This scapula (French : scapula, omoplate), is placed upon the upper and back part of the the thorax, occupies the space from the second to the seventh rib, and forms the posterior part of the shoulder. Its form is irregularly triangular and flat. It presents for examination two surfaces, three borders, and three angles.
The elbow-joint [articulatio cubiti] Class. - Diarthrosis. Subdivision. - Ginglymus.is a complete hinge, and, unlike the knee, depends for its security and strength upon the configuration of its bones rather than on the number, strength, or arrangement of its ligaments.
The stomach [Latin: ventriculus ; gaster; French: estomac] is a dilation of the alimentary canal succeeding the esophagus. In the stomach the food is mixed with the gastric juice and reduced to a viscid, pulpy liquid, the chyme [chymus], which undergoes a certain amount of digestion and absorption before passing into the duodenum.
The shoulder articulation [articulatio humeri] is one of the most perfect and most movable of joints, the large upper end of the humerus playing upon the shallow glenoid cavity. Like the hip, it is a ball-and-socket joint. It is retained in position much less by ligaments than by muscles, and, owing to the looseness of its capsule, as well as to all the other conditions of its construction and position, it is exceedingly liable to be displaced; on the other hand, it is sheltered from violence by the two projecting processes - the acromion and coracoid. The ligaments of the shoulder-joint are:
The scapula is connected with the clavicle by a synovial joint with its ligaments at the acromio-clavicular articulation; and also by a set of ligaments passing between the coracoid process and the clavicle. So, that we have to consider: the acromio-clavicular articulation, the coraco-clavicular ligaments, the proper scapular ligaments are also best described in this section - viz., the coraco-acromial and transverse.
The sterno-costo-clavicular articulation Class. - Diarthrosis. Subdivision. - Condylarthrosis.
At this joint the large medial end of the clavicle is united to the superior angle of the manubrium sterni, the first costal cartilage also assisting to support the clavicle. It is the only joint between the upper extremity and the trunk, and takes part in all the movements of the upper limb. Looking at the bones, one would say that they were in no way adapted to articulate with one another, and yet they assist in constructing a joint of security, strength, and importance. The bones are nowhere in actual contact, being completely separated by an articular disc. The interval between the joints of the two sides varies from one inch to an inch and a half (2.5-4 cm.).
Before describing the movements of the thorax as a whole, it must be premised that there are some few modifications in the movements of certain ribs resulting from their shape. Thus, the firs rib (and to a less extent the second also), which is flat on its upper and lower surfaces, revolves on a transverse axis drawn through the costo-vertebral and costo-transverse joints. During inspiration and expiration, the anterior extremities of the first pair of costal arches play up and down, the tubercles and the heads of the ribs acting in a hinge-like manner, the latter having also a slight screwing motion. By this movement, the anterior ends of the costal arches are simply raised or depressed, and the sternum pushed a little forward; it may be likened to the movement of a pump-handle.
These articulations at the front of the thorax may be divided into four sets, viz.: The intersternal joints, or the union of the several parts of the sternum with one another. The costo -chondral joints, or the union of the ribs with their costal cartilages. The chondro-sternal joints, or the junction of the costal cartilages with the sternum. The interchondral joints, or the union of five costal cartilages (sixth, seventh, eighth, ninth, and tenth) with one another.
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