1. Protective barrier (duh!)

2. Thermoregulation (sweating)

3. Protection from UV (melanocytes)

4. Excretion (sweating)

5. Metabolism (Vit D synth)

1. Epidermis - Strat SE with some melanocytes, Langerhans and Merkel cells

2. Dermis - CT.

-Superficial Dermis -> areolar CT

-Deep dermis -> dense irregular CT

3. Hypodermis (subcutaneous) - Not really part of the skin. Loose CT and adipose

1. Stratum basale (bottom)

2. Stratum spinosum

3. Straum granulosum

4. Stratum lucidum

5. Stratum corneum (top)

-Single layer of Cub/Column cells

-Bound to neighboring keratinocytes by desmosomes, basal lamina by hemidesmosomes

-High degree of mitotic activity (constant renewal)

-Cub/flat cells with abundance of keratin fibers

-Bundles of tonofilaments (tonofibrils) bind cells together at desmosomes

-Serve as anchor for abrasion, give layer "spiny" appearance

-3-5 layers of polyg/flat cells with large basopilic Keratohyaline Granules

-Have lamellar granules-

-Membrane coated structure composed of lipid bilayers that make lamellar disks.

-Contents spewed out to form cement (seal skin, prevent dessication)

-Translucent layer, flat keratinocytes visible in think skin

-Have no nuclei, almost all keratin filaments

-Layers of flatened keratinocytes

-No nuclei, lots of keratin

-Each HORN cell is only proteins and thick cell membrane, constantly exfoliated

-Stratum corneum thickness reduced

-No stratum lucidum

-Reduced or missing stratum granulosum

-Derived from neural crest cells

-Rround, many dendritic processes entened in bottom 2 layers of skin

-Anchored with hemidesmosomes to basal lamina

-Produce 2 types of pigment: eumelanin (dark brown), pheomelanin (red)

-Melanin aggregates around cell nuclei, protects from UV

-Fuses with lysosomes in upper layers (no melanin)

-Reside in statum spinosum

-Play role in immune system

-Dendrictic cells, process and present antigens to T cells

-Contain raquet shaped Birback granules

-Found in palms, soles, fingertips, oral mucosa, base of hair follicle

-Present in Strat basale, attached to keratinocytes by desmosomes

-Closely associated with unmylenated sensory nerves

-mechanoreceptors

-CT that provides physiologic and mechanical support for epidermis

-Binds to hypodermis

1. Papillary dermis

2. Reticular dermis

-Right under epidermis, separated from it by basement membrane

-Thin layer of areolar CT. Contains collagen, elatic, reticular fibers, capillaries, Meissner's corpuscles, and leukocytes

-Near surface, has projections called dermal papillae that stick into epithelial ridges

-Use anchoring collagen fibrils, extend from basal lamina to dermis

-Thicker that papillary

-Dense irregular CT (less cellular)

-Network of elastic fibers is present, inserts into basal lamina, gives skin elasticity

Blood vessels

Lymphatics

Nerves

Hair follicles

Sweat/sebaceous glands

Arrector pilli muscles

-Derived from invaginations of surface ep. (hair follicle)

-Has widened terminus called hair bulb and base structure called the dermal papilla

-Contains network of capillaries that prvide nourshment for hair follicle

-Epidermal cells that cover dermal pap. are the Hair Root (which produces the hair shaft)

-Equivalent to stratum basale

1. Medulla -  central portion of shaft composed of vacuolated/partially keratinized cells.

2. Cortex - Surrounds medulla. Heavily keratinized/compacted root cells

3. Cuticle - Outermost, cub. cells become columnar oward upper portion of hair bulb. Become flattened as hair grows.

-Surrounds lower hair bulb

-Degenerates at level of sebaceous glands

-Coninuous with epithelium of skin

-Near dermal papilla (corresponds to statum basale)

1. Hair has more compact keratin than skin

2. Keratinization is only at hair root

-Encompasses CT around hair follicle

-Separated from HF by glassy membrane (thickened basal lamina)

-CT is more dense in area

-Arector pilli muscles stretch between here and papillary dermis

-Flat plates of heavily keratinized epithelial cells

1. Nail Root

2. Eponychium

3. Nail plate

4. Nail bed

5. Nail matrix

Proximal portion of nail embedded in the nail groove

-Stratum corneum of epithelial nail groove

-Has folded underneath itself and contacts nail plate

-The nail itself

-Equivalent to stratum corneum of skin

-Epidermis that nail plate rests upon

-Composed only of stratum basale and spinosum

-Epithelium that give rise to nail plate

-Cells divide, move distally, and cornify

-Nail plate moves forward

-Acinus Holocrine glands

-Present in dermis

-Form at puberty, sex H's regulate secretion

-drain into hair follicle or epidermis

1. Eccrine - coiled, open to epidermis.

-Myoepithelial cells surround gland

-Ducts are Strat. Cub. Ep.

-Watery secretion, Merocrine

2. Apocrine - present in armpits (axillary), areolar and anal regions.

-Reside in hypodermis

-Viscous secretion, Merocrine