Topic 3: Integumentary System

Functions of Epidermis

1. Protection

2. Regulation of body temperature

3. excretion

4. provides sensory information

5. synthesis of vitamin D3 and of lipid reserves

6. coordinates immune responses of the skin

Layers of the Integumentary system

1. Epidermis

   • Surface Layer

2. Dermis

   • Blood Vessels and nerves present

3. Hypodermis

   • aka subcutaneous layer, subcutaneous fat

Types of skin (epidermis)

• thick skin (5 layers) (found on palms, soles of feet)

• thin skin (4 layers)

• keratinized skin

  • keratin = protein

5 layers of epidermis

1. stratum germinativum (stem cells)

2. Stratum spinosum (bundles of protein filaments) (callus)

3. Stratum granulosum (keratination layer (keratohylalin, keratin)

4. Stratum lucidum (thick skin only)

5. Stratum corneum (15-30 layers)

Main cell type in integumentary system

Keratinocyte (stratified squamous epithelium)

Melanocyte

Produce melanin which prevent skin damage by absorbing UV radiation

• UV exposure causes melanocytes to increase melanin synthesis and transfer

• Skin color is due to the amount of melanin and skin vascularization

Dermis Layers

1. Papillary layers (under epidermis)

   • Loose CT proper

   • contains capillaries and nerve endings or sensory apparatus (Merkel cells and dendrites)

2. Reticular layer

   • Dense irregular CT proper

   • contains blood vessels, hair follicles, nerves, sweat glands, sebaceous glands, collagen fibers

Hypodermis (subcutaneous layer)

• Loose CT proper

• Contains abundance of fat cells (adipose) — energy store

• Distribution/accumulation of adipose tissue in hypodermis is sex dependent

• Important in stabilizing the position of the skin in relation to underlying tissue

Hair Follicle

• An accessory structure of the integumentary system.

• Deep into the dermis

• features root hair plexus: nerve ending to sense movement of hair

Sebaceous glands and sebaceous follicles

accessory structure: produce sebum: a natural oil secretion that is vital to health of skin and hair

Sweat Glands

apocrine and merocrine glands.

Coil-like structures in the integumentary system, deep in subcutaneous

Merocrine glands: up to 300 glands per square inch in palms and soles of feet

Apocrine in armpits, releasing stinky secretions

Nails

Nail body covers the nail bed

Nail root: production of nail begins

features lunula: small visual at bottom of nail, palish coloration, in area where blood vessels are comprimised

• pick up on mineral or vitamin deficiency by feeling and texture (cap refill)

Aging and the Integumentary system

• Thin epidermis

  • slows repair

  • decreased vitamin D

  • reduced number of Langerhans cells(immune cells)

• Fewer Melanocytes

  • Pale skin

  • reduced tolerance for sun exposure

• Reduced sweat glands

  • tendency to overheat

• Reduced blood supply

  • Slow healing

  • reduced ability to lose heat