Accessory Structures and Pigmentation

Hair composition

Non living - keratin and cuticle, grow from follicle in epidermis down into dermis, extends above skin surface, follicle surrounded by ct then sensory neuron

Hair function

Protects from uv damage, helps cushion light impact, reduce insect and pathogen entry, important as sensory receptors - sensory neurons around base of every hair follicle with great sensitivity, contraction of errector pili muscles = hairs upright

Nail composition

Keratinised epidermal cells forming a clear, solid covering over distal ends of digits, nail body grows from nail root and extends over nail bed

Nail functions

Protects exposed or distal tips of digits, helps digit withstand distortion and counters pressure when subjected to mechanical stress, allows manipulation and grip of small objects, allows scratching of body

Apocrine sweat glands

Pubic and axillary regions and around nipples, secrete sweat into hair follicles, odour as bacteria use it for nutrition

Merocrine sweat glands

Secrete onto skin surface, palms and soles have highest numbers, comprised of water, electrolytes, organic compounds and an antibiotic peptide dermcidin that works in high salt conditions

Function of merocrine sweat glands

Cools skin surface to reduce body temp, excrete water, electrolytes and some drug metabolites, dilutes harmful chemicals on skin, discourages microbial growth by flushing off skin via dermcidin

Sebaceous glands

Oil glands that discharge sebum into hair follicles and onto skin, sebaceous follicles discharge sebum directly onto epidermal surface to lubricate skin surface, located on face, back, chest, nipples and external genitalia

Sebum

Comprised from triglycerides, cholesterol, proteins and electrolytes, inhibits bacterial growth, lubricates and protects keratin of hair shaft

Melanin

Brown, yellow-brown to black, protects against uv damage, produced by melanocytes and transferred to keratinocytes

Carotene

Orange-yellow, stored in epidermis and in adipose cells, can be converted to vitamin a, needed by retina

Melanocytes and pigment production

Increase pigment production in response to sun exposure, but too slowly to prevent sunburn

Pigmentation

Relative coloration of skin depends on the amount of melanin produced by melanocytes in stratum basale and taken up by keratinocytes