Chapter 6: Functions of Integument; Hair

What are the functions of the integument?

• protection from external environment

• vitamin D synthesis

• secretion

• absorption

• immune function

• temperature regulation

• sensory reception

What does protection from external environment mean?

• Protects body from injury, harmful substances, microbes, extreme temperatures, and UV radiation

• Prevention of water loss/gain

  • Epidermis is water resistant, not waterproof

  • Water lost by sweat and transpiration

What does vitamin D synthesis mean?

• Formation of vitamin D₃

• precursor to calcitriol = increases absorption of calcium and phosphate from diet

• regulates blood calcium levels

What does secretion mean?

Waste products secreted onto skin surface during sweating

What does absorption mean?

• Skin absorbs some chemicals/drugs but blocks others

• Selectively permeable

• Suitable for transdermal administration of some drugs

What does immune function mean?

Dendritic cells in epidermis and dermis capable of initiating immune response

What does temperature regulation mean?

Dermal blood vessels capable of vasoconstriction to conserve heat or vasodilation to release heat

What does sensory reception mean?

Receptors detect stimuli (e.g., touch, pressure)

What is hair?

• found almost everywhere on the body

• keratinized cells form slender filament

• Grows from hair follicles

• three types:

  • lanugo, vellus, terminal

What is lanugo hair?

• fine, unpigmented, downy hair, appears in last trimester

• newborn hair

What is vellus hair?

fine hair, primary human hair, found on upper and lower limbs

What is terminal hair?

• coarser, pigmented, longer, on scalp, eyebrows, and eyelashes, men’s beards

• during puberty, replaces vellus hair in axillary and pubic regions

What are the components of hair?

• Hair follicle: oblique tube surrounding hair root, extends into dermis and sometimes subcutaneous layer

• Arrector pili: thin ribbons of smooth muscle extend from hair follicle to dermal papillae, elevates hair with contraction, “goosebumps”

What are the functions of hair?

• Protection on head, from sunburn and injury, in respiratory system and ears – hair traps particles, debris

• Heat retention

• Sensory reception: root hair plexuses detect light touch

• Visual identification