Origin and Approach
A skeletal muscle is attached via tendons , i.e. the connective tissue part of a muscle, at at least two points, which in anatomy are called the origin and insertion . Most of the attachments and origins of the muscles are attached to the skeleton , some muscles are also attached to fasciae , which can be reinforced to form aponeuroses . Anatomically, the terms are also used for the attachment points of ligaments .
The distinction between muscle insertion ( insertio ) and origin ( origo ) is often arbitrary. The mostly immobile part ( punctum fixum ) is referred to as the origin, the moving part ( punctum mobile ) as the attachment . However, this distinction cannot be easily applied to many muscles; above all, the term pair punctum fixum / punctum mobile is terminologically not synonymous with the term pair origin / attachment . Furthermore, the punctum fixum and punctum mobile cannot be absolutely fixed, since a muscle can sometimes move one attachment point, sometimes another. Thus the bears quadriceps femoris belonging rectus femoris while lying on his back to the straightening of the upper body at. It has its origin in the iliac bone , which is usually also the fixed punctum (e.g. when the thigh is lifted while standing). In the above-mentioned case, however, this attachment point to the iliac bone and thus to the upper body to be lifted, that is to say moved, is the punctum mobile . However, the definition of this point as the origin is retained.
On the limbs , the attachment near the trunk (proximal) is generally referred to as the origin, and the attachment remote from the trunk (distal) as the attachment. For the muscles of the shoulder girdle , the attachment to the trunk is usually referred to as the origin, and those on the shoulder girdle as the attachment. In the case of the back muscles , the origin is below (in the case of animals behind), the attachment further above (in front). In some cases they are simply set arbitrarily.
A muscle can have several origins, these different origins are called the muscle head ( caput ). The number of heads gave some muscles their name. In humans, for example, the biceps brachii muscle ("two-headed muscle of the upper arm") has two tendons of origin that arise at different points on the shoulder blade . A muscle can also have several attachments in which the end tendon divides and attaches to different bone points. The biceps brachii muscle, for example, also has two attachments, namely to the ulna and radius .
Attachment to the skeleton
In the apophyseal tendon attachment zones, fiber cartilage is found at the bone-tendon transition , which mineralizes at the transition to the bone. Here there is a gradual transition from tight, parallel- fiber connective tissue (tight connective tissue ) via a non-mineralized (with cartilage cells scattered between the connective tissue fibers ) and mineralized fiber cartilage zone to the bone. The cartilage cells dampen jerky tension in the tendon through their elasticity and thus indirectly act as a shock absorber.