Overview
The skin has three layers. The epidermis is a thin, waterproof outer layer without blood vessels; its deepest cells divide constantly and melanocytes give skin its color. The dermis holds collagen, blood vessels, nerves, hair follicles, sweat glands and oil (sebaceous) glands. The hypodermis (subcutaneous tissue) is fat and connective tissue that insulates and cushions.
Skin integrity depends on blood flow, nutrition, moisture and mobility. When pressure squeezes capillaries against bone for too long, tissue dies, which is why pressure injuries form over bony prominences such as the sacrum, heels and hips.
Main functions
- Barrier against microorganisms, chemicals and water loss
- Temperature regulation through sweating and blood flow
- Sensation: touch, pressure, pain and temperature
- Vitamin D synthesis with sunlight
- Excretion of small amounts of water, salt and urea
Key structures
-
Skin
The outer covering of the body and its largest organ.
The layers of the skin
When the body is hot, dermal blood vessels dilate and sweat glands release fluid that cools the skin as it evaporates. When the body is cold, vessels constrict and hair stands up (goosebumps) to keep heat in.
Wound healing moves through hemostasis, inflammation, proliferation (new tissue and blood vessels) and maturation. Protein, vitamin C, zinc, oxygen and good circulation are essential at every stage.
Nursing assessment
- Inspect color (pallor, cyanosis, jaundice, erythema), checking the conjunctivae, lips and nail beds in darker skin.
- Palpate temperature, moisture, texture and turgor (tenting suggests dehydration; less reliable in older adults).
- Check for edema and grade pitting from 1+ to 4+.
- Assess pressure points every shift using a risk tool such as the Braden Scale (18 or below indicates risk).
- Describe lesions by size, shape, color, distribution and drainage; use ABCDE for moles: asymmetry, border, color, diameter over 6 mm, evolving.
Common conditions
| Condition | What happens | Key signs | Nursing priorities |
|---|---|---|---|
| Pressure injury | Localized damage over a bony prominence from pressure or shear | Stage 1: non-blanchable redness on intact skin. Stage 2: partial-thickness loss. Stage 3: full-thickness, fat visible. Stage 4: bone, tendon or muscle exposed | Reposition at least every 2 hours, pressure-redistribution surfaces, keep skin clean and dry, nutrition, lift rather than drag |
| Burns | Tissue damage from heat, chemicals, electricity or radiation | Superficial (red, painful), partial-thickness (blisters), full-thickness (white or leathery, may be painless) | Airway first in facial burns, fluid resuscitation by the Parkland formula, infection prevention, pain control |
| Cellulitis | Bacterial infection of the dermis and subcutaneous tissue | Warm, red, swollen, tender area that spreads; fever | Mark the borders, elevate the limb, antibiotics |
| Melanoma | Malignant tumor of melanocytes | Changing mole that meets ABCDE criteria | Sun protection teaching, skin self-exams |
| Psoriasis | Chronic immune-mediated overgrowth of skin cells | Raised red plaques with silvery scales | Topical therapy teaching, emotional support |
Labs and normal values
| Test | Typical adult range | Why it matters |
|---|---|---|
| Albumin | 3.5–5.0 g/dL | Low levels slow wound healing (also check prealbumin) |
| Prealbumin | 15–36 mg/dL | Short-term nutrition marker |
| Wound culture | No growth of pathogens | Collect before antibiotics, from clean wound bed tissue |
| Braden Scale score | 19–23: no or low risk | 18 or below: at risk for pressure injury; 9 or below: very high risk |
Reference ranges differ between laboratories and textbooks. Use the values your program and facility use.
Exam tips
- Stage pressure injuries by the deepest tissue visible; if the base is covered by slough or eschar, it is unstageable.
- Do not massage reddened skin over bony prominences.
- Rule of nines for adult burns: head 9%, each arm 9%, front of trunk 18%, back 18%, each leg 18%, perineum 1%.
Practice questions
8 NCLEX-style questions on the skin system. Pick an answer to see the rationale.
-
A client has an area of non-blanchable redness over the sacrum with intact skin. What stage is this pressure injury?
Show the answer and rationale
Answer A: Stage 1. Stage 1 is intact skin with non-blanchable erythema.
-
Which Braden Scale score indicates that a client is at risk for pressure injury?
Show the answer and rationale
Answer C: 16. Scores of 18 or below indicate risk; lower scores mean higher risk.
-
Using the rule of nines, what is the burn percentage for an adult with burns to the entire front of the trunk and the entire right arm?
Show the answer and rationale
Answer B: 27%. Anterior trunk is 18% and one arm is 9%, for a total of 27%.
-
Which action helps prevent pressure injuries?
Show the answer and rationale
Answer C: Reposition at least every 2 hours and use a lift sheet. Repositioning relieves pressure and lift sheets prevent shear. Massage damages fragile tissue and high head elevation increases sacral shear.
-
Which mole finding should the client report?
Show the answer and rationale
Answer B: Irregular border with several colors, 8 mm and growing. Asymmetry, irregular borders, multiple colors, diameter over 6 mm and evolution are warning signs of melanoma.
-
For a client with facial burns from a house fire, which assessment is the priority?
Show the answer and rationale
Answer B: Airway and breathing. Inhalation injury can cause airway swelling within hours; hoarseness, stridor and singed nasal hair are red flags.
-
Which lab value most suggests that poor nutrition will slow wound healing?
Show the answer and rationale
Answer A: Albumin 2.8 g/dL. Low albumin reflects poor protein status, which delays tissue repair.
-
Where is jaundice best assessed in a client with dark skin?
Show the answer and rationale
Answer B: Sclera. The sclera and hard palate show yellowing more reliably than skin.