Tissues, Organ Systems and
Homeostasis
At Last!! Systems!
To refresh:
Atoms form molecules
Molecules (like proteins,
carbohydrates, lipids, and nucleic
acids) form cell organelles as well
as just float around in cells and
between cells.
Amino Acid
Cell Organelles
•  carry out specific jobs
in the cells, like
making certain
molecules or
digesting waste
materials
Cells
•  Are the basic unit of
life that is capable of
carrying out all the
functions of living
things independently
•  Work together to form
tissues
•  Metabolism
•  Homeostasis
•  Ability to reproduce/Genetic
material
•  Growth and Development
•  Response to stimuli
Homeostasis
•
•
The body must
maintain conditions
within certain
parameters
This means control
over things like:
•  temperature
•  pH
•  blood gases (oxygen,
carbon dioxide)
Homeostatic mechanisms operate to maintain
the body within tolerable limits by using:
•  a. Sensory receptor cells
detect specific changes in
the environment.
•  b. Integrators act to direct
impulses to the place
where a response can be
made.
•  c. Effectors perform the
appropriate response.
•  5 senses,
temperature sensors,
etc
•  Brain and spinal cord
•  Muscles and glands
Everything has a role to play in
homeostasis
•  The combined contribution of cells and the
tissues they form, and the organs and
systems formed from these all work to
maintain a stable internal environment for
a living being
What do the pieces of the body do
to help?
•  Cells are bathed in fluid: 4 Gallons of
extra-cellular fluid (between cells- called
interstitial fluid)
•  Each cell carries out metabolic activities to
ensure the survival of the cell
•  Cells of each tissue act together to
perform one or more duties that contribute
to the survival of an organism as a whole
by forming organs that work together in a
system
Feedback Mechanisms (2
types)
Positive
•  Causes the situation to intensify
•  Cough up germs, produce more mucus, cough
more, irritate throat, cough more, more mucus…
•  Sexual response
•  Oxytocin production in labor causes uterine
cramping, which causes production of oxytocin
which causes cramping which causes more
oxytocin production….
Negative feedback
•  Causes the situation to stop/ reverse
conditions
•  Like a thermostat turns off the heat when it
gets to a preset temperature
•  Usually things are just turned on or off;
you produce insulin (or other hormone)
and when you have enough, production
stops; when you need more, you produce
more
On to the
Integumentary System
(the Skin)
Skin: Your Birthday Suit (also, a
marvel of biology)
Skin (a little closer)
Skin description: Use the vocabulary
from the image to write a description of skin
Skin: The Integumentary System
from the Latin integere- to cover
•  Demonstrates all of the tissues working
together to keep on organism alive
•  The average person has 9 pounds of skin
•  The skin is about 15-20 square feet
Functions of the skin:
•  prevents dehydration
•  Prevents microbial
invasion/ infection
•  Prevents abrasion
•  Stores blood
•  Provides cushioning
•  Insulation (temp,
physical)
•  Receives stimuli
(touch, temp,
pressure)
•  Temperature
regulation
•  Produces vitamin D
•  Pheromone secretion
•  Excrete salt waste
(small counts)
Skin Structure
• 3 layers
(top)
•  Epidermis
•  Dermis
•  Subcutaneous
Layer (AKA the
Hypodermis)
The Epidermis
•  Has no nerves
•  Dead layers of flat epithelial cells; the very top is
called the stratum corneum
•  Contains keratin: a tough protein that
waterproofs the skin
•  Quite a bit gets rubbed off each day (dust)
•  Skin color is due to
–  melanocytes (pigmented cells- genetics and sun
exposure play roles)
–  blood flow
–  carotene
Layers of the Epidermis
•
•
•
•
•
Stratum corneum
Stratum lucidum
Stratum granuosum
Stratum spinosum
Stratum basale (basal cell layer)
The Dermis of the skin
Made from mostly connective tissue
–  Irregular and dense CTs
•  Role is mainly to protect underlying tissues
Contains:
–  Blood vessels
–  Lymph vessels
–  Nerve endings
–  Sweat glands
–  Oil glands
–  Hair
–  Nails
More on the dermis and sweat
glands…
•  Sweat (sudoriferous) glands are
present to control temperature,
but respond to
– Stress (frightened, upset, etc)
– pain, and
– sexual stimuli
Types of Sweat Glands
– Two types:
• Eccrine glands (mostly temperature
regulation sweat)
– Foredead, neck, back,
» palms and soles from stress
• Apocrine glands (“scented” sweat
glands; sweat is broken doen by
bacteria, producing a scent)
– Found in the axillary and inguinal areas
More on the dermis and sweat
glands…
•  Sweat is made up of
– water,
– salts,
– ammonia,
– vitamin C,
– other wastes and
– (possibly) pheromones
Pheromones
•  Are chemicals secreted by the body that other animals of
the same species respond to (communication molecules)
–  Usually associated with reproduction, but not always
•  Are well documented in animals
–  Syrian golden hampsters (dimethyl disulfide to attract,
aphrodisin to copulate)
–  Cockroaches (periplanone B)
–  Ethiopian civet cat and Himalayan musk deer (musk)
–  Pigs (androstenone)
•  Usually have no smell associated with them
•  Secreted in very small amounts
•  Some evidence for pheromone presence in humans
–  VNO (vomeronasal organ) in people; used to detect pheromones
in animals
Functions of Pheromones:
Oil glands….
•  Otherwise known as sebacious glands
•  Lubricate hair and skin by producing
sebum (fatty substance that includes lipids
and cellular debris made in holocrine
glands)
•  Oil kills microbes (bacteria)
•  None present on soles of feet or the palms
of the hands (but they are present on the
fingertips)
We leave prints behind…
•  The oil produced from our fingers seeps
into the ridges and is left behind when we
touch an object
–  (Locard’s exchange principle: we leave things
behind wherever we go, and pick up things
wherever we go
•  Every contact leaves a trace
•  Lint, hair, fingerprints, tracks, saliva, etc)
A few things about prints…
•  Ridge patterns and the details in small areas of friction
ridges are unique and never repeated.
•  Friction ridges develop on the fetus in their definitive
form before birth.
•  Ridges are persistent throughout life except for
permanent scarring.
–  They can not be burned or scratched off- they will grow back!
•  Friction ridge patterns vary within limits which allow for
classification.
Fingerprints
•  AKA friction ridge patterns
–  b/c the ridges help increase the friction when
we pick up an object, helping us hold onto it
•  Fingerprints are “the result of genetic
factors and random physical stresses and
tensions during development on the
stratum basale”, the lowest layer in the
epidermis.
Print Formation
•  Formation begins at 10 weeks after
conception
•  Is complete at 24 weeks gestation(6
mo of pregnancy)
– (**some sources say complete at 14
wks)
Dermal papillae
Print patterns
•  5% of prints contain
arches
•  65% of all prints
contains loops
•  30% of all prints
contain whorls
Print patterns
http://www.fbi.gov/hq/cjisd/takingfps.html
How unique are you?
•  Chances are one in a quintillion (1 in
100,000,000,000,000,000,000) that
someone will have the same print
(singular, not for all 10 fingers) as you
– identical twins have similar patterns, but
the prints are not the same
– Boimetric identification: using
fingerprints, ear prints, iris patterns to ID
you, as they are each unique
Matching prints
Minutia
points
are the
small
marks in
the
loops,
arches,
or whorls
Biometrics take the print and
make a digital map that is
unique
Skin and Sensation
•  Pacinian corpuscles
–  Heavy pressure, pain
•  Meissner’s corpuscles
–  light touch
•  Thermoreceptors
–  Temperature (warm and cold)
•  Pain receptors
–  Acute (quick)
–  Chronic (slower)
The Subcutaneous Layer: The
Hypodermis
•  The hypodermis is made up of
–  Adipose
•  To insulate (temperature regulation)
–  Loose connective tissue
•  Collagen
•  Elastin
–  Both to protect
–  Fibers run parallel to the skin
–  Rete cutaneum: network of blood vessels at
“border” of dermis
Hair…
(a slight diversion for a moment or
two…)
I went looking for a picture of hair…
I found a
few…
There were more than a few I had
to share…
It was sort of like a train wreck…
Bad vacation destinations...
Yes, even more…
I guess it had to stop somewhere….
Hair….
•  Keratinized cells that push up and overlap
each other- made from dead skin cells
(This is the
graphic I went
looking for in
the first
place…)
Scalp
Hair
•  Develops from a follicle
–  Holds the root
–  Nourished from dermal blood supply found in
the connective tissue around the follicle
–  New hair cells push old hair cells up and away
from the new growth
–  The old cells get keratinized and die
Hair Growth Cycle
•
•
•
•
90% of your hair is in a growth phase
Grows 2-6 years
Falls out- rests for 3 months
Gets replaced by new growth
–  If not replaced, baldness (allopecia)
•  Androgenic or areata
•  Normally lose 20-100 hairs per day
–  Stressors can alter this
Nails
•  Nail plate (nail itself)
•  Nail Bed (under the nail)
•  Lunula (half-moon area;
nail grows from there
•  Cuticle
Temperature regulation:
Homeostasis (Negative Feedback)
•  Sensory receptors (input)
–  thermoreceptors in skin
•  Warm receptors
•  Cold receptors
–  Hypthalamus
•  Effectors (response)
–  Muscles in skin (arrector pilli)
–  Muscles of body
–  Blood vessels
–  Sweat (eccrine) glands
•  Integrators
–  Hypothalamus (region of brain)
Too high
Too low
Just right…37°C (98.6°F)
•  (give or take; the average is merely the average, there is a
range that is normal of +/- .9 F
•  Your average temperature changes over the course of the
day
•  The location of where the temperature is taken makes a
difference
•  Oral
•  Axillary
•  Rectal
•  Forehead
Temperature Regulation
•  Radiation: primary means of loss of body
heat
–  Heat goes out into the air
•  Conduction: something touching your skin
carries body heat away
•  Convection: hot air from the body moves
up, and cool air replaces it
•  Evaporation: sweat (or other liquid on
surface) takes heat energy to evaporate
off
Too hot?
•  You sweat to cool yourself
–  Eccrine glands secrete sweat
–  Stop sweating when you have reached an appropriate
temp (negative feedback)
•  Increase in the diameter of surface blood
vessels (vasodilation)
–  Allows more heat from blood to escape through skin
•  Deeper blood vessels constrict
(vasoconstriction)
•  Extreme overheating: hyperthermia (heat exhaustion)
•  Caused by:
–  Being in extreme temperature
•  ie being trapped in a hot car (temporary, but caused by
environment, not individual)
–  Fever (pyrexia) / illness (temporary, in normal temp environment)
•  Attempt to kill organisms by denaturing their proteins
•  Can kill you!
•  Uncontrolled temperatures (above 105°F) in people, it
can denature proteins (specifically enzymes) needed to
survive and kill you
Dehydration
•  a major cause of overheating ( because if
you can’t sweat anymore to cool off, you
overheat)
•  Symptoms of dehydration
–  Fatigue
–  Dizziness
–  Headache
–  Nausea/ vomiting
–  Muscle cramps
Hyperthermia, con’t
•  If sweat can’t evaporate, the body can’t
cool itself
–  Reduces radiative cooling
•  Especially if the air is hotter than the body
–  Reduces conductive cooling
–  Reduces convective cooling
Too cold?
•  Constriction of blood vessels
(vasoconstriction) near surface
–  Diverts blood from surface to visceral organs
•  Hair stands on end (goosebumps- arrector
pilli making hair stand up)
•  Shivering- muscle contraction creates
–  Shivering is multiple repeated contractions
that create a lot of heat
Skin Cancer
•  Skin cancer is the most common form of cancer
in the United States. More than 3.5 million skin
cancers in over two million people are diagnosed
annually.
•  Each year there are more new cases of skin
cancer than the combined incidence of cancers
of the breast, prostate, lung and colon.
•  One in five Americans will develop skin cancer in
the course of a lifetime.
•  The good news is that skin cancer is the most
treatable form of cancer. It’s also one of the most
preventable forms.
What is skin cancer?
•  Skin cancer is the uncontrolled growth of
abnormal skin cells. It occurs when
unrepaired DNA damage to skin cells
(most often caused by ultraviolet radiation
from sunshine or tanning beds) triggers
mutations, or genetic defects, that lead the
skin cells to multiply rapidly and form
malignant tumors.
•  Malignant means…very bad, threatening
to a life, extremely harmful or dangerous
Melanoma, basal cell carcinomas,
and squamous cell carcinomas are
the most common types.
What to look for:
•  Do a complete body check once a month, and
have a dermatologist check you once a year.
•  You are looking for any changes that fit one or
more of the following:
–  Asymmetrical shape
–  Borders that are not even
–  Color that changes
–  Diameter larger than a pencil eraser
–  Evolution- any changes in color, size, texture, etc
•  The earlier a skin cancer is detected, the better
the chances of survival
What to look for:
Human skin in UV (ultraviolet)
& visible light
•  As you can see UV light behaves completely
differently than visible light and shows all of the
sun damage & hyper pigmentation. The melanin
in the skin absorbs ultraviolet light to protect the
skin. The more tan the skin, the more melanin is
released from melanocytes and the more
absorption of ultraviolet light occurs. You can
also see that the eyes appear entirely black in
the UV image, this is because eye
chromophores absorb UV rays for protection
against UV light damage.
Skin damagevisible under UV
photography
Types of UV Radiation: UVA, UVB,
and UVC
•  UVA rays have the longest wavelengths,
•  UVB have the mid level- wavelengths
•  UVC rays which have the shortest
wavelengths.
•  UVA and UVB rays are transmitted
through the atmosphere, all UVC and
some UVB rays are absorbed by the
Earth’s ozone layer. So, most of the UV
rays you come in contact with are UVA
with a small amount of UVB.
UVB rays reach the the epidermis only
UVA rays can penetrate the dermis
Things that affect your risk for
skin cancer
•  Genetics
–  Family history of skin cancers
–  Fair skin (but darker-skinned people can also
get skin cancers, too, and usually detect them
later than those with fair skin.
–  Fair hair (red heads especially!)
–  Light colored eyes (blue especially)
•  Behaviors
–  Sun exposure:
•  Use of sunscreen correctly, time outside, covering
up or not (including sunglasses)
Tanning?
•  Tanning = highly increased risks of skin
cancer
•  There is NO safe amount of tanning
•  All tanning (outdoor and tanning beds
indoors) are associated with increased
risks of invasive skin cancers
–  In fact, indoor tanning is MORE intense and
concentrated than sun exposure outdoors in
terms of UVA radiation, the type that causes
more aging
Impacts of tanning
•  Photo-aging can cause:
–  Wrinkles
–  Invasive cancers
•  Even if you NEVER get a skin cancer, you
will look older at a younger age when it
comes to wrinkles and age spots
–  And while you can treat these (not cure), they
are expensive and uncomfortable to treat
•  Lasers, facelifts, and expensive creams that don’t
really do much
Smoking and Sun DamageTwins
Twin A
Twin B
Left side damage due to UV
exposure
How do you reduce your risk?
•
•
•
•
Seek the shade, especially between 10 AM and 4 PM.
Do not burn.
Avoid tanning and UV tanning booths.
Cover up with clothing, including a broad-brimmed hat and UVblocking sunglasses.
•  Usa a broad spectrum (UVA/UVB) sunscreen with an SPF of 15 or
higher every day. For extended outdoor activity, use a waterresistant, broad spectrum (UVA/UVB) sunscreen with an SPF of 30
or higher.
•  Apply 1 ounce (2 tablespoons) of sunscreen to your entire body 30
minutes before going outside. Reapply every two hours, or
immediately after swimming or excessive sweating.
•  Keep newborns out of the sun. Sunscreens should be used on
babies over the age of six months.
Factors that affect exposure
•
•
•
•
•
•
Geography
Altitude
Time of year
Time of day
Weather conditions
Reflection
UV Index:
Provides
information
about the risk
of UV
exposure at
that time; part
of the
weather
forcast
Sunscreen is your friend
However, you
probably aren’t
using nearly
enough or applying
it frequently enough
to really