What is the composition of the nail body?
dead, tightly compressed epidermal cells packed with keratin
As we age, muscle weakness occurs, due partially to which of the following?
decreased epidermal production of vitamin D3
Wrinkles in elderly individuals are the result of
loss of elastic filaments in the reticular layer of the dermis.
Vitamin D3 formed within the skin has all of these effects on other organ systems
is essential for absorption of calcium and phosphorus by the digestive system.
functions as a precursor for the hormone calcitriol in the endocrine system.
is essential for bone maintenance.is essential for bone growth
During wound repair, the activity of which cells leads to the appearance of collagen fibers and typical ground substance?
Which structural features of spongy bone are oriented along stress lines and are cross-braced extensively?
Layered structure of Hair (from innermost to outermost)
Internal root sheath (surrounds hair root; deeper only)
External root sheath (entire length of follicle)
Glassy membrane (thick, clear basal lamina)
Connective tissue sheath
Base of Hair contains...
hair bulb (epithelial cap) and hair papilla (peg of connective tissue with blood vessels and nerves)
2 types of sweat Glands & Myoepithelial cells
apocrine sweat glands and merocrine sweat glands
myoepithelial cells squeeze gland to discharge secretion (function to wash epidermal surface)
Apocrine Sweat Glands
strongly influenced by hormones, include ceruminous glands and mammary glands, limited distribution (axillae, groin, nipples)
Merocrine sweat glands
found in most areas of skin, produce watery secretion with electrolytes, influenced by nervous system, important in thermoregulation and excretion.
near the root the dermal blood vessels may be obscured, leaving pale crescent known as lunula
Age related skin changes
fewer melanocytes, thinning drier epidermis, diminished immune response (The number of dendritic cells
decreases to about half), Merocrine sweat glands
become less active, and with
impaired perspiration, REDUCED BLOOD SUPPLY, slower skin repair, fewer active follicles
increase epidermal thickness, accelerate wound healing, increase number of dendritic cells protecting against cancer cells and pahogens
Epidermal growth factor
peptide that has widespread effects on epithelia, produced by salivary glands and glands in duodenum. Promote cell division in stratum basale and spnosum, accelerate production of keratin, stimulate epidermal development and repair.
stimulates fibroblast activity and collagen production, thickens epidermis, promotes wound repair
Sunlight and diet, UV radiation causes epidermal cells of stratum spinosum & basale to convert steroid to cholecalciferol
Step 2 (several hours)
blood clot or scab forms to restrict entry of microorganisms. Macrophages patrol damaged area & phagocytizing debris and pathogens, cells of stratum basale undergo rapid division
Step 3 (after one week)
blood clot begins to dissolve, fibroblasts create more collagen fibers and ground substance