The arm is the upper limb in man, connected with the thorax or chest by means of the scapula or shoulder-blade, and the clavicle or collar-bone. It consists of three bones, the arm-bone (Humerus), and the two bones of the forearm (radius and ulna), and it is connected with the bones of the hand by the carpus or wrist. The head or upper end of the arm-bone fits into the hollow called the glenoid cavity of the scapula, so as to form a joint of the ball-and-socket kind, allowing great freedom of movement to the limb. The lower end of the humerus is broadened out by a projection on both the outer and inner sides (the outer and inner condyles), and has a pulley-like surface for articulating with the fore-arm to form the elbow-joint. This joint somewhat resembles a hinge, allowing of movement only in one direction. The ulna is the inner of the two bones of the fore-arm. It is largest at the upper end, where it has two processes, the coronoid and the olecranon, with a deep groove between to receive the humerus. The radius - the outer of the two bones - is small at the upper and expanded at the lower end, where it forms part of the wrist-joint. The muscles of the upper arm are either flexors or extensors, the former serving to bend the arm, the latter to straighten it by means of the elbow-joint. The main flexor is the biceps, the large muscle which may be seen standing out in front of the arm when a weight is raised. The chief opposing muscle of the biceps is the triceps. The muscles of the fore-arm are, besides flexors and extensors, pronators and supinators, the former turning the hand palm downwards, the latter turning it upwards. The same fundamental plan of structure exists in the limbs of all vertebrate animals. Research Arm
The cephalic vein extends along the biceps muscles to the shoulder where it eventually merges with the axillary vein just below the clavicle . In some people, this vein is connected to the external jugular vein or subclavian vein by a branch that extends in front of the clavicle. Research Cephalic Vein
In human anatomy, the clavicle is a long bone which lies almost horizontally at the root of the neck. It serves two main functions; to act as a prop which braces back the shoulder and enables the limb to swing clear of the trunk. And to transmit part of the weight of the limb to the axial skeleton. Research Clavicle
The conoid ligament is part of the coracoacromial ligament which extends from the base of the coracoid process to the conoid tubercle on the underside of the clavicle. It is responsible for controlling and regulating the gliding motions of the clavicle and the sternum, especially of the back and forth rotation of the scapula. Research Conoid Ligament
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 innominate artery is one of the large arteries rising from the arch of the aorta. It is the largest branch arising from the transverse portion of the arch, and divides into the right common carotid artery and the right subclavian, just behind the articulation of the right clavicle with the sternum at its upper edge. Research Innominate Artery
The jugular veins lie deep inside the neck. They receive the blood from the brain, face and neck and return it to the heart. The external jugular vein is larger than the other veins in the neck, sometimes double their size. It has two pairs of valves to assist in transporting blood. The first pair is placed at the entrance to the subclavian vein and the second pair is about an inch and a half above the clavicle. The internal jugular vein lies deeper in the neck and runs parallel to the carotid artery. It joins with the subclavian vein at its base to form the innominate vein. Like the external jugular vein, it also has two pairs of valves to assist in the transportation of blood. As the pockets of the valves fill with returning blood, the valves close and shut off part of the vein. Then, the muscles in the vein contract and help push the blood forward. The valves also make certain that the blood in the veins will never flow backward. Research Jugular vein
The pectoralis major muscle is located at the front of the thoracic cage. It is a thick, fan-shaped muscle and is divided into three parts that begin at the armpit and cover most of the front of the chest. The upper, or clavicular, part (clavicular head) originates from the clavicle. The lower, or sternocostal portion (sternocostal head), originates from the sternum and the costal cartilage of the first to sixthribs. The abdominal portion originates from the external oblique muscle. The three portions unite, covering a wide area and then narrowing to insert into the crest of the greater tubercle of the humerus. The pectoralis major muscle is innervated by the anterior thoracic nerve and supplied by the thoracic artery. This muscle is used when you bring your arms across the chest, raise and lower the arms and to rotate the arms. The clavicular portion will raise the arm, while the sternocostal portion will pull it down. Research Pectoralis Major
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Arm
