Common Skin Conditions (Burns, Acne, Dermatitis) - Anatomy and Physiology
- Which skin layers are damaged in a superficial (first-degree) burn, and how does it appear?
- Only the epidermis. It is red and painful without blisters, like a mild sunburn.
- Using the adult rule of nines, what percentage of body surface area is burned if the head and both entire arms are burned?
- 27 percent: 9 for the head plus 9 for each arm.
- Which skin glands are central to the development of acne?
- The sebaceous glands of the pilosebaceous unit, whose sebum and shed cells plug the follicle.
- Why does an open comedone (blackhead) look dark?
- The follicle opening is open to air, and oxidized lipids and melanin darken the plug. It is not trapped dirt.
- Which type of hypersensitivity causes allergic contact dermatitis, such as a poison ivy rash?
- Type IV (delayed, T cell-mediated) hypersensitivity, appearing 1 to 3 days after contact.
- What causes burn shock, the main early life-threatening complication of extensive burns?
- Massive loss of fluid and electrolytes through damaged skin and leaky capillaries, causing hypovolemia.
- Why is a full-thickness (third-degree) burn often painless at its center?
- It destroys the entire dermis, including its sensory nerve endings. The area looks white, leathery, or charred.
- What is atopic dermatitis (eczema)?
- A chronic, itchy inflammatory skin condition linked to a defective skin barrier and often to asthma and allergies.
- Where does seborrheic dermatitis typically occur, and what does it look like?
- In areas rich in sebaceous glands, such as the scalp and nasolabial folds, as red patches with greasy yellowish scales.
- Which skin layers are damaged in a superficial partial-thickness (second-degree) burn, and how does it appear?
- The epidermis and upper dermis. It is red, very painful, and blistered.
- Using the rule of nines, what percentage of an adult's body surface area is one entire leg?
- 18 percent (9 percent anterior and 9 percent posterior).
- Which hormones increase sebum production and trigger acne at puberty?
- Androgens, which enlarge sebaceous glands and increase their secretion in both sexes.