what percent of your body is skin

16%

largest organ in your body

• 90% keratinocytes
• 8 % melanocytes
• 2 % you don't have to know

composed of keratinized stratified squamous epithlium

Function: protection

• protein that protects the skin form heat, microbes, chemicals.
• made by keratincytes

• pigment that absorbs uv light and gives skin its color
• secreted and produced by melanocytes

Thin Skin

• has only 4 layers instead of 5.
• missing stratum lucidum
• the stratum corneum (top layer) is also thin
• location: elbows and chest

has all 5 layers plus a very thick layer of stratum corneum.

Location: heels, palms, fingers.

stratum corneum

stratum lucidum

stratum granulosum

stratum spinosum

stratum basale

• top layer
• 25-30 rows of dead cells that are continuously shed and replaced by cells of the deeper strata

• 3-5 layers of dead cells
• missing in thin skin

• 2-5 layers of cells
• undergoing apoptosis (programmed cell death)
• transition between active strata(live cells) and dead strata(dead cells)

• deepest layer
• single row of cuboidal or columnar cells
• some of the cells are stem cells, which can undergo cell division and produce new cells
• new cells are produced here

The whole process takes ~4 weeks

• new cells form in stratum basale and are pushed to surface from one layer to the next
• as they are pushed up they accumulate keratin
• dead cells then fall off and are replaced by the cells from below

Layer of skin deep to the epidermis

composed of:

• blood vessels
• nerves
• ct
• glands
• hair follicles

1. papillary region
2. dermal papillae
3. Reticular region

• makes up top 1/5 dermis
• made of areiolar CT with Elastic Fibers

found in papillary region
projections in the dermis into the epidermis
Function: give blood to the stratum basale and provide the sensations of warmth, coolnes, pain and tickling

Contains:

• blood vessels, misseners corpusles, free neve endings

• deeper 4/5th of the dermis
• made of dense irregular ct
• Function: gives strength, extensibility, and elasticity to skin
• This is the area of skin that stretches while u are pregnant

It absorbs UV light to protect your skin

The difference in skin color is due to the Amount of pigment produced by the melanocytes, not the number of melanocytes present in your body

yellow/ orange pigment found in carrots and eggs.

precursor for Vitamin A. Vitamin A is used for vision

to much carotene can turn you orange

Function: protect by proventing heat loss

made up of dead columns of epithelium bound together by proteins

genetics and hormones influence the thickness and pattern of hair.

attached to each follicle, made of smooth muscle and is connected from the root of the follicle to the superficle dermis

Function: to contract during cold or fright to pull hair shaft perpendicular to skin to help keep heat close body

• visible hair is dead epithelium
• Scalp hair typically grows for 2-6 years then rest for 3 months
• you typically loose 70-100 hairs a day

• illness
• radiation
• chemo
• age
• stress
• gender
• hormones

oil gland that is connected to a hair follicle

Funciton: secrete an oily substance called seabum to keep hairs from drying out

seabum also works to prevent water evaporation fromt he skin, aka keeps skin soft.

sweat gland

function: release sweat on to the skins surface through pores

Eccrine

and

Apocrine

simple most common sweat gland

found in most regions of body especially palms, forehead, and soles

Function: help regulate temperature through evaporation

Sweat Contains:

• 90% water
• sodium and chloride ions
• urea
• glucose
• ammonia
• lactic acid

found in axilla, groin and bearded area.

function: to lubricate

secretion contains thicker fluid due to the presents of lipids and proteins. They are stimulated during emotional stress and sexual excitement aka cold sweats

location: external ear

Function: secretes curumen (earwax) to provide a sticky barrier to prevent foreign particles from reaching the ear drums

plates of packed dead keratinized epithelial cells.

nails grow at a rate of 1 mm a wk depending on season, diet and temp

Function:

protect fingers

grasp small objects

scratch

• Thermoregulation
• Blood Reservoir
• Protection
• Cutaneous Sensations
• Excretion & Absoprtion
• Synthesis of Vit D

touch, pressure, vibrations, and thermal sensations are all located in the dermis

secretes: salts, carbon dioxide, ammonia, and urea.

Absorbs: Vit E, D, K, A and steroids

Sythesis of Vit D

when wound extends to dermis. scar tissue forms and there is a loss of normal function. 4 phases of healing:

1. inflammatory
2. migratory
3. proliferative
4. maturation