CHAPTER 5

The Integumentary System

The Integumentary System

The parts of the integument:SkinSweat and Oil glands hairsNails

The Integumentary System: The Skin

The skin is pliable yet tough, allowing it to take constant punishment from external organs.

Facts:Covers 2.2 meters, weighs 4 to 5 kg, and

accounts for about 7% of total body weight in the average.

Thickness varies from 1.5 to 4.0 mm or more in some areas.

Millions of dead cells rub off dailyA totally new epidermis every 25 to 45 daysThe average person sheds 18kg (40lbs) of skin

flakes in a lifetime

The Skin

The Skin: Epidermis

The epidermis is a keratinized stratified squamous epithelium consisting of four distinct cell types or five distinct layers.

Cells of the epidermis:1. Keratinocyte produce keratin2. melanocyte produce melanin3. Langerhans’ cell are

macrophages4. Merkel cells (epidermal

dendritic cells) function as a sensory receptors for touch

Layers of the EpidermisThick skin: covers the

palms, fingertips, and soles of the feet

Five Layers (strata) from deep to superficial

1. stratum basale2. stratum spinosum3. stratum granulosum4. stratum lucidum5. stratum corneum

Thin skin: covers the rest of the body

**stratum lucidum is absent and the other strata are thinner

The Skin:Dermis

The dermis, composed mainly of dense, irregular connective tissue, is well supplied with blood vessels, lymphatic vessels, and nerves.

Cutaneous receptors, glands, and hair follicles reside within the dermis

Layers of the dermis

From superficial to deep:1. papillary layer exhibits

dermal papillae that protrude into the epidermis above and the epidermal ridges that produce fingerprints.

2. reticular layer is thicker and the connective tissue fibers are much more densely interwoven.

Skin Color

Skin color reflects the amount of pigments (melanin and carotene) in the skin and the oxygenation level of hemoglobin in blood

1. Melanin is the only pigment made in the skin.

ranges in color from yellow, redish brown, to black

Stimulated by exposure to ultraviolet radiation in sunlight and protects the nuceli from damaging effects of UV radiation

Homeostatic Imbalance

1. stiae = stretch marks Tears in the dermis

2. blisters = separation of dermis and epidermis

Homeostatic imbalance

Excessive sun exposure can cause clumping of elastin fibers, leading to

leathery skin, temporarily depresses the immune systemAlter the DNA of skin cells which may cause

cancer

Homeostatic Imbalance

1. Cyanosis = poorly oxygenated blood

Homeostatic imbalance

Redness, or erythema = redding of skin

Pallor or blanching

Homeostatic balance

Jaundice or yellow cast =

Homeostatic imbalance

Bronzing =

http://www.aldfoundation.org/materials.html

Homeostatic imbalance

Black-and-blue marks; bruises; hematomas

Appendages of the Skin

Skin appendages, which derive from the epidermis, include:

HairsHair folliclesNailsGlands

Sweat (Sudoriferous) Glands

Found all over the body except the nipples and the external genitalia

More than 2.2 million per person

Sweat glands: Eccrine glands

Merocirne glandsFound over most

of the bodyThermoregulationSweat is 99%

waterSalts, Vit C.,

antibodies, metabolic wastes and lactic acid

Sweat Gland: apocrine

Largely confinded to the axillary and anogenital areas

Larger than eccrine glands and their ducts empty along hair follicles

Start production around puberty

Function is unknownCerunminous glandsMammary glands

Sebaceous (oil) glands

Located all over body except palms of hands

SebumFunctions to softens

and lubricates the hair and skin

Prevents hair from becoming brittle, and slows water loss from the skin

Bacterialcidal action

Homeostatic imbalance

WhiteheadsBlackheadsAcne Seborrhea “cradle

cap”

Hairs and Hair Follicles

Hair: main function is sensory protection