Of the Latissimus dorsi muscle is a striated skeletal muscle of the secondary back muscles, which makes up the largest muscle in the human body. The tasks of the back muscle are adduction, internal rotation and retroversion of the arms. Damage to the thoracodorsal nerve can paralyze the muscle.
The back muscles consist of autochthonous and secondary muscles. The secondary back muscles include various skeletal muscles, including the latissimus dorsi muscle. In the literal translation, the Latin name means something like "widest back muscle"In the German specialist literature, the muscle is sometimes dated large back muscle the speech.
The muscle acts on the shoulder girdle from the dorsal direction and corresponds to a muscle located superficially on the back. In terms of area, the latissimus dorsi muscle is the largest skeletal muscle in the human body. The structure extends the entire length of the spine. In its course at the upper edge of the pelvis, parts of the muscle are covered by the trapezoid muscle, of which it is the antagonist. In the human body, there are four different parts of the muscular structure: the pars vertebralis, the pars costalis, the pars iliaca and the pars scapularis.
The muscle is motorized by the thoracodorsal nerve, which originates from the infraclavicular part of the brachial plexus and thus from segments C6 to C8. Like all other skeletal muscles, the latissimus dorsi muscle has a striated pattern and is therefore assigned to the striated muscles.
The striated muscles are made up of homogeneous, small-sized functional units known as sarcomeres. These sarcomeres are made up of the myofilaments myosin and actin, some of which overlap each other. The striated shape lies on light I-bands from actin and dark A-bands from myosin.
The latissimus dorsi muscle originates from the trunk and extends from the sacrum and iliac bone over the spinous processes of the thoracic and lumbar vertebrae. The skeletal muscle arises over a wide area and also includes the supraspinal ligament, the thoracolumbar fascia, the ninth to twelfth ribs, the sacrum and the iliac crest on the ilium as origins. The fibers move cranially and laterally from the original surfaces in order to attach to the sulcus intertubercularis of the humerus in the immediate vicinity of the musculus teres major.
The skeletal muscle runs through the armpit to the upper arm and forms a characteristic pattern with the anterior sawtooth muscle. The thoracodorsal artery, the thoracodorsal vein and the thoracodorsal nerve run on the inside of the muscular structure.
Skeletal muscles are part of the voluntary musculature. This makes voluntary movements their job. The latissimus dorsi muscle is involved in the backward rotation of the arm with the palms facing outwards. This function is popularly known as "Apron binder muscle“Given.
The main effect of the skeletal muscles is when the arm is raised. From this position he can lower his arm and move his trunk upwards at the same time. This form of movement is relevant, for example, for sports exercises such as pull-ups. Together with the teres major muscle, the latissimus dorsi muscle forms the posterior fold of the armpit. The skeletal muscle is also a synergist in the extension (stretching) and lateral flexion (sideways bending) of the lumbar spine. When the arm is fixed, the latissimus dorsi muscle also pulls the upper body towards the arm. It is a correspondingly important muscle for forms of movement such as climbing or rowing. In addition, the skeletal muscles are counted among the auxiliary breathing muscles.
In this regard, the contraction of its anterior fibers helps with the forced exhalation. The rear fibers, on the other hand, help with forced inhalation. Sometimes the muscle is also referred to as the cough muscle, since the muscular structure supports the lungs when breathing heavily. As a skeletal muscle, the latissimus dorsi muscle is equipped with a so-called motor end plate through which commands from the central nervous system reach it. These commands are transmitted in the form of bioelectrical excitation via the descending motor thoracodorsal nerve to the motor endplate and from there to the muscle fibers.
Due to its flatness, the latissimus dorsi muscle plays a role as a tissue donor for plastic surgery. Skeletal muscle flaps are often used as autologous grafts and aid reconstructive surgery in covering defects after severe injuries and tumor removal. However, the muscle can also gain pathological relevance.
This is the case with bursitis, for example, with inflammation of the bursa subtendinea musculi latissimi dorsi. This bursa is located directly at the junction of the latissimus dorsi and teres major muscles. In this region, the phenomenon of bursitis may be causally related to incorrect loading of the latissimus dorsi muscle. Infections are also a common cause. The bursitis is usually expressed in this area as a result of severe pain which, due to the strain, occurs primarily during forms of movement such as swimming, chopping wood or other contractions of the latissimus dorsi muscle.
Like any other muscle in the body, the skeletal muscle can be paralyzed under certain circumstances. In particular, inflammatory, traumatic or compression-related damage to the supplying thoracodorsal nerve causes structural paresis. Symptomatically, the muscle becomes narrower if the paralysis persists. The posterior axillary fold decreases. In addition, patients with paralysis of the latissimus dorsi muscle usually protrude from the inferior angle of the scapula. Depending on the severity of the nerve injury, people may have difficulty pushing their arm down and forward against resistance.