The Integumentary System

Components

• Skin

• Nails

• Hair follicles

• Sebaceous glands(oil and wax)

• Sweat (sudoriferous) glands

Functions of the Skin– Protection (1st line of defense)

– Regulates body temp.

– Conserves water inside body

– Contains sensory receptors

– Makes biochemicals

– Excretion of wastes

*Skin is the largest organ of the body

Layers of SkinSkin has 3 layers1. Epidermis - outer layer2. Dermis – middle layer3.subcutaneous/hypoderm- bottom/deepest layer

1. Epidermis

• Outer layer of skin cells• Avascular- lacks blood vessels,

fed by diffusion• Acts as a mechanical barrier• Made of many layers of cells• Top cells dead• Bottom layer alive- multiply and

new cells are pushed upward (EX-”Ashiness” is caused by this layer of dead

skin cells being very rough and raggedy.DUST you see around is made up of dead skin

cells! )

Epidermis• Keratinization- process where

keratin develops in a cell, which hardens it, and makes the cell layer waterproof– Contains melonocytes- cells

which contain the pigment melanin

– Difference is skin color is due to % of melanin in the cell .( We all have the same # of cells, just produce a different amt. of melanin.)

– Amt. of melanin increases with UV light exposure

– Too much exposure=melanoma (skin cancer)

The Skin

Layers of Epidermis5 layers “Cows Love Grass So Badly”

1)Stratum corneum (corny/scaly)

2)Stratum lucidum (palms of hands, feet, absent in thin skin)

3)Stratum granulosum(granular)

4)Stratum spinosum(spiny/prickly)

5)Stratum basale (base/bottom)

*1st degree burns

Epidermis

2. Dermis• Thick layer under the epidermis

• Collagen, elastic layer

• Contains blood vessels

• Oil glands (sebaceous)

• sweat glands• Hair follicles• Nerves*2nd degree burns

3. Subcutaneous LayerAKA- Hypodermis

• Contains Fat tissue in adipose cells– Thickens w/ weight gain

• Stabilizes position of skin• Insulates(temp. regulation)• Larger branches of blood vessels

*3rd degree burns

Human Anatomy, 3rd editionPrentice Hall, © 2001

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Review-Layers of Skin

1. Name the 3 layers of the skin.2. What are the 5 layers of the epidermis from

the outside of the body to the inside?3. The top layer of the skin is the?4. The layer that contains fat and thick blood

vessels is _____________.5. Which layer is avascular?6. What layers have been burnt if a second

degree burn occurs?

Accessory Organs of the Skin

1. Hair/hair follicles

2. Sebaceous glands

3. Nails

4. Sweat glands

Hair Structure

– Found in Dermis of skin– Cells of hair follicle grow and develop in the

blood vessels– As cells move upwards they become

keratinized and die– Melanin – pigment that contributes to dark

hair color

Arrector Pili

–Smooth muscle attaches to follicle

–Raises hairs

–Response to fright or cold

–Pulls hairs upright to create a layer of warm air on surface of skin

Functions of Hair–Protection

–Sensory perception

–Thermoregulation (insulation)

-Minor role in humans (exception-

Hypertrichosis)

Hair Structure

Sebaceous Glands

• Connected to hair follicles

• Secrete a waxy, oily substance (sebum)

• Functions of Sebum-

-keeps skin soft

-keeps skin pliable

-keeps skin waterproof

• Secretion increases at puberty

Sebaceous Glands

Nail Function and Structure– Function-

Protective covering on fingertip used for picking, scratching, grooming

– Keratinized, stratifies squamous cells make nails hard– Nail root bed – area where new cells are formed

Sweat Glands

– Sweat glands• Found just about everywhere on body• Dermis layer of skin• Produce sweat aka perspiration

–Water, salt, wastes (toxins), urea, and uric acid

• Function – cooling of the body, releasing scent, producing milk, ear wax

Sweat Gland Types

Eccrine and Apocrine, two types are different in size and the age they become active –Eccrine- most numerous type, found all over the body particularly on the palms, soles of the feet, and forehead, exits pores–Apocrine is mostly the armpits. They end in hair follicles instead of or pores.

• modified- includes scent glands, mammary glands, ceruminous (produce ear wax), ciliary- eyelid

The Skin with Sweat Glands

Checkpoint

1. What are accessory organs of the skin?

2. What is attached to each hair that produces oil?

3. Sweat glands are located in the ________.

4. What type of fluid is created by the sebaceous gland?

5. What is sweat made of?

6. What are functions of sweat?

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The skin also helps control body temperature- Homeostasis!

• When you sweat, heat leaves the body through your pores.

• When the sweat hits the outer surface of the skin, it is cooled by the air.

• This lowers your body temperature.

Regulation of Body Temperature• Normal body temp- 37 C, 98.6-98.8 F

• Controlled by hypothalamus of brain

• Amt. of heat produced is balance by the amt. of heat lost

• Cellular chemical rxns create heat

• Muscle contraction creates heat

• Homeostatic response when exposed to an increase in

temp. or a dec. in temp.

What happens if body temp. is too high?

What happens if body temp. is too high?

Body has mechanisms to rid itself of excess heat-

1.Warmed blood reaches hypothalamus nerve impulses respond more blood sent to limbs flushed skin

2.Vasodilation- blood vessels dilate, skin releases heat

3.Activation of sweat glands- moisture allows more heat to be released

Outcome- Overall temp. decreases

What happens if body temp. is too cold?

What happens if body temp. is too cold?

Mechanisms to save heat and create heat in response to cold-

1.Thermoreceptors send signals to hypothalamus

2.Vasoconstriction- blood vessels constrict to reduce heat loss more blood in corepale

3.Deactivation of sweat glands

4.If temp. is still too low, muscles will contract (shivering) to create heat

Outcome- Increase in overall body and blood temp.

Checkpoint

1. What is the normal body temperature?

2. What part of the brain controls temp.?

3. How does the body respond to too much heat?

4. How does the body respond to cold temp.?

5. What type of muscle contracts to cause shivering?

6. What is the difference between vasoconstriction and vasodilation?