Tendons serve to transmit traction between muscles and bones. They represent the fibrous end piece with which the muscle attaches to its bone. The attachment points are usually visible as bony protrusions (apophyses) on the bone.
These must be particularly resistant, as they absorb the force transmitted by the muscle via the tendon. In addition to the normal attachment and original tendons, there are also intermediate tendons that connect two bellies of a muscle, as well as flat tendon plates (aponeuroses), such as those on the sole of the foot and the palm of the hand. The tendons are separated from ligaments that connect movable skeletal parts.
In contrast to tendons, they are stretched between two bones and serve to stabilize the skeletal system. Tendons consist of taut connective tissue, namely collagen fibers and a few elastic fibers. The entire tendon in turn is surrounded by a layer of loose connective tissue, which provides for its anchoring and at the same time for its mobility.
The inside of the tendon is divided by fine layers of connective tissue into individual fiber bundles, which serve, among other things, as nerve-vascular roads. Overall, however, tendons contain only a few vessels and nerves, which also explains why they have such a poor ability to regenerate. There are two types of tendons, the compression tendons and the tensile tendons.
- Tensile tendons are subjected to tensile stress and consist of taut connective tissue that is aligned parallel to the corresponding direction of traction.
- Compression tendons are subjected to pressure and, in contrast to the tensile tendon, pull around the bone. The bone serves as an abutment. On the side adjacent to the bone, these tendons consist of fibrous cartilage, which is not supplied with blood.
For better gliding, some tendons, especially those that run directly on the bone, are surrounded by a tendon sheath (vagina synovialis).
This sheath is similar in structure to a joint and contains a small amount of fluid that increases the gliding ability of the tendon. This can also reduce the friction between the tendon and the bone. Tendon sheaths are mainly located around the tendons of the hand and foot muscles.
Under heavy strain (e.g. always the same hand movement when writing) the tendon sheaths can become inflamed (tendovaginitis). Tendons are generally very tear-resistant. In all movements, they transfer great forces to the bone.
In addition, tendons also have a spring effect. When stretched passively, they store part of the energy and release it again when the movement is performed. In this way, movement sequences can be made much more efficient, since the muscles do not have to apply all the force on their own.
Due to the high load, the tendon tissue is often subject to wear and tear (degenerative changes). However, tendon injuries are also often caused by incorrect loading, twisting or shearing forces in the context of sports injuries. In the case of minor injuries, immobilisation of the affected region is usually sufficient; in the case of larger injuries or even a tear of the tendon, surgery is required. It usually takes 4-6 weeks until complete healing is achieved, after which the tendon should be spared for several months.
