Lecture 7 - The Pectoral Girdle

Question 1

What is the pectoral girdle?

Answer 1

• Wraps around the upper portion of the thoracic cage
• Support structure for the upper limb; clavicles (2) & scapulae (2)

Question 2

Shoulder (pectoral) girdle stability vs mobility?

Answer 2

• structurally it is very mobile
• but it is relatively less stable

Question 3

Pelvic girdle stability vs mobility?

Answer 3

• it is structurally very stable
• but it is relatively less mobile

Question 4

What is the clavicle ?

Answer 4

• it serves as a strut that extends laterally to support the scapula
• transmits forces acting on the upper limb to the sternum & axial skeleton
• it protects the nerves & blood vessels as they pass

Question 5

Why is the clavicle called a “little key”?

Answer 5

• it attaches the upper limb to the body

Question 6

What are the 3 regions of the clavicle ?

Answer 6

• shaft
• sternal end
• acromial end

Question 7

What makes the shaft of the clavicle & why is it important?

Answer 7

• the shaft has a “subclavian groove” which gives attachment to the Subclavius
• the shaft is also used to identify where muscles are attached

Question 8

What is the sternal end of the clavicle ?

Answer 8

• a triangular shape that articulates with the manubrium portion of the sternum
• forms the sternoclavicular joint (SC joint)

Question 9

What is the acromial end of the clavicle ?

Answer 9

• articulates with the acromian of the scapula, which is the portion that forms the bony tip of the shoulder
• this forms the acromialclavicular joint (AC joint)

Question 10

What is the sternoclavicular joint (SC joint)?

Answer 10

• its the only bone apart of the clavicle
• this joint allows considerable mobility, allowing the clavicle & scapula to move in upward/downward & anterior/posterior directions
• it is a synovial saddle joint (bi-axial)

Question 11

What are the functions of the clavicle?

Answer 11

• Has a moveable rigid support; Which suspends scapula & upper limb
• Allows the scapula to move on the thoracic wall
• Rotates to assist with normal shoulder movement
• Forms a passageway between neck & upper limb
• Transmits shock from the upper limb to the axial skeleton

Question 12

What is the scapula?

Answer 12

• Thin, flat, triangular bone with 3 borders; have a right & left one
• located on the posterior side of the shoulder
• Overlies ribs 2-7
• Held against the thorax by muscles only

Question 13

What are the 3 borders of the scapula ?

Answer 13

• vertebral (medial) border
• axillary (lateral) border
• superior border

Question 14

What is the vertebral (medial) border of the scapula?

Answer 14

• it is closest to the vertebrae
• it is smooth

Question 15

What is the axillary (lateral) border of the scapula?

Answer 15

• axillary = armpit
• it is the thickest part of the border

Question 16

What is the superior border of the scapula?

Answer 16

• it is the upper component
• it extends from the superior angle to the coracoid process

Question 17

What is the suprascapular notch?

Answer 17

• located lateral to the midpoint of the superior border
• in line with the T10-T12
• serves as a passage for the suprascapular nerve

Question 18

What is the spine of the scapula?

Answer 18

• Divides posterior aspect into the infraspinous & supraspinous fossa

Question 19

What is the supraspinous fossa?

Answer 19

• a narrow depression located on the posterior scapula, superior to the spine
• it gives attachment to muscles that act in rotating the arm

Question 20

What is the infraspinous fossa ?

Answer 20

• a broad depression located on the posterior scapula, inferior to the spine
• it externally rotates the humerus & stabilize the shoulder joint

Question 21

What is the acromian process?

Answer 21

• forms the bony tip of the superior shoulder region & articulates with the lateral end of the clavicle
• forms the acromioclavicular joint

Question 22

What is the acromiclavicular joint (AC Joint)?

Answer 22

• allows additional ROM to the scapula and assist in arm movement such as shoulder abduction & flexion
• it is a Synovial gliding joint
• Supported by the acromioclavicular ligament
• Shoulder “separations” occur here

Question 23

What is the coracoacromial ligament ?

Answer 23

• Runs from the coracoid process to the acromion process
• Provides some superior stability to the shoulder joint

Question 24

What is the coracoclavicular ligament ?

Answer 24

• Runs from the undersurface of the clavicle to the coracoid process
• it provides indirect support of the AC joint
• has Two parts; Concoid & Trapezoid

Question 25

What are the movements of the scapula ?

Answer 25

• Elevation, Depression, Protraction (abduction), Retraction (adduction), Upward/downward rotation

Question 26

What is scapulohumeral rhythm ?

Answer 26

• Movement of the scapula relative to movement of the humerus
• Normal ROM for shoulder abduction and flexion is 180°, 120° comes from shoulder joint, 60° comes from scapulothoracic joint
• First 30° is mainly comes from the shoulder, scapulothoracic involvement is minimal, After 30° shoulder and scapulothoracic joints are both involved