PAL Muscles of Upper Limb Worksheet Pectoral Girdle 1. The shoulder joint does not have a neat ball and socket like the pelvis does. The joint is held into place by four muscles known as the rotator cuff. The primary function of these muscles is to stabilize the joint during motion. a) Complete the following table. Muscle name Location relative to Secondary Motion shoulder (e.g. anterior) b) What is the advantage of using muscle’s to stabilize a joint instead of a boney socket? c) What are the disadvantages? d) Imagine someone using a bench press or doing push-ups. What is the primary muscle involved? e) Look at pictures of the above muscle and rotator cuff muscles. Why do you think people can damage their rotator cuff when lifting weights that are too heavy? 2. Complete the below table to list all of the other muscles that cross the shoulder joint. Muscle Origin Insertion Action Muscles from axial skeleton to scapula Muscles from scapula to humerus Muscles from axial skeleton to humerus b) Consider lifting your arms sideways to form a T-shape with your arms and body. What is the primary muscle used for this ? c) Imagine a gymnast doing an iron cross formation on the rings. What muscles would be the primary muscle used to get into this position from a hanging position? Why is this different? Hint: Think about what part of the body is stationary and what part moving. Arm and Forearm The biceps and triceps both have multiple heads, some of which cross one joint, some of which cross more than one joint. List the origin for each of the heads, and then discuss what the action(s) the different heads cause on which joints. One of the best ways to organize muscles is to group them by the action they produce. Work as a group to list all the muscles that do each of the blow functions. flex the shoulder flex the elbow flex the wrist flex the fingers flex the thumb extend the shoulder extend the elbow extend the wrist extend the digits abduct the shoulder abduct the wrist abduct the thumb pronate the wrist supinate the wrist As additional practice. Look at the below diagrams for origins and insertions of the muscles of the arm and forearm. Work as a group to put figure out the action for each of the muscles on these figures. .