1. Epidermis

2. Dermis

1. Protection

2. Sensation

3. Thermoregulation

4. Metabolic function

5. Excretory

6. Absorption

7. Regeneration

1. UV light
2. Dehydration
3. Mechanical (damage to internal organs)
4. Thermal (heat and cold)
5. Chemical insults
6. Invasion of microorganisms (bacteria)

What are the major layers of epidermis?

(5)

1. Stratum Corneum
2. Stratum Lucindum
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basale

Dermis

Location

Inderneath epidermis

Vascular

connective tissues and nerves

Excretory fuction for skin

(3)

• Most common cells in epidermis
• Produce keratin
• Begins synthesis of vitamin D using UV light for calcium homeostasis - converts 7-dihydrocholesterol to D3

• Produce melanin, packages it, and exports into keratinocyte to protect the nucleus from uv rays
• Found in stratum basale and hair follicles (gives you the color of your hair; if your hair is white, you have no or little melanin)

• APC (Antigen presenting cell)- Phagocytic that engulfs bacteria, which breaks it apart, sending pieces of it to membrane (wants to tag itself to make the immune systems cells aware of what it engulfed)
• When stimulated, they migrate via the dernal lymphatics to nearby lymph nodes
• Present antigen to T cells

- Dense irregular connective tissue

- Type I collagen

- Networks of elastic fibers

- Blood vessels

- Nerves and nerve endings

- Interdigitations ("finger-like" projections sticking out of papillary layer) of the dermis and the epidermis which counteract shearing force betweek the two layers

- Prominent in areas that grip or experience friction

- Ex. Finger tips, palms, soles of feet, etc

- Composed of loose connective tissue

- Vasuclar

- Meissner's Corpuscles (very prominent on fingertips- ridges)

- Consists of dense irregular connective tissue

      - Does have loose connective tissue, but arent as prominent

- Cells are mainly fibroblasts/fibrocytes (makes matrix and fibers)

- Pacinian corpuscles- deeper in dermis and is meant for deep pressure

- Downward folds of epidermis - rete ridges

- Upward projections of dermis - dermal papilla

- Arrangement enhances adhesion of the skin

- Fingerprints

- Allows us to pick up things (ex. turn pages, pick up earring)

- Light descriminatory touch

- prominent on fingertips

deeper in dermis and is meant to sense deep pressure

- In skin, joints, connective tissues of organs, etc

1. Meissner's corpuscle

2. Dermal papilla

3. Rete ridge

- Produced by hair follicles

- Consists mostly of dead, keratinized cells

- 2 chief regions- shaft and root

- Hair structure- 3 concentric layers of keratinized cells (medulla, cortex, and cuticle)

- Hair pigment

1. Medulla

2. Cortex

3. Cuticle

- The central core layer of the keritinized cells in the structure of hair

- keeps most animals warm (humans too sparse for this function)

- Hair on scalp protects against physical trauma (protection of brain), heat loss, and sunlight

- Eyelashes and eyebrows shield the eyes from debris

- Smooth muscle attached to the base of the hair follicle; when stimulated, causes hair to stand on end

- Involuntary (smooth muscle)

- Ex. Cats, porcupines 

- Rate of hair growth varies in different body regions (ex. eye brows vs hair on head)

- Life span varies and is under the control of many genes

- Follicles have 3 phases in their growth cycles  (active phase, regressive phase, and resting phase)
- Follicles of the scalp remain active for 6-10 years vs eyebrows of 3-4 months

1. Active Phase

2. Regressive Phase

3. Resting Phase

Active Phase of the follicle growth cycle

(lifespan)

Regressive phase of the follicle growth cycle

(lifespan)

- When follicles reach their limited number of cycles

- Max growth is from teens to 40's

- Occurs when hair is not replaced as fast as it is lost

      - Male Pattern baldness

      - Minoxidil

- Hair thinning can be caused by high fever, surgery, severe emotional trauma, certain drugs, protein deficiency, lactation

- Type of sweat gland

- Exocytosis (just product of cell)

- Found in most areas of the skin 

- Secretes watery fluid

- Thermoregulation (sweat evaporates)

- Type of sweat gland

- Found in axillary and genital regions

- Viscus type of secretion that is discharged into the hair follicles

- Sebaceous gland (cuboidal cells that are packed together)

- Whole cell will be destroyed and secretion will be excreted

- Associated with hair follicles

- Secretes oils into follicle

- Originates in stratum spinosum

- Caused by enviromental factors

- Lesion appears scaly reddened elevation

- Tends to grow rapidly and metastasizes if not removed

Where do most skin cancers originate?

(2)

- Most dangerous skin cancer bc its highly metastic and resistant to chemotherapy

incidence on the rise, can begin anywhere there is pigment, usually appears as a spreading brown to black patch

- Early detection is key

Burns 

(definition)

- Tissue damage caused by intense heat, electricity, radiation, or certain chemicals

- Immediate threat is catastrophic loss of body fluids containing proteins and electrolytes

- Volume of fluid lost can be estimated by computing the percentage of body surface burned - rule of nines

Apply the ABCD(e) rule:

A- Asymmetry; one half has a different shape or pigment spots do not match on each side

B- Border irregularity- the border around the patch is oddly shaped and irregular

C- Color variation- contains several colors in different parts of the patch

D- Diameter - spot larget than 6mm (pencil eraser)

(E)- Elevation above skin surface

- Fluids

- Thousands of extra calories per day for tissue repair - gastric/IV lines to supply supplementary nutrients 

- Burned skin sterile for 24 hours; then bacteria fungi, and other pathogens invade burned area

- Immune system becomes deficient within 1-2 days after injury

- Only epidermis is damaged

- Localized redness, swelling, pain

- Sunburn

Epidermis and upper region of dermis are affected, blisters appear, skin regeneration occurs with little or no scarring

What burn classification involves full thickness of skin, the skin appears gray-white, cherry red, or blackened, and where skin grafting is necessary