Pectoral Girdle, Scapular Movements and Muscles

Question 1

label the pectoral girdle

Answer 1

Question 2

what is the pectoral girdle?

Answer 2

the set of bones which connects the upper limb to the axial skeleton on each side

Question 3

the entire upper limb and pectoral girdle articulate at one small joint only - which is this?

Answer 3

glenohumeral joint

Question 4

which part of the clavicle is weakest and commonly breaks (fractures) during a fall? why is this?

Answer 4

• the junction of lateral and middle thirds
• the weight of the arm drags the lateral part inferiorly

Question 5

label the scapula

Answer 5

Question 6

what type of synovial joint is the acromioclavicular (AC) joint?

Answer 6

plane synovial joint

Question 7

what type of synovial joint is the sternoclavicular (SC) joint?

Answer 7

synovial saddle joint

Question 8

describe the scapulo-humeral rhythm

Answer 8

Abduction of the arm occurs in 2 stages:
- The first 30 degrees of abduction is caused by muscles acting at the shoulder (gleno-humeral) joint.
- Beyond 30 degrees, the abduction relies on the scapula being pulled ipwards (elevated) and laterally rotating on the chest wall (‘scapula-thoracic’ movement).

Question 9

what are the main muscles involved in elevation of the scapula?

Answer 9

1. upper trapezius
2. levator scapulae

Question 10

What are the actions of the trapezius muscle?

upper, middle and lower fibres

Answer 10

The upper fibres of the trapezius elevate the scapula and rotates it during abduction of the arm. The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly. The lower fibres of the trapezius depress the scapula.

Question 11

what is the action of the levator scapulae muscle?

Answer 11

elevation of the scapula

Question 12

what is the main muscle involved with depression of the scapula?

Answer 12

lower trapezius

Question 13

what is the main muscle involved with protraction (forward movement) of the scapula?

Answer 13

serratus anterior

Question 14

what are the main muscles involved with retraction of the scapula?

Answer 14

middle trapezius and rhomboids

Question 15

what are the actions of the major and minor rhomboids?

Answer 15

retracts and rotates the scapula

Question 16

what are the main muscles involved in Lateral (upward) rotation of the scapula?: Elevating Glenoid Cavity - Shrugging your shoulders!

Answer 16

upper and middle trapezius

Question 17

label all the scapula muscles 1-9

Answer 17

1. trapezius
2. levator scapulae
3. rhomboideus minor
4. rhomboideous major
5. supraspinatus
6. infraspinatus
7. teres minor
8. teres major
9. lattisimus dorsi