pectoral girdle

Question 1

what are the common finger injuries in rock climbing?

Answer 1

• Tendovaginitis
• Joint capsular damage
• Arthritis
• Rupture or sprain of digital flexor annular pulleys

Question 2

What are the functions of the pectoral girdle?

Answer 2

• provides a link between the upper limb and the axial skeleton via the shoulder and sternoclavicular joints respectively
• scapula provides many attachment areas for muscles, some of which anchor the pectoral girdle to the thorax while others control the position of the upper limb
• The clavicle acts as a strut holding the upper limb away from the trunk
• both bones are always involved in the movements of the upper limb

Question 3

what is the position and movement of the scapula determined by?

Answer 3

the activity of the muscles attached to it

Question 4

movements between the scapula and thorax are allowed due to what?

Answer 4

the fascia covering adjacent layers of muscle facilitating sliding and gliding movements

Question 5

what is retraction of the shoulder girdle?

Answer 5

movement of the scapula whilst maintaining its vertical position, such that it’s medial border approaches the vertebral column, as in bracing the shoulder. The glenoid fossa thus comes to face more directly lateral

Question 6

what is protraction of the shoulder girdle?

Answer 6

movement of the scapula forwards around the chest wall, as in rounding the shoulders. There may be some associated lateral rotation in this movement. The glenoid fossa comes to face more directly forwards

Question 7

What is elevation of the shoulder girdle?

Answer 7

where the pectoral girdle is lifted upwards as in shrugging your shoulder

Question 8

what is depression of the shoulder girdle?

Answer 8

Where the pectoral girdle is puller downwards

Question 9

what is lateral rotation of the shoulder girdle?

Answer 9

a complex movement in which the inferior angle of the scapula moves laterally around the chest wall, while the clavicle results in a concomitant upwards movement of the scapula, thus causing the glenoid fossa to be turned increasing upwards

Question 10

What is medial rotation of the shoulder girdle?

Answer 10

returns the scapula to its resting position from lateral rotation

Question 11

which muscles retract the pectoral girdle?

Answer 11

rhomboid major
rhomboid minor
trapezius

Question 12

what is the action of the rhomboids?

Answer 12

• retract the scapula
• also active in medial rotation of the pectoral girdle
• act as stabilisers of the scapula when other muscle groups are active

Question 13

What is the action of the trapezius?

Answer 13

• stabilises the scapula

- retracts the pectoral girdle

Question 14

what is the action of the middle fibres of trapezius?

Answer 14

• pull the scapula towards the midline, that is retraction and may be aided by the upper and lower fibres contracting together to produce a ‘resolved’ force towards the midline

Question 15

what is the action of the upper fibres of trapezius?

Answer 15

• elevate the pectoral girdle and maintain the level of the shoulders against the effect of gravity, or when a weight is being carried in hands
• also produce lateral flexion of the neck when acting singularly

Question 16

what is the action of the lower fibres of trapezius?

Answer 16

pull down the medial part of the scapula and thus lower the shoulder, especially against resistance e.g. when getting out of a chair

Question 17

what happens to the scapula is trapezius becomes paralysed?

Answer 17

can result in the scapula moving forwards around the chest wall with the inferior angle moving medially

Question 18

what muscles protract the pectoral girdle?

Answer 18

Serratus anterior

Pectoralis minor

Question 19

what is the action of serratus anterior?

Answer 19

• major protractor of the pectoral girdle, involved with thrusting, pushing, punching movements, where the scapula is driven forwards carrying the upper limb with it
• stabilises scapula during movements of the upper limb and contracts strongly to hold the medial border of the scapula against the chest wall when the arm is flexed or when a weight is being carried in front of the body
• the lower digitations work together with trapezius to rotate the scapula laterally

Question 20

what happens is serratus anterior becomes paralysed?

Answer 20

loss of rotation action which means the upper limb cannot be abducted by more than approx 90’, causing limitation of the functional capacity of the upper limb

Question 21

what is the action of pectoralis minor?

Answer 21

• by exerting a strong pull on the coracoid process, the scapula can be pulled forwards and downwards during pushing and punching movements
• when leaning on the hands it helps to transfer weight of the trunk to the upper limb
• its attachments to the coracoid process allows it to help produce medial rotation of the scapula against resistance
• may be used as an accessory muscle of inspiration during respiratory distress

Question 22

what muscles elevate the pectoral girdle?

Answer 22

• trapezius (upper)

- levator scapulae

Question 23

what is the action of levator scapulae?

Answer 23

• working with trapezius, can produce elevation and retraction or resists its downward movement, as when carrying a load in hand
• again working with trapezius, contraction of both sides produces extension of the neck, while one side produces lateral flexion of the neck
• also helps stabilise the scapula and is active in producing medial rotation of the scapula

Question 24

what muscles laterally rotates the pectoral girdle?

Answer 24

trapezius

serratus anterior

Question 25

what is the action of trapezius and serratus anterior?

Answer 25

- both muscles are well positioned to cause the inferior angle of the scapula to move laterally around the thoracic wall - the clavicle acting like a strut resists movement at the acromion, so that the overall effect of their action is to elevate the acromion and move the inferior angle laterally, thereby enabling the glenoid fossa to face more directly upwards - this movement is very important for increasing the range of movement possible, particularly in terms of abduction and flexion of the upper limb

Question 26

How does trapezius contribute to rotation in relation to laterally rotating the pectoral girdle?

Answer 26

- by contraction of its upper fibres which lift the lateral end of the clavicle and acromion upwards while at the same time its lower fibres pull downwards on the medial end of the scapula

Question 27

How does serratus anterior contribute to rotation in relation to laterally rotating the pectoral girdle?

Answer 27

- more important of the 2 muscles - pulls strongly on the inferior angle of the scapula, where the majority of its muscle fibres insert, to pull it laterally around the chest wall

Question 28

what muscles medially rotate the pectoral girdle?

Answer 28

- Rhomboids - pectoralis minor - Levator scapulae

Question 29

what are isotonic contractions?

Answer 29

generate force by changing the length of the muscle and can be concentric contractions or eccentric contractions

Question 30

what are concentric contractions?

Answer 30

causes the muscle to shorten, thereby generating force

Question 31

what are eccentric contractions?

Answer 31

causes the muscle to elongate in response to a greater opposing force

Question 32

what is the action of the rhomboid muscles, pectoralis minor and levator scapulae in relation to medially rotating the pectoral girdle?

Answer 32

Pectoralis minor exerts a downwards pull on the lateral side of this axis via its attachment to the coracoid process, while the rhomboids and levator scapulae pull upwards on the medial side

Question 33

what is the action of subclavius?

Answer 33

- to steady the clavicle by pulling it towards the disc of the sternoclavicular joint, and the sternum during movements of the pectoral girdle - this action tends to depress the lateral end of the clavicle

Question 34

what muscles stabilise the clavicle?

Answer 34

subclavius