how does your arm work

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your bones and muscles

  • Humerus: This bone runs down from the shoulder socket and joins the radius and ulna at the elbow.
  • Radius: A forearm bone, it runs from the elbow to the thumb side of the wrist.



    • Ulna: This forearm bone runs from the elbow to the “pinkie” side of the wrist.







how does your bones work on your arm

In' anatomical 'terms, the word "arm" refers to the part of the upper limb between the shoulder and the elbow. The term "forearm" describes the part of the upper limb between the elbow and the wrist.In a more common use, the term "arm" refers to the whole upper limb, with the terms upper arm and lower arm describing the two parts. In this section we will use the more common definition of "arm" to mean the whole upper limb.The arm consists of three large bones. The humerus bone is in the upper arm. One end connects with the scapula at the shoulder joint. The other end connects with the radius and ulna at the elbow joint. The radius and ulna bones are in the lower arm, connecting between the elbow joint and the wrist. One easy way to remember which bone is the radius and which is the ulna is that the radius connects to the thumb side of the wrist.


The upper limb consists of three movable joints. These are the shoulder, elbow and wrist. These joints allow you to raise your arm, rotated in circles and bend it. These joints allow movements such as throwing a ball, picking up a book, or waving good-bye.

how does your muscles work

Skeletal muscles only pull in one direction. For this reason they always come in pairs. When one muscle in a pair contracts, to bend a joint for example, its counterpart then contracts and pulls in the opposite direction to straighten the joint out again. Without this arrangement you wouldn't be able to straighten your legs when you walk or bend your fingers to grip something.Skeletal muscles only pull in one direction. For this reason they always come in pairs. When one muscle in a pair contracts, to bend a joint for example, its counterpart then contracts and pulls in the opposite direction to straighten the joint out again. Without this arrangement you wouldn't be able to straighten your legs when you walk or bend your fingers to grip something.

how does your muscles and bones work alltogether

When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are similar to ligaments, except that ligaments join bones to each other. Muscles move the body by contracting against the skeleton. When muscles contract, they get shorter. By contracting, muscles pull on bones and allow the body to move.Muscles can only contract. They cannot actively extend, though they can move or relax back into the non-contracted neutral position. Therefore, to move bones in opposite directions, pairs of muscles must work in opposition. Each muscle in the pair works against the other to move bones at the joints of the body. The muscle that contracts to cause a joint to bend is called the flexor. The muscle that contracts to cause the joint to straighten is called the extensor. When one muscle is contracted, the other muscle from the pair is always elongated.For example, the biceps and triceps muscles work together to allow you to bend and straighten your elbow. When you want to bend your elbow, your biceps muscle contracts (Figure below), and, at the same time, the triceps muscle relaxes. The biceps is the flexor, and the triceps is the extensor of your elbow joint. Other muscles that work together are the quadriceps and hamstrings used to bend and straighten the knee, and the pectorals and trapezius used to move the arms and shoulders forward and backward. During daily routines we do not use muscles equally. For example, we use our biceps more than our triceps due to lifting against gravity.

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