Essentially the second half of your question is what happens when a muscle contracts on a larger scale. On a much smaller scale, the contraction of muscle is caused by myosin proteins pulling themselves along the surface of an actin protein, which shortens the muscle. Muscles pull the bone that they are attached to at their point of insertion towards their point of origin.
shortens
When a muscle contracts, it shortens in length.
A muscle that contracts shortens whereas a muscle that relaxes lengthens.
muscle tissue
Muscles are attached to two different bones. When a muscle contracts, it shortens. When it shortens, the shortens the angle between the two bones causing movement.
Isotonic contractions. This happens when the muscle shortens as it contracts
Origin and Insertion One of the points of attachment is the ORIGIN (typically the non-moving point of attachment). The other point of attachment is the INSERTION (typically the moving point of attachment). For example - when the brachialis muscle (located on the upper arm) contracts - it shortens the distance between the origin (on the humerus - the upper arm bone and the insertion (on the radius - the forearm bone). The humerus does not move, but the radius does move - it moves closer to the humerus.
when a muscle contracts or shortens the attached bones are pulled closer to each other
shortens
when the muscle shortens (contracts), the two bones come closer together, isometric contraction excepted.
Origin and Insertion One of the points of attachment is the ORIGIN (typically the non-moving point of attachment). The other point of attachment is the INSERTION (typically the moving point of attachment). For example - when the brachialis muscle (located on the upper arm) contracts - it shortens the distance between the origin (on the humerus - the upper arm bone and the insertion (on the radius - the forearm bone). The humerus does not move, but the radius does move - it moves closer to the humerus.
The Muscle tissue is the one to contract and shorten when it moves or stretches it pulls on the bone to create movement and it shortens and in some cases it contracts