U3 - Epidermis and Intro to Integumentary System

integumentary system

- skin and its appendages

- largest organ of the body is skin

- two (maybe three) layers of this system: epidermis, dermis, hypodermis

epidermis

keratinized stratified squamous epithelium

cells: keratinocytes, melanocytes, merkel cells, Langerhans cells

dermal-epidermal junction

- separates dermis and epidermis

- glue-like layer

- basement membrane

dermis

- made of dense (fibrous) CT

- contains blood vessels, nerves

hypodermis

- areolar and adipose tissue

-> superficial fascia

-> subcutaneous tissue

protection function

waterproof (retention); impermeable to chemicals, heat, cold, bacteria; screens UV

synthesis function

creates Vitamin D with UV light

regulation function

___________ body temperature

excretion function

just small amounts of wastes in sweat

sensory reception

the skin contains nerve endings

immune system

contains cells from this system that help with fighting off bacteria

keratinocytes

most abundant type of cell in the epidermis; produce tough, fibrous protein called keratin

melanocytes

make the dark skin pigment, melanin in the epidermis

every person has the same number of melanocytes - it is the ACTIVITY LEVEL of the melanocytes

Merkel cells

cells in the epidermis associated with sensory nerve endings

Langerhans cells

macrophage-like dendritic (branching) cells in the epidermis

stratum basale (germinativum)

deepest layer of epidermis; single row attached to the dermis, contains the youngest cells

- close to the blood supply in the dermis

-> only stratum healthy enough to reproduce

-> daughter cells here are pushed upward as more cells are produced and eventually die

-> will be hardened with keratin as they make their way to the top

Britney

stratum spinosum

second deepest layer of epidermis; includes tonofilaments (help with flexibility)

Spears

stratum granulosum

flattened keratinocytes; one of the middle layers of the epidermis (either middle or second most superficial)

Grows

stratum lucidum

layer of epidermis found ONLY in the thick skin of palms, soles, and fingers (second most superficial if present)

Like

stratum corneum

most superficial layer of the epidermis consisting of dead cells; many layers thick

Candy

carotene

yellow-orange pigment used in skin color, derived from carrots and yellow veggies

hemoglobin

oxygen carrying pigment, refers to the pink of light skin

melanin

most important type of skin pigment

-> more active melanocytes = more melanin in keratinocytes = darker skin

Two Different Types: eumelanin & pheomelanin

Production Determined By:

- UV exposure

- genetic makeup (polygenic inheritance & multiple alleles)

- size of melanocytes

- disease conditions

eumelanin

the most common form of melanin; brownish in color

pheomelanin

reddish-brown color often associated with freckles and red hair

UV radiation

- destroys / mutates DNA

- promotes cancer

- destroys folate

+ permits Vitamin D production

Three Different Types in the Picture