1215 Ch.13 Skin, Hair, Nails

The skin is the largest organ system, covering 20 square feet of surface area. It protects the body from environmental stresses and adapts to various influences such as heat and cold.

The skin provides protection, prevents penetration of microorganisms, allows perception of sensations, regulates temperature, and aids in fluid balance.

Eccrine glands produce a dilute saline solution (sweat) that helps cool the body, while apocrine glands produce a thicker secretion that becomes active during puberty.

The subcutaneous layer stores fat for energy, provides insulation, and aids in protection through its cushioning effect.

Nails are hard plates of keratin that are pink due to the underlying nail bed, with a lunula at the proximal end and cuticles protecting the nail matrix.

The ABCDEF rule helps identify suspicious lesions that may indicate melanoma by assessing asymmetry, border irregularity, color variation, diameter, elevation, and funny-looking characteristics.

The epidermis is completely replaced every 4 weeks.

Melanin protects the skin against harmful UV rays, which is why individuals with darker skin have a lower incidence of skin cancer.

The two main layers of the skin are the epidermis (outer layer) and the dermis (inner layer).

Aging leads to loss of elasticity, thinning of the skin, decreased vascularity, and reduced function of sweat and sebaceous glands, resulting in dry skin.

The dermis provides support and elasticity to the skin, containing connective tissue, nerves, sensory receptors, blood vessels, and lymphatics.

Risk factors include personal or family history of melanoma, presence of atypical moles, high UV exposure, and advancing age.

Melanocytes produce the pigment melanin, which gives brown tones to the skin and hair.

Common conditions include dry skin, increased bruising, and the development of skin lesions such as actinic keratosis.

Sebaceous glands produce sebum, which oils and lubricates the skin and hair, helping to prevent water loss.

Increased metabolism leads to dilated peripheral vasculature, increased secretion from sweat and sebaceous glands, and fat deposits for nursing.