Chapter 22 Section 4

List 4 functions of the skin

Describe the 2 layers of the skin

Describe the structure and function of hair & nails

Describe 2 kinds of damage that can affect skin

1 sq. inch of skin can hold as many as: 650 sweat glands 20 blood vessels More than 1,000 nerve endings

No 2 people have the same fingerprints

More than ¾ of the dust in some homes is made up of dead skin cells!!!!!!

Only mammals have true hair

Visible signs of aging occurs most in this system: age spots, wrinkles, gray hair, less active seat glands

Hair that is kept short grows an average of 2cm per month; growth slows to 1cm per month for hair longer than 30 cm

Fingernails grow ~ 2 cm each year (middle finger is the fastest!) 3x quicker than toenails!

Composed of the skin, hair, nails

Covers your body and helps to maintain homeostasis

1. Protects: keeps water in your body and foreign particles out

2. Nerve endings keep you in touch with the outside world; you can feel the world around you

3. Helps to regulate body temperature (sweat glands)

4. Helps to get rid of wastes; removed in sweat

Skin color is determined by melanin

A lot of melanin, skin is dark; little melanin, light

Melanin absorbs UV light from the sun

Helps to reduce damage that can lead to skin cancer (all skin still needs to be protected!)

Skin is a complex organ:

Composed of: Blood vessels Nerve fibers Hair follicles Muscle fibers Oil glands Sweat glands

http://www.factmonster.com/images/ESCI351SKIN003.gif

Skin is the largest organ in the body

In an adult it covers an area of about 2m²

2 main layers Epidermis: outermost layer

Dermis: the thicker layer that lies beneath

Made of epithelial tissue

Made of many layers of cells, but is only as thick as 2 sheets of paper (thicker on palms of hands & soles of feet)

Most cells here are dead

The cells are filled with a protein called keratin (makes the skin tough)

http://www.naturalrussia.com/nr/images/skin_structure.gif

http://www.dermnetnz.org/doctors/principles/images/epidermis.jpg

Lies beneath the epidermis

Has many fibers made of a protein called collagen (fibers that provide strength)

Collagen fibers let skin bend without tearing

Contains many smaller structures Sweat glands, follicles, nerve fibers, fat cells,

blood vessels, oil glands, muscle fibers

http://1stholistic.com/Beauty/images/skin-section.GIF

Important part of the system

Like skin, hair & nails are made of living & dead cells

Hair forms at the bottom of a tiny sac called a hair follicle

Hair grows as new cells are added at the hair follicle

Older cells get pushed upward

Only living cells are in the follicle

Like skin, hair gets its color from melanin

Hair helps protect skin from UV light

Keeps particles (dust, insects) out of eyes and nose

Helps regulate temperature (muscles in follicles contract) – trap warm air and warm body

http://www.infovisual.info/03/037_en.html

Nails grow from living cells in the nail root at the base of the nail

As new cells form, the nail grows longer

Protect the tips of fingers and toes

Allows your fingers and toes to remain sensitive for touch

http://www.drstandley.com/images/fingernail.gif

Your skin can usually repair itself when injured

Damage to genetic material can cause skin cancer

Skin is also affected by hormones (over produce in oil glands) – leads to acne when bacteria clog hair follicles

http://www.path.cam.ac.uk/partIB_pract/P03/image04.jpg

A blood clot forms over a cut to stop bleedingKeeps bacteria from entering the woundBacteria fighting cells come to kill bacteria in the areaDamaged cells are replaced through cell divisionA scar is all that is left on the surface

What are the 4 functions of the skin?

Describe 2 layers of the skin