The back muscles consist of autochthonous and secondary muscles. Secondary back muscles include various skeletal muscles, including the latissimus dorsi muscle. In the literal translation, the Latin term means as much as "widest back muscle". In the German technical literature, the muscle is sometimes referred to as the large dorsal muscle.
The muscle acts from the dorsal direction on the shoulder girdle and corresponds to a superficial on the back muscle. In terms of surface area, the latissimus dorsi muscle is the largest skeletal muscle in the human body. The structure extends over the entire length of the spine. In its course at the upper edge of the pelvis, parts of the muscle are covered by the trapezius muscle whose antagonist it is. In the human body, four different parts are part of the muscular structure: the vertebral pars, the pars costalis, the pars iliaca and the pars scapularis.
The muscle is motorized by the thoracodorsal nerve, which originates from the pars infraclavicularis of the brachial plexus and thus from the segments C6 to C8. Like all other skeletal muscles, the latissimus dorsi muscle carries a striated pattern and is therefore associated with striated muscle.
The striated muscles consist of homogeneous, small-sized functional units known as sarcomeres. These sarcomeres are composed of the myofilaments myosin and actin, which partially overlap each other. The striated form is due to bright I bands of actin and dark A bands of myosin.
The latissimus dorsi muscle originates at the trunk and extends from the crura and ilium over the spinous processes of the thoracic and lumbar vertebrae. The skeletal muscle originates from a large area and also includes the supraspinal ligament, the thoracolumbar fascia, the ninth to twelfth ribs, the sacrum, and the iliac crest on the ilium. From the originating surfaces, the fibers move cranially and laterally to attach to the intertubercular sulcus of the humerus adjacent to the teres major muscle.
Through the armpit, the skeletal muscle pulls to the upper arm and forms a characteristic pattern with the front sawtooth muscle. On the inside of the muscular structure, the thoracodorsal artery, the thoracodorsal vein and the thoracodorsal nerve run.
Skeletal muscles are part of the voluntary musculature. Arbitrary movements are their task. The latissimus dorsi muscle is involved in the backward rotation of the arm in outward-facing palms. This feature has been popularly called "apronbinder muscle" by the muscle.
Its main effect unfolds the skeletal muscle with raised arm. From this position, he can lower his arm and at the same time move the fuselage upwards. This form of exercise is relevant, for example, for sports exercises such as pull-ups. Together with the musculus teres major, the latissimus dorsi muscle forms the posterior crease of the axilla. The skeletal muscle is also a synergist in extension and lateral flexion of the lumbar spine. When the arm is fixed, the latissimus dorsi muscle also pulls the upper body against the arm. For movement forms such as climbing or rowing he is a correspondingly important muscle. In addition, the skeletal muscle is counted as respiratory aid muscle.
In this context, the contraction of its anterior fibers helps in the forced exhalation. By contrast, the posterior fibers help with forced inhalation. The muscle is also sometimes referred to as the cough muscle, since the muscular structure supports the elimination of the lungs during violent breathing movements. As a skeletal muscle, the latissimus dorsi muscle is endowed with a so-called motor end plate, through which it receives commands from the central nervous system. These commands are transmitted in the form of bioelectric excitation via the descending motor thoracodorsal nerve to the motor end plate and from there to the muscle fibers.
Due to its flatness, the latissimus dorsi muscle plays a role as tissue donor for plastic surgery. Skeletal muscle lobes are often used as autologous grafts and help with reconstructive surgery for defect coverage after major injury and tumor removal. However, the muscle can also gain pathological relevance.
This is the case, for example, with bursitis, with bursa inflammation of the bursa subtendinea musculi latissimi dorsi. This bursa lies directly at the junction of the latissimus dorsi muscle and the teres major muscle. The phenomenon of bursitis in this region may be causally related to abnormal loading of the latissimus dorsi muscle. Also infections are a common cause. Most of the bursitis in this area is characterized by severe pain, the stress primarily initially in motion such as swimming, chopping wood or other contractions of the latissimus dorsi muscle occur.
Like all other muscles in the body, skeletal muscle may be affected by paralysis in certain circumstances. In particular, inflammatory, traumatic or compression-related damage to the supplying thoracodorsal nerve causes paresis of the structure. Symptomatically, the muscle narrows with persistent paralysis. The rear axillary fold decreases. In addition, patients with paralysis of the latissimus dorsi muscle usually have the inferior anterior to the scapula. Depending on the severity of the nerve injury, sufferers have difficulty pushing the arm forward against resistance.Tags: