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32 Cards in this Set

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Integumentary System (skin)
*Epidermis (keratinized stratified squamous epithelium) and Dermis (dense CT)
- Hypodermis (contains variable amts of adipose tissue arranged into lobules separated by CT septa).

*Skin Derivatives:
- hair follicles and hair
- sweat glands
- sebaceous glands
- nails
- mammary glands

* 2 Subclasses:
- thick (hairless skin- ex: palms of hands)
- thin (thinner epidermis elsewhere)
Skin Function
- barrier (keeps infection out and keeps water in; also UV protection)
- immunological
- homeostasis (regulates body temp, water loss)
- sensory (conveys sensory info about the external environment)
- endocrine (hormones, growth factors)
- excretion (sweat, oils, etc)
Epidermis (4 layers)
Bottom to Top:
- Stratum Basale
- Stratum Spinosum
- Stratum Granulosum
- Stratum Corneum
- Stratum Lucidum

*the top of the epidermis is stratified squamous, the bottom is more cuboidal
Stratum Basale
aka stratum germinativum
- presence of mitotically active cells, the stem cells of the epidermis
Stratum Spinosum
-striped outer margin; tonafilament
- also called the spinous or prickle cell layer because of the characteristic light microscope appearance of short processes extending from cell to cell
Stratum Granulosum
3-5 cells thick; produce keratin-containing cells
- contains numerous intensely staining granules
Stratum Corneum
keratinized outermost layer' gets sluffed off; anucleate (few organelles)
- composed of keratinized cells
Stratum Lucidum
even more keratinized; found in very thick skin
- considered a subdivision of the stratum corneum
Keratinocyte (85% of skin cells)
*Major cell type of the epidermis
*2 functions:
- produce keratin and set up water barrier
*Keratinization:
- kertohyalin granules:
filaggrin and trichohyalin (proteins of kertohyalin granules)

*keratinocytes in the stratum spinosum produce (besides keratohyalin granules) lamellar bodies

*Basal cells of keratinocytes start creating tonafilaments (precursors of keratin)
Water Barrier
- start appearing at spinosal layer

*Cell envelop:
- insoluble proteins on inner plasma membrane (loricrin (major structural protein) cross-linked with others)
- SPRs (small proline-rich proteins)

*Lipid envelop:
- lipid layer attached to outer membrane
- lamellar bodies
Melanocytes
- pigment-producing cell
- develop UV barrier via Melanin production
- melanocyte found only in stratum basale

*Dendritic cells with long processes that extend btwn the karatinocytes
*Epidermal-melanin unit (ratio of melanocytes to karatinocytes- varies over body areas)
Two main pigments produced by melanocytes
1. Eumelanin (brown)- most common
2. Pheomelanin (red)

- the amount of each is genetically determined
Pigment donation
- developing melanosomes and their melanin contents are transferred to neighboring keratinocytes by pigment donation)

*premelanosomes (initial reaction of melanin production occurs here; these are membrane-bound structures derived from the Golgi apparatus)
*early melanosomes (have a low melanin content)
*mature melanosomes (as more melanin is produced, the internal structure of the premelanosome becomes obscured until the mature melanosome is formed and then appears as an electron-opaque granule)

*Variation in skin color:
- degradation
- pigment type
- UV

*melanin surrounds nucleus to protect from UV

*granules are phagocytosed into keratinocyte
Albinism
caused by a defect in enzyme necessary for melanin production
Two other cell types
1. Langerhans cells (induce immune response)
- they are antigen presenting cells in the epidermis
- dendritic
- MHC I and MHC II (these are expressed here- macrophages have these too)

2. Merkel's Cells (sensory)
- associated with nerve ending
- Merkel's corpuscle (the combination of the neuron and epidermal cell)
- found in stratum basale
- they are most abundant in skin where sensory perception is acute, such as fingertips
Skin "disorders"
- excessive melanocyte production
- freckles are localized excess production of melanin
- it is a genetic component and is more noticeable in fair skin
- age-related (most disappear as we age)
UV
* Basal Cell Carcinoma- mutation of basal cells causing uncontrolled division

*Melanoma- melanocyte damage; most dangerous form of skin cancer; can be fatal

- carcinomas are rarely fatal if detected early
- squamous cell carcinoma= basal and squamous cell damage
Cancer Detection
A= asymmetrical
B= irregular border
C= color
D= large diameter
Psoriasis

Addison's disease
- a pronounced flaking. It's a higher amount of division going on in the basal cells, so basal cell lifecycle is shorter.

- hormone imbalance; darkening of the skin (exposed and unexposed areas). JFK had it.
Vitiligo
-melanocytes in certain regions get destroyed and it causes white patchiness. Occurs in all races, not sure of the cause. (this is what Michael Jackson says he has)
Dermis
* Dermal papillae- extend upward
* Epidermal ridges- extend downward
- these two give the skin adhesion and are thicker in areas of wear and tear

*Two layers:
- papillary layer- where the papillae are
- reticular layer- underneath the layer; dense CT

- the hypodermis is the region between the dermis and CT
Nerve Supply
*Free Nerve Endings:
- terminate in stratum granulosum
- lack CT or Schwann cells
- touch, heat, cold
- also surround hair follicles

- free nerve endings are endings coming up and terminating in epidermis and the free axons are in the epidermis. Involved in senses (touch, heat, cold); no Schwann cells.

- Merkel's cells- in epidermis, react with free axons to help sense touch, etc.
Encapsulated Nerve Endings
1. Pacinian- axon coming in, terminating, and multilayers around the nerve ending

2. Meissner- multiple axons coming into encapsulated structure; seen in dermal papillae. Found in areas with no hair (lips, feet).

3. Ruffini- good at sensing stretch (found in joints); branching.
Skin Appendages
*Hair follicles
- hair is their product
*Sebaceous glands
- sebum is their product
- sebaceous glands a lot of times dump their products directly into the follicle of the hair
* Eccrine Sweat glands
- sweat is their product
*Apocrine Sweat glands
- have a mixed product (a protein-rich secretion containing pheromones)
- these glands are limited to the axilla, areola and nipple of the mammary gland, skin around the anus, and the external genitalia.
Hair Follicles
* Hair follicle:
-Dermal Papillae- circulatory system; critical in producing hair; at the base of the bulb
- Hair bulb:
Medulla (in center, made of cells that become keratinized when they come up)
Cortex (much more highly keratinized and melanocytes are associated and give our hair its color)
Cuticle (outermost layer)
- Internal Sheath (starts out multilayered and decreases. It is a cellular covering that surrounds the deep part of the hair)
- External Sheath (starts out single layered and becomes multilayered; becomes connected to epidermis. It is the outer root sheath)
*Arrector pili muscle
Skin vs Hair keratinization
Skin:
- relatively soft keratinized outer layer
- continuous and over entire surface
- mature cells similar

Hair:
- hard compact keratinized layer
- intermittent
- differentiate into various cell types
Nails
* Eponycium- aka cuticle
* nail root- underneath; where the nail itself is being produced
* hyponycium- where nail connects to the skin

- vascularization gives the nails their color
- it is a highly keratinized structure
Glands
- merocrine- secretory product is delivered in membrane-bounded vesicles to the apical surface of the cell.
- apocrine- the secretory product is released in the apical portion of the cell.
- holocrine- the entire cell layer releases/ruptures. The secretory product accumulates within the maturing cell, which simultaneously undergoes programmed cell death.
Glands of Skin- Sebaceous
- embedded in dermis
- responsible for producing sbum (oily substance). May have an antibacterial component.

*dermis
*holocrine gland
*acinar gland
*connects with follicle
*produces sebum
Seborrheic dermatitis
overproduction of sebaceous glands; about 10-30% of population; starts in your 30's and causes flakiness or redness
Glands of skin- sweat
*Sweat glands- two main groups:
1. Apocrine- not uniform (concentrated in certain areas- ex: armpits); secrete into hair follicles and out. Bacteria causes the smell.

2. Merocrine- uniformally distributed throughout the body; ducts lead directly into skin and involved in thermoregulation. 99% of the sweat is water.
Epidermal Ridges in CSI
- the ridges come up in certain areas (fingers, palms of hands, feet)
- multiple genes are associated with this ridge pattern.