Musculoskeletal system

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The musculoskeletal system, or simply the musculoskeletal system, is an organ system in anatomy . It ensures that the body remains in a fixed shape, but can still be moved in a targeted manner. For this, it is composed of fixed and movable organs.

The bony skeleton is responsible for the shaping of the body. It is moved by the skeletal muscles . For this purpose, tendons serve as power transmitters, which are attached to the bone on one side and anchored in the muscle on the other . Ligaments are used to strengthen and secure joints .

In orthopedics, the term “supporting apparatus” also refers to orthoses that are used in the event of functional impairments to the supporting and musculoskeletal system.


The skeleton consists of differently shaped bones ( long bones , flat bones and others) that are partly fused together, such as the pelvis . It not only has the task of ensuring the shape of the body and thus ensuring the mobility of the organism, but also has protective functions for internal organs (again skull and pelvis) or the task of making their work possible in the first place (the chest without the the breathing may not work). In addition, the inside of the bones, the bone marrow , is an important place where blood cells form .

The bones are connected to one another by joints that determine the direction and radius of movement of the bones.


The skeletal muscles connect two different bones by attaching their tendons to the bones through at least one joint . When a muscle shortens, it pulls the two bones in the joint closer together. Muscles only have the opportunity to contract, but not to stretch themselves back to their original position. To do this, they need one or more muscles that attach to the other side of the joint and cause the opposite movement. Such muscles are called opponents ( Latin : antagonists ).

Skeletal muscles do not necessarily have to be attached to a single point on a bone. Some muscles are divided into two or more parts, which, although they start in a common tendon on one side, end in different places on the same or even different bones on the other. Such muscles are called biceps (with two muscle heads ), triceps (three muscle heads) or quadriceps (four muscle heads).

Skeletal muscles consist of individual cells ( muscle fibers ). Several of these muscle fibers form muscle fiber bundles, several of which are surrounded by a firm, net-like skin, the fascia , and together form the muscle.

Tendons and tendon sheaths

In order for the force that is developed by the muscles to be converted into movements of the bones, both assemblies must be connected to one another. This is the job of the tendons . They consist of firm but flexible collagen connective tissue . Their fibers are parallel to the direction of pull. Tendons are fused with the muscle fibers in the muscle and attach to protrusions or roughened areas on the bone.

In addition to the "normal" tendons, there are also tendon plates (medical: aponeuroses ). They are not in the form of a rope, but rather a firm, thick skin. Several muscles or muscle heads can be attached to them together (e.g. the tongue aponeurosis , aponeurosis linguae ).

In order to save the tendons unnecessary friction, which can damage them, particularly long tendons are placed in tendon sheaths . These are tubes made of two layers of skin with fluid ( synovia ) between them . This creates a sliding surface that significantly reduces the friction between the tendon and the surrounding tissue.


Even bands ( lat. : Ligaments ., Sing ligament ) are usually made of collagen fibers, rare but also of elastic connective tissue . They either lie around joints or in them (for example the cruciate ligaments of the knee joint ). They support the joints or inhibit the mobility of the bones with one another and thus help to avoid overstretching muscles or tendons.

There are also ligaments in the abdominal cavity that hold organs in place. However, they have nothing to do with the ligaments of the supporting apparatus and were referred to in the outdated Jena Nomina Anatomica (JNA) as chorda or plica ; occasionally this term can still be found in the literature.


In places that pose a particular danger to tendons , the body installs additional padding to protect the tendon against chafing : the bursa ( Latin : bursa synovialis ). These pads are small skin pads that are filled with a liquid and placed under the tendon on the vulnerable side. The fluid distributes the pressure of the tendon evenly over a larger area.

Sesame bones

A sesame bone is a small bone that has grown into a tendon and provides additional space to the bone. This creates more leverage for the tendon, so less force is required to move the bone attached to the tendon.

The best-known example of a sesamoid bone is the kneecap , which is embedded in the tendon of the quadriceps femoris muscle . This construction allows the lower leg to be easily stretched without the thigh needing any more muscle mass.


  • Basic structure of the human musculoskeletal system. In: Hans Albert Richard, Gunter Kullmer: Biomechanics: Basics and applications on the human musculoskeletal system . Springer-Verlag, 2014, ISBN 9783834886118 , p. 1ff.
  • Franz-Viktor Salomon: Structure of the body according to organ systems. In: Salomon / Geyer / Gille (Hrsg.): Anatomy for veterinary medicine. Enke Stuttgart. 3rd ext. Edition 2015 ISBN 978-3-8304-1288-5 , p. 18.