What is an organ?
What is the largest organ
in
the
body?
A. Liver
B.
C.
D.
E.
Skin
Brain
Stomach
Large intestine
An organ is made up of at least 2 main tissues types (Chapter 4) that
work together for a common function?
Describe how the skin is an organ after you study it.
Integumentary system: The skin and
its derivatives such as hair and nails.
• Protection: Covers all of the body. There is a layer of fat
below the skin that acts as a cushion. The skin protects us from
dehydration as well.
• Regulation of body temp: Skin does this through
sweating and hairs on the skin (when hair stands on end it helps
warm the body = goose bumps). Fat also acts as an insulator
just below the skin.
• Defense: Covers the body to act as a first line of defense
to keep things out. There are also white blood cells in the skin to
act as defenders.
• Helps synthesize “vitamin D”: Precursor to
vitamin D is made in the skin when exposed to sunlight.
• Sensory reception: Many sensory receptors in the
skin that gives us information about the world around us.
How many skin cells do you think
you can shed per second?
A.
B.
C.
D.
4,000
15,000
25,000
40,000
Much of the dust found in your house is made up of dead skin cells.
There are also dust mites feeding on these skin cells, even in your bed.
Sleep well and don’t let the bed mites bite (they don’t bite you). 
They actually help clean up your mess. 
Epidermis: Remember this is a thin layer (only mm
thick). This picture shows a blown-up image of the epidermis to
show detail.
•
•
•
•
Made of epithelial tissue
Replaced often
Waterproof (keratin in cells)
Made up mostly of
keratinocytes
• Contains melanocytes
(produce melanin that gives
color to the skin and
some protection from the sun).
• No blood vessels (thin enough
layer that things can diffuse in and
out from the blood vessels in the
dermis).
Skin color originates in the epidermis
People all have about the same number of melanocytes.
How active they are and thus how much melanin they
produce results in the different skin colors we see.
That is it! Skin color tends to be darker towards the equator
while it tends to be lighter towards the poles. There is a
hypothesis that suggest skin color is the result of
balancing certain nutrients made and destroyed by the
sun to help with fetal development.
Dermis
• Mainly dense fibrous
connective tissue
• Lends strength &
flexibility to the skin
• Contains many
structures such as
glands, muscle,
blood vessels,
nerves etc…
Hypodermis
• Layer just below the skin and mostly
made of adipose tissue
• Anchors skin
• Acts as a cushion and insulator
ASK YOUSELF THESE QUESTIONS:
Where is nervous tissue found in the skin?
Where is muscle tissue found in the skin?
Where is epithelial tissue found in the skin?
Where is connective tissue found in the skin?
See if you can answer these questions before
looking at the next slide. The answers are
provided here. 
ASK YOUSELF THESE QUESTIONS:
Where is nervous tissue found in the skin?
Mostly in the dermis (I left some information out that you don’t
Need to know)
Where is muscle tissue found in the skin?
Dermis
Where is epithelial tissue found in the skin?
Epidermis is made of epithelial tissue and the glands in the dermis
Where is connective tissue found in the skin?
Dense fibrous tissue and blood vessels in dermis, also adipose below
in the hypodermis
30%
65%
5%
These are a
result of ridges
at the top of the
dermis. They
are unique in
all humans, even
among twins.
What gives fingerprints their patterns?
Dermal ridges
at the top of the
dermis
/hypodermis
Miocrobiota (microbiome) – microbes
that live on and in you
Made up of bacteria, mites and fungi
Microbiota
Bacteria and yeast that are normally found in and
on our body such as on the skin in moist areas such
as the groin, feet, folds and armpits as well in the
digestive system. They are beneficial to us.
Skin
Microbiota:
they get on
and in
everywhere.
A new
perspective
on your skin!
Microbiota
varies
between
regions:
Oily, moist and
dry areas with
host different
microbes. I
thought this
was fun to
look at!
Microbiota varies between people as well.
We are different in so many ways!
Sharing microbiota
• http://www.scientificamerican.com/video/wh
y-we-live-in-a-cloud-of-microbes/ - Required:
listen to this short 2-minute audio clip!
Who lives in your home?
A study was done looking at dust on the tops of doors in 1100
homes and this is what they found (Dec 2015):
• Dogs appear to alter indoor bacteria more extensively than
humans or cats.
• Men shed more bacteria into their surroundings than women
do and thus have a bigger impact on the variety of bacteria
inside a home, too. The variation comes down to skin biology
and maybe body size and hygiene practices.
• The bacterial signatures of each of these living beings are
unique enough that by simply testing dust in a home,
investigators can accurately predict if more women or men
live there and if dogs or cats do as well.
https://www.theguardian.com/science/2015/aug/26/house-dust-can-revealwho-you-live-with-and-what-your-pet-is-study-shows - optional, article is
summarized on this slide
Writing Response 1 Assignment:
Be sure to read the microbiota essay at the link under
assignments (link is below as well) and then type a 2 paragraph
(a good 8-10 sentence minimum) response which should be at
least 1 page in length, double-spaced, 12-point font and 1”
margins. The first paragraph should be what you learned
whether it be one thing that most interested you or many and the
second paragraph should be what it made you think about
and/or your opinion. Write everything in your own words. Do not
copy anything from the essay even if you put quotations around
it. Save your response as a word DOCX or PDF, click on the
title of the assignment on Blackboard and attach it using the
browse my computer button. Click submit. Effort counts!!!!!!
http://michaelpollan.com/articles-archive/some-of-my-bestfriends-are-germs/
Due by Wednesday, February 24th, by 11:59pm.
Remember it must be in PDF or DOCX format!!!!
The skin, sunlight and cancer
Damages of sunlight on the skin
• Cells in the epidermis can be damaged
• Fibers in dermis are damaged (think
wrinkles)
• Small blood vessels
• DNA (think cancer)
A sunburn is essentially a first degree burn. The red
color is from the dilated blood vessels.
What effect does sun (UV light)
have on the skin?
• Ages skin
– Wrinkles
– Age spots
– Leather-like
skin
• Cancer
Age spots to the left. Result of sun exposure.
Above you see the loss of elasticity of the
dermis and results in wrinkles.
Where does skin cancers occur…all
skin cancers originate in the epidermis.
The 3 arrows show the origin of the 3 skin cancers:
1. Basal cell carcinoma
2. Squamous cell carcinoma
3. Melanoma
Skin Cancers: Melanoma is the least common but most dangerous. It is
the most likely to metastasize. The important thing is for early detection of skin cancer!
Basal cell
Squamous cell
Melanoma
Signs of skin cancer: Things to look for!
A
B
C
D
ABCDE’s of Skin Cancer
Evolution (not shown in the picture). There is a change in the size,
shape, symptoms (such as itching or tenderness), surface (especially
bleeding) or color of a mole or patch of skin.
Check your
skin regularly
for changes!