skin structure & function

The SKIN“STRUCTURE & FUNCTION”

General Info……..• Skin has 3 layers• Epidermis - outer layer• Dermis – inner layer• Hypodermis – sup. Fascia

or fat

• Sweat glands excrete sweat through pores.

• Body’s first line of defense!

• Largest organ of the body.

The “Birthday Suit”

– Combination of 4 main tissues:•Epithelial – outer layer•Connective – underlies dermis•Smooth Muscle – goose bumps•Nervous – sensory receptors

Epidermis and Dermis– Epidermis is avascular (no blood

vessels) & arises from ECTODERM– Dermis is highly vascular (has

blood vessels) & arises from MESODERM

– Epidermis receives nourishment from dermis

– Cells far away from nourishment die

EPIDERMIS DERMIS

Embryonic origin

Type of Tissue

Epidermis• Outer tough layer of dead

skin cells called cuticle .• Layer you see everyday.• Under the cuticle is

another layer of living epithelial cells that make up the rest of the epidermis.

Epidermis

What about stratum lucidum…???

Dermis• Thick layer under the epidermis

• Contains – blood vessels – Nerves– Oil glands– Sweat glands– Hair follicles– Fat tissue– Connective tissue

Two layers– Papillary layer (upper dermal region)

• Projections called dermal papillae – Contain capillary loops containing

blood– Pain receptors and touch receptors

– Reticular layer (deepest skin layer)• Blood vessels• Sweat and oil glands• Pressure receptors

•

FOR YOUR KNOWLEDGE……..

In the thick skin on the palms and soles, the epidermis conforms to the shape of the underlying dermal papillae, forming ridges and valleys that we know as fingerprints. These ridges provide traction that helps people grasp objects and surfaces

• Some dermal papillae (mostly THICK SKIN) contain touch receptors called Meissner’s corpuscles, and many contain loops of tiny blood vessels.

Which plays an important role in the regulation of body temperature.

What causes Normal Skin Color…???

•Melanin– Yellow, brown, or black pigments

•Carotene– Orange-yellow pigment from some vegetables

•Hemoglobin– Red coloring from blood cells in dermal

capillaries– Oxygen content determines the extent of red

coloringFOR YOUR KNOWLEDGE……

All races have the same number of MELANOCYTES, but the amount of melanin produced determines whether the colour of the individual will be BLACK, BROWN or white

Types of SKIN No. Structure Thin skin Thick skin

1. Epidermis : stratum lucidum & epidermal ridges

Absent Present

2. Hair follicles Present Absent

3. Sebaceous glands Present Absent

4. Sweat glands Few More

5. Sensory nerve ending

Few More

What Else Comes from the Epidermis?

I think so “SKIN APPENDAGES”

–Hair–Glands–Nails

Hair

Glands

Nail

FUNCTIONS of SKIN1. Protective

– Mechanical– Chemical– Biological– Radiational

2. Sensations3. Maintaining

Balance– Electrolytes balance– Thermal balance

4. Metabolic– Fat– Vit - D

5. Esthetic6. Absorptive7. Excretion

– Sweating 8. Storage

– Fat, water, Cl- & sugar

BLOOD SUPPLY of SKIN

NERVE SUPPLY

Use the following vocabulary to label the diagram: 1. hair2. oil gland 3. fat cells, 4. erector pili muscle, 5. blood vessels, 6. nerve endings, 7. epidermis, 8. dermis, 9. Dead cells, 10. Live cells, 11. hair root, 12. sweat gland, 13. connective tissue