Chapter 5: Skin

Functions of the Skin

1. Protective barrier

2. Prevents loss of moisture

3. Reduces effects of UV radiation

4. Acts as a sensory organ

5. Regulates temperature

6. Produces vitamin D

Layers of the Skin

1. stratum corneum

2. stratum lucidum

3. stratum granulosum

4. stratum spinosum

5. stratum basalis

Stratum basale

one row of cuboidal or columnar cells that produces keratinocytes

stratum spinosum

8-10 layers thick, cells flatten as they become more superficial, cells produce keratin, provides flexibility to the skin

stratum granulosum

keratinocytes are flatten and undergo cell death

stratum lucidum

only found in thick skin, cells are clear and dead, they contain keratin and thickened plasma membranes

stratum corneum

thin cells in many layers, cells no longer contain organelles, top layer of the skin

Cells found in the epidermis

1. Keratinocytes

2. Melanocytes

3. Langerhans cells

4. Merkel cells

Keratinocytes

The most abundant epidermal cells, they function mainly to produce keratin, travel from bottom layer to the top

Melanocytes

cells that produce melanin and protect against UV damage

Pigments that determine skin color

melanin, carotene, hemoglobin

Langerhans cells

Type of immune cell that originates in the bone marrow and migrates to the epidermis

Merkel cells

touch receptors in the skin located within and just below the deepest layer of the epidermis

Regions of the dermis

papillary and reticular

papillary region

the top layer of the dermis composed of connective tissue and the dermal papillae

reticular region

the deeper part of the dermis consisting of dense irregular connective tissue

Tattoos are created in the…

Dermis

Jaundice

yellowing of the skin and the whites of the eyes caused by an accumulation of bilirubin in the blood, indicates liver disease

Cyanosis

a bluish discoloration of the skin resulting from poor circulation or inadequate oxygenation of the blood

Erythema

redness of the skin due to capillary dilation

Functions of epidermal ridges

1. Create fingerprints

2. Increase grip

3. Increase nutrient exchange from dermis

4. Strengthens against shear forces

subcutaneous layer

connective and adipose tissue layer just under the dermis that binds the skin to the organs

Functions of the hair

1. protects eyes

2. heat retention

3. sensory reception

4. Decreases sunburn

Structure of the hair

1. Shaft (visible)

2. Root (below the surface)

3. medulla, cortex, cuticle

Arrector pili

a smooth muscle attached to hair follicles that causes "goose bumps" to appear on the skin when contracted, contract with cold or fear

Hair root plexis

Detects hair movement

Lanugo

fine downy hair of newborn infant

vellus

fine, pale hair that replaces lanugo by time of birth

terminal

pigmented hair that replaces vellus during puberty

Structure of nails

1.free edge

2. body

3. lunula

4. eponychium (cuticle)

5. nail root

Glands of the skin

1. Sebaceous (oil) glands

2. Sudoriferous (sweat) glands

3. Ceruminous (wax) glands

4. Mammary (milk) glands

sebaceous glands

secrete sebum (oil) into the hair follicles where the hair shafts pass through the dermis, moistens hair, softens skin, inhibits bacteria

sudoriferous glands

Sweat glands, eccrine are extensive, apocrine only in axilla, pubis, and areolae

ceruminous glands

modified sweat glands, located in external ear canal, secretes cerumen (earwax)

Epidermal wound healing

Abrasion or minor burn Basal cells migrate across the wound Epidermal growth factor stimulates cell division Full thickness of epidermis results from further cell division

Deep wound healing

inflammatory phase, migratory phase, proliferative phase, maturation phase

Aging of the skin

Epidermal replacement slows, skin becomes thin, dry and itchy (decreased sebaceous gland activity) Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles

basal cell carcinoma

Most common and least severe type of skin cancer, occurs in basal cells, often characterized by light or pearly nodules

squamous cell carcinoma

Type of skin cancer more serious than basal cell carcinoma, arises from squamous cells, often characterized by scaly red papules or nodules.

Melanoma

The most serious form of skin cancer arising from melanocytes, very aggressive and spreads rapidly

ABCDE Method

Asymmetry, Border irregularity, Color, Diameter, Evolution

1st degree burn

only epidermis is damaged, skin functions remain, heals in 3-6 days

2nd degree burn

epidermis and part of dermis damaged

3rd degree burn

All three layers have been effected, most skin functions lost, skin graft may be needed for healing