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From this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus; the middle fibers passing vertically, the anterior obliquely backward and laterally, and the posterior obliquely forward and laterally.
Though traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin. The insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge. It additionally give off extensions to the deep brachial fascia. Furthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa. [16]
The deltoid is supplied by the posterior circumflex humeral artery.[17]
The deltoid is innervated by the axillary nerve.[17] The axillary nerve originates from the ventral rami of the C5 and C6 cervical nerves, via the superior trunk, posterior division of the superior trunk, and the posterior cord of the brachial plexus.[citation needed]
The axillary nerve is sometimes damaged during operations on the axilla, such as for breast cancer. It may also be injured by anterior dislocation of the head of the humerus.[citation needed]
When all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane. The arm must be medially rotated for the deltoid to have maximum effect[citation needed]. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.
The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. The anterior deltoid is weak in strict transverse flexion but assists the pectoralis major during shoulder transverse flexion / shoulder flexion (elbow slightly inferior to shoulders). The anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.[18]
The posterior fibers are strongly involved in transverse extension particularly as the latissimus dorsi is very weak in strict transverse extension. Other transverse extensors, the infraspinatus and teres minor, also work in tandem with the posterior deltoid as external (lateral) rotators, antagonists to strong internal rotators like the pecs and lats. The posterior deltoid is also the primary shoulder hyperextensor, more so than the long head of the triceps which also assists in this function.[19]
The lateral fibers perform basic shoulder abduction when the shoulder is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated. They are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.[20]
An important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads. The function of abduction also means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk. It also ensures a precise and rapid movement of the glenohumeral joint needed for hand and arm manipulation.[2] The lateral fibers are in the most efficient position to perform this role, though like basic abduction movements (such as lateral raise) it is assisted by simultaneous co-contraction of anterior/posterior fibers.[21]
The deltoid is responsible for elevating the arm in the scapular plane and its contraction in doing this also elevates the humeral head. To stop this compressing against the undersurface of the acromion the humeral head and injuring the supraspinatus tendon, there is a simultaneous contraction of some of the muscles of the rotator cuff: the infraspinatus and subscapularis primarily perform this role. In spite of this there may be still a 1–3 mm upward movement of the head of the humerus during the first 30° to 60° of arm elevation.[2]
- 어깨를 30-60도 들어올릴때 상완골두는 1~3mm 위로 움직임.
The most common abnormalities affecting the deltoid are tears, fatty atrophy, and enthesopathy. Deltoid muscle tears are unusual and frequently related to traumatic shoulder dislocation or massive rotator cuff tears. Muscle atrophy represents the end result of many causes, including aging, disuse, denervation, muscular dystrophy, cachexia, and iatrogenic injury. Deltoideal humeral enthesopathy is an exceedingly rare condition related to mechanical stress. Conversely,deltoideal acromial enthesopathy is likely a hallmark of seronegative spondylarthropathies and its detection should probably be followed by pertinent clinical and serological investigation.[22]
- 삼각근이 파열되는 것은 흔하지 않음.
- 삼각근은 물건을 들때 어깨가 탈구되지 않게 하는 근육이고, 어깨 탈구 또는 회전근개 파열시 파열됨.
- 삼각근 위축은 나이, 불사용, 탈신경, 근위축, 악액질, 손상 등에서 발생
삼각근 Trp 탐구
삼각근 운동법
삼각근 스트레칭 방법
에반스의 삼각근 후방섬유 isolated stretching
에반스의 삼각근 전방섬유 isolated stretching
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