Quiz 1: THE SHOULDER AND POSTERIOR ARM

What are the 6 muscles of the shoulder that insert into the humerus and originate from the scapula?

Deltoid, Supraspinatus, Infraspinatus, Teres minor, Subscapularis, Teres major

How can you get additional range of motion at the shoulder?

If you want to lift your arm above horizontal, your scapula will need to laterally rotate. If you want to reach down to touch your toes, your scapula will need to rotate downwards or medially rotate.

How do you remember the borders of the quadrangular and triangular spaces? How do you remember the triangular interval borders?

Take your left hand make the peace sign with two fingers. Take your right hand, and orient it perpendicular to the fingers of the left hand, with the middle finger of hte right hand on top and the index finger beneath the two fingers of hte left hand. The top border (middle finger of right hand) is the teres minor. The bottom border (index finger of right hand) is teres major. The middle finger of the left hand is the humerus/lateral head of the triceps brachii. The index finger of the left hand is the long head of the triceps brachii.

What are the actions, innervations and origin/insertion of the teres major?

The actions of the teres major are to adduct the arm and medially rotate the arm. Teres major is innervated by the lower subscapular nerve. It originates from the lateral border of the scapula and inserts into the shaft of the humerus.

What are the actions, innervations and origin/insertion of the teres minor?

The actions of the teres minor are to laterally rotate the arm. The teres minor is innervated by the axillary nerve. The teres minor originates from the lateral border of the scapula and inserts into the greater tubercle of the humerus.

What are the actions, innervations and origin/insertion of the deltoid?

The deltoid is responsible for arm flexion/extension, medial and lateral rotation, and abduction. The deltoid is innervated by the axillary nerve. The deltoid originates from the clavicle, acromion, and the scapular spine and inserts into the deltoid tuberosity.

What are the actions, innervations and origin/insertion of the infraspinatous?

The infraspinatus is responsible for lateral rotation of the arm and for securing the glenohumeral joint. It is innervated by the suprascapular nerve. It originates from the infraspinous fossa and inserts into the greater tubercle of the humerus.

What reinforces the glenohumeral joint?

The shoulder joint is reinforced in several ways that still permit a broad range of movement. The acromion and coracoid process of the scapula help to shelter the joint, and the tendons of a group of shoulder muscles, the rotator cuff muscles, also reinforce the joint. Finally, a tendon of one of the large muscles of the arm, the biceps brachii, helps to hold the humerus in place.

What are the actions, innervations and origin/insertion of the subscapularis?

The subscapularis medially rotates the arm and secures the glenohumeral joint. It is innervated by the upper and lower subscapular nerves. It originates from the subspinous fossa and inserts into the lesser tubercle.

What are the actions, innervations and origin/insertion of the supraspinatous?

The supraspinatus is responsible for the first 15 degrees of abduction, and for securing the glenohumeral joint. The supraspinatous is innervated by the suprascapular nerve. This muscle originates from the suprascapular fossa and inserts into the greater tubercle of the humerus.

What are the 4 rotator cuff muscles?

The supraspinatus, infraspinatus, teres minor and subscapularis muscles are the rotator cuff muscles. By definition a rotator cuff muscle takes origin from the scapula and inserts onto either the greater or lesser tubercle of the humerus. Most help "rotate" the humerus and they form a secure "cuff" to hold the head of the humerus in place, especially when the shoulder is moving. A "torn rotator cuff" is a common injury in athletes. It is usually a tear of the supraspinatus tendon. The mnemonic "SITS" may help you remember the 4 rotator cuff muscles.

What are the actions and origin/insertion of the triceps brachii?

The triceps brachii extends the the forearm. The lateral head and the medial head originate from the shaft of the humerus, while the long head originates from the infraglenoid tubercle. The long head and the lateral head insert into the tendon of the triceps brachii, which inserts into the olecranon of the ulna. The medial head inserts into the olecranon fossa of the humerus.

What is the muscle in the posterior compartment of the arm?

The triceps brachii, which has a medial head, a lateral head, and a long head. the triceps brachii is innervated by the radial nerve C7 and C8 fibers.