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!