Chapter 5 PHYL141

Integumentary System

Functions of Integumentary System

1. Defense

2. Sensory

3. Vitamin D Synthesis

4. Temperature Control

5. Blood

6. Exocrine System

Layers of the Skin

1. Epidermis 

2. Dermis 

3. Hypodermis

Epidermis

Top layer 

• Stratified squamous epithelium 

• Stratum Basale → Stratum Corneum

Dermis

Middle Layer

• Dense irregular connective tissue

• Contains collagen, immune cells, elastic fibers

• Provides nutrients to epidermis

• 2 layers: Papillary & Recticular

Scarring in Dermis

• Fibroblasts deposit collagen

• Causes raised scar tissue

2 Layers of Dermis

1. Papillary Layer: Creates skin ridges, contains blood vessels & fibroblasts, protects epidermis from pathogens 

2. Reticular Layer: Fibroblasts & collagen, provides nutrients 

Hypodermis

Deepest layer

• Loose connective (subcutaneous tissue)

• Areolar & adipose tissue

Layers of Epidermis

1. Stratum Basale (Deepest): Attached to the basal lamina

2. Stratum Spinosum: Connected keratinocytes

3. Stratum Granulosum: Keratinocyte granules

4. Stratum Lucidum: Characterizes thick skin, hydrophobic

5. Stratum Corneum (Highest): Full of keratin

Keratin

Protects from injury & cellular invasion

• Hydrophobic/fibrous

• Produced by keratinocytes (basal layer)

Keratinization

Epidermal keratinocytes die and form the protective Stratum Corneum

Melanin & Melanocytes

Melanin: Hydrophobic molecule that provides black/brown/red pigment on the body

• Absorbs UV light

• Colors keratinocytes

Melanocytes: Cells that produce/stores melanin

Albinism & Vitiligo

Albinism: Melanocytes don’t produce melanin

Vitiligo: Low melanin in some areas of the body

Ultraviolet Lights (UV)

Breaks hydrogen bonds of DNA - Can cause incorrect proteins → uncontrollable cell division

• UVA: Deeper & weaker - melanin

• UVB: Shallow (epidermis) & stronger - melanocytes

• Collagen breakdown: Unravels proteins and causes wrinkles

Cancers of the Skin

• Metastases: Spreading of cancer 

1. Basal Cell Carcanoma: Stratum basal cells grow uncontrollably - low risk of metastases 

2. Melanoma: Melanocytes grow uncontrollably 

ABCDEs of Melanoma

A - Asymmetry 

B - Border 

C - Color 

D - Diameter 

E - Evolves

Blisters

Epidermis & dermis detach

• Fluid build-up

• Friction based

Bed Sores

Decubitus Ulcers

• Skin necrosis forms from long-term pressure

• Blood flow, oxygen, and nutrients gets cut off from tissue’

• 4 stages of bed sores: Epidermis → Epidermis + Dermis → Subcutaneous → Exposed muscle/bone

Burns

Injuries from heat/radiation/chemicals/electricity

• Skin rapidly loses water

4 Degrees of Burns

1. Epidermis

2. Epidermis + Dermis

3. Dermis + Nerves

4. Muscle + Bone

Intradermal Injections

• TB test, collagen

• 10-15 degrees into Dermis

• Slower absorption

Subcutaneous Injections

• Insulin, flu shot, blood thinners, medicine

• 45 degrees into Hypodermis

• Medium slowness (faster than ID)