Cell Bio- Lecture #3 (Skin & Glands)

Integument

Made up of 2 parts: the cutaneous membrane (skin) and accessory structures (hair, nails, glands)

Cutaneous membrane

The skin; composed of the epidermis + dermis layers

Epidermis

Composed of stratified squamous epithelium; avascular

Dermis

Located between epidermis and subcutaneous layer; anchors epidermal accessory structures

Accessory Structures

Hair, nails, and glands; begin in the dermis and extend through the epidermis

Epidermal ridges

Attached to the dermal papillae; increased surface area improves adhesive strength

Dermal papillae

Structures the epidermal ridges attach to

Keratinocytes

The most abundant cells in the epidermis; produce large amounts of keratin

Keratin

Water-repellent protein produced by keratinocytes that protects from abrasion

Melanocytes

Cells that produce melanin and export it to keratinocytes

Thin Skin

Covers most of the body; has 4 layers of keratinocytes

Thick Skin

Covers the palms of the hands and soles of the feet; has 5 layers

Strata

The 4 (or 5) layers of the epidermis, from basal lamina to surface

Stratum germinativum (basale)

Contains stem cells, melanocytes, and sensory cells in hairless skin

Stratum spinosum

Keratinocytes attach to each other with desmosomes; contains immune cells

Stratum granulosum

Cell division ends, keratin production increases, cells dehydrate & die

Stratum lucidum

Flattened & densely packed keratinocytes with no organelles left (only in thick skin)

Stratum corneum

Surface of the skin; keratinized, interlocked, water-resistant, dead cells, shed after ~2 weeks

Pigments

Along with circulation, influences skin color

Circulation

Along with pigments, influences skin color

Carotene

Orange-yellow pigment found in many vegetables; accumulates in epidermal cells, protects against UV, convertible to vitamin A

Melanin

Pigment (pheomelanin or eumelanin) produced by melanocytes in stratum germinativum; protects against UV

Melanosomes

Transport vesicles in which melanin is stored

Dendrites

Structures via which melanosomes are transferred from melanocytes to keratinocytes

Cyanosis

Bluish skin tint caused by severe reduction in blood flow or oxygenation

Albinism

Inability to produce melanin; results in higher risk for cancer & burns

ABCD

Mnemonic for melanoma warning signs: Asymmetry, Border irregular, Color mottled, Diameter (>5mm is bad)

Jaundice

Bile pigments accumulate in blood due to liver dysfunction; skin & eyes take on a yellow color

Addison's disease

Disease of the pituitary gland causing skin darkening due to increased ACTH secretion

Vitiligo

Loss of melanocytes, causing loss of pigment on patches of skin

Papillary layer

Outer layer of the dermis; areolar tissue containing small capillaries, lymphatics, sensory neuron processes

Reticular layer

Deep layer of the dermis; dense irregular connective tissue with large blood vessels, lymph vessels, nerve fibers

Striae

Stretch marks; result of stretching skin past elastin's tolerance limits

Verhoeff stain

Stain used to make elastin fibers more clearly visible (black)

Shaft

Upper part of hair

Root

Lower part of hair, attached to the integument

Arrector pili

Involuntary smooth muscle that causes hairs to stand up

Sebaceous glands

Oil glands that lubricate hair and control bacteria; holocrine glands secreting onto hair follicles

Hair bulb

Where germinal cells grow hair, and melanocytes provide pigment

Trichrome

A type of stain used in histology

Nail body

Visible portion of the nail; covers the nail bed

Nail root

Hidden site of germination (nail production)

Exocrine

Glands that secrete via ducts onto an external epithelial surface

Endocrine

Glands that secrete into the interstitial fluid/bloodstream

Merocrine

Secretion via vesicular exocytosis

Apocrine

Secretion where the cell sheds part of itself filled with vesicles

Holocrine

Secretion where the cell fills with vesicles and then bursts, killing the cell

Sebum

Oily mixture secreted by sebaceous glands; lubricates, waterproofs, inhibits bacteria

Sebaceous follicles

Secrete directly onto the skin (not associated with hair); contain lipids

Eccrine (Sweat glands)

Sweat glands that secrete on the surface of skin to cool skin and excrete water/electrolytes via merocrine secretion

Apocrine (sweat glands)

Sweat glands in armpits, areolae, near anus; begin function in puberty, secrete into hair follicles

Mammary glands

Modified apocrine sweat glands that produce milk (combination of apocrine & merocrine secretion)

Ceruminous glands

Produce cerumen (earwax); protect the eardrum