What are skeletal muscles

Skeletal muscles

Synonyms: locomotor muscles, textus muscularis striatus skeletalis (Terminologia histologica)
English: skeleton muscles, skeletal striated muscle

1 definition

To Skeletal muscles count the muscles that are fixed to the skeleton or - in a broader sense - that ensure the movement of the body. Like the heart muscle, they belong to the striated muscles.

annotation: The term "skeletal muscle" is somewhat misleading in that it also includes muscles that are not directly attached to the skeleton, such as the tongue muscles, the larynx muscles and parts of the facial muscles.

see also:List of skeletal muscles

2 anatomy

2.1 Macroscopic anatomy

Roughly anatomically, skeletal muscles can be divided into one Muscular head (Caput) and one Muscle belly (Venter). According to the number of muscle heads, one can differentiate into

Furthermore, one differentiates between the Muscle origin and the Muscle insertionwhich is "sinewy" or "fleshy" related to the bone. A skeletal muscle can have several original surfaces - even on different bones.

Another macroscopic feature of skeletal muscles is their feathering. A distinction is made between simple and double-pinnate muscles.

2.2 Functional anatomy

The skeletal muscles can also be further subdivided according to functional or biomechanical aspects. With regard to the interaction of muscles, a distinction is made between:

Skeletal muscles that work in the same direction, i.e. complement each other in their effect, are called agonists. If they work in the opposite direction, one speaks of antagonists.

According to their dominant direction of movement, one divides into:

2.3 Systematics

In order to structure the human skeletal muscles in a didactically manageable manner, they can be divided into different muscle groups according to topographical and functional aspects.

2.4 histology

A skeletal muscle consists of the actual muscle fibers that are responsible for contraction and auxiliary tissues. From the outside, the skeletal muscle is enveloped by a tough layer of connective tissue, the fascia. From here, connective tissue branches pull into the muscle, which further subdivide it into fiber groups and are also known as septa. A muscle can be subdivided into several hierarchically structured functional units, with the sarcomere being the smallest functional unit of the muscle.

The connective tissue that surrounds the muscle fibers or muscle fiber bundles unite at the muscle heads to form the tendons of the muscle that attach to the bone. They also contain the nerves and blood vessels that supply the muscle.

The main components of the skeletal muscles are the contractile proteins actin (3% of the total weight of the skeletal muscle) and myosin (7% of the total weight of the skeletal muscle), as well as the Z-disks to which the actin fibers are connected. The distance between the Z-slices is called the sarcomere. The contractile proteins account for around 100 mg per gram of skeletal muscle.

3 physiology

Skeletal muscles are responsible for body statics and motor skills. In their entirety, they form the muscle mass of the human body.

The functioning of the skeletal muscles is described by the sliding filament theory. The skeletal muscles are controlled by motor nerves, which transmit electrical impulses to the motor end plate via the release of acetylcholine. Muscle activity is controlled both voluntarily (motor cortex) and involuntarily (spinal reflexes). The adjustment of the muscle length to the respective joint position is carried out by the length control system.