Interesting Facts About the Human Body
1. If all the arteries, veins and capillaries in your body could be
stretched out together to their full length, they would reach a
distance from Minnesota to California to New York and back to
Minnesota again-a total of 12,000 miles.
2. The heart pumps 8,000 gallons of blood through this circulatory
system every day.
3. Muscle fibers can hold loads of up to 1,000 times their own weight
if a real emergency occurs.
4. In an average day, your lungs move enough air to and fro to blow up
over 1,000 balloons.
5. Each square inch of skin contains:
 78 nerves
 19 or 20 blood vessels
 1300 nerve ending for
recording pain
 160-165 pressure points
for the sense of touch
 65 hairs and muscles
 650 sweat glands
 78 sensory mechanisms
for heat
 13 sensory mechanisms
for cold
 95-100 sebaceous
glands
 19, 500 cells
6. If you could spread all you lung tissues out flat, it would cover half a
tennis court.
7. Stomachs can stretch to twice their normal size when full. An adult
stomach is about eight inches long from top to bottom and four
inches across.
MUSCULAR AND SKELETAL SYSTEM
Your musculoskeletal system is the partnership forming the framework
and movement mechanism of your body.
The skeletal system is made up of over 200 strong bony rods, blocks
and plates cushioned by cartilage and linked by joints. The
different bones of the skeletal system have several functions. Some
shield and protect vital organs. Some are muscle-operated levers
providing body movement. Most bones have semi-soft centers
containing bone marrow, which manufactures or makes blood and
stores reserve supplies of elements needed by the body.
Bones must be held together to form the skeleton. Places where bones
connect are called joints. Most joints are movable, such as the
shoulder, elbow, and knee. Some joints aren’t movable, such as those
holding the sections of skull together. Many bones are held together
by strong bands of flexible tissue called ligaments. Strong cords of
tissue called tendons anchor
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muscles to bones. These tendons pull the bones to make them
move around your joints.
The muscular system holds and moves the skeleton and gives
the body its shape. You have over 600 muscles working
together in different combinations. In fact, over 100 muscles
are at work in your face and neck alone. It takes more muscles
working to frown then to smile. Want to exercise your face
muscles? Eat, laugh, smile, cry, and look around.
There are three basic kinds of muscles:
1. Skeletal muscle. These muscles are joined to bones and make them
move. Each muscle consists of fibers (little strips) which are bound
together into bundles by connective tissues. These fiber bundles are
organized by tasks they perform. Skeletal muscles are called
voluntary muscles because our brains toll them what to do; however,
sometimes they also work automatically in reflex actions, as when
you jerk your hand away from something hot.
2. Smooth muscles. These muscles line the organs of your body and
make up the walls of your blood vessels. They are also called
involuntary muscles because you can’t control them. They are not
under direct control of the brain but contract at a rate influenced by
hormones and the autonomic nervous system.
3. Cardiac, or heart muscles. Your heart muscle is striped like a
skeletal muscle but contracts automatically like smooth muscle. It’s
so strong that it beats continually from about 6 months before you’re
born to the day you die. That’s 2 1/2 to 3 billion times!
Muscles work by contacting and relaxing. When one muscle relaxes
another one contracts.
How Many Bones?
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Skull and upper jaw 21 bones
3 tiny bones in each ear
Lower jaw (mandible)
Front neck bone (hyoid)
Backbone or spine (26 separate bones or vertebrae)
Ribs (12 pairs - same number for men and women)
Breastbone
Each upper limb has 32 bones: 2 in shoulder, 3 in arm, 8 in wrist, 19 in hand
and fingers.
Each lower limb has 31 bones: 1 in hip (one side of pelvis), 4 in leg, 7 in
ankle, 19 in foot and toes.
Total = 206 bones
NERVOUS SYSTEM
The nervous system is like a vast telephone system with billions of
interconnected cells called neurons serving as its wires. Without it, all
body systems would be immobilized. The job of the nervous system is to
receive messages from inside and outside the body and react by sending
signals to the appropriate muscles and glands and then receiving
messages back from these muscles and glands back to the brain.
The nervous system centers on the brain spinal cord but has three main
parts:
1. The central nervous system is the brain cranial nerves from the
brain and spinal cord. It’s the command center of the body.
2. The peripheral nervous system included the sensory and motor
nerves leading to and from the spinal cord. The peripheral nervous
system has two overlapping parts: the somatic nerves and the
autonomic nerves. There are 31 pairs of somatic motor and sensory
nerves branching from the spinal cord, supplying limbs and trunk.
There are also 12 pairs of cranial nerves arising from the brain to
supply ears, eyes, nose, tongue and other facial and skin muscles
and various internal organs.
3. The autonomic nervous system is the part of the peripheral nervous
system that normally functions automatically, or outside our
conscious, willed control. It controls the smooth muscle of internal
organs (like the heart, stomach, blood vessels, and bladder) and
some glandular secretions (as adrenal glands and sweat glands).
CIRCULATORY SYSTEM
Your heart is the muscle that is the center of the circulatory
system. Its function is to circulate blood throughout the body.
Blood is the life-stream of the body. This fluid must flow to all
parts of the body to nourish the cells with food substances and
oxygen. It also carries away waste products such as carbon
dioxide and dead cells.
The heart pumps the oxygen-rich blood into arteries that lead to
your arms, legs, and organs of your body. The arteries split into
tiny blood vessels called capillaries. Capillaries supply oxygen
to the muscles for movement and also carry the wastes that
muscles make when they burn food for energy. Capillaries lead
from muscles and organs into bigger blood vessels called veins.
The job of the veins is to collect blood from all over the body
and return it to the heart. The heart then pumps the oxygendepleted blood back to the lungs for a new supply of
oxygenated blood. Your blood makes 1,000 complete trips
around your body each day and each trip takes less than one
minute!
RESPIRATORY SYSTEM
---Deals with the breathing of the body
The purpose of this system is to bring oxygen into the
bloodstream and to get rid of carbon dioxide and other gases.
Organs of the respiratory system include:
 the lungs
 diaphragm
 the muscles and ribs of the chest cavity (these muscles
expand and decrease the size of the chest cavity as you
breathe and breathe out)
Only about ¼ of the air you take into the lungs is exchanged in
any one breath. About 15 to 20 times a minute (that’s 21,600
times a day) you breathe air in through your nose or mouth.
WHAT HAPPENS?
1. Air comes into the nasal cavity and is warmed and filtered in
the nasal cavity.
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2. Air passes past the epiglottis (which closes when food is
swallowed to keep it from entering the passage), through the
larynx (voice box), and down a long tube called the trachea
(windpipe).
3. It is then divided into two bronchial tubes which enter the
lungs. Each tube passes into each lung. In each lung, the tubes
divide into smaller and smaller passageways until the end in over
6 million tiny air sacs called alveoli.
These
alveoli are branched out like grapes on a vine to make a huge
spongy area with tiny blood vessels running through it. These air
sacks are like a swap shop for gases in you body. The oxygen and
the carbon dioxide pass through their walls, and the oxygen is
carried off by the red blood cells. The carbon dioxide is exhaled
in the next breath.
DIGESTIVE SYSTEM
The food you eat contains nutrients from fat, carbohydrates, and
proteins, but these nutrients have to be digested (broken down)
into smaller building blocks so the cells can absorb them into
your bloodstream.
The 32foot (from the mouth to the rectum) digestive track does
the breaking down of these foods in the following steps:
1. Food is taken into the mouth, mixed with the saliva,
and chewed by the teeth.
2. The tongue then pushes the partially ground up food to
the back of the mouth.
3. Food is then swallowed through the esophagus to the
stomach. The epiglottis is the flap that shuts to stop food
from entering the nasal cavity or the windpipe. This
swallowing movement takes about 4 to 6 seconds.
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4. Then the food passes to the stomach where it remains for 1 to 6
hours. In the stomach, the food mixes with digestive enzymes
(stomach acid-hydrochloric acid) to continue to digest the food.
This acid is strong enough to burn skin, but does not attack the
stomach’s walls because of its protective mucous coating. The
average meal stays in the stomach churning for 3-5 hours where
the sugar, salt, water, and alcohol are absorbed directly into the
bloodstream. The remainder of the partly digested food is then
travels to the small intestine.
5. The small intestine is a 22 foot long track where most of your
food’s digestion takes place. It takes food 2 to 9 hours to pass
through the small intestine. The intestine uses pancreatic juices
(from the pancreas) and bile (from the liver) to complete the
breakdown of the food. The broken down nutrients in the food
are then absorbed into the bloodstream through little finger-like
projections in the lining of the small intestines called the villi
and microvilli.
6. Not all of the food eaten is digested and absorbed. The large
intestine (also known as the colon) takes the remainder of the
unused food (now called waste) and turns it into feces and
stored until it is time to go to the bathroom and is exited through
the rectum. The large intestine is a 5 foot track that ends the
digestive system.
The appendix is an organ in the body that has little known value to the
body and can even be hurtful to the body if it gets inflamed. Serious
complications occur if the appendix ruptures in the body. This organ can
be removed from the body without any bad effects.
URINARY SYSTEM
The urinary system eliminates wastes the body cannot use. The
kidneys are the major urinary organs. The human body has two
kidneys each about the size of an adult’s fist. These kidneys
filter about 50 galleons of blood daily, taking from it vital
substances needed by the body. These substance then rejoin the
filtered blood, and the remaining waste materials are passed out
of the kidneys into the ureter tube and then into the bladder.
The bladder serves as a storage place for the urine so that,
although the kidneys constantly produce urine, it can be
eliminated at intervals.
Urine is about 96% water and 4% chemicals, minerals, and
dissolved salts. If the urinary system were to stop functioning,
this material would poison the body’s blood stream, and death
would eventually occur.