The Integumentary system

Chapter 5

The Skin

• Most accessible organ/system to the outside world

• 16% of total body weight• Constantly under attack from the environment• The human body’s first line of defense.

The integument

• Body covering• Interconnected with blood vessels and

sensory receptors.

Two Major Components1. Cutaneous membrane2. Accessory structures

Cutaneous Membrane

EpidermisDermis

Superficial Underlying

connective tissues

Blood Vessels

NervesGlands

Accessory Structures

Hair, nails, exocrine glands

Primarily found in the dermis but protrude (poke through) the epidermis.

Yet another layer. . .

• Below the dermis you can find the hypodermis or subcutaneous layer

– Various connective tissues that separate the skin from other organs

ie: muscles and bones

Skin Functions

• 1. Temperature• 2. Sensory• 3. Moisture Control• 4. Protection

Skin Functions

1. Protection – separate inside from outside2. Excretion salts, water, wastes3. Maintenance body temperature4. Produce melanin5. Produce keratin6. Synthesize vitamin D7. Store lipids and various fat cells8. Detect sensation touch, pressure, pain,

temperature

The Epidermis

• Upper skin surface• Protective, keeps micro-organisms out• Avascular

– Having no blood cells

Made up mostly of keratinocytes (contain large amounts of proteins)

Thick skin vs. Thin skin

Thin Skin• Covers most of the body• Has 4 layers• About the thickness of a

plastic sandwich baggie

Thick Skin• Found on the palms and

soles of feet• And the soles of your feet• Contains an extra layer

• About the thickness of a paper towel

Layers of the Skin

• Stratum Germinativum• Major layer of the skin containing multiple

different cell types

Basal CellsMelanocytesMerkel Cells

Basal Cells – stem cells that become keratinocytes

Melanocytes – produce melanin (skin pigments responsible for skin tone)

Merkel Cells – Sensitive to touch

The other skin layers . . .

1. Stratum spinosum2. Stratum granulosum3. Stratum lucidum4. Stratum corneum

Stratum corneum

Stratum granulosum

Stratum spinosum

Stratum germinativumor Stratum basale

Dermis

The Life of Skin

• Cells move from layer to layer• This process takes between 15-30 days

– Stratum germinatvum stratum corneum

• Last about two weeks before they are shed

Skin Color

2 factors

1. Pigments found in the epidermis2. Circulation through the dermis

Pigments

Carotene• Orange-yellow pigment• In fatty tissues• Tends to be more dominant

in light skinned individuals

Melanin• Brown, yellow, or black

pigment

• Aide in protection and use of UV radiation

Dermal Circulation

• Blood flows through the dermis adding a pink hue to the skin

Epidermal fun facts

When the blood supply to the skin is reduced, the skin turns pale.

Embarrassment usually causes a rush of blood to the surface blood vessels resulting in a flushed appearance.

Sustained circulatory reduction causes cyanosis - blue lips and fingernails. (caused by cold, heart attack, oxygen depletion).

UV exposure causes melanocytes over-production (tan) and the production of vitamin D3 or cholecalciferol.

The liver converts this to a hormone called calcitriol which is necessary for normal Ca and P absorption in the small intestine.

The Dermis

• Lies between the epidermis and subcutaneous

• Has capillaries, connective tissues, and glands• Sensory nerves

a. Nociceptors

Fast pain—sharp (deep cut, needle) Slow pain—burning, aching, throbbing

Thermoreceptors. Free nerve endings 3 - 4 x more cold receptors than warm

Accessory Structures

I. Hair Nonliving—produced in follicles

- 98% on general body surface (not head)

- lose 50/day.

• 3 types: lanugos (prenatal)

vellums (peach fuzz—most of the body)

terminal (heavy, usually deeply pigmented, head).

Glands - two types of exocrine glands: Sebaceous & Sweat.

A. Sebaceous glands (oil glands). Secretes sebum

Sebum—inhibits bacterial growth, lubricates hair and skin.

Sweat glandsApocrine sweat glands are found in the arm

pits, groin, nipples.

This secretion along with bacteria yields 2,3 hexonoic acid.

Merocrine sweat glands are more numerous and more widely distribute.

Adults—2.5 million, high concentration in palms of hands.

Modified sweat glands: mammary glands - milk /ceremonious glands - ear wax

Nails – dead, tightly compressed cells packed with keratin.

Protect exposed tips of fingers and toes.

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Review integumentary repair Review the integration of the integumentary

system with other systems Review burns and grafts

Burns

• 1st Degree Burn• - superficial (involves the epidermis)

- painful, tender and swollen

• 2nd Degree Burn• - partial thickness (involves the dermis and

above)- painful, discolored, blisters, oozing liquid

• 3rd Degree Burn - full thickness burn (beyond the dermis) - not painful, charred(black), or white.