Tendons and Ligaments

Tendons

Tendons are strong connective tissue structures linking muscles to bones or other tissue. Tendons come in a variety of shapes, not just the tubular shape that is commonly considered when thinking of the term 'tendon'.  A special name is given to the flat sheet like type of tendon, which we call an aponeurosis.

Origin and Insertion

Muscles have an origin and a insertion, usually but not always anchored with a tendon to bone. Memorizing which end of a muscle is the origin and the insertion can be done, but would be very time consuming and arguable of little value. It is easier to understand the general convention which you can apply to whichever muscle you are considering.

The origin of a muscle is the end of the muscle which is attached to a structure closer to the centerline of the body (i.e. the proximal end) and/or is the more stable (less mobile) point.

The insertion of a muscle is the end of he muscle which is attached to a more distal location from the centerline of the body (i.e. the distal end) and/or is the more mobile structure. 

Ligaments

Ligaments are strong connective tissue with a similar microanatomy structure to tendons (i.e. dense regular connective tissue). However, we use the word ligament when two structures are connected by connective tissue where a muscle is not part of the arrangement.  Most commonly, these are connective tissue bands spanning from one bone to another bone (for example, the ACL, anterior cruciate ligament of the knee).

However, we also use the term ligament for non-muscular connective tissue connections between soft tissue, and not just bone. So you will see terms such as the pericardiophrenic ligament (which connects the pericardium covering of the heart to the diaphragm).  So don't be confused if you see the term ligament associated with non-bone structures!