The Skin

Question 1

Briefly describe the layers of the epidermis (epithelium)?

Answer 1

Epidermis:

(upper layer of the skin, non-vascularized)

• Stratum basale = deepest layer, thin single layer with kerotinocytes (stem cells) that are modified for cell division.
• Stratum spinosum = several layers (3 to 5) made with kerotinocytes that have intermediate filaments and spiked cells. Mature cells do not have spikes.
• Stratum granulosum = several layers, where changes in kerotinization seen. Accumulation of granules seen (kerotinohyalin = resp. for kerotinization in upper layers, lamellar = water-resistant, resp. for protection against waterloss. )
• Stratum lucidum = thin clear layer that cover the stratum granulosum)
• Stratum corneum = upper layer, 3/4 of the epidermis, anucleated.

Question 2

Briefly describe the layers of the dermis (connective tissue)?

Answer 2

Dermis:

(deepest layer of skin, strong and flexible with cells: mast cell, macrophages, whit blood cells, fibroblasts, fibers = collagen, elastin and reticular fibers. highly vascularized with blood vessels, lymph vessels and nerve fibers)

• Papillary = thin upper most layer, collagen and elastin form loose connective tissue. peg like projections called dermal papillae
• Reticular = makes up 80% of the dermis, made of irregular dense connective tissue. ECM has thick collagen fibers.

Question 3

Briefly describe the associated appendages of the skin?

Answer 3

• Sweat glands = found all over skin except at external genitalia. Eccrine are found at forehead, palms and soles feet and Apocrine at axillary and anogenitalia.
• oil glands = found all over skin except at palms and soles of feet. secrete sebum which lubricates hair and skin
• Hair and hair follicles = found all over body except at palms, soles of feet, nipples, lips and external genitalia.
• Nails = scale-like modifications that contain keratin.

Question 4

List the major functions of the skin and relate these functions to its histological structure?

Answer 4

• Protection = hair protects from sun damage, heat loss and water loss
• Excretion = sweat glands
• Body temperature regulation = hair, sweat glands
• Metabolic regulation
• Blood reservoir
• Cutaneous sensation = hair and hair follicles