Do Now

  • Follow the directions on the Task Card to complete your Do Now slip.

  • Share results w/ a partner. Be prepared to discuss what you think is happening.

1. Overview

  • Do Now
  • Unit Overview
    • 3D Skull Puzzle
  • Dissection: Chicken Wing
  • Notes
    • Basic Terminology
    • Disorders
  • Exit Ticket

What's Going On?

Task 1

You are using “proprioceptors” in your muscles, tendons, and joints to judge your body's position.

Most of us need visual cues (e.g. looking at the position of the X) AND proprioception to give us fine detail of position.

Task 2

Most people find that vision is not an important cue in reproducing written words, because we're used to
the "feel" of writing provided by proprioceptors
in our hands and fingers


Hypothesis: “You are using proprioceptors in your muscles, tendons, and joints to judge your body's position.”

Turn & Talk

1.What evidence can you think of that might support this hypothesis?

2. What gives support and shape to your muscles, tendons, and joints?

3. What else gives you cues to help you judge your body’s position?

Unit Overview: Musculoskeletal System


1. Overview [Dissect: Chicken Wing]

2. Micro - Tired Muscles [Lab: Muscle Fatigue]

3-4. Micro - Healing Bone [Lab: Collagen & Calcium]

5-8. Macro - Fractures [Engineering Challenge: Build a Bicep]

9-17. Final Project: Prosthetics Prototype & Showcase

What else do human bones and muscles do?

From this… to this!

Create a Skull!

CUT OUT each piece of the skull.

LABEL it in pencil with your name in case you lose it.

FINISH CUTTING for HOMEWORK and assemble with your group.

Each group’s skull will be due
at the end of the marking period.

Alternative papercraft:

If students need refresher on skull or assistance with identifying parts of the 3d papercraft puzzle


  • Wash hands w/ soap & water before & after lab.
  • You may use gloves or your bare hands.
  • To reduce the chance of jabbing or cutting yourself, the only tools you will need are scissors and tweezers.

Clean Up

  • Hand in lab write-up.
  • Wash all equipment in hot soapy water.
  • Discard the chicken wing and parts at the end of this exercise.
  • Get Exit Ticket.

A Safe Lab Is A Happy Lab!

1. What are the hazards?


2. What’s the worst that can happen?


3. What do I DO to prevent it from happening?


4. What do I do IF it happens?


Dissection: Chicken Wing


Examine the intact wing

Source: only the skin

Examine the soft tissues

Dissection: Chicken Wing


  • Practice dissection lab skills.
  • Identify structure and function of Gallus domesticus

Clean Up

Next: Take notes on

  • Terminology Overview
  • Muscular Disorders

How do we move our muscles?

  • Threshold Stimulus

Minimal strength required to cause a contraction 

Motor neuron releases enough acetylcholine to reach threshold

  • All-or-None Response

Fibers do not contract partially, they either do or don't

  • Motor Unit


The muscle fiber  +   the motor neuron 

  • Recruitment

more and more fibers contract as the intensity of the stimulus increases

  • Muscle Tone

Sustained contraction of individual fibers, even when muscle is at rest

  • Hypertrophy  - muscles enlarge  (working out or certain disorders)



  • Atrophy - muscles become small and weak due to disuse

  • Muscle Fatigue -  muscle loses ability to contract after prolonged exercise or strain

  • Muscle Cramp  -  a sustained involuntary contraction

  • Oxygen Debt oxygen is used to create ATP, -- not have enough oxygen  causes Lactic Acid to accumulate in the muscles Soreness

                                           *See Magic School Bus 

11. Origin and Insertion

--Origin = the immovable end of the muscle

--Insertion = the movable end of the muscle

The biceps brachii has two origins
(or two heads).

12. Action Potential

the change in electrical potential, passage of an impulse along the membrane (sarcolemma) of the muscle cell

What is rigor mortis?

A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours.

Crime Scene Investigation

What is tetanus?

Tetanus causes cholinesterase to not break down the acetylcholine in the synapse.  This results in a person's muscles contracting and not relaxing.

A tetanus shot must be administered shortly after exposure to the  bacteria.

Once you develop tetanus, there is no cure.

Disorders of the Muscular System

What is Myotonia?

delayed relaxation of the skeletal muscles after voluntary contraction, electrical stimulation, or even being startled.

These “fainting” goats have myotonia congenita

What is Myasthenia Gravis?

  • Means "grave muscular weakness."
  • Autoimmune disease
  • Acetylcholine receptors are damaged


  • A drooping eyelid
  • Blurred vision
  • Slurred speech
  • Difficulty swallowing
  • Weakness / Fatigue

What is muscular dystrophy?

Muscles progressively get weaker, often resulting in inability to walk, talk or breathe.

Duchenne MD occurs in boys (sex-linked inheritance pattern)


ALS, or amyotrophic lateral sclerosis, is a progressive neurodegenerative disease.

The motor nerves that are affected are the motor neurons (motor unit) that provide voluntary movements and muscle control.

A-myo-trophic comes from the Greek language. "A" means no. "Myo" refers to muscle, and "Trophic" means nourishment – "No muscle nourishment." When a muscle has no nourishment, it "atrophies" or wastes away.

Poisons that Affect the Neuromuscular Junction




Lowers the threshold level for an action potential, making it more likely the muscles will contract

Death occurs from convulsions and asphyxia

Strychnine is an antagonist of glycine, glycine is an inhibitor of acetylcholine


classified as a neuromuscular blocking agent—it produces flaccidity in skeletal muscle by competing with the neurotransmitter acetylcholine at the neuromuscular junction

Exit Ticket

Label the parts of the skull:

  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________
  • ________________________________________________________

Numbers are randomized per 3 exit tickets.

Potential Review questions to use instead:

Review Questions:

Do Now

1. How much calcium does a pinto bean contain per serving?

2. How many servings do you need to eat of almonds to equal the calcium absorbed from 1 cup of milk?

3. What do you think causes the difference between the calcium your food contains vs. the calcium you absorb?

Do you know how much calcium is in your diet?

Media Moment

Who is the intended audience?

What do you think the purpose
of this science educational video is?

How might this video be improved &
adapted for teen audiences?

Intro to bone biology

Turn & Talk

What gives bones their strength?

What do you need to build strong bones?

Do bones need to be flexible as well as strong?

What is bone made of?

Task 1 of 3. Refresh. Label the model below with the correct parts of the skeletal structure.

Task 2 of 3.

  • Draw your bone under dissecting scope in DETAIL.
  • Draw a line connecting bone on left w/ term on right.

Magnification level: ______

  • Spongy bone
  • Compact bone
  • Periosteum
  • Diaphysis
  • Epiphysis
  • Marrow

Task 3 of 3. Review. Which parts of the bone make up the following physical features?

Physical Feature


Spongy bone

Compact bone






a) What gives bones their strength?

b) What do you need to build strong bones?

c) Do bones need to be flexible as well as strong? Why?









Initial hypothesis in an if/ then format:

(For example, ‘If a deer rib is soaked in pure distilled water for 8 months, then it’s mass will not change)

Your instructor has placed bones in (a) vinegar, (b) bleach, and (c) water already for you to compare.

When you are ready, complete submerge the bone in its treatment

Label it clearly with – YOUR NAMES and ITS INITIAL MASS (g);

Put it on the designated shelf in the greenhouse.

will affect bone composition by...

a. Bleach will affect bone composition by...

b. Vinegar will affect bone composition by...

c. Water will affect bone composition by...

Type of solution

Col A

Initial average weight (g)

Col B

Final average weight (g)

Percent change
in mass (%)

(ColB–ColA)÷Col A

Do you think the mass will increase or decrease or stay the same?

a) Bleach

b) Vinegar

c) Water

3. Explain how your data (appearance, mass) helps you make a convincing claim about its composition.

4. Why did the bone change mass in each solution? Where did the mass go? Explain.

5. How does the data from the bone in water help us answer our question?

Watch AFTER Lab:

Osteoclasts & Osteoblasts

Watch AFTER lab

Development of Bone

In this investigation we placed bone in vinegar, water, and bleach to observe the effects. How can we explain what we see?

  • Examine your data. Discuss w/ your group and CIRCLE evidence you think is relevant to the claim.
  • For each EVIDENCE blank, fill out the lab data that helps you connect the concept to the claim. Explain why evidence logically connects to reasoning. Why is it important that we discovered this evidence? So what?
  • When done, call instructor over to check & receive exit ticket.

Exit Ticket

Directions: Complete the sentences below. Where possible, include what convinces you of your answer.

Bones get stronger when…

...nutrition contains ___________________________________________________________

....bone diameter is ___________________________________________________________

.…bone length is ___________________________________________________________

Do Now

1. Based on the Bone Growth reading, predict the steps the human body takes to repair bone.

2. In the space below, list or illustrate all the directions and angles you imagine a single bone might break. Circle which one you think is the most common, then explain why.


Do Now

Build a Cast

Bone Modeling & Remodeling

Bone Broth?

How do collagen supplements work?

What makes tough bones?

How do bones lose strength & flexibility?

“I soaked some bones for 4 days in vinegar. I soaked more bones overnight in dilute hydrochloric acid, which removes any inorganic salts from the bone matrix. I also have dried chicken bone that I just stripped of meat.

I also baked more chicken bones at 250º F for 3 hours. Cooking bone removes protein and other organic substances from bone matrix. We have protractors and string, and I want students to think about: what characteristic(s) of fresh bone seem to be due to these organic substances? Please design a lab using the setup. Include a hypothesis and predictions before you begin.”

Osteoporosis &

A Broken Back

What is osteoporosis?

Diagnosing Osteoporosis

Bone Fracture Healing Cards

  • Put the steps of healing in order by numbering them.
  • Write a description of each step using
    • Osteoblast
    • Osteoclast
    • Hematoma
  • Cut them out and add them to your notebook in order.

Phases of Fracture Healing

Image source: 2013 OpenStax College, Wikimedia Commons

Healing Times & Calcification

As the days post-fracture increase, the formation of the callus around the fracture site becomes visible.

Image source: M. Wullschleger, R. Steck, R. Matthys, J. Webster, M. Woodruff, D. Epari, K. Ito and M. Schuetz, "A New Model to Study Healing of a Complex Femur Fracture with Concurrent Soft Tissue Injury in Sheep," Open Journal of Orthopedics, Vol. 3 No. 2, 2013, pp. 62-68. doi: 10.4236/ojo.2013.32012

Lab: Long Bone Strength

A typical long bone consists of compact and spongy bone. Long bones are covered by connective tissue, the periosteum. The shaft of a long bone is the diaphysis and the ends are the epiphysis. In growing individuals, the metaphysis is located between the diaphysis and the epiphysis and is the site of new bone growth. After bone growth is complete the metaphysis is replaced by the epiphyseal lines. Long bones have a cavity filled with bone marrow. Red bone marrow produces red blood cells and yellow bone marrow is fatty. The outer portion of a long bones is compact bone. Osteons contain osteocytes arranged in concentric lamellae around centrally located Haversian canals. The interion of compact is spongy (cancellous) bone. The spaces between spongy are filled with marrow. Spongy bone reduces weight and gives strength. Bones are remodeled throughout life. In fetal development, most bones form from endochondral development, in which cartilaginous templates are ossified. Some bones form by intramembranous bone development, in which bones develop from noncartilaginous connective tissue templates. Osteoblast produce collagen fibers which calcium phosphate crystalizes. Osteoblast break down bone which is necessary for bone growth and remodeling. Osteoblast and osteoclast function together during an entire lifetime.


1. What type of stress do
collagen fibers resist?

2. What type of stress do
mineral salts resist?

3. What benefit does bone
have by having BOTH
collagen and salts?

4. To continue strengthening bones,
what other characteristics do bones have?

5. How do bones break usually?

Compact bone appears like tree rings under the microscope. Each “tree” like structure is called an ________________ which is a vast network of cells and blood vessels. __________________ are mature bone cells encased in a protective ________________, almost like a jacket. Each of these jackets create circular rings that are visible under the microscope called ___________________. All of these rings center around a central ____________________ which supplies _____________________. Connecting the cells together are tiny ________________ which allow for sharing and transporting of nutrients.


1. Get 20 sheets of paper, tape, & string.

2. Starting w/ the 1st sheet of paper, roll it lengthwise as tightly as possible. The paper roll should be 11” long. If needed, use a small piece of tape to hold it together.

4. Continue rolling the sheets of paper around the paper roll using tape as needed, until all 20 sheets have been added, to create a very thick roll of paper. This paper roll represents the concentric shape of a long bone and/or an osteon.

5. Cut approximately a 24” section of string and tie it tightly around the center of the paper roll. Tie the other end of the string around the handles of the bag. Make sure there is enough room to fit textbooks in the bag.

6. Place the very ends of the paper roll (long bone/osteon) at the ends of two desks or chairs, so that the bag hangs between the desks/chairs and does not touch the ground.

7. Place a textbook into the bag. Continue to place textbooks into the bag until the paper roll (long bone/osteon) bends and falls off the desks/chairs. If you completely fill the bag and the paper roll still has not bent, add another string and bag to the paper roll and continue filling the bag with textbooks until it bends.

8. Record the number of textbooks before the paper roll (long bone/osteon) bent in the table below.

9. Use the scale to weigh one of the textbooks and record its weight.

10. Multiply (# of textbooks it took to bend the paper roll) x (textbook weight) = how much total weight the paper roll was able to withstand (support/resist) before bending.

Turn & Talk
Compare “truss construction” to “spongy bone”.

  • Similarities? Alike?
  • How do they add
    strength & support?

Exit Ticket

When designing new materials and methods to help heal the body, what sorts of issues and possible problems do you think the engineering team must consider?

  • biocompatibility with the human body
  • chances of infection
  • material degradation
  • patient stress
  • cost.

When designing new materials and methods to help heal the body, what sorts of issues and possible problems do you think biomedical engineers must consider? These factors contribute to the development of a treatment plan implemented by doctors.


Do Now

Have you ever broken a bone or dislocated a limb?

  • If so, write about your own experience.
  • If not, find someone in class who has and interview them. Write notes from the interview below:

Suggested questions:

  • Where did it break? Direction? Size?
  • How long did it take to heal?
  • What was the worst part about the healing process?
  • How did it feel during the injury, during healing, and when it was healed?

What causes injuries in sports?

What do we think
happened here?

Try to break your bone!

  • Record each attempt to catch the moment of breakage. (Try engineering a Slo-Mo setup for someone’s phone.)

  • How many kilograms (kg) did your bone support before it broke?

  • Remember to clean up and yell CLEAR so no one gets hurt.

Industrial Testing to Fracture

Bones can break for many reasons. On the left is an X-rays of an arm bone broken while arm wrestling. Second from the left is another arm that has both the radius and ulna bones broken. Sometimes bones need help to heal, like in the X-rays of the ankle bone showing screws and a metal plate used to hold the bone together while it heals. In some cases bones can fracture and not come completely apart. The X-ray of the hand on the far right shows what is called a boxer's fracture.

X-ray of a right humerus bone including elbow joint and a portion of the shoulder joint. Image by Chrisnorlin – via Wikimedia Commons.

X-ray of broken forearm radius and ulna bones. Image by Peter Dowley – via Wikimedia Commons.

X-ray of a broken ankle with plate and screws. Image via LFGSS.

Fracture of the fourth metacarpal bone commonly known as a boxer's fracture. Image by Louis Philippe Lessard – via Wikimedia Commons.

8 Bone Fracture Types

  • Transverse: at a right angle to the bone’s long axis.
  • Oblique: diagonal to the bone’s long axis, often with a has a curved or sloped angle.
  • Spiral/torsion: part of the bone has been twisted.
  • Comminuted: broken into several pieces.
  • Avulsion: Part of the bone is separated from its main part.
  • Impacted: Bone fragments have been driven into each other.
  • Fissure: Incomplete; crack is only in the outer bone layer.
  • Greenstick – A fracture in which only one side of the bone is broken.
    • The bone usually has a bend to it and the fracture is located at the outside of the bend. Considered an incomplete fracture in which the bone is bent; occurs most often in children because their bones are not yet as hard as adult bones.

Forces are exerted on the body at all times, but why do some bones break? What forces cause them to lose their structure? After a bone break occurs, the body must attempt to repair the fractured bone. How does the body create new bone matrix to be used in repair? When the injury is beyond the body's ability to heal, what are some surgical methods of restoring the bone to its original structure and function? This is part of what biomedical engineers do: creating devices and approaches that can be used to repair fractures too severe for the body to heal on its own.

Type of fracture



Occurs straight across the long axis of the bone


Occurs at an angle that is not 90 degrees


Bone segments are pulled apart as a result of a twisting motion


Several breaks result in many small pieces between two large segments


One fragment is driven into the other, usually as a result of compression


A partial fracture in which only one side of the bone is broken

Open (or compound)

A fracture in which at least one end of the broken bone tears through the skin; carries a high risk of infection

Closed (or simple)

A fracture in which the skin remains intact

1. Transverse Fracture

A fracture straight across the bone, usually the result of sharp, direct blows or stress fractures caused by prolonged running.

The break occurs at a right angle to the bone’s long axis.

X-ray image of a transverse fracture of the middle-third of the right humerus with anterior dislocation of the glenohumeral joint. It was treated with modified intramedullary nailing.

Image source: National Library of Medicine, National Institutes of Health

A bone fracture caused by
a twisting force.

3. Spiral/Torsion Fracture

baseball pitcher’s broken arm ➔

(left) An s-ray image of a humeral shaft spiral fracture (upper arm) in a major league baseball pitcher.

(right) A spiral fracture of the distal fibular (calf bone) and distal tibial (shinbone) metaphysis.

Image sources:

(left) National Library of Medicine, National Institutes of Health

(right) National Library of Medicine, National Institutes of Health

5. Impacted Bone

One bone pushes into another end

(here in the pictures, it’s teeth)

An x-ray image of impacted teeth. The situation of an impacted tooth is analogous to an impacted fracture, which is when the broken end of a bone is pushed into the other broken end. For impacted teeth, the new teeth push up into other teeth as they are trying to grow.

The arrows point to where the new teeth are pushing into other teeth causing pain.

Image sources:

(left-vertical) 2005 Albert, Wikimedia Commons

(right-horiz) 2009 Gaming4JC, Wikimedia Commons

4. Comminuted Fracture

broken into several pieces

An x-ray image of a comminuted fracture of humerus. Multiple pieces of bone are clearly seen.

Image source: 2004 Bill Rhodes, Wikimedia Commons

Compound or Open Fracture

- one end of the broken bone breaks the skin

- multiple types of fracture



An open/compound fracture is one in which one end of the broken bone breaks the skin.

In this image, the tibia and fibula both have compound fractures.

Image source: 2008 Saltanat ebli, Wikimedia Commons

Joint Fractures require movement

left capitulum humeri (fractured)

X-ray image of an elbow fracture. The left capitulum humeri is fractured.

Fractures at joints require special treatment to maintain mobility of the joint. For example, a cast left on too long on an elbow results in calcification, which causes the bone to remain in the same position. Thus, it is essential that joints stay mobile during the healing process.

Image source: 2010 Thomas Zimmermann, Wikimedia Commons

Treatment Options Depend On...

  • Location, fracture type and its characteristics
  • The person’s age
  • The person’s activity level
  • Bone quality

Exit Ticket

1. Describe the process of natural bone repair within the human body.

2. Describe four different types of bone fractures.

3. Which types of fractures are most difficult to repair? Explain why.

Exit Ticket

4. What factors might affect bone strength?

5. Research and describe at least three different types of surgical fracture repair.

6. What factors do engineers need to consider when designing new treatments?

Do Now

Linear motion:

one-dimensional movement along a straight line

1. List 3 activities based on linear motion.

Angular motion:

motion of a body about a fixed axis
(or fixed point)

2. List 3 activities based on angular motion.

6-9. Macro - Fractures & Interventions

  • Do Now - Angular & Linear Motion Activities (Engage)
  • Videos: Biomechanics? Bite Force?
  • Gallery Walk: Hard or Fast biter?
  • Jeopardy! Card Match - Review Lever Terminology (Engage)
  • Engineering Challenge: Build-A-Bicep (Elaborate)
  • Exit Ticket

Why Study Biomechanics?

Kicking a Soccer Ball: What Happens?

  • Take a long step forward with the opposite foot so that it lands just beside and slightly in front of the ball.
  • The body leans forward.
  • The kicking leg and hip lag behind.
  • Swing the hip and upper kicking leg (lever) forward.
  • The lower leg lags behind. The knee stays bent.
  • The toe points away from the ball.
  • Arms at side for balance, body leans back.
  • As the hip and upper leg continue forward, swing the lower leg forward as the knee straightens.
  • The foot lags behind.
  • The foot makes contact with the ball after the leg is almost straight.
  • Follow through with the leg well after the kick.

Put these in order of when they happen

Moveable Levers

  • 1st class lever:
    • Skull - extension against resistance with the spine as the fulcrum
  • 2nd class lever:
    • Gastrocnemius/Soleus - plantarflexion against resistance with the ball of the foot as the fulcrum
  • 3rd class lever:
    • Biceps—elbow flexion against resistance with the elbow as the fulcrum

Jaws as Levers

An excellent example of levers in nature is our jaw. Its shape

is just a little bit different than a simple plank and pivot

point, but the system still behaves the same.

The jaw is an “L” shape with the effort force provided by a

muscle that pulls on the vertical portion of the jaw and it

rotates. The rotational point acts as a fulcrum. This results

in a force at the front teeth. The total force is partially

determined by the muscle strength attached to the jaw,

but that initial force is still translated


Review: Which Class Lever? Why?


The fulcrum and load are at opposite ends of the lever and the effort lies between. An example of

this is a biceps curl. The load is in the hand, the fulcrum is at the elbow and the biceps make the


Fulcrum = Elbow joint.

Load = Weight of the forearm and dumbbell.

Effort = Bicep muscles working to flex arm and lift weight.

Third class levers are the most common in the human body but are not that efficient (in comparison to second class levers) in terms of applying force. The location of the fulcrum, load and effort determines the mechanical advantage and the lever class. The force you apply in third class levers must always be greater than the load.

Review: Which Class Lever? Why?


The fulcrum is between the effort and the load and both. An example of this can be heading a football where the neck and head are being flexed and extended. The head pivots on the atlas (fulcrum). The load is the weight of the head going down and the effort is the muscles at the back of the neck pulling down. Fulcrum = Joint between head and first vertebra Load = Weight of the head (cranium) Effort = Muscles used to flex and extend the head and neck (eg trapezius)

Effort and load are acting in the same direction. There are very few first class levers in the human body

Tricep dips. A football player moving their head backwards to perform a glancing header. A gymnast tucking their chin to chest to perform a forward roll.

Review: Which Class Lever? Why?


The fulcrum is at one end of the lever and the effort is at the opposite end with the load in the middle of the lever. An example of this is stepping up onto your toes. The fulcrum is at the toes. The load is that of the body going through the middle of the foot and the effort is in the calf muscles pulling the body upon to the toes. Fulcrum = Joints between metatarsals Load = Weight of the body Effort = Muscles used to create the movement of plantar flexion (eg gastrocnemius)

The direction of effort is the opposite direction to the load.

Summary from:

Gallery Walk: Hard or Fast biter? Why? Which is better?

Video: T-Rex Bite Force

Mammals vs dinos

Video: Pirahna Bite Force

Jeopardy! Card Match - Review Lever Terminology





EXAMPLE of 1st class lever


EXAMPLE of 2nd class lever


EXAMPLE of 3rd class lever



DIAGRAM of 1st class lever

DIAGRAM of 2nd class lever

DIAGRAM of 3rd class lever

Work = Force × Distance

Levers consist of a rigid bar, a fulcrum (pivot point), the load (what you want to move) and the effort force you need to exert to lift the load. They work by translating the effort force into the force that moves the load. This can give you a mechanical advantage, which can be found by using the principle of work.

The effort force times the distance to the fulcrum needs to be the same for the resulting force on the load times the distance of the fulcrum. The mechanical advantage is the ratio of the effort force to the load force (or the load distance over the effort distance).

“Force Advantage” - It’s Mathematical!

If the distances are equal, then the force “in” is equal to the

force “out”. But if the force is small over a larger distance,

that translates to a large lifting force over a small distance

when the fulcrum is close to the load. Similarly, a fulcrum

closer to the effort force, means a small force over a small distance results in a smaller force over a larger

distance. This is not a great lever for gaining force

advantage, but it is seen in nature quite often because

it can give a different advantage – speed.

Jaws as Levers

An excellent example of levers in nature is our jaw. Its shape

is just a little bit different than a simple plank and pivot

point, but the system still behaves the same.

The jaw is an “L” shape with the effort force provided by a

muscle that pulls on the vertical portion of the jaw and it

rotates. The rotational point acts as a fulcrum. This results

in a force at the front teeth. The total force is partially

determined by the muscle strength attached to the jaw,

but that initial force is still translated

Jaws as Levers

Speed vs. Power?

In nature there is a wide variety of jaw shapes. Some are

rather short, meaning the effort and load lengths are

comparable and the force provided by a jaw muscle (effort)

is equal to or more at the end of the jaw, resulting in a hard

bite. Some jaws are long and slender, meaning the distance

to the load is much longer than the distance to the effort

provided by the muscle making the force advantage more

or less non-existent. There is however a speed advantage.

This speed advantage comes from solid body rotation.

When a rigid body rotates, everything moves together.

The point farther from the fulcrum (rotation point)

has a larger turning radius, meaning it has a larger

circumference in which in to turn. Since the whole jaw

rotates together, the farther point needs to move along

a longer arc in the same amount of time to keep up,

meaning it rotates faster. The speed at which a muscle

contracts in order to close the jaw then gets translated

to a faster speed at the end of a longer jaw. The

distance at which the lever moves in the same amount

of time is proportional to the distances between the

fulcrum. The velocity is just those distances over the

same amount of time.

Mini-Lab: Musculoskeletal Biomechanics & Levers

Optional: Simpler Penny Lab

1) Set up your lever as shown in picture 1. Then try to lift

the book by pushing with one finger at the effort point.

Keep adding books until you can’t lift them with just one

finger. Record the distance between the load and fulcrum

and the effort and fulcrum. Move the pencil (fulcrum)

around to see where it’s easier or harder to lift the book,

recording the distances again.

2) Set up your lever as shown in picture 2. Then try to

lift the book by using one finger at the effort point and

repeating the rest of step 1.

3) Set up your lever as shown in picture 3. Then try to

lift the book by using one finger at the effort point and

repeating the rest of step 1.

Explore: Force Advantage

Measure the mass of a single penny and record this


2) Set up a first class lever using a pencil for the fulcrum

and ruler. Place the pencil (fulcrum) 2 times closer to the

load than the effort and tape it to the ruler. Then tape a

cup to either end of the ruler. Place about 15 pennies in

the cup on the load end.

3) Calculate the force of the pennies on the load end

exerting downwards as a result of gravity.

Force = masspennies x 9.8 m/s2

4) Make a prediction for how many pennies it will take in

the effort cup to lift the load cup.

5) Start putting pennies into the effort end one at a

time until the load lifts up. Record the number of

pennies and calculate the mass of the pennies.

The force of the effort is then the mass of the

pennies x 9.8 m/s2

. Record this information.

6) Repeat all steps with different fulcrum points

(equal distance between load and effort and 2 times

closer to the effort). Record all the information


7) Graph your results of mechanical advantage vs.

effort distance

Explore: Speed Advantage

1) Set up a first class lever by placing a pencil underneath

the ruler. Place it anywhere you want to begin and note

the distance of the pencil (fulcrum) from the point where

you will push on the ruler and the distance from the

other end. Record this information.

2) Measure the height of the end you will be pushing on

and record that information.

3) Push that end of the lever. Then measure and record the

height of the other end. As you push you can time how

long it takes. If you do not have a stopwatch or it is too

fast, assume it took 1-second.

4) Use the information recorded to calculate the speed of

the end you pushed and the speed of the other end of the

ruler: Speed = height/time.

5) Repeat steps 1-4 with the fulcrum at different points

under the ruler.

6) Create a plot that shows the speed vs. effort distance to

the fulcrum

1) How does the lever offer a force advantage?

2) How do levers offer a speed advantage?

3) Is there a trade-off between force and speed?

4) What is the relationship (qualitative or quantitative)

between levers and their speed/force advantage?

5) What kind of lever is a jaw? Explain.

6) Based on what you have learned can you identify

whether or a not an animal is speed or force adapted

based on the shape of its mouth? Explain.

Exit Ticket

  • How do levers offer a speed advantage?
  • What kind of lever is a jaw? Include a labeled illustration in your answer.
  • In your own words, explain the relationship between the ratio of [effort distance] and [load distance] to the fulcrum.

Engineering Challenge: Build A Bicep!

Engineering Challenge Today

Goal: create a device to help muscle recovery of a bicep by assisting it, allowing it to REST more and RECOVER sooner.

Materials: string, rubber bands, spring scale, ruler, scissors, paper

Your prototype will be tested for:

  • Force applied (how much pulling force a device has when arm is unbent)
  • Distance applied (how far a device helps the arm bend)
    • (don’t want rubber bands too tight or break)


  • Shoulder harness
    • 2 loops of rope like a figure 8, one around arm and the other around chest
  • Hand harness
    • Figure 8, one loop going around middle finger and wrist
  • Use rubber bands to connect shoulder harness

Treatment Options Depend On...

  • Location, fracture type and its characteristics
  • The person’s age
  • The person’s activity level
  • Bone quality

Nonsurgical Treatment Options




Splints, casts and braces are designed to immobilize the broken ends of the bone until the body can heal the fracture on its own.

Image sources:

(left) splint: Emergency First Aid

(upper right-cast) 2009 Enareksi, Wikimedia Commons

(lower right-brace) © Author Megan Ketchum, University of Houston

Show students this inspiring 3D-printed cast that uses ultrasound to speed bone healing (good image) at:

Newest tech: 3D-printed cast that uses an ultrasonic pulse generator to speed up bone healing

Turn & Talk

  • What are the advantages
    of a 3D-printed cast vs. traditional plaster casts?
  • How might the pulse
    increase healing speed? Explain.

Surgical Treatment: External Fixation

Bolts or screws are inserted into uninjured bone surrounding the fracture. Often used to repair open fractures.

Holes in the skin require diligent would care to avoid infection.

Internal fixation involves the placement of plates and/or screws on the bone itself, without the external stabilizing device.

Image sources:

(top) 1999 Professor Mitura of the Technical University of Lodz, Poland, Wikimedia Commons

(bottom-forearm & hand) 2006 Dekkanar, Wikimedia Commons

Internal vs. External Fixation

Internal fixation – nothing protrudes through the skin

External fixation – part of the stabilizing device is outside the skin; the circular fixator can also be used to lengthen bones.

Biomedical engineers design these types of devices that are used in surgical bone repair.

Image sources:

(top-left) 2008, National Institutes of Health, Wikimedia Commons

(bottom-left) 2011 Nevit Dilmen, Wikimedia Commons

(top-right) 2005 liegt vor Wikimedia Commons

(bottom-right) 2011 Nevit Dilmen, Wikimedia Commons

Show a video on leg lengthening (external fixation) and how it works at:

Location of Fracture

  • Which bones are more likely to break?

Ribs, wrists, fingers, toes, collarbones

  • Why are certain bones more likely to fracture?

The body is designed to withstand forces.

Legs receive impact while
walking and jumping.
Thus, leg bones require a
significant amount of force
to break.

Image source: Microsoft clipart:|mt:2|

How Does Treatment Depend on Location?

  • Certain treatments cannot be used on some fractures due to the location.

For example:

    • Casts cannot be used on all parts of the body,
      such as moving joints.
    • Finger or toes are often treated by using a
      nearby finger or toe as splint.
  • The forces the body withstands at certain locations allows only some treatments.

Healing Times & Calcification

As the days post-fracture increase, the formation of the callus around the fracture site becomes visible.

Image source: M. Wullschleger, R. Steck, R. Matthys, J. Webster, M. Woodruff, D. Epari, K. Ito and M. Schuetz, "A New Model to Study Healing of a Complex Femur Fracture with Concurrent Soft Tissue Injury in Sheep," Open Journal of Orthopedics, Vol. 3 No. 2, 2013, pp. 62-68. doi: 10.4236/ojo.2013.32012

Phases of Fracture Healing

Image source: 2013 OpenStax College, Wikimedia Commons

Step 8 of 8: Create an infomercial

Use phones to film and upload.

Step 1: ASK questions of each other

Step 2: BRAINSTORM ideas

Step 3: PLAN design in worksheet

Step 4: Get plan approved by instructor

Step 5: Get materials

Step 6: Test APPLIED force

  • Wear but keep hand harness off, pull harness down so rubber bands (if you used any) are as long as they would be with arm extended.
  • Attach spring scale to where rubber bands meet hand harness or where your finger meets your device and measure force applied by rubber bands.
  • Record measurements in Newtons.

Stronger force = bicep works LESS to bend arm.

Do Now: Start building the 2nd prototype of your device from yesterday. Test FORCE and RANGE (distance).

Step 7: Test DISTANCE force

  • Wear device, pull hand harness down.
  • Place ruler where rubber bands attach to hand harness.
  • Slowly raise hand harness until rubber bands are no longer stretched.
  • Measure distance the rubber bands are stretched.
  • Record measurements in centimeters.

Greater distance = longer machine helps raise arm.

Upload Infomercial to Google Classroom

You’ll be assigned another group’s to watch & give feedback on..

Clean up and take a break!

  • Class code: #######
  • Tap Share something with your class…
  • Tap paper clip to attach a file
  • Name it w/ PRODUCT name & group names)

Exit Ticket

1. How do levers offer a speed advantage?

2. What kind of lever is a jaw? Include a labeled illustration in the box as part of your answer.

3. Explain the relationship between the ratio of [effort distance] and [load distance] to the fulcrum.

Do Now


  • List activities children (K-12) tend to do or like to do. Of the places you listed, what are 3 major categories that stand out to you?

  • List places children (K-12) tend to hang out in. Of the places you listed, what are 3 major categories that stand out to you?

  • List risks or dangers these places (from #2) might present or have a high chance of having. Of the risks you listed, what are 3 major categories that stand out to you? How did you decide how to sort them?

How might these be connected?

  • Land Mines

2. Children

3. Amputation

How are these connected?


CONTENT: amputated limb

What do we know about Afghanistan?

How does this all connect?

Afghani noodle-making

Mine Kafon: first iteration; prototyping using recyclables, etc.

Mine Kafon 2.0

Keep going!

Practice Step: Connect to the Client

  • Take 5 minutes to tell your partner how you get ready in the morning.
  • Identify 1 thing that bugs you about your morning routine.
  • Switch.

Practice Step: Define the Problem

  • “What I hear is…”
    “It sounds like a problem might be…”

  • “Not exactly…”
    “Yes, that’s what it is...and…”

Outcome: Define a problem & share.

To set up for next time, complete:

  • Team Jobs & Agreements (p. 3)

2. Define the Problem by filling out Fact Pages (p. 4-5)

Due at end of class: Packet through page 7
(Before Disability Awareness).

Last time...

No More Peg Legs
and Hooks

Better Prosthetic Design through


No More Peg Legs and Hooks Presentation > The Pirates of Prosthetics: Peg Legs and Hooks lesson >

Image source: 2006 J.J., Wikimedia Commons,,_vector_version.svg

History of Prostheses

  • Used in Greek and
    Roman times
  • Prosthetic toe found on
    3000-year-old Egyptian mummy
  • Before 1840s, few survived amputation and prosthetic supplies were often scavenged
  • Surgery advances (anesthesia in 1842) > more precise surgeries and better prosthetic fit
  • So many amputees from WWI and WWII increased the need for better prosthetic designs

Image sources:

(top left; ancient Egyptian replacement plaster toe laced onto rest of foot) 2007 Jon Bodsworth, Wikimedia Commons

(top right; artificial hand and harness) 1812 Pierre Ballif, Prussia via Wikimedia Commons

(bottom left; soldier with two prosthetic legs) 1948 U.S. Library of Congress via Wikimedia Commons

(bottom right; hand prosthesis holds baseball) 2007 U.S. Navy via Wikimedia Commons

How Do Prostheses Work?

Purpose and benefits:

  • To restore functionality and capabilities of lost limb
  • Enables patients to regain mobility, conduct daily living activities, keep a job

Engineering design considerations:

  • Location (at a joint? cosmetic vs. functional?)
  • Strength vs. weight
  • Attachment method
  • Available materials
  • Cost

Which hand is a prosthesis? ➔

Engineering Design Considerations

Location of amputation: Does the prosthesis need to include a movable joint, such as a knee or elbow? Is the purpose of the prosthesis to improve appearance only (an eye or ear) or to perform some of the lost functions of the original limb, or both?

Strength vs weight: The material needs to be strong enough to perform and hold body weight if necessary, but light enough to move easily. May be a trade-off to balance strength vs. weight.

Attachment: How will the prosthesis attach to the body? How do you keep it from falling off?

Available Materials and Cost: What materials are available to use? What materials make sense for the particular prosthesis? How much do they cost? Is the cost reasonable so that patients can afford the prostheses? May be a trade-off to balance available materials with cost of materials.

Image source: (A soldier practices his fine motor skills using his prosthetic hand.) 2007 Fred W. Baker III, U.S. Dept. of Defense

Parts of a Prosthesis

  • Interface (socket): Where the prosthetic
    device meets the remaining part of the limb

Usually includes a suspension system
that uses an attachment method:

    • A suction valve forms a seal with the limb
    • Locking pin
    • Belt and harness
  • Components (pylon): The internal
    working parts of the prosthesis
  • Foot: Or hand, in the case of an arm prosthesis
  • Cover: May be covered in a material so more lifelike



Image source: (drawing of leg prosthetic showing basic parts) Figure 4, U.S. Department of Veterans Affairs

Main Types of Artificial Limbs

  • Transradial: Replaces an arm from below the elbow (includes the wrist, hand and fingers)
  • Transhumeral: Replaces an arm from above the elbow (includes the elbow, wrist, hand and fingers)
  • Transtibial: Replaces the leg from below the knee (includes the ankle, foot and toes)
  • Transfemoral: Replaces the leg from above the knee (includes the knee, ankle, foot and toes)



The more joints that are included in a prosthesis, the more complicated the design must be to successfully emulate the complexity of natural body movements and functions.

Image source: (silhouette of body; modifications by Controle su diabetes (pdf), Centros para el Control y la Prevencion de Enfermedades (CDC)

Modern Materials

Modern materials make prostheses stronger, lighter and more realistic in appearance and use:

  • Advanced plastics
  • Carbon fiber composites
  • Electronic components for control

A brain-controlled prosthetic limb➔

Image description: This brain-controlled modular prosthetic limb is controlled by surface electrodes that pick up electric signals generated by the muscles underneath the skin. The electrodes then convert those patterns into a robotic function.

Image source: U.S. Navy

Categories of Modern Prostheses

  • Specialty

2. Functional

2. A brain-controlled functional arm prosthesis built to closely mimic natural hand movements; 2011 FDA/Johns Hopkins University Applied Physics Laboratory

Categories of Modern Prostheses

3. Cosmetic

    • Eye
    • Fingers
    • Leg


3. Cosmetic prostheses restore the appearance of lost structures (sometimes ALSO have functional abilities)

(eye; replacement eyeballs) 2014 U.S. Dept. of Defense

(fingers; thimble prostheses for right, middle and ring fingers; before/after) VA Research & Development

(thumb prosthesis) VA Research & Development

(leg prosthesis) National Library of Medicine/National Institutes of Health

Controlling the Prosthetic

Electronic systems:

Electrodes implanted in residual limbs (forearm in this example) control muscle movements ➔

Electrodes implanted into the brain (neural implants) provide residual limb muscle control via neuron signals

External cable/switch control systems➔

Image sources:

(Top; cable control system for a below-elbow prosthesis actuated by gross body movements) VA Research & Development

(Bottom; man opens door using prosthetic robotic hand actuated by electrodes implanted in his forearm) Sharon Holland, U.S. Department of Defense

Biomedical & Mechanical Engineers

Engineers apply their expert knowledge of:

    • anatomy
    • neurology
    • biomechanics
    • sensor motor control

to design prostheses and other medical devices that improve mobility and function for people

The DEKA arm features six preprogrammed grips so users can perform a variety of everyday tasks, from handling small, delicate objects to using tools.

More info on the prosthesis in the photo: The DEKA system is a huge leap forward in technology from existing prosthetic arms and hands. Still today, most upper-limb amputees use a hook or split-hook prosthesis that offers only limited function, or an artificial hand that looks natural on the outside but provides no finger movement or grasp. The DEKA arm offers a variety of firsts: It has multiple powered joints and degrees of freedom and can carry out several movements at the same time. It uses an array of sensors and switches and has wireless control. The wrist and fingers adjust into six different grips, enabling users to perform a range of everyday functions: picking up a grape or a glass, holding a tube of toothpaste, turning a key in a lock, using a power tool. Many features of this arm are unprecedented.

Image source: 2014 U.S. Dept. of Veterans Affairs

Review: Design Engineering

2 practice engineering challenges

Engineers solve problems

  • Today we are going to practice our problem-solving skills
  • We will use:
    • DESIGN

Design Engineering Loop

  • Process is not always linear
  • Can skip steps or go in reverse
  • “Iterative” process requires repetition to solve problem
  • Define requirements/constraints

Image retrieved from

Practice Engineering Design Solution—

  • REQUIREMENT: Build the tallest freestanding tower possible from 5 index cards
  • CONSTRAINTS: Time limit of 8 minutes; no tape allowed; must be freestanding for 10 seconds

Assign a recorder to your group to document on paper where you are in the design process; keep a record and be ready to share triumphs/problems


  • What went well?
  • What would you change if you could do it again?
  • What did you learn from this process?
  • What stage in the loop is this?

Bioengineering Challenge:

Prosthetic Hand

  • Design a “bionic” hand that can pick up a paper cup using common materials; present to class
  • Sketches of design and materials list are required
  • When prototype finished, take photos and share on Google Classroom.
  • Compare your prosthetic hand’s ligaments, tendons, bones, and muscles to actual biological equivalent hand/arm tissues (For instance, if you used tape to link bones together, then tape is your prosthetic “ligament” material).


Points Assigned

Self-Evaluation Group Score

Teacher Score

Preliminary sketches
and materials list



Final prototype

  • Can pick up paper cup
  • Not larger than 50 cm x 30 cm in size



Class presentations

  • Explain function of final design
  • What would your team change? Keep?



Recap summary showing analogous biological parts of prosthetic hand



Final prototype: Task achievement

  • Device can pick up a small paper cup (bonus points if weight is added to cup)
  • Must hold cup for 5 seconds without dropping
  • Engineer can hold the prototype with one hand while stimulating muscle movement with another. Only one student at a time can manipulate the prosthetic hand while completing the task.
  • Used available or approved materials
  • Within size constraints

Prosthetic hand: Class Presentation

  • HOW: Explain the methods used to construct your hand
  • 😅😎What challenges/successes did you encounter?
  • What would you improve if you could make another iteration of your prosthetic hand?

Prosthetic Hand: Final Video Due

On Google Classroom:

Post video showing:

  • 1. Introduce your group
  • 2. Show your bionic hand picking up a cup; explain function
  • 3. Successes/failures?
  • 4. Explain muscles, tendons, bone, ligaments in prosthetic hand

Sources and inspiration used for this lesson:

  • has great ideas, along with some guidelines for a prosthetic hand and intro STEM activity to help show the design process
  • Scientific American/Science Buddies link on how to build a prosthetic hand:
  • Santa Ana, CA school district has a fantastic collection of science lesson plans and units of study combining common core and NGSS best practices. Highly recommended! I took inspiration from this lesson:

P. 8, Part B

Disability Experiment

  • See what it’s like to live without a lower leg.
  • Use the cloth in front to tie your ankle to your thigh.

Do Now - Physiology

  • Find your Prosthetics Workbook.
  • Get a laptop.
  • Research 3 prosthetic ideas.
  • Finish by p. 14 by the end of class.

By end of class:

_ homework (extra copies @front counter)

_ proposed shopping list (p. 13)

_ peer evaluation form (@front counter)

_ 2 IDEATE designs with PROs and CONs (p.14)

Final Physiology Build Day

  • Finalize prototype
  • Rehearse presentation?
  • Create poster with
    • Product name
    • Inventor names
    • Pros
    • Cons
    • Cost
  • Present & grade each other

See instructor for:

  • How to cut the PVC pipe
  • Springs (extension & compression)
  • Any materials you can’t find

consider: stability, strength, flexibility, adjustability, patient use

Prosthetics Unit Slides - Google Slides