Page 57 - Alaska A & P Primer

ple plane joints among the tarsal bones of the posterior foot (intertarsal joints) and thus are not motions that take place at the ankle joint.
Protraction and retraction are anterior-posterior movements of the scapula or mandi- ble. Protraction of the scapula occurs when the shoulder is moved forward, as when push- ing against something or throwing a ball. Depression and elevation are downward and upward movements of the scapula or mandible. Excursion is the side to side movement of the mandible.
Superior and inferior rotation are movements of the scapula and are defined by the direction of movement of the glenoid cavity. Opposition is the thumb movement that brings the tip of the thumb in contact with the tip of a finger. Thumb opposition is pro- duced by a combination of flexion and abduction of the thumb at this joint.Returning the thumb to its anatomical position next to the index finger is called reposition
9.6 Synovial Joints
Each synovial joint of the body is specialized to perform certain movements. The move- ments that are allowed are determined by the structural classification for each joint. For example, a multiaxial ball-and-socket joint has much more mobility than a uniaxial hinge joint. However, the ligaments and muscles that support a joint may place restrictions on the total range of motion available. Thus, the ball-and-socket joint of the shoulder has lit- tle in the way of ligament support, which gives the shoulder a very large range of motion.
The atlanto-occipital joint is formed by the articulations between the superior articular processes of the atlas and the occipital condyles on the base of the skull. This articulation has a pronounced U-shaped curvature, oriented along the anterior-posterior axis. This al- lows the skull to rock forward and backward, producing flexion and extension of the head. This moves the head up and down, as when shaking your head “yes.”
The temporomandibular joint is the articulation between the condyle of the mandible and the mandibular fossa and articular tubercle of the skull temporal bone. An articular disc is located between the bony components of this joint. A combination of gliding and hinge motions of the mandibular condyle allows for elevation/depression, protraction/ retraction, and side-to-side motions of the lower jaw.
The glenohumeral (shoulder) joint is a multiaxial ball-and-socket joint that provides flexion/extension, abduction/adduction, circumduction, and medial/lateral rotation of the humerus. The head of the humerus articulates with the glenoid cavity of the scapula. The glenoid labrum extends around the margin of the glenoid cavity. Intrinsic ligaments, in-
cluding the coracohu- meral ligament and glenohumeral liga- ments, provide some support for the shoul- der joint. However, the primary support comes from muscles crossing the joint whose tendons form the rotator cuff. These muscle ten- dons are protected from friction against the scapula by the subacromial bursa and subscapular bursa.
The elbow is a uniaxial hinge joint that allows for flexion/extension of the forearm. It in- cludes the humeroulnar joint and the humeroradial joint.
9.6 OBJECTIVES
1. Describe the structures that support and prevent excess movements at each joint
This content is available for free at https://cnx.org/content/col11496/1.7
State of Alaska EMS Education Primer - 2016
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