tissue

Dermis layer #2 : Reticular Layer (80 %) Contains: 1. Blood vessels 3. Sweat Glands 2. Sebaceous glands 4. Pressure Receptors * Rich blood supply helps with body temp control

Appendages of the Skin: Sweat Glands Sebaceous Glands Hair follicles

Sweat Glands: Sudoriferous Glands Two Types: 1. Eccrine: merocrine • most numerous • Palms , soles, forehead • Coiled gland, tubular gland • Secretory part in dermis

Sweat Glands: Sudoriferous Glands 2. Apocrine Glands: • Larger than eccrine glands • Lie deeper in dermis • Empty secretions into hair follicles

Sebaceous Glands: oil glands • Found all over body • Small on trunk, large on face, neck and chest • Secrete sebum • Secreted into hair follicle or directly on skin surface • Hormone induced

Hair Follicles: Structures of hair follicles: • Bulb • Plexus • Arrector pili • Papilla