Skin Structure and Functions

Study Notes

The skin is composed of three main layers:
- Epidermis (outermost layer): keratinocytes, melanocytes, Langerhans cells, and Merkel cells
- Dermis (middle layer): collagen, elastin, blood vessels, nerve endings, and hair follicles
- Hypodermis (innermost layer): subcutaneous fat, connective tissue, and blood vessels

Barrier function: protects the body from external factors (water, temperature, pathogens)
Regulatory function: regulates body temperature, water loss, and electrolyte balance
Immune function: detects and responds to pathogens and foreign substances
Sensory function: detects and responds to sensations (touch, pressure, pain, temperature)

Primary lesions:
- Macule: flat, discolored area
- Papule: small, raised area
- Plaque: flat, raised area
- Nodule: large, raised area
- Vesicle: small, fluid-filled blister
- Bulla: large, fluid-filled blister
Secondary lesions:
- Scale: dry, flaky skin
- Crust: dried serum, pus, or blood
- Erosion: loss of epidermis
- Ulcer: loss of epidermis and dermis

Acne: inflammatory condition characterized by comedones, papules, and pustules
Eczema: inflammatory condition characterized by itching, redness, and dryness
Psoriasis: chronic condition characterized by scaly, red plaques
Skin Cancer: malignant growth of skin cells (melanoma, basal cell carcinoma, squamous cell carcinoma)

The skin is composed of three main layers: epidermis, dermis, and hypodermis.
The epidermis is the outermost layer, containing keratinocytes, melanocytes, Langerhans cells, and Merkel cells.
The dermis is the middle layer, comprising collagen, elastin, blood vessels, nerve endings, and hair follicles.
The hypodermis is the innermost layer, consisting of subcutaneous fat, connective tissue, and blood vessels.

The skin serves as a barrier against external factors such as water, temperature, and pathogens.
It regulates body temperature, water loss, and electrolyte balance.
The skin has immune functions, detecting and responding to pathogens and foreign substances.
It also has sensory functions, detecting and responding to sensations like touch, pressure, pain, and temperature.

Primary lesions include macules, papules, plaques, nodules, vesicles, and bullae.
Macules are flat, discolored areas, while papules are small, raised areas.
Plaques are flat, raised areas, and nodules are large, raised areas.
Vesicles are small, fluid-filled blisters, and bullae are large, fluid-filled blisters.
Secondary lesions include scales, crusts, erosions, and ulcers.
Scales are dry, flaky skin, while crusts are dried serum, pus, or blood.
Erosions involve the loss of epidermis, and ulcers involve the loss of both epidermis and dermis.

The skin exam involves three main techniques: inspection, palpation, and auscultation.
Inspection is a visual examination of the skin.
Palpation is an examination of the skin by touch.
Auscultation is an examination of the skin using a stethoscope, though it is rarely used.

Acne is an inflammatory condition characterized by comedones, papules, and pustules.
Eczema is an inflammatory condition characterized by itching, redness, and dryness.
Psoriasis is a chronic condition characterized by scaly, red plaques.
Skin cancer includes malignant growth of skin cells, such as melanoma, basal cell carcinoma, and squamous cell carcinoma.