Transcript The Muscular system

Muscles
Muscle: organ that can relax, contract,
and provide the force to move your body
parts
 Energy is used and work is done
 More than 600 muscles in the body

Can you think of an activity
you do that doesn’t require
muscles?

No! As long as you are alive, your
muscles are still moving
 Digestive system, beating heart, and
breathing all require moving muscles
Muscles are divided into 2
main categories – can you
name them?
Voluntary muscles

Muscles you are able to control

Used when you lift your leg, move your
pencil, raise your hand, etc.
Involuntary muscles

Muscles you can’t control consciously

Control activities such as pumping blood
through blood vessels and moving food
through digestive system
Muscle tissue

Muscles are made of tissue

There are 3 types: can you name them?
Skeletal muscle
Muscles that move bones
 Most common muscle type
 Attached to bone by tendons: thick
bands of tissue
 Look striped/striated when you look at
them under a microscope
 Contract quickly and tire more easily
 Are skeletal muscles voluntary or
involuntary?


Voluntary
Skeletal muscle
Smooth muscle

Found in intestines, bladder, blood vessels,
and other internal organs

Not striated (striped)

Involuntary

Slowly contract and relax, do not tire easily
Smooth muscle
Cardiac muscle

Makes up the walls of the heart

Striated like skeletal muscle

Involuntary like smooth muscle

Contracts about 70 times per minute
Cardiac muscle
How muscles work
Always pull, never push
 Often work in pairs (one contracts while the
other relaxes)
 Can become larger or smaller over time
depending on how they are used
 Need energy to contract and relax

 Contracting muscles release mechanical energy
(movement) and thermal energy (heat)
Assignment – pick one!
Write a poem comparing and contrasting
the three types of muscle
 Draw a picture of the human body’s
muscular system. Label 2 places where you
can find each of the 3 muscle types and
explain how you know you can find them
there
 Use clay to make a model of each muscle
type. Your models must clearly show the
identifying features of that type of muscle
 Due Friday, 2/11

What is the largest
organ (not solid) in the
human body?
What are the 3 layers of the
skin?
Epidermis
Outer, thinnest layer
 Outermost cells are dead and water
repellent
 Cells rub off constantly

Dermis
Middle layer
 Contains blood vessels, nerves,
muscles, sweat glands

Fatty layer
Innermost layer
 Insulates the body

What is melanin?
Melanin
Pigment that protects skin and gives it
color
 Lighter skin tones mean you have less
melanin
 Less melanin means less protection
from sun’s rays

What does skin do for your
body?
Main functions of the skin
Vitamin D formation
 Heat and waste exchange
 Protection
 Rids body of waste
 Sensory response

Bruises
Blood vessels under skin burst
 Blood cells release hemoglobin, which
breaks down into pigments
 Pigments cause skin to change color
 Bruise turns yellow as pigment breaks
down and reenters bloodstream

Cuts
Cut: any tear in the skin
 Blood flows until clot forms
 Scab covers opening to prevent bacteria
from entering body
 Scar: thick tissue that forms to fill
opening

Skin grafts
Pieces of skin that are cut from one part
of a person’s body and moved to
another area
 Used for bad injuries or burns
 Must be taken from victim’s own body or
an identical twin to be successful

 Skin transplants from cadavers or other
sources will typically be rejected in a few
weeks
Assignment – pick one!
Pretend that you are skin, and you have
just gotten a bruise or cut. Write a story
(as the skin) explaining what has
happened, including the healing process
you must go through.
 Draw a diagram that shows how skin
may get injured and how it repairs itself.
 Interview a skin cell, asking it to explain
how it functions, the hard times in its life,
and how it overcomes them.
 Due Monday, 3/7
