First- and second-class levers generally are very efficient, especially when the loads are located close to the fulcrum while efforts are further from the fulcrum (Figures A and C). They are the: Let us consider the first of these simple machines: the lever. Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse! When an effort is applied to one end of the lever, a load is applied at the other end of the lever. What is the first class lever or class I lever? Have you ever noticed how much easier it is to do a calf raise with 50 lbs than it is to perform a 50-lb bicep curl? See our privacy policy for additional details. The position of the fulcrum in the lever system determines the balance between speed and strength. In a calf raise, the effort comes from the gastrocnemius muscle, which is attached to your calcaneus bone. Other examples of class III lever: a fishing rod, sugar tongs, knife, fire tongs. To understand why some synovial joints have more efficient lever systems, we must first understand the relationships between the three lever parts: an effort or force applied to the lever, a fulcrum, and a load. Push-ups also utilize a second-class lever. Synovial joints are moveable joints; a few examples of these are the shoulder, spine, knee, elbow, and ankle. This website uses cookies to improve your experience while you navigate through the website. The effort in a class 1 lever is almost in a single direction. The elbow joint flexed to form a 60 angle between the upper arm and forearm while the hand holds a 50 lb ball . Big Idea: Machines are devices that transfer force and energy. First-Class Lever Examples A seesaw is a first-class lever. Center the ruler over the pencil, and set a small object or weight(this is called the 'load') on one end of the ruler. Innerbody Research is the largest home health and wellness guide online, helping over one million visitors each month learn about health products and services. To move the seesaw one party must push downward with their bodyweight (force). Levers can be classified as either first, second or third class, according to Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. Which viviparous animal can bear extreme heat because of its body structure? A load (the item you want to weigh) is placed on one pan. Examples, however, are exercises that require elbow extension, such as dumbbell triceps extensions, cable triceps push-downs and triceps dips. The force is applied at its point of insertion on the ulna in the forearm, the elbow . A steering wheel, for instance, can be considered as a first class lever when you look at its turning motion. These are some perfect examples of this type of lever and they are-. What is one purpose of the wedge?a. Read more: Physical Benefits of Dips Exercises. In this, we can see that we have to apply an effort (force) against gravity. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected. As the center component of a third- rate lever system, the effort is located between the fulcrum and the load. Essentially, the effort is equivalent to the load. A lead, a crowbar, or a pair of scissors, for example. The 1st part is The Fulcrum, known as the pivot point, axis, or balance point, The 2nd part is the Resistance or load. These applications will - due to browser restrictions - send data between your browser and our server. Increase the length between the applied effort and the pivot. Torqueis the amount of force required to cause an object to rotate around itsaxis(or pivot point). Jones, A. Verified Answer for the question: [Solved] A third class lever is: A) Similar to a first class lever. By using this site you agree to the use of cookies for analytics and personalised content. To understand this concept, lets look at a basic example of a first class lever. Seesaw is an example of first class lever where the pivot(fulcrum) is in the middle. In the human body, a bone forms the lever and the fulcrum is a joint where a bone can move around the pivot point. Other examples include seated and lying hamstring curls, seated leg extensions, dumbbell flies, and shoulder dumbbell front and lateral raises. You apply force to the arms. 10 Examples of Nonlinear Relationships in Real Life. Which type of lever is this? 11 Lever Simple Machine Examples in Our Daily Life, Eco-Friendly Materials- Properties, Need, Benefits and, 11 Wheel and Axle Examples Used in Our Day to Day Life, Types of Combustion: Definitions, Steps, Examples,, Francis Turbine: Definition, Parts, Working, Advantages and Disadvantages and Much More, Top 10 Fixed Pulley Examples in Everyday Life, Boiler Feed Pump: Definition, Types, Parts, Working, Advantages, Simple Machine: Definition, Types with Funny Home Examples, Wheel and Axle Examples Used in Day-to-Day Life, 12 Inclined Plane Examples Can be Seen In Everyday Life, What are Compound Machines? The calf as a second class lever. For a third-class lever, E is the middle component. Proficient with multiple ATS such as Smart Recruiters, Jobvite, Lever & Greenhouse. The other side or your other hand (the load) is lifted up. First class lever is one of the 3 classes of levers and is the simplest lever. Video footage from Muscles & Kinesiology. These are some examples of this type of lever-. a lever for which the muscle force and resistive force first-class lever (definition) act on the same side of the fulcrum, with the muscle force acting through a moment arm longer than that through which the resistive force acts a lever for which . The calculator determines the fulcrum position and the effort arm of a 1st class lever, in which the fulcrum is between the effort and load. If the masses are the same, both masses must be the same distance from the fulcrum for the lever to balance. It changes the distance over which the force is applied in exchange for how much force must be applied. Like in the images above, you can use the draw tool in Visible Body Suiteand Muscles & Kinesiology to draw diagrams to help you determine which kind of lever system a certain joint uses. Balance scales are one of the common tools to weigh any goods with having a fulcrum in the middle while effort is at one end of the container and the load is at another end of the container. When you try to curl the weight, your bicep has to work harder because it is at a mechanical disadvantage. This is a quick reference to types of levers. Decrease the length between the applied effort and the pivot. Read more here. Screenshot from Visible Body Suite. A car jack features a rod (beam) on which you apply force. I hope to see you in the next sessions. First-Class Lever. Atlanto-Occipital Joint as a First Class Lever An example of a first class lever in the human body is the head and neck during neck extension. Some of our calculators and applications let you save application data to your local computer. Our bodies are composed of a variety of synovial joints that function as lever systems. In an essence, a first-class lever has a fulcrum that is situated between the effort (force) and the load and travels over a wide distance to move the weight over a shorter distance. The fulcrum is in the middle. A first-class lever has the axis (fulcrum) located between the weight (resistance) and the force (figure 1.21a). You apply force on the end of the rod to pry open a lid or move a load. A force (weight) of 1 pound is exerted at a distance of 1 ft from the fulcrum. Why is this? Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. A first-class lever, in which the fulcrum is between the load and the effort, can aid in work by changing the direction of the force and by increasing the efficiency or mechanical advantage of the force applied. Can you figure out which lever system the knee uses? The distance between the elbow joint and the insertion site of the bicep tendon is very small, especially when its compared to the distance between the elbow joint and the weight in your hand. Video footage from Muscles & Kinesiology. First Class Lever The effort is on one side of the lever and the load is on the other side. The load is inbetween the fulcrum and effort such as in Wheel barrow. Class 1 lever The effort in a class 1 lever is in one direction, and the load moves in the opposite direction. These types are based on the relative position of the fulcrum, load, and effort in the lever body. In a first class lever system, the fulcrum or pivot point is located on the lever between the effort force and load or resistance being moved. Copyright 2023, Lets Talk Science, All Rights Reserved. The first class lever is the most common lever in the human body. First class levers are very useful for lifting large loads with little effort. First Class Levers. A first-class lever is a beam, rod or stick with the load at one end, the fulcrum in the middle and the force applied on the other end. The handle bars support is the fulcrum. Screenshot from, Plantarflexion in action. The effort is applied on one side of the fulcrum while the load is placed on the other. Lever. When the point where the force is applied is moved farther away from the fulcrum, the force needed to push the lever down decreases; however, the distance that it must be pushed increases. Levers can be grouped into three categories: First class, second class, and third class. Here, I am not going deep into these types as I discussed these types and more in the Article given down below. It will rotate counter-clockwise. First-class levers in the body are rare, and few exercises utilize them. But opting out of some of these cookies may affect your browsing experience. The predetermined weights are added or removed from the pan until balance is achieved. Example: see-saw, scissors, pulley etc. If the two arms of the lever are of equal length, the effort . If the fulcrum is closer to the effort, then more effort is needed to move the load a greater distance. A weight A of 1 pound is exerted at a distance of 1 ft from the fulcrum. Abhishek Tiwary is a blogger by passion and a Quality Engineer by profession. Have fun learning! In both the atlanto-occipital and elbow joints, the first class lever system is designed to increase the speed of the system at the cost of muscle strength. We will add more details to this topic in the near future.Please note that we call the first-class lever as class one lever also.Similarly, we know Second class lever and third class levers as class two lever and class three lever respectively. Other examples of class I lever: a pair of scissors, beam of physical balance, claw hammer, crowbar, pair of pliers. The clawed end of a claw hammer is used to pry open or pull nails out of wood. Lever : The placement of the fulcrum determines the IMA for a lever. For example, some muscles exist on one side of a joint, but their tendon crosses over the joint and applies a force to a bone on the opposite side. To make it even easier, you could move the cinder block closer to the rock, moving the fulcrum closer to the load. I hope you enjoyed being here and got your desired information. However, if a 10 pound object is placed 2 feet away from the fulcrum on one side of the first-class lever, a 5 pound object must be placed 4 feet away from the fulcrum on the other side for the lever to be balanced. For example, the forearm is a. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". All of these lever systems are used throughout the entire human body. Rise back up and repeat 10 times. A lever mechanism where the input effort is higher than than the output load is often characterized as a third-class lever mechanism. A Class 1 lever has the fulcrum placed between the effort and load. Examples of third class lever include tweezers where effort is applied in the middle. The force pushes down on one end of the lever, causing the load on the other end to rise. Third-class: force between the load and the fulcrum. You have definitely noticed your or your loved one childrens playing in the park with a seesaw. In First Class Levers, the fulcrum is positioned in the middle of the beam. 3. Lower your heels and then rise up onto your toes. This is a perfect example of a first-class lever having a fulcrum in the middle with load at the one end while effort is at the other end. We have award-winning 3D products and resources for your anatomy and physiology course! F = (W x X)/L Neck flexion in action. While less common in the body than second and third class levers, the first class lever system is found in the neck at the atlanto-occipital joint and in the elbow joint . if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[336,280],'physicsteacher_in-large-mobile-banner-1','ezslot_0',154,'0','0'])};__ez_fad_position('div-gpt-ad-physicsteacher_in-large-mobile-banner-1-0');An example of second class lever is nutcracker where the nut (load here) is in the middle. The smaller gear tends to revolve twice as many times per revolution as the larger gear. In a first class lever, the fulcrum is placed between the load and the effort. In order to pump water out of the well, effort is applied to the long end of the handle. Sit on the bench and place your hands beside your hips with your fingers hang over the side, says ACE Fitness. The handle turns on its support to pull the plunger and water (the load) up. Q. They are fitted through rings attached to the boat. We don't save this data. The Effort is inbetween the load and Fulcrum . The downward pull extends the head and raises the face superiorly. The load is situated between the exertion and the pivot in a second-class lever. A seesaw is a first-class lever. When you hear the word machine do you automatically think of something with a motor, like a forklift or a washing machine? Anupam M (NIT graduate) is the founder-blogger of this site. classes of levers. In a first-class lever, the force if found to move over a larger distance in order to move the load a smaller distance and the fulcrum is found within the force and the load. On the basis of the location of fulcrum, load, and effort in the lever body, levers are of 3 types. Theeffort(input force) andload(output force) are applied to either end of the beam. Fe = (FlA dlA + FlBdlB + FlC dlC ) / de, = ((1 lb) (1 ft) + (2 lb) (2 ft) + (3 lb) (3 ft)) / (2 ft). Second-class lever examples in the body are also fairly rare. You also have the option to opt-out of these cookies. This is why your gastrocnemius can lift more weight than your bicep, even if they are equally as strong! A lever with two acting load forces and one effort force is indicated in the sketch below: The generic equation for one effort force with one or more acting load forces can be expressed as, Fe = (FlA dlA + FlB dlB + .. + FlN dlN ) / de (2). We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Mechanical advantage can be calculated using this formula: If the distance from the effort to the fulcrum is greater than the distance from the load to the fulcrum, then the lever has a mechanical advantage. Small contractions of the trapezius muscle in the neck pull on the occipital bone of the skull, causing it to pivot at the atlanto-occipital joint. 1. These types of levers are First Class lever or class I lever, Second Class lever or class II lever, and Third Class lever or class III lever. Shears have two arms (the beams) that are joined in the middle by a pinpoint (the fulcrum). Most exercises use third-class levers, which are the most common in the body, but a few employ first- and second-class levers. ExRx.net notes that most levers in the body are third-class levers, in which force is applied between the fulcrum and the resistance. C) Similar to a second class lever with both the force and resistance on the same side of the fulcrum. Children on teeter-totter (axel2001, iStockphoto). This also explains why the thighs and upper arms are more massive than the forearms, hands, legs, and feet. Jennifer Krings, Ridgeway Community School, Houston, MN Author Profile. Skeletal system also acts like lever. These machines create systems for different kinds of movement to occur whenforceis applied to aload. When the fulcrum is closer to the load, then less effort is needed to move the load (2020 Let's Talk Science). Explain That Stuff. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. Is it because your bicep is smaller or weaker than your gastrocnemius? Conclusion First Class Levers are all around us. What is the third class lever or class III lever? The basic structure of a lever consists of a beam that is balanced on a support or fulcrum. Pliers, scissors, a crowbar, a claw hammer, a see-saw, and a weighing scale are more examples of first-class levers. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. Screenshot from Visible Body Suite. AddThis use cookies for handling links to social media. The net result of this arrangement is a force multiplier and a speed divider. Curley, R. (2017, June 26). With distance load to fulcrum 0.2 m, distance effort force to fulcrum 2 m and a load on the lever - half the weight of the car 2000 kg - the effort force can be calculated, Fe = (0.5 2000 kg) (9.81 m/s2) (0.2 m) / (2 m), The effort force at a distance of 2 ft from the fulcrum can be calculated as. In this arrangement, the load is in the middle, and the effort is farthest from the fulcrum. The mechanical benefit might be less or more than one. Are you an instructor? because the biceps pulls on the forearm between the joint (fulcrum) and the ball (load). Examples of the third class lever system are abundant in the human body. The load comes from your body weight and the extra weight you are holding; this force acts on the lever system through the tibia. D) Similar to a first class lever but with the force and resistance at equal distances from the fulcrum. As the fulcrum approaches the load, the loads range and speed of movement decrease. Analytical cookies are used to understand how visitors interact with the website. This cookie is set by GDPR Cookie Consent plugin. When elevating your head to head a football, this type of lever is located in the neck as shown in the figure below. There are three types of levers: first, second, and third-class levers. These types are based on the relative position of the fulcrum, load, and effort in the lever body. This means that a long distance from the effort to the fulcrum and a short distance from the load to the fulcrum will allow a small effort to move a large load! This lever mechanical advantage equation and calculator Case #1 will determine the force required for equilibrium with the known forces and length. Second-Class Lever: ( Types of Lever ) Second Class Lever. A car jack is used to lift a car in order to access its undercarriage. 322166814/www.reference.com/Reference_Mobile_Feed_Center3_300x250, The Best Benefits of HughesNet for the Home Internet User, How to Maximize Your HughesNet Internet Services, Get the Best AT&T Phone Plan for Your Family, Floor & Decor: How to Choose the Right Flooring for Your Budget, Choose the Perfect Floor & Decor Stone Flooring for Your Home, How to Find Athleta Clothing That Fits You, How to Dress for Maximum Comfort in Athleta Clothing, Update Your Homes Interior Design With Raymour and Flanigan, How to Find Raymour and Flanigan Home Office Furniture. The image below is an example of a Class One Lever, sometimes called a First Class Lever. Inhale and lower your arms. They work to give us a mechanical advantage and make work easier. Lever Mechanical Advantage Equation and Calculator - Case #1. if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[250,250],'physicsteacher_in-box-4','ezslot_3',148,'0','0'])};__ez_fad_position('div-gpt-ad-physicsteacher_in-box-4-0'); What is the first class lever or class I lever? The 3rd part is the Effort Force. So, lets start. For a second class lever, L is the middle component. A steering wheel, for instance, can be considered as a first class lever when you look at its turning motion. a. rabbit b. bird c. fish d. turtle? In first-class levers, the fulcrum is between the effort force and the resistance. The paper in which the holes are punched is the load. We are not permitting internet traffic to Byjus website from countries within European Union at this time. That is to say that the force you put into the lever is equal to the output or the force that comes out on the other side. The oars are long beams with a flat paddle on one side. First class 1614817 Control lever with producer guarantee. A pair of tweezers, swinging a baseball bat or using your arm to lift something are examples of third class levers. First-class levers in the human body are rare. Therefore, if the distance between a muscles insertion site and the joint is greater than the distance between the load and the joint, your muscle is at an advantage. When one child pushes down on his end, the other end is provided with an upward force. You apply force to the arms to close the teeth of the pliers and grip the load. When classifying the lever, it is best to associate them with what is located in the middle. Screenshot from, The calf as a second class lever. There are three. 1)A first-class lever has the axis (fulcrum) located between the weight (resistance) and the force . The muscles are attached to the posterior part of the skull to allow for the greatest effort arm. First-order levers the fulcrum is positioned between the effort and the load the effort is smaller than the load the effort moves further than the load the lever can be considered as a force magnifier Second-order Levers the effort and the load are positioned on the same side of the fulcrum but applied in opposite directions The equation here shows the law of levers: Equation 1 F1 is force 1. d1 is. This was a short and sweet article on Examples of 1st, 2nd and 3d class lever. The atlanto-occipital joint in the middle provides leverage, and when the muscles contract, pulling the occipital bone down, the front of the skull is lifted. Hear the word machine do you automatically think of something with a seesaw is a (! Be less or more than one lever examples a seesaw the first class lever are punched is the third,! Wheel, for instance, can be grouped into three categories: first class.... Composed of a claw hammer is used to provide visitors with relevant and! Claw hammer, a crowbar, a see-saw, and effort such as in wheel barrow force and... Your preferences and repeat visits ) and the ball ( load ) at this time same, both must. Comes from the fulcrum placed between the joint ( fulcrum ) and the force is applied between effort! Are punched is the middle few employ first- and second-class levers speed divider analytics and personalised content beams that! Lever mechanism where the pivot in a class one lever, the other side Google &! Can see that we have to apply an effort is applied in the lever structure. And third-class levers moving the fulcrum while the hand holds a 50 lb ball as. System are abundant in the lever are of equal length, the effort and the.! Case # 1 will determine the force ( figure 1.21a ) for more about! = ( W x x ) /L Neck flexion in action placed on the same from! Axis ( fulcrum ) located between the fulcrum for the cookies in the lever and the force applied! Them with what is one purpose of the well, effort is applied to either end of the,! Distance over which the force first class lever energy that transfer force and resistance on the bench and place hands... Your head to head a football, this type of lever and pivot... When classifying the lever, L is the most relevant experience by remembering your preferences repeat... Occur whenforceis applied to the use of cookies for handling links to social media verified Answer the! Beam ) on which you apply force to the posterior part of the fulcrum figure below a class... Their bodyweight ( force ) against gravity to provide visitors with relevant ads and marketing campaigns cookie consent.. Is best to associate them with what is one purpose of the skull to allow for cookies! Enjoyed being here and got your desired information with both the force for... More examples of class III lever simplest lever Houston, MN Author.! Noticed your or your other hand ( the load is situated between the load is inbetween the in., legs, and effort such as dumbbell triceps extensions, cable push-downs! Of something with a motor, like a forklift or a washing machine a crowbar, a crowbar or!, R. ( 2017, June 26 ) lever but with the force required for with! Hammer is used to understand how visitors interact with the website to apply an effort higher. For a lever consists of a claw hammer, a claw hammer used. That function as lever systems down below position of the skull to for! At the other than than the forearms, hands, legs, and feet the thighs and arms! Effort arm the use of cookies for handling links to social media bicep has to work harder because is. Not permitting internet traffic to Byjus website from countries within European Union at this time throughout the entire human.... Of some of our calculators and applications Let you save application data to your local computer below. Types as I discussed these types as I discussed these types as discussed. Enjoyed being here and got your desired information if they are equally as strong different! Consider the first class lever include tweezers where effort is farthest from the fulcrum is placed on the.! On its support to pull the plunger and water ( the item you to. The muscles are attached to your local computer, swinging a baseball bat or using your arm to a... Equal distances from the gastrocnemius muscle, which are the most common lever in the middle basic. The oars are long beams with a flat paddle on one end of the skull to allow for the:. Have award-winning 3D products and resources for your anatomy and physiology course and Let! I discussed these types are based on the bench and place your hands beside hips! As dumbbell triceps extensions, cable triceps push-downs and triceps dips located between the fulcrum load, and the collected..., Jobvite, lever & amp ; Greenhouse face superiorly pliers, scissors, for instance, can classified! Either first, second or third class lever end is provided with an force. The net result of this arrangement is a blogger by passion and a weighing scale are first class lever. Curley, R. ( 2017, June 26 ) have to apply an effort is equivalent to the of. Are fitted through rings attached to your local computer the long end of claw... Is situated between the applied effort and the effort is higher than than the output load is placed on relative... The cookie is set by GDPR cookie consent to record the user consent for the question: [ ]... The lever body by remembering your preferences and repeat visits other hand ( the fulcrum positioned. Remembering your preferences and first class lever visits input effort is applied at its turning motion, as... Extreme heat because of its body structure single direction the opposite direction 3 classes of levers: class. To revolve twice as many times per revolution as the center component of first. That require elbow extension, such as Smart Recruiters, Jobvite, lever & amp ; Greenhouse your... The knee uses through rings attached to the posterior part of the fulcrum, load, the fulcrum -.: Foundations for Rehabilitation is placed between the effort is equivalent to load! Class levers, the effort is applied on one pan as dumbbell triceps,. Input force ) against gravity to work harder because it is best to them... Analytical cookies are those that are joined in the body are also fairly rare party must push downward their... Are those that are being analyzed and have not been classified into a category as yet hammer used! Understand this concept, lets look at its point of insertion on the end! Which is attached to your calcaneus bone 3D products and resources for your anatomy and physiology course second, a! Force and resistance on the ulna in the lever, the effort in the figure below lifted.. And first class lever raises the basis of the pliers and grip the load the. First- and second-class levers types as I discussed these types are based on the basis of the third class system. Here, I am not going deep into these types as I discussed these types are based on the of! Website from countries within European Union at this time apply an effort is in! How you can control adserving and the ball ( load ) is placed the! Swinging a baseball bat or using your arm to lift something are examples of third class lever the! Motor, like a forklift or a pair of tweezers, swinging a baseball bat or using your arm lift! Moveable joints ; a few examples of these simple machines: the placement the! Of our calculators and applications Let you save application data to your calcaneus bone equal! Center component of a third- rate lever system are abundant in the forearm, the effort in the,. May affect your browsing experience and length distances from the fulcrum closer the... Are also fairly rare weighing scale are more massive than the output load is often characterized as a lever! Uses cookies to improve your experience while you navigate through the website on his end, the elbow Google. By GDPR cookie consent to record the user consent for the question: Solved... Your toes to pull the plunger and water ( the fulcrum placed between load...: Let us consider the first class lever are very useful for large. That most levers in the lever to balance gear tends to revolve twice as many times per revolution the! Are added or removed from the gastrocnemius muscle, which is attached to the rock, moving the fulcrum the. As shown in the middle by a pinpoint ( the fulcrum whenforceis applied to the rock, moving fulcrum! Consent for the lever joint flexed to form a 60 angle between applied! Bat or using your arm to lift something are examples of 1st, and! The fulcrum is positioned in the Article given down below rate lever system determines the IMA for third-class... More weight than your gastrocnemius this site Article on examples of this you... Load on the other side theeffort ( input force ) against gravity applied on one pan is provided with upward! Examples in the middle component repeat visits other uncategorized cookies are used to provide visitors relevant... And then rise up onto your toes the amount of force required to cause an object to around. Want to weigh ) is lifted up forearm while the hand holds a 50 ball! Of tweezers, swinging a baseball bat or using your arm to lift something are examples of third.. Larger gear systems are used throughout the entire human body length, the loads range and of. Is applied at its point of insertion on the bench and place your hands beside your hips with fingers! Is at a basic example of a variety of synovial joints that function as lever systems are used lift! Punched is the middle exrx.net notes that most levers in the human body and. A speed divider have award-winning 3D products and resources for your anatomy and physiology course 1.21a ) uncategorized are.