1. Epidermis

2. Dermis

1. Skin

2. Epidermal derivatives (sweat glands, sebaceous glands, hair, nails)

1. Epidermis

2. Dermis

3. Interface

4. Hypodermis

1. Composed of cells derived from ectoderm

2. Aligned as a keratinized, stratefied, squamous epithelium

3. Wet mucosal areas not keratinized

4. Varies in thickness

1. Dense irregular connective tissue

2. Derived from mesoderm

3. Interdigitated with epidermis

1. Separated by basement membrane

2. Components are contributed by cells in the epidermis (basal lamina) and dermis (reticular lamina)

3. Dermal papillae

4. Vascularized

5. Downward growth of epithelial cells

1. Varying degrees of adipose cells

2. Superficial fascia

1. Barrier agains pathogens

2. Photoprotection

3. Immune recognition and surveillance

4. Damage repair to surface areas

5. Senses the environment via nervous tissue

6. Thermoregulation

1. Dermis

2. Stratum basale

3. Stratum spinosum

4. Stratum granulosum

5. Stratum corneum

1. Germinal layer of skin

2. Single layer of cuboidal cells with a basophilic cytoplasm

3. Undergo mitosis to form keratinocytes

4. Cells in lower layers synthesize cytoplasmic protein and keratin, and are pushed into the upper layers (and eventually die)

1. Thickest layer

2. Contains polyhedral to flattened cells

3. Cells in basal aspect mitotically active and add to number of keratinocytes

4. Rich in intermediate filaments

5. Spiny appearance due to desmosomal junctions

6. Cytoplasm stains eosinophilic

1. 3-5 layers of flattened keratinocytes in most superficial layer

2. Nuclei are large, irregularly shaped basophilic keratohyaline granules not membrane bound

3. Keratin filaments pass through granules

4. Cells also contain membrane-bound granules that form sheets of lipid-rich substance that acts as waterproof barrier

1. Only present in thick skin

2. Lightly staining thin acellular layer just superficial to granulosum

3. Devoid of nuclei and organelles

4. Flattened cells contain keratin filaments oriented parallel to the skin surface

1. Several layers of keratin-containing dead cells (squames)

2. Superficial layer of skin, but cells lack nuclei and organelles and are filled with keratin filaments embedded in an amorphous matrix

1. Arranged in 5 layers

2. Constantly being sloughed off from surface (constantly renewed by cells in stratum basale)

3. Dead at surface

1. Derived from neural crest

2. Reside in stratum basale

3. Cells are round to columnar in shape and extend processes

4. Produce melanin pigment

5. Tyrosinase packaged into melanosomes, activated by UV light, and converted to melanin, thus darkening of the skin

1. Differences directly related to number of melanocytes

2. Variations in races due to an increase in tyrosine kinase activity for darker skin

1. Located in stratum spinosum and originate from stem cells in the bone marrow

2. An antigen presenting cell

1. A layer of skin located deep to the epidermis and is derived from mesoderm

2. Dense, irregular connective tissue composed primarily of type I collagen and networks of elastic fibers

3. Functions to support epidermis and bind skin to underlying hypodermis

4. Papillary layer

5. Reticular layer

1. Loose areolar CT

2. Interdigitates directly with epidermis, but separated by basement membrane

3. Has reticular fibers made of type III collagen fibers  and elastic fibers that form reticular lamina

4. Linked to basal lamina by type IV collagen

5. Capillary loops

6. Sensory receptors (Meissner's corpuscles)

1. Epidermally-derived structures (sweat glands, hair follicles, sebaceous glands) surrounded by dense irregular CT

2. Type I collagen and elastic fibers

3. Cells are sparse

4. Smooth and skeletal muscle present

5. Mechanoreceptors (Pacinian corpuscles and Ruffini corpuscles)

1. Important for thermoregulation

2. Coiled tubular configuration

3. Release sweat through merocrine secretion

4. Derived from ectoderm

5. Deepest aspects become glandular or secretory portion of the gland, while superficial aspects remain as ducts

1. Smaller cuboidal cells that appear darker than the secretory cells because of paucity of cytoplasm

2. Follow helical path to surface (where forms pore)

3. Can be simple or stratefied cuboidal

1. Cells that secrete mucous

2. Myoepithelial cells

1. Cell inside the basal lamina of gland cells and contains actin and myosin filaments that impart the ability to contract

2. Surround secretory portion of the gland and contract to express fluid sweat

3. Stimulation by postganglionic fibers of the sympathetic nervous system causes contraction for release of sweat

1. Only in axilla and area of nipple

2. Arises from the epithelium of hair follicles as an epithelial bud and develops into a gland

3. Secretion is under the influence of hormones and doesn't begin until puberty

4. Secretory products are odorless upon secretion, but when metabolized by bacteria, presents distinct odor

5. Myoepithelial cellls surround secretory portion and assist in expresssing secretory product

6. Secretory cells are cuboidal to low columnar, large lumen

7. Product released through merocrine secretion into canals of hair follices just superficial to ducts of sebaceous gland ducts

8. Innervation from postganglionic sympathetic nervous system

1. Secrete sebum

2. Dermis-hypodermis interface

3. Appendages of hair follicles (like apocrine)

4. Under hormonal control

5. Lobular design

6. Smaller basal cells with rounded nucleus

7. Center of the lobule are cells in different stages of degeneration (pale staining)

8. Holocrine secretion

1. Positioned in stratum basale

2. Attached by desmosomal junctions

3. Prominent in fingertips and lips

4. Function as mechanoreceptors for recognition of touch

5. Unmyelinated sensory fibers traverse basal lamina forming terminal disc at base of cell

6. Neuroendocrine-like granules in cytoplasm

1. Serve as pain receptors

2. Terminal, unsheathed aspects of myelinated nerve fibers, but branch in the dermis prior to extending into epidermis

1. Unmyelinated fibers, lacking Schwann cells and a connective tissue capsule located on areas of the skin especially sensitive to touch (face)

2. Wrapped around the base and shaft of hair and function in touch perception

1. Encapsulated mechanoreceptors

2. Sense fine touch

3. Located in dermal papillae of hairless skin

4. 3-4 nerve terminals and associated Schwann cells encapsuled in corpuscle

5. Stacks of epitheloid cells

1. Mechanoreceptor

2. Senses deep pressure, vibration

3. Located in dermis-hypodermis layer

4. Core formed by modified fibroblasts

5. Core contains single, nonmyelinated fiber that extends the entire length of the capsule with ensheathing Schwann cells

6. Appears like sliced onion

1. Root sheath may be responsible for generation of apocrine sweat glands, sebaceous sweat glands, and replacement of epithelial cells after injury

2. Arrector pili muscles- smooth muscle that extends from the midshaft of the hair follicle into the papillary layer of the dermis controlled by postganglionic neurons  in the sympathetic nervous system  and control the erection of hairs ("goose bumps")

Represent keratinized epithelial cells arranged in plates of hard keratin

1. Hyperpigmented spots located on areas of the skin exposed to sunlight

2. Usually appear around 3 yrs of age

3. Result from an increase in melanin (not an increase in melanocytes)

1. Characterized by an increased proliferation fo keratinocytes

2. Results in increased turnover and accumulations in the stratum corneum that appear as patchy lesions on the surface

3. Incurable

1. Benign epidermal growths that arise from an infection of the papillomavirus

2. Epidermis is thickened and dermal capillaries grow in toward the scaly epidermis

1. Characterized by neoplastic growth  of cells in the stratum basale due to exposure to sunlight

2. Rarely metastasize

1. Presents as a hyperkeratotic scaly plaque that results from proliferation of keratinocytes

2. Locally invasive, may metastasize

3. Caused by carcinogenic agents, soot, UV irradiation, x-irradiation, and arsenic

1. Results from an exposure to UV light

2. Those with red or blone hair and fair skin at increased risk

3. Highly metastatic