Practical - Layers of Skin & Special Features

epidermis

• outermost layer of skin

• keratinocytes arranged into layers called strata

difference between thin and think skin

• thin skin epidermis has 4 strata layers

• thick skin epidermis has 5 strata layers (palms and soles)

strata (layers) of the epidermis

• stratum corneum

• stratum lucidum (THICK SKIN ONLY)

• stratum granulosum

• stratum spinosum

• stratum basale

stratum corneum

• outermost layer

• strengthened to provide a protective barrier by the presence of keratohyalin

  • protein structure within keratinocytes

stratum lucidum

• found only on the palms of the hands and soles of the feet

• densely packed dead cells filled with keratin

keratin

structural protein that gives skin, hair, and nails its hard, water-resistant properties

stratum granulosum

keratinocytes that have stopped dividing and started producing keratin

keratohyalin

granulated protein which accumulate as lamellar granules within cells

• waterproof

stratum spinosum

• layers of keratinocytes bound together by desmosomes

• dendritic cells defend against microorganisms and superficial skin cancers

stratum basale

• deepest layer of epidermis

• highest rate of reproduction of new skin cells

• melanocytes and merkel cells

  • production of melanin and touch sensation

dermis

• composed mainly of connective tissue

• contains blood vessels, hair follicles, sweat glands

• supports the epidermis

layers of dermis

• papillary layer

• reticular layer

• hypodermis

papillary layer

• dermal papillae in this region (ridges of skin that make fingertips)

• loose areolar connective tissue

• contains capillaries, lymphatic vessels, and sensory neurons

reticular layer

• dense irregular connective tissue

• collagen fibers

• contains blood vessels, nerve fibers, accessory organs (hair follicles, sweat glands)

elastin fibers

increase elasticity of the dermis

cleavage lines

• orientation of collagen fibers in dermis

• generally parallel to underlying muscle fibers

• where surgeons try to cut along to minimize scaring

hypodermis

• connective tissue connecting skin (dermis) to underlying bone and muscle

• provides insulation and padding

• dominated by adipose tissue