Skeletal muscles attach to other structures directly or by means oftendons. A tendon is a dense band of white connective tissue thatconnects the belly of a muscle to its attachment on the skeleton.Tendons are nonelastic, flexible, and extremely strong. They concentratethe force produced by the contractile muscle belly, transmittingit to the structure to be moved. Tendons decrease the bulkof tissue around certain joints, obviating the need for long fibers inthe belly portion of the muscle. For example, in the forearm andlower leg, long tendons shift the weight away from the hand andfoot, making the ends of the arm and leg lighter.Influence on surface formSkeletal muscles can be thought of as independent convex forms placed in layers on top of the underlying skeleton. Although theforms of adjacent muscles tend to blend with each other, furrowsor grooves are present between some muscles and muscle groups,especially between those that have different or opposing actions.This arrangement of muscles is visible on the surface as a seriesof convexities, especially when the muscles are put into action.In their relaxed state, however, muscles are soft and appear lessdefined, even hanging loosely because of the pull of gravity .Upon contraction, the belly of muscles become shorter and thicker.In superficial muscles, this change in shape can be observed on thesurface where the muscle’s relief becomes increasingly defined.When muscles with narrow tendons contract, the tendons oftenstand out prominently on the surface of the skin. For example, someof the tendons of the forearm muscles can be seen on the wrist whenthe fingers are clenched into a fist. In superficial muscles, the areaof attachment of a tendon and its muscle belly is often apparent onthe surface.
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