Appendicular Muscles- Upper Extremities

Question 1

What are the muscles of the pectoral girdle? (7)

Answer 1

• Pectoralis minor, serratus anterior, subclavius, trapezius, levator scapulae, rhomboid minor, rhomboid major

Question 2

What do the pectoral girdle muscles do?

Answer 2

• Attach the scapula and clavicle to the axial skeleton
• Both stabilize the scapula and move it to increase the range of motion of the arm
• Classified according to their location in the thorax as either anterior or posterior thoracic muscles

Question 3

What is the pectoralis minor?

Answer 3

• An anterior thoracic muscle
• Thin, triangular and flat muscle deep to pectoralis major
• Helps depress and protract (pull anteriorly) the scapula
• When you are hunched over, this muscle is engaged

Question 4

What is the serratus anterior?

Answer 4

• An anterior thoracic muscle
• Large, flat, fan-shaped muscle positioned between the ribs and the scapula
• This muscle is the agonist (prime mover) in scapula protraction (pull anteriorly) which means it works together with pectoralis minor
• Stabilizes the scapula against the posterior side of the rib cage
• Powerful superior rotator of the scapula and acts to move the glenoid cavity superiorly

Question 5

What is the subclavius?

Answer 5

• A small, cylindrical muscle named for its location inferior to the clavicle
• Main action is to stabilize and depress the clavicle

Question 6

What is the trapezius?

Answer 6

• Posterior thoracic muscle
• Large, flat, diamond-shaped muscle that attaches medially to the skull and vertebral column
• Attached laterally to the scapula and clavicle
• Can elevate, depress, retract, or rotate the scapula depending on which fibers of the muscle contract
• Superior fibers: elevate and superiorly rotate the scapula
• Middle fibers: work with rhomboid muscles to retract the scapula
• Inferior fibers: depress the scapula

Question 7

What is the levator scapula?

Answer 7

• Posterior thoracic muscle
• Narrow, elongated muscle that is deep to both the trapezius and sternocleidomastoid muscles
• Its multiple heads attach superiorly to the transverse processes of the cervical vertebrae and attaches inferiorly to the superior angle of the scapula
• Its primary action is to elevate the scapula
• It can also inferiorly rotate the scapula so that the glenoid cavity points inferiorly

Question 8

What is the rhomboid minor and major?

Answer 8

• Located deep to the trapezius
• Parallel bands that that run inferolaterally from the vertebrae to the scapula
• Often are indistinct from each other
• Help elevate and retract (adduct) the scapula
• When you stand up straight with shoulders back you engage this muscle
• Also inferiorly rotate the scapula

Question 9

What are the muscles that move the glenohumeral joint/arm? (8)

Answer 9

• Latissimus dorsi, pectoralis major, deltoid, coracobrachialis, teres major, suprascapularis, supraspinatus, infraspinatus and teres minor
• The glenohumeral joint is crossed by 11 muscles however (biceps brachii and triceps brachii also cross)
• Attach to the arm (humerus) or forearm (radius and ulna)

Question 10

What is the latissimus dorsi?

Answer 10

• Primary attachment of the arm to the trunk
• Broad, triangular muscle located on the inferior part of the back (referred to as the swimmer’s muscle)
• Agonist for arm extension and also adducts and medially rotates the arm
• Antagonist with pectoralis major with respect to arm flexion and extension
• Work together with pectoralis major when adducting and medially rotating the humerus

Question 11

What is the pectoralis major?

Answer 11

• Primary attachment of the arm to the trunk
• Large, thick, fan-shaped muscle that covers the superior part of the thorax
• Agonist for arm flexion and also adducts and medially rotates the arm
• Antagonist with latissimus dorsi with respect to arm flexion and extension
• Work together with latissimus dorsi when adducting and medially rotating the humerus

Question 12

What are the scapular muscles? (7 remaining glenohumeral/arm muscles)

Answer 12

• Move the humerus at the glenohumeral joint
• Proximal attachment is almost entirely on the scapula
• Include deltoid, coracobrachialis, teres major and the 4 rotator cuff muscles

Question 13

What is the deltoid?

Answer 13

• Thick, powerful muscle that is the agonist for arm abduction and forms the rounded contour of the shoulder
• Primary arm abductor muscle
• Anterior fibers: flex and medially rotate the arm
• Middle fibers: abduct the arm
• Posterior fibers: extend and laterally rotate the arm

Question 14

What is the coracobrachialis?

Answer 14

• Works together with the pectoralis major in flexing and adducting the arm

Question 15

What is the teres major?

Answer 15

• Works together with the latissimus dorsi by extending, adducting and medially rotating the arm

Question 16

What are the 4 rotator cuff muscles?

Answer 16

• Subscapularis, supraspinatus, infraspinatus, and teres minor
• Provide strength and stability to the glenohumeral joint
• Attach the humerus to the scapula
• Each of the 4 muscles is best described in the action of pitching a ball

Question 17

What is the subscapularis?

Answer 17

• Rotator cuff muscle
• Used when you wind up for a pitch
• Medially rotates the arm

Question 18

What is the supraspinatus?

Answer 18

• Rotator cuff muscle
• Used when you start to execute the pitch
• Helps to abduct the arm

Question 19

What is the infraspinatus and teres minor?

Answer 19

• Rotator cuff muscles
• Used to help slow down the pitching arm upon completion of the pitch
• Adduct and laterally rotate the arm

Question 20

How are arm and forearm muscles that move the elbow joint/forearm organized?

Answer 20

• Organized into compartments, which are separated by intermuscular septa and are surrounded by deep fascia
• Each compartment houses functionally related skeletal muscles as well as their associated nerves and blood vessels
• Anterior compartment: primarily contains elbow flexors (biceps brachii and brachialis)
• Posterior compartment: mostly contains contains elbow extensors (triceps brachii and anconeus)

Question 21

What is the biceps brachii?

Answer 21

• Flexor compartment muscle (anterior)
• Large, two-headed muscle on the anterior surface of the humerus
• Flexes the forearm and is a powerful supinator of the forearm when the elbow is flexed
• Tendons of both bicep brachii heads cross the shoulder joint
• Also helps flex the humerus as well

Question 22

What is the brachialis?

Answer 22

• Flexor compartment muscle (anterior)
• Deep to the biceps brachii and lies on the anterior surface of the humerus
• Most powerful flexor of the forearm at the elbow

Question 23

What is the brachioradialis?

Answer 23

• Flexor compartment muscle

- Prominent muscle on the lateral surface of the forearm that flexes the forearm at the elbow

Question 24

What is the triceps brachii?

Answer 24

• Extensor compartment muscle (posterior)
• Large, three-headed muscle on the posterior surface of the arm
• Antagonistic to the biceps brachii
• Only the long head crosses the glenohumeral joint, where it helps extend the humerus
• All 3 parts merge to form a common attachment to the olecranon of the ulna

Question 25

What is the anconeus?

Answer 25

• Extensor compartment muscle (posterior)
• Weak elbow extensor
• Small and crosses the posterolateral region of the elbow

Question 26

What is the pronator teres and pronator quadratus?

Answer 26

• Muscles that pronate the forearm
• Rotate the radius across the anterior surface of the ulna to pronate the forearm
• Located in the anterior compartment of the forearm

Question 27

What is the supinator?

Answer 27

• Antagonist muscle to the pronator teres and quadratus
• In the posterior compartment of the forearm
• Works together with the biceps brachii to supinate the forearm