Integumentary System
Your skin is the human body’s largest organ. It is
the first line of defense against pathogens disease-causing agents such as bacteria, viruses
and fungi. Your skin helps regulate your body
temperature, removes waste products through
your sweat glands, and provides protection from
UV radiation.
The skin has 3 main layers.
1. Epidermis – This is the outermost layer of skin. The epidermis
contains 5 layers. The top or uppermost layer is called the stratum
corneum which means “horny layer”. It is a flattened layer of dead
cells that are typically sloughed off every few days. This allows for a
new layer of skin cells to emerge from beneath the stratum corneum.
The epidermis contains no blood vessels which is why you don’t
bleed when you get a paper cut.
2. Dermis – The dermis lies beneath the epidermis. The dermis
contains 2 layers. It contains blood vessels, sweat glands,
sensory receptors, nerves, smooth muscle and hair follicles.
3. Hypodermis – The hypodermis is a fatty layer located
beneath the dermis. It acts as a foundation or support for the
layers above it. Along with fat, it contains blood vessels and
nerve fibers. Fat is also called “adipose tissue”.
~Why do we need to have fat on our body?
1. protection (of internal organs)
2. insulation (from temperatures)
3. stored energy
Keratin – This is a tough, fibrous protein. Hair, skin
and nails are composed of keratin. Hair and nails
contain no nerves, which is why cutting them isn’t
painful!
Gross Fact: Your skin weighs 8 pounds! During
your entire lifetime, you will shed approximately
40 pounds of skin. So keep vacuuming all the
places your spend the most time in such as your
house and car. And don’t forget to change the
sheets on your bed!
Sweat glands remove water and salts through pores in
your skin. This ensures that your body can excrete toxins
and cool you off at the same time. The average human
has over 2.6 million sweat glands, and approximately 650
sweat glands in 1 square inch of skin.
What causes sweat to have an odor? Bacteria on your skin mixes
with your sweat causing an odor.
Sebaceous glands surround a hair follicle. They provide the skin
with much-needed oil to naturally keep the skin moisturized and
supple. However, anywhere there is a sebaceous gland, there is
also the potential for acne.
Arrector pili muscles are connected to hair follicles. When this
muscle is engaged, it causes the hair shaft to stand on end, causing
“goose bumps.”
Stratum
corneum
Hair shaft
Sebaceous
gland
dermis
epidermis
Arrector pili
muscle
Hair follicle
Nerve fibers
Sweat gland
Blood vessels
hypodermis