How is movement possible

In this position, the radius and ulna are parallel to each other. When the palm of the hand faces backward, the forearm is in the pronated position , and the radius and ulna form an X-shape. Supination and pronation are the movements of the forearm that go between these two positions. Pronation is the motion that moves the forearm from the supinated anatomical position to the pronated palm backward position. This motion is produced by rotation of the radius at the proximal radioulnar joint, accompanied by movement of the radius at the distal radioulnar joint.

The proximal radioulnar joint is a pivot joint that allows for rotation of the head of the radius. Because of the slight curvature of the shaft of the radius, this rotation causes the distal end of the radius to cross over the distal ulna at the distal radioulnar joint.

This crossing over brings the radius and ulna into an X-shape position. Supination is the opposite motion, in which rotation of the radius returns the bones to their parallel positions and moves the palm to the anterior facing supinated position.

It helps to remember that supination is the motion you use when scooping up soup with a spoon see Figure 4. Dorsiflexion and plantar flexion are movements at the ankle joint, which is a hinge joint. Lifting the front of the foot, so that the top of the foot moves toward the anterior leg is dorsiflexion, while lifting the heel of the foot from the ground or pointing the toes downward is plantar flexion.

These are the only movements available at the ankle joint see Figure 4. Figure 4. Supination and pronation. Inversion and eversion are complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot intertarsal joints and thus are not motions that take place at the ankle joint.

Inversion is the turning of the foot to angle the bottom of the foot toward the midline, while eversion turns the bottom of the foot away from the midline.

The foot has a greater range of inversion than eversion motion. These are important motions that help to stabilize the foot when walking or running on an uneven surface and aid in the quick side-to-side changes in direction used during active sports such as basketball, racquetball, or soccer see Figure 5.

Protraction and retraction are anterior-posterior movements of the scapula or mandible. Protraction of the scapula occurs when the shoulder is moved forward, as when pushing against something or throwing a ball. Retraction is the opposite motion, with the scapula being pulled posteriorly and medially, toward the vertebral column.

For the mandible, protraction occurs when the lower jaw is pushed forward, to stick out the chin, while retraction pulls the lower jaw backward. See Figure 5. Figure 5. Inversion, eversion, protraction, and retraction.

Depression and elevation are downward and upward movements of the scapula or mandible. The upward movement of the scapula and shoulder is elevation, while a downward movement is depression. These movements are used to shrug your shoulders. Similarly, elevation of the mandible is the upward movement of the lower jaw used to close the mouth or bite on something, and depression is the downward movement that produces opening of the mouth see Figure 6.

Figure 6. Depression, elevation, and opposition. Excursion is the side to side movement of the mandible. Lateral excursion moves the mandible away from the midline, toward either the right or left side. Medial excursion returns the mandible to its resting position at the midline. Superior and inferior rotation are movements of the scapula and are defined by the direction of movement of the glenoid cavity.

These motions involve rotation of the scapula around a point inferior to the scapular spine and are produced by combinations of muscles acting on the scapula. During superior rotation , the glenoid cavity moves upward as the medial end of the scapular spine moves downward. This is a very important motion that contributes to upper limb abduction.

Without superior rotation of the scapula, the greater tubercle of the humerus would hit the acromion of the scapula, thus preventing any abduction of the arm above shoulder height.

Test your knowledge. What are you wondering? Wonder Words joints need feat brain speed force favor complex desire conscious tendons feedback particular immediate coordinated effortlessly conjunction deliberately Take the Wonder Word Challenge. Join the Discussion. Ethan The Dalek May 13, May 15, Thanks for sharing, Ethan! We hope your pulled muscles healed quickly!

Sadie Apr 24, So your brain sends signals to the rest of your body. So does that mean that when certain parts of your body don't function is that damage in the brain or body part? Apr 25, Great question, Sadie! Tigist Mar 25, Mia Mar 25, Mar 26, Mar 13, Ligaments connect bones to other bones. Sophia May 7, So basically the skeletal system gives you support and the muscular system gives you posture and keeps you from being all flappy? May 24, Apr 20, Isn't that an incredible feat, conner??

Hersh Jul 13, Do reply immediately, are you a computer set to reply? Jul 13, Apr 26, As cool as the other side of the pillow, Joeve! G's Class Jan 25, Thank you for helping us learn about moving our bodies! It's cool that your brain tells your body what to do. It's cool that your brain sends messages.

Love Mrs. G's Class. Jan 25, Jan 18, Awesome, Jacobo! Glad we could help. Niko Nov 21, Nov 22, Thanks for commenting, Niko! We use our muscles, tendons, and joints to move our bones! Ryan Roybal Nov 10, Nov 11, We look forward to hearing from you again soon. Jacob Sep 20, Sep 21, That's awesome, Jacob! It's so much fun to discover new things! Sep 1, Maleah Aug 25, Aug 25, We're glad you liked it, Maleah!

Howdy, carson! Thanks for stopping in at Wonderopolis! Aug 23, Between A and B there are an infinite number of points right? Wouldn't it take an infinite amount of time to move across an infinite number of points? Why does it then only take a finite amount of time for the ball to get to B? This is incorrect. Infinite number of points does not necessarily mean infinite distance. In fact, to see whether a distance is infinite or not, you simply cannot use the count of the points it contains. You cannot measure the size of an 1D object i.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How is movement possible?