• Protection- mechanical, chemical, bacterial

• Body temperature regulation• Prevent water loss• Metabolic- synthesize vitamin D• Cutaneous Sensation• Blood reservoir• Excretion• Prevent UV damage

An organ, cells constantly dying and being replaced

Facts:• Weighs 9-11 lbs• s.a. = 1.5-2m2

• 1 cm2 has 70 cm blood vessels, 55 cm nerves, 100 sweat glands, 15 oil

glands, 230 sensory receptors• New skin produced in 25-45 days

• Keratinocytes (90%)- waterproofs & protects

skin, nails, hair, stratum corneum

• Melanocytes (8%)- produce melanin

• Merkel Cells- slow mechanoreceptors

• Langerhans’ Cells- immunological defense

• Stratum Corneum

• Stratum Lucidum

• Stratum Granulosum

• Stratum Spinosum

• Stratum Basale-

(Germinativum)

Dermis

papillary dermis

reticular dermis

a. Cellular

Fibroblasts (synthesize collagen, elastin, and reticulin), histiocytes, endothelial cells, perivascular macrophages and dendritic cells, mast cells, smooth muscle, and cells of peripheral nerves and their end-organ receptors.

b. Fibrous

Collagen & reticulin - provide tensile strength

Elastic fibers- provide for restoration of shape after a deformation

c. Ground substance

glycosaminoglycans: hyaluronic acid, chondroitin sulfate, and dermatan sulfate.

This layer contains adipose tissue and serves to attach the dermis to its underlying tissues.

Hypodermis

Some variations in human skin color(Sub-Saharan African, Indian, Southern European, and Northwest European)

Melanin Pigments:• Eumelanin: • Phaeomelanin

> Eumelanin:Phaeomalanin- darker skin and hair color;< Eumelanin:Phaeomalanin- lighter skin and hair color

Skin color due to: Melanin, Carotene & Hemoglobin

I -light skinned, burns easily, never tans

II - light skinned, burns easily, tans some

III - light skinned, burns occasionally, tans well

IV - light skinned, tans well, rarely burns

V - brown skinned (Asian, Indo-Asian, Chinese, Japanese), tans well, burns rarely, can sunburn after prolonged exposure to UVR

VI - black skinned (Afro-Caribbean), deeply pigmented, can burn after prolonged exposure to UVR

25% US pop

Human complexions are generally classified into six skin types:

• Cyanotic• Jaundice• Erythema• Pallor

• Pigmentation levels usually increase with age.

- exception: premature graying• Normal pigmentation may be altered by

genetic defects or by acquired diseases. -Hyperpigmentation- age spots -Hypopigmentation- vitiligo, albinism

External agents can also alter skin color.

• lightening agents

• carotene

• dyes

• Some internal compounds--such as the byproducts of hemoglobin metabolism--may color the skin.

            

                Sunless tanning

Malignant melanoma

• 2% of all cancers

Risks:

1. Skin type

2. Sun exposure

3. Family history

4. Age

5. Immunological status

            

                

• A= asymmetry

• B= border

• C= color

• D= diameter

Normal mole Melanoma

Sweat Glands

• Eccrine (merocrine) glands- sweat• Apocrine glands- axillary & anogenital areas• Ceruminous glands- ears canal• Mammary glands- female reproductive glands

Ceruminous glands

Sweatglands

Sebaceous

Hair

Sebaceous gland

Hair shaft

Hair root

Hair bulb in follicle

Nail

1st Degree: epidermal damageEx. sunburn

2nd Degree: epidermis & upper dermis

Ex. blisters

3rd Degree: entire thickness of skin

Skin replacement: http://www.youtube.com/watch?v=eXO_ApjKPaI

• Blood vessels dilate• WBC & clotting agents released• Scab forms

• Granulation tissue forms• Capillary beds invade clot• Clean up begins

• Scar area has contracted • Epithelium regeneration begins

1. In which lay of skin are blood vessels located? 2. Where does epithelium regeneration begin?3. What color is a persons skin if they are cyanotic?4. List the layer of the epidermis in order from top to

bottom.5. What is the primary tissue of the hypodermis?