Integumentary system

ANP 1106

Structure of skin

• Is 1.5 -4 mm consisting of 2 distinct regions

• 2 main layer: Epidermis/dermis

Epidermis

• Superficial epithelial region: layered-thick

• keratinized stratified(multilayered) squamous(flat) epithelium

Dermis

Dense connective tissue ; vascularized

Hypodermis

• Superficial fascia(connective tissue that wraps around)

• not part of the skin, hence subcutaneous

• Mostly adipose tissue

4 types of epidermal cells

• Keratinocytes

• Melanocytes

• Dendritic (Langerhans) cells

• Tactile (merkel) cells

Keratinocytes

• Make up 95% of thin cells

What is the main function of keratinocytes? To make keratin

What is the lifespan of a keratinocyte?

What is epidermal growth factor?

Melanocytes

• Produce melanin which is packed into melanosomes; deepest layer of epidermis; numerous branching processes for melanosomes transfer to adjacent cells.

• Why is melanin important? To protect nucleus from damaging UV rays of the sun

Dendritic (Langerhans) cells

• epidermal dendritic cells (star-shaped); migrate to epidermis from bone marrow. Can differentiate into macrophages

• macrophages activate immune system

Tactile (Merkel) Cells

• epidermis/dermis boundary

• have disc-like sensory nerve ending - touch receptors

Epidermal cells and layers of the epiderm

stratum = layers

5 distinct layers of epidermis

Thick Skin: Contains 5 layers (strata) and is found in high abrasion(hands, feet)

Thin skin contains only 4 strata

5 layers of skin:

• Stratum corneum

• Stratum lucidum

• Stratum granulosum

• Strum spinosum

• Stratum Basale

Dermis

• Strong, flexible connective tissue

• cells include fibroblasts, macrophages, and occasionally mast cells and WBCs

• Semi-fluid matrix heavily embedded with collagen, elastin and reticular fibers

  • Fibers in matrix bind body together

    • Makes up the hide used to make leather

• COntains nerves, blood vessels, and lymphatic vessels, epidermal hair follicles, oil glands and sweat glands