1. Chapter 5

2. Structure of the skin Inte- whole Gument – body
Made up of Epithelial and Connective Tissues
Is the largest and thinnest organ in the body
appendages: hair, nails, glands
one square inch of skin contains more structures than some entire organs
thick skin produces prints and has no hair
cutaneous membrane referred to as the integument

3. cutaneous membrane referred to as the integument
Cutaneous Membrane : covers the external body surfaces
Adult skin is about sq. ft and lbs.
thick skin produces prints and has no hair
Ex. Eyelids 1/50” thickness
Ex. Heels 1/8” thickness

4. Structure of the skin Layers of the skin:
epidermis: outermost, made of a thin sheet of stratified squamous epithelium
Epi: above
Has hair
dermis: deepest layer, thicker, made mostly of connective tissue
Lacks hair
subcutaneous layer (hypodermis): lies beneath the dermis
made mostly of loose areolar and adipose tissue
insulates, stores energy, shock absorber
Injections are quick and relatively pain free vs. muscle injections
Fat: up to 10 cm in obese individuals

6. Epidermis Contain keratin: a tough fibrous protein
strata = layers
melanocytes: cells that produce pigment
cells of the epidermis are held together by desmosomes (cell junctions)
Most of the body is covered by thin skin
Ex. Back, arms, etc (hairy skin)
Thick skin
Palms and feet (no hair)

7. Cell layers of the epidermis
1. Stratum corneum; outer most layer of skin
cells continually flake off
Average person sheds about 40 lbs of dead skin cells during their life
25-30 dead cell layers (flat keratinocytes)
millions of epithelial cells reproduce daily to replace the ones shed
Contains keratin and is our bodies 1st line of defense
2. Stratum lucidum: clear layer
found in thick skin
Gel substance “eleidin” that will turn into keratin

8. Cell layers of the epidermis
3. Stratum granulosum: keratinization begins
Process of cells moving layers – gain keratin as they move up!
Cells begin to regenerate
4. Stratum spinosum:
Spiny layer (contains RNA)
5. Stratum basale: base layer (single layer of columnar cells)
only layer where mitosis occurs
new cells move toward surface
Contains keratinocytes (Keratin cells and some stem cells produce new keratinocytes
Stratum Spinosum and Stratum basale make up the growth layer

10. Epidermal growth and repair
Takes about 35 days to regenerate skin
About 5 weeks
this process will speed up if skin is damaged
Constantly replacing itself all of the time
calluses form when mitotic activity increases due to friction
Causes a thick stratum corneum

11. Dermis Deeper of the two layers and much thicker
Called the “true skin”
contains a specialized network of nerves to process sensory info: pain, pressure, touch, and temp
Also includes sweat, oil (subcutaneous gland), blood vessels, and hair follicles.

12. Layers of the dermis
1. Papillary layer: made of collagenous and elastic fibers
when elastic fibers decrease wrinkles develop
dermal papillae: parallel rows of projections
binds skin layers together
form ridges and grooves for prints
ridges develop before birth and never change
allow us to walk upright and grip things
Ridges produce friction which give us traction

13. Layers of the dermis
2. Reticular layer: dense irregular Connective Tissue with collagen & Elastic Fibers
Serves as part of attachments for many muscles
arrector pili muscles: muscle that contracts only when you are frightened or cold (goosebumps)

14. Dermal growth and repair
Doesn’t continually regenerate as epidermis does, only during the healing process
Langer’s lines (cleavage lines): patterns formed by the white collagenous fibers
incisions made parallel to cleavage lines will heal better
elastic fibers that are stretched will weaken and tear (stretch marks)
Pregnancy, growth, and weight
Bluish furrows with jagged edges
Heal and lose color (white)
Scars = Dense mass of Connective Tissue
Blisters – separation in epidermis and dermis layers

15. Skin color Melanin: determines skin color
number of melanocytes is the same, but the amount of pigment produced varies from person to person
Melanocytes = melanin producing cells
The hormone tyrosinase regulates the release of melanin
Albinism – enzyme tyrosinase is absent at birth

16. Factors that determine Skin color
Heredity
Age
Inherited from parents
Lower tyrosinase activity = gray hair
Sunlight – prolonged exposure increase melanin
carotene: yellow pigment that also contributes to skin color
People that live near the equator
Hormones produced by the pituitary gland
ACTH and MSH

17. Skin color Skin can change color depending on blood flow and oxygen
Hemoglobin
Oxygen carrying pigment in RBCs
cyanosis: decrease in blood flow causes the skin to turn bluish gray
Not enough oxygen in the blood
Vessels constrict = pale
Vessels dilate = pinker