appendages: hair follicle, sweat gland, sebaceous gland

keratins

translucid scleroproteins made of 6-8 polypeptides

melanocytes

cells that produce melanin

UV-induced melanogenesis

1. UV induces the production of active a-MSH and its receptor, MC1R (melanocortin-1-receptor)

2. MC1R stimulation induces adenylate cyclase, leading to cAMP production, protein kinase (PKA) activation, Mitf upregulation, and tyrosinase and TRP1 upregulation

3. ultimately leads to enhanced melanin synthesis (pigmentation)

trichohyalin granules

acidophilic/eosinophilic structures in Huxley’s layer of the internal root sheath

sebaceous gland

• non-squamous stratified epithelium

• found in the dermis at the point where the internal root sheath ends

• lined by a basement membrane

• lipid droplets containing cholesterol, phospholipids, triglycerides, and glycogen

  • substances are released when the cells die and is called sebum

• stimulated by androgens, inhibited by estrogens

• holocrine secretion

• lined by basal cells that migrate toward the center of the gland where they swell and the nuclei undergo degeneration (cell is also vacuolated)

• uses the space where the internal root sheath was as a duct

sweat gland

• simple, coiled, tubular

• derived from an invagination of the epithelium

• lined by a basement membrane

• merocrine secretion

• releases water, urea, ammonia, NaCl

• thermoregulation by evaporative cooling

secretory portion of sweat gland

• in hypodermis only

• highly coiled

• made of a single layer of pyramidal-shaped cells

• appears lighter and larger than the cells of the duct portion

• surrounded by myoepithelial cells

• secrete a watery solution rich in electrolytes (serous gland)

duct portion of sweat gland

• in hypodermis and dermis

• less coiled than the secretory portion

• made of a double layer of cuboidal cells

• appears more darkly stained (basophilic) than the secretory portion

• has a smaller lumen than the secretory portion

myoepithelial cells

contractile cells that appear bright pink and lie within the basement membrane

hair

• elongated, obliquely oriented, keratinized structure

• derived from an invagination of the epithelium called hair follicle

• lined by a basement membrane called the glassy membrane

• ends in a bulb with a core of connective tissue called the dermal papilla

• in dark hair, there is a central medulla area

arrector pili muscle

when contraction occurs, the sebaceous gland is compressed, leading to the release of sebum, which acts as an insulator

merocrine secretion

secretion through secretory vesicles

apocrine secretion

pinched off portion of the cell is the secretion

holocrine secretion

mature cell dies and becomes secretory product

endocrine glands

hormones are secreted into blood

exocrine glands

chemicals are secreted onto skin surface

shape classification of glands

• tubular vs alveolar

• simple (duct does not branch) vs compound (duct branches)

serous glands

secrete a watery, protein-rich fluid

mucous glands

secrete a viscous, carbohydrate-rich substance

sebaceous glands

secrete lipids/oils

identify the indicated structure

hair shaft