|
The acromion is the lateral projection from the spine of the scapula. The plough blade-like projection serves as a site of attachment for both the trapezius and deltoid muscles, which assist in giving the shoulder its strength during flexion.
 Research Acromion
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 infraspinatus muscle is attached along the broad inner edge of the scapula. It originates from the infraspinous fossa of the scapula and narrows into a strong tendon that inserts firmly to the top of the humerus. This muscle is innervated by the suprascapular nerve from the fifth to sixth cervical nerves and supplied by the circumflex artery. The infraspinatus muscle sits on the back of the shoulder blade below the spine and under the deltoid muscle. It works with the supraspinatus muscle to help lift and twist the upper arm. These two muscles also help support and protect the shoulder joint by keeping the head of the humerus in place.
Research Infraspinatus
The platysma (platysma myoides) muscle is a broad, thin sheet of muscle that originates in the pectoral and deltoid muscles and runs upward over the collar bone and inward along each side of the neck and in the skin near the mandible. It is innervated by the facial nerve (VII cranial nerve) and supplied by branches of the internal carotid artery. This muscle works to draw the lower lips and corner of the mouth sideways and down partially opening the mouth. It is used when expressing surprise, fear, or horror. It also increases the diameter of the neck as seen during intense breathing from fast running.
Research Platysma
The spine of the scapula is a ridge which runs laterally along the posterior surface of the bone. This spine separates the surface of the back of the scapula into two unequal areas: the supraspinous fossa and the infraspinous fossa. The spine continues laterally to form the coracoid process and the acromion (which articulates with the clavicle). The spine and these two projections serve to anchor much of the connective tissue in the shoulder. The trapezius and deltoid muscles are especially responsible for giving the scapula its stability and strength during movement.
Research Spine of the Scapula
|
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
|
|
|
Abbreviations
