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The deltoid is a large, thick powerful muscle with a triangular form and a coarse texture. The muscle is divided into three portions: an anterior (clavicular) portion, and acrominal portion, and a posterior portion. The anterior portion forms the broad side of the muscle and the posterior portion is located on the back of the shoulder. The muscle originates from the clavicle and from the spine of the scapula covering the outer side of the shoulder joint, giving the shoulder its rounded appearance, and inserts in the humerus. The deltoid is innervated by the 5th and 6th cervical nerves through the circumflex nerve and supplied by the circumflex artery.
Almost any movement of the shoulder and upper arm involves the deltoid muscle. The anterior portion is used to raise the arm from the body and to lower it again. The acrominal portion is a powerful abductor and the posterior portion is used to move the arm backward. It works with the pectoralis major to move the arm forward and works with the teres major and latissimus dorsi to move the arm back.
 Research Deltoid
The latissimus dorsi is a wide, flat triangular muscle located on the lower half of the back. It is the broadest of the back muscles. It originates along the lumbar and lower half of the thoracic vertebrae and the iliac crest and sacrum far below. The muscle fibres at its tip insert under the scapula and join to the humerus in the shoulder. The latissimus dorsi is innervated by the thorocodorsal nerve and supplied by the thorocodorsal artery. This muscle gives the arms motion. It is used when swimming or when swinging the arms back when jogging. It is also used to reach up to grab something above the head.
Research Latissimus Dorsi
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The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
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