Chapter 5 of 5 - Integumentary System Course
When the integumentary system is damaged or diseased, the consequences range from cosmetic concerns to life-threatening emergencies. Understanding skin pathology and wound repair is essential for biology and clinical medicine.
| Classification | Depth | Appearance | Healing |
|---|---|---|---|
| Superficial (1st degree) | Epidermis only | Red, painful, no blisters | 3-5 days, no scarring |
| Partial thickness (2nd degree) | Epidermis + upper dermis | Red, blisters, very painful | 2-3 weeks, possible scarring |
| Full thickness (3rd degree) | Epidermis + entire dermis | White/brown, leathery, painless | Requires grafting, scarring |
| 4th degree | Through to muscle/bone | Charred, black | Amputation may be needed |
The Rule of Nines is used to estimate the total body surface area (TBSA) affected by burns in adults: head = 9%, each arm = 9%, anterior trunk = 18%, posterior trunk = 18%, each leg = 18%, perineum = 1%.
Quick Check
Why are full-thickness (3rd degree) burns painless despite being the most severe?
Skin cancer is the most common form of cancer worldwide. UV radiation damages DNA in skin cells, particularly affecting tumor suppressor genes like p53.
Basal Cell Carcinoma
Squamous Cell Carcinoma
Melanoma
The ABCDE Rule for Melanoma
Fill in the Blank
The most dangerous type of skin cancer is________, which originates from melanocytes and has a high potential to metastasize to other organs.
| Condition | Key Features |
|---|---|
| Acne vulgaris | Blocked sebaceous glands, bacterial infection (Cutibacterium acnes), hormonal influence |
| Eczema (dermatitis) | Chronic inflammation, itchy, dry, red patches; linked to immune dysfunction |
| Psoriasis | Autoimmune - rapid keratinocyte turnover (3-4 days vs normal 25-45); silvery plaques |
| Vitiligo | Loss of melanocytes causing white patches; autoimmune etiology |
| Athlete's foot (tinea pedis) | Fungal infection of the skin between toes; warm, moist conditions |
1. Hemostasis (seconds to minutes)
Blood clotting - platelets form a plug, fibrin mesh seals the wound
2. Inflammation (hours to days)
Neutrophils and macrophages clear debris, pathogens, and dead cells
3. Proliferation (days to weeks)
Granulation tissue forms, angiogenesis, fibroblasts lay down collagen, re-epithelialization
4. Remodeling (weeks to years)
Collagen cross-linking and reorganization; scar matures (reaches ~80% original strength)
Wounds can heal by primary intention (clean edges brought together, e.g., surgical incision - minimal scarring) or secondary intention (edges too far apart, wound fills in from the bottom with granulation tissue - more scarring). Healed skin typically recovers about 80% of its original tensile strength.
Quick Check
During which stage of wound healing do fibroblasts lay down new collagen and new blood vessels form (angiogenesis)?
Fill in the Blank
During hemostasis, platelets aggregate at the wound site and a________mesh forms to seal the wound and prevent further blood loss.
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