Transcript Health Science 1

Did You Know?
• Each day an average
heart “beats” (expands
and contracts) 100,000
times and pumps about
2,000 gallons of blood.
In a 70-year lifetime, an
average human heart
beats more than 2.5
billion times.
Did You Know?
• The cycle of hair growth is different in different parts of the
body. Scalp hair grows steadily and continuously for 2-6 years.
Growth stops, and after three months, the hair is shed. Three
months later a new hair starts to grow from the same follicle.
On the other hand, eyebrows have a growing phase of only
about 10 weeks, which is why eyebrow hair is not very long.
Did You Know?
• Scientists first saw cells by
using traditional light
microscopes. In fact, it
was Robert Hooke (16351703), looking through a
microscope at a thin slice
of cork, who coined the
word “cell.” He chose the
word to describe the
boxlike holes in the plant
cells because they
reminded him of the cells
of a monastery.
Did You Know?
• Stress sets off an alarm in
the brain, which responds
by preparing the body for
defensive action. The
nervous system is aroused
and hormones are
released to sharpen the
senses, quicken the pulse,
deepen respiration, and
tense the muscles.
Did You Know?
• The skin is commonly
thought to have the
greatest exposure to air
of any body part. In
reality, the lungs have
the greatest exposure,
with a surface area
exposed to air of 300
square feet at rest and
up to 1,000 square feet
during a deep breath.
Did You Know?
• There may be
between 100 trillion
and a quadrillion
synapses in the brain.
Did You Know?
• Alexander Fleming discovered penicillin, the
first naturally occurring antibiotic, in 1927 (the
same year that Charles Lindbergh made his
solo flight to Paris).
Did You Know?
• At rest, the skin and
skeletal muscles
receive about 20
percent of the cardiac
output. During
exercise, more blood
is sent to the active
skeletal muscles, and,
as body temperature
increases, more blood
is sent to the skin.
Did You Know?
• The immune system is
amazingly complex. It
can recognize and
remember millions of
different enemies, and
it can produce
secretions and cells to
match up with and
wipe out each one of
them.
Did You Know?
• In ancient China as early
as 3000 to 1000 B.C.,
the classic Yellow
Emperor’s Book of
Internal Medicine first
described the principle
that human harmony
with the world was the
key to prevention and
that prevention was the
key to long life.
Did You Know?
• In 1675, Anton van
Leeuwenhoek of
Holland—the inventor
of the microscope—
first described
protozoa as viewed
under his instrument.
Did You Know?
• The word cortex
is from the Latin
word for bark.
• The cortex is
about as thick as
a stack of 2 or 3
dimes.
Did You Know?
• Muscle tissues
produce heat by
shivering, which
produces heat from
contractions that are
not synchronized (and,
as a result, produce
no motion).
Did You Know?
• As we age, lung tissue
loses much of its
elasticity, and the
muscles of the rib cage
shrink. As a result,
maximum vital
breathing capacity
progressively diminishes
in each decade of life,
beginning at about age
20.
Did You Know?
• Bacteria are so small,
a line of 1,000 could
fit across the eraser
of a pencil.
• More than 500 types
of bacteria live in the
human mouth.
Did You Know?
• Stretched end-to-end,
the arteries, veins,
and other vessels of
the human circulatory
system would
measure about 60,000
miles.
• That’s enough to
encircle the earth
more than twice.
Did You Know?
• Blood accounts for
7-9% of the body’s
weight.
• About 50% of your
blood is in your
veins at any time.
Did You Know?
• A fungus is actually a
primitive vegetable.
Thousands, perhaps
millions, of different types
of fungi exist on Earth. The
most familiar ones are
mushrooms, yeast, mold,
and mildew. Some live in
the human body, usually
without causing illness. In
fact, only about half of all
types of fungi cause disease
in humans.
Did You Know?
• A person blinks once
every 5 seconds—a
total of almost 30
minutes while you are
awake each day.
Did You Know?
• The average adult
inspires approximately
10,000 to 20,000 liters
of air per day.
Did You Know?
• The axon of a single
nerve cell can run half
the length of a human
body.
Did You Know?
• X-rays were
discovered in 1895
by Wilhelm Konrad
Roentgen, a
German physicist.
Did You Know?
• A tomato is 95% water.
One ear of corn is 80%
water, a chicken is 75%
water, and the human
body is 66% water.
Did You Know?
• French hatters of the 17th century discovered
that mercuric nitrate aided greatly in the
felting of fur. Such use led to chronic mercury
poisoning so widespread among members of
that trade that the expression “mad as a
hatter” entered our folk language.
Did You Know?
• You are not as tall in the evening as you are in
the morning. You become about one inch
shorter during a day of standing and sitting.
(This is less true of older people.)
• After a good night’s rest in a horizontal
position, your discs regain their original
thickness (and you regain your original
height).
Did You Know?
• Nearly 500 species of
microbes in all, most
of which are not
harmful, will colonize
the oral cavity. The
microbes form a
biofilm, in which their
numbers greatly
exceed the number of
humans on Earth.
Did You Know?
• Old bone breaks down
and new bone is
formed on a
continuous basis.
Modeling and
remodeling continue
throughout life so that
most of the adult
skeleton is replaced
about every 10 years.
Did You Know?
• The skin is the largest
organ in the body—
both in weight and
surface area.
Did You Know?
• There are 5,000-10,000
white blood cells per
cubic millimeter of
blood.
• A cubic millimeter of
normal adult blood
contains approximately
5,000,000 red blood
cells.
Did You Know?
• Urination accounts for
the greatest fluid loss
daily. About 1300
millileters of urine are
excreted by the
normal person each
day.
Did You Know?
• Hawks and eagles
have vision almost 8
times better than
humans’ vision.
Did You Know?
• Normal pupils are
rounded, centrally
placed, and generally
equal in size. About
25% of normal
individuals have pupils
slightly unequal in
size.
Did You Know?
• There are countless numbers of bacteria on
Earth—most are harmless and many are even
beneficial to humans. In fact, less than 1% of
them cause diseases in humans. For example,
Lactobacilli acidophilus live in human
intestines, where they help to digest food,
destroy disease-causing microbes, fight cancer
cells, and give the body needed vitamins.
Did You Know?
• Every cell in an
organism contains
the same set of
instructions
encoded in DNA.
Did You Know?
• The first nursing schools, formed in the late
1800s, included both men and women. Men
dominated the field in the South and in the
military. In the early 1900s, there was a push
to professionalize the field, efforts that were
often led by women who were also active in
the suffragette movement. Over the course of
the 20th century, nursing became
professionalized and a predominantly female
field.
Did You Know?
• A human being has
some 100 trillion cells.
Did You Know?
• Enamel is the hardest
substance of the
human body.
Did You Know?
• About 300 million
alveoli are found in
the human lungs—
equal to the
surface area of a
tennis court!
Did You Know?
• One human eyeball
weighs ¼ ounce.
Did You Know?
• Unlike taste cells,
olfactory cells can
respond to many
thousands of odorants,
including ones that have
been newly synthesized.
Millions of olfactory
receptors line a
postage-stamp-sized
area in the upper part
of the nose, the
olfactory epithelium.
Did You Know?
• Respiration occurs around-the-clock, but most
people are not aware that they are exhaling
fluid in the form of water vapor every time
they breathe. We become aware of the vapor
loss during cold weather when the vapor can
be seen as it is exposed to low temperatures.
About 450 milliliters of fluid are lost during a
24-hour period by respiration.
Did You Know?
• Toxicology is the study
of the nature and
action of poisons. The
term comes from a
Greek word referring
to the poison in which
arrows were dipped.
Did You Know?
• The heart and blood
vessels, with the blood
they contain, are the
efficient internal
transportation system of
the body. The system is
dual: the right side of the
heart pumps blood only to
the lungs, the left side
pumps the freshly aerated
blood to the rest of the
body.
Did You Know?
• In an average lifetime,
the heart pumps
approximately one
million barrels of
blood—enough to fill
more than 3
supertankers—
through the
circulatory system.
Did You Know?
• Even as you rest, your
heart is working twice
as hard as your leg
muscles would if you
were running at full
speed.
Did You Know?
• In 1903, Dutch physiologist
Willem Einthoven invented the
electrocardiograph, a machine
that measures the minute
electrical currents generated
by the heart. Initially, it was a
cumbersome and costly device,
taking five technicians to
operate. During the procedure,
patients had to place both
hands and both feet in buckets
of water.
Did You Know?
• The FDA defines drugs as
products intended for
treating or preventing
disease or for affecting the
structure or any function of
the body. Antiperspirants
are considered drugs
because they affect the
function of the body by
reducing the amount of
sweat that reaches the skin.
• Deodorants are regulated as
cosmetics because they
promote attractiveness only
by masking odor, not by
reducing sweat.
Did You Know?
• In June 2004, the Food and Drug Administration
cleared the first application for leeches (Hirudo
medicinalis) to be used in modern medicine as
medical devices.
Did You Know?
• Early attempts at transfusion
led to serious adverse
reactions. However, in 1901,
Austrian scientist Karl
Landsteiner discovered that
individuals belonged to one of
four different blood groups
(O, A, B, and AB), and that
transfusions between people
in different blood groups
could be unsafe.
Did You Know?
• Since its introduction
in 1899, aspirin
(acetylsalicylic acid)
has been the most
popular drug of all
time.
Did You Know?
• Laws against dissecting
human corpses began to
relax during the Renaissance.
As a result, the first truly
scientific studies of the
human body began. Surgery
rose in quality by the 18th
century, largely due to this
new outlook towards
anatomy. The painful practice
of cautery to stop bleeding,
for example, was replaced by
ligatures and dressings.
Did You Know?
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