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Lesson 33Comparing the Major
Systems of the Human
Body Part 2
Skeletal and
Muscular Systems
In our last lesson, we learned that the
circulatory system is a system that helps blood to transport nutrients, oxygen,
carbon dioxide, blood cells, etc. to and from
cells in the body to nourish them and help
them to survive.
We learned the circulatory system is composed of the heart and
blood vessels, including arteries, veins, and capillaries.
Also in our last lesson we learned that the respiratory system
allows much needed oxygen in the air to be taken into the body,
while also enabling the body to get rid of
carbon dioxide from the body using the air the body breathes out. lungs
Respiration is when the body exchanges the oxygen it takes
in for the carbon dioxide it needs to get rid of.
All of this breathing couldn't happen
without the respiratory
system, which includes the nose, throat, voice box,
windpipe, and lungs.
These two systems work well together.
The respiratory
system brings the air into
the body and releases
carbon dioxide from the body.
And the circulatory
system transports the oxygen to the cells
and the carbon
dioxide to the lungs to be released.
Today we are going to learn
about two more systems that
work well together. Today
we will learn about the skeletal
system and the muscular system.
What is a skeletal system?
A Skeletal system is made up of the bones of
the body.
Every single person has a
skeleton made up of many bones.
These bones give your body
structure, let you move in many
ways, protect your internal organs,
and more.
The adult human
body has 206 bones!
Your skull protects the most important part of all, the brain. You can feel your skull by pushing on your head, especially in the back a few inches above your neck.
Although you can't see it, the smallest bone in your whole body is in your head, too. The stirrup bone
behind your eardrum is only .1 to .13 inches (2.5 to 3.3
millimeters) long!
Your lower jawbone is the only bone in your head you can move. It opens and closes to let you talk
and chew food.
Your heart, lungs, and liver are all very important, and luckily you've
got ribs to keep them safe. Ribs act like a cage of bones around your
chest.
It's easy to feel the bottom of this cage
by running your fingers along the sides and front of your body, a few
inches below your heart. If you breathe in deeply, you can easily feel your ribs right in the front of
your body, too.
Your ribs come in pairs, and the left and right sides of each pair are
exactly the same. Most people have 12 pairs of ribs
All 12 pairs of ribs attach in the back to the spine. The first seven pairs of ribs
attach in the front to the sternum, a strong bone in the center of your chest that holds those ribs in place.
Your spine is one part of the skeleton that's easy to check
out: Reach around to the center of your back and you'll feel its bumps
under your fingers.
The spine lets you twist and bend,
and it holds your body upright. It
also protects the spinal cord, a
large bundle of nerves that sends information from your brain to the
rest of your body.
The spine is special because it isn't made
of one or even two bones: It's made of 33
bones in all! These bones are called
vertebrae and each one is shaped like a
ring.
The arm is made up of three bones: the
humerus which is above your
elbow, and the radius and ulna which are below
the elbow.
Your legs are attached to a circular group of bones called your pelvis. The pelvis is a bowl-shaped structure that
supports the spine.
The pelvis acts as a tough ring of protection around parts of the digestive system, parts of the
urinary system, and parts of the reproductive system.
Your leg bones are very large and strong to help
support the weight of your body. The
bone that goes from your pelvis to your knee is called the
femur, and it's the longest bone in
your body.
Below the knee are two other leg
bones: the tibia and the fibula. Just like the three bones
in the arm, the three bones in the
leg are wider at the ends than in the middle to give them strength.
https://www.youtube.com/watch?v=lUP-D4dKp14
Let’s watch a video about the skeletal system.
What is a muscular system?
A Muscular System is made up of the muscles of the body.
Did you know you have more than 600 muscles in your body? They
do everything from pumping
blood throughout your body to
helping you lift your heavy backpack.
You control some of your muscles, while others —
like your heart — do their jobs without you
thinking about them at all.
Muscles are all made of the same material, a type of elastic tissue
(sort of like the material in a rubber band). Thousands, or even tens of thousands, of small fibers
make up each muscle.
You have three different types of muscles in your body: smooth muscle, cardiac (muscle, and
skeletal muscle.
Smooth muscles — sometimes also called involuntary muscles —
are usually in sheets, or layers, with one layer of muscle behind
the other.
You can't control this type of muscle. Your brain and body tell these
muscles what to do without you even thinking about it.
But smooth muscles are at
work all over your body. In your stomach and
digestive system, they contract
(tighten up) and relax to allow food to make its journey through the body.
Smooth muscles are also found in
your bladder. When they're relaxed,
they allow you to hold in urine (pee) until you can get to the bathroom. Then
they contract so that you can push
the urine out.
You'll find smooth muscles at work behind the scenes in your eyes,
too. These muscles keep the eyes focused.
The muscle that makes up the heart is called cardiac muscle. The thick muscles of the heart contract to pump blood out, and then relax
to let blood back in after it has circulated through the body.
Just like smooth muscle, cardiac muscle works all by itself with no
help from you.
A special group of cells within the heart are known as the pacemaker
of the heart because it controls the heartbeat.
Skeletal muscles are sometimes called striated muscle because
the light and dark parts of the muscle fibers make them look
striped (striated is a fancy word meaning striped).
Skeletal muscles are voluntary
muscles, which means you can
control what they do. Your leg won't bend to kick the
soccer ball unless you want it to.
These muscles help to make up
the musculoskeletal
system — the combination of
your muscles and your skeleton, or
bones.
Together, the skeletal muscles work with your bones to give your body
power and strength. In most cases, a skeletal muscle is attached to one end of a bone. It stretches all the way across a joint (the place where two bones
meet) and then attaches again to another bone
Skeletal muscles are held to the bones with the help of.
Tendons are cords made of tough
tissue, and they work as special
connector pieces between bone and
muscle.
The tendons are attached so well that when you contract one of
your muscles, the tendon and bone move along with
it.
Skeletal muscles come in many different sizes
and shapes to allow them to do many types of jobs. Some of your
biggest and most powerful muscles are in
your back, near your spine. These muscles help keep you upright
and standing tall.
They also give your body the power it needs to lift and
push things. Muscles in your
neck and the top part of your back
aren't as large, but they are capable of
some pretty amazing things.
Try rotating your head around, back and forth, and up
and down to feel the power of the
muscles in your neck. These muscles also hold your head
high.
I will list just a few of the major
muscles. In each of your shoulders
is a deltoid muscle. Your
deltoid muscles help you move your shoulders
every which way.
The pectoralis muscles are found
on each side of your upper chest. These are usually called pectorals, or pecs, for short. Many athletes and bodybuilders have
large pecs, too.
Below these pectorals, down
under your ribcage, are your
rectus abdominus muscles, or abdominals. They're often called abs for
short.
When you make a muscle in your arm, you tense your biceps muscle.
When you contract your biceps muscle, you can actually see it push
up under your skin.
Your quadriceps or quads, are the muscles on the
front of your thighs. Many
people who run, bike, or play sports
develop large, strong quads.
https://www.youtube.com/watch?v=rGR1eUGV-tA
Let’s watch this video about the skeletal system.
https://www.youtube.com/watch?v=uxBe-BgmNTs
Let’s watch this video about both the skeletal and muscular
systems.
Let’s review what we have learned
about the skeletal and muscular
system. Answer the attached
questions on the worksheet entitled
L#33 Systems of the body part 2.
In our next lesson we will look at
the digestive
system and the nervous system in
multicellular
organisms.
Good Job Today!
And remember to….
See you next time!