Anatomy of the Back - Latissimus Dorsi and Triceps
Latissimus Dorsi Location and Structure: The latissimus dorsi is a large and powerful muscle, it is the largest superficial muscle in the body. It is located in the lower part of the back and the outer side of the chest in a triangular shape, and the upper arm is pulled upwards (pull-ups). It is covered over the ventral surface of the torso, like the trapezoid covers the superior part of the body, it extends to the back and side, connecting to the upper portion of the humerus, therefore from the lower back and pelvic bone it anchors to the spinous processes of all lumbar vertebrae, the iliac crest outer third, and enters the medial inner edge of the deltoid muscle in the humeral tuberosity. The muscle bundles converge outwards upwards, passing through the posterior wall of the axilla, in front of the anterior lateral head of the deltoid, terminating at the lateral crest of the humerus. Triceps Location and Structure: The triceps is a triangular muscle that tapers upwards from a base, located beneath the skin of the shoulder, the prominent shoulder bulge forms the shape of the muscle. It is divided into three parts, the central muscle fibers are in a feather-like manner. The anterior edge is separated from the sternal notch of the pectoralis major, the posterior edge is free.
Latissimus Dorsi Function: One, internally rotate and extend the arm, two, abduct the humerus, rowing motion, three, when the upper limb is raised upwards, it can elevate the torso like an incline motion, the nerve innervation is the thoracic nerve, the dominant nerve for the latissimus dorsi. Triceps Function: The anterior head of the triceps abducts and flexes the upper arm, the middle head of the triceps abducts the upper arm, the posterior head of the triceps abducts, extends, and laterally extends the upper arm and rotates it internally.
Latissimus Dorsi Presentation: One, pain in the entire shoulder, unable to raise the shoulders outwards, there is a friction sound. Two, when the arm is raised forward, sideways raised difficult, three, shoulder tongteng, movement range small. Four, injuries to the latissimus dorsi inhibit arm extension, because when the arm is raised and forward raised must involve the latissimus dorsi.
Triceps Presentation: One, the entire shoulder pain, unable to raise the shoulders outwards, there is a friction sound. Two, when the arm is raised forward, sideways raised difficult, three, shoulder tongteng, movement range small. Four, any part of the triceps injury or fatigue can affect the movement of the shoulder and the raising of the arm, therefore it can seriously affect sports or work performance, it is possible to attribute the injury or fatigue of the triceps to the bursa y, joint y or shoulder y.
Nerve Innervation: The thoracic nerve innervates the latissimus dorsi. The axillary nerve C4-C6 innervates the triceps. The axillary nerve at the quadrilateral hole is the key position for the triceps to be affected.
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