Anatomy (integumentary system) (skin)

functions of skin

- keeps water inside the body
- resistance to trauma and infection (cushioning)
- barrier to UV light
- Sensory receptors (pain and pressure)
- Thermoreceptors through sweating
- Excretion and secretion
- Nonverbal communication

epidermis

outermost layer of skin

dermis

middle layer of skin

hypodermis

(subcutis or subcutaneous)

- flexible connection between the skin and underlying muscles and bones

-fat storage (areolar tissue)
- store energy
- insulates

- Contains elastin and collagen fibers loosely arranged to allow the skin to stretch and move independently to underlying structure

- highly vascular (many blood vessels)

stratum corneum

outermost layer of the epidermis, which consists of flattened, keratinized cells

stratum lucidum

skin that makes up the thick skin of the palms and soles of the feet

- translucent layer found in thick skin, absent in thin skin

stratum granulosum

a layer of the epidermis that marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata

- contains visible granules

stratum spinosum

a layer of the epidermis that provides strength and flexibility to the skin

- appears to have thornlike projections

stratum basale

deepest epidermal layer made of a single row of cells that undergo rapid cell division

papillary layer

outer layer of the dermis, directly beneath the epidermis

- has muscles that produce goosebumps and nerve receptors

- areolar connective tissue layer underneath basement membrane

reticular layer

Deeper layer of the dermis that supplies the skin with oxygen and nutrients

- has nerves and blood vessels

- thick dermal layer containing dense irregular connective tissue

Dermal papillae

Found in the upper layers of the dermis, they create your fingerprint pattern

- projections of dermis that causes epidermal ridges

subpapillary vascular plexus

intrinsic network of capillary loops that supply nutrients to cells of epidermis

arrector pili muscle

Involuntary muscle that causes hair to stand on end and goose bumps to appear

subaceous glands

glands that secrete oil into the hair follicle and to the epidermal layer of skin

Eccrine glands

glands that produce sweat; found over most of the body

hair follicle

sac within which each hair grows

hair root

lower part of the hair, attached to the integument

keratinocytes

The most abundant epidermal cells, they function mainly to produce keratin, which makes keratinocytes very tough, scaly, and water resistant

- 90% of epidermis

Melanocytes

-8% of epidermis cells

-produce pigment melanin, contributes to skin color, absorbs damaging UV light

- in the stratum basale

Langerhans cells

(or dendritic cells) ~1% of epidermis

- detects and fights pathogens that attempt to enter the body through the skin
- Epidermal macrophages
- Arise from bone marrow and migrate

Merkal cells

Keratin

tough, fibrous, waterproof protein made and stored in the cells

genetic

(heredity) All people have the same number of melanocytes, but vary in the amount of melanin produced

- Varying distribution and size of melanin granules

- Albinos inherit mutation in melanin genes (lack melanin)

Environmental

- Sun & UV light

- X rays

Physiological

- Oxygenation in blood of dermal blood vessels:
- Pinkish (hemoglobin)
- Cyanosis (bluish)
- Vasodilation/ vasoconstriction of dermal blood vessels

- Accumulation of carotene pigment from diet (carrots and tomatoes)

- Jaundice

apocrine gland

Sweat glands in the pubic and underarm areas secrete thicker sweat, that produces odor when it comes in contact with bacteria on the skin

- hair sweat