Lecture 3: Pectoral girdle

Question 1

What does the “pectoral girdle” refer to and what is its main function

Answer 1

These are the two bones: (scapula + clavicle) part of the upper limb that link it to the axial skeleton. Its main purpose is to allow the wide range of movement of upper limb required for manipulation of the environment by acting as a mobile base for muscle attachment which stabilises the shoulder joint

Question 2

Differentiate pectoral girdle vs shoulder joint

Answer 2

Pectoral girdle is clavicle and scapula which articulate at the acromioclavicular joint whereas shoulder joint is between glenoid fossa of the scapula and the head of the humerus

Question 3

Describe the clavicle main purpose and appearance

Answer 3

A sinuous long bone with medial convexity pointing anteriorly, largely subcutaneous forming a strut between manubrium and acromial process of scapula, holding it out against the chest muscles pulling it in. It takes a lot of the force from the arm, therefore more likely to break in the medial curve where it isn’t supported by muscle attachments.

Question 4

What are the three main features on the inferior view of the clavicle for attachment of ligaments/ muscle (medial to lateral). What are these important for

Answer 4

All important for stabilising the clavicle.

• First costoclavicular roughened area for attachment of costoclavicular ligament
• Subclavian groove for subclavius muscle attachment
• Coracoclavicular ligament attachement ridge

Question 5

What are the anterior muscles that have origin from the axial skeleton and insert on the humerus

Answer 5

Pectoralis major

Question 6

What are the anterior muscles that have origin from the axial skeleton and insert on the pectoral girdle

Answer 6

Pectoralis minor, Subclavius and Serratus anterior

Question 7

Describe innervation, origin and insertion of pectoralis major

Answer 7

Nerve: Lat & med pectoral n.
2 Origins: Sternocostal head and clavicular head (closer to sternum)
Insertion: Lateral intertubercular groove of humerus

Question 8

Primary movements of pectoralis major

Answer 8

Attaches horizontal across the chest so

• adducts humerus
• internally rotate humerus
• protract scapula by pulling on humerus

Question 9

Describe innervation, origin and insertion of pectoralis minor

Answer 9

Nerve: med pectoral n.
O: 3,4,5 ribs
I: coracoid process of the scapula

Question 10

Primary movements of pectoralis minor

Answer 10

Attaches northeast on the chest so

-can depress scapula

Question 11

Describe innervation, origin and insertion of subclavius

Answer 11

Nerve: C5
O: costal cartilage of 1st rib
I: subclavian groove of clavicle

Question 12

Primary movements of subclavius

Answer 12

Braces the clavicle by stopping it being pulled out when clavicle moves up

Question 13

Describe innervation, origin and insertion of Serratus anterior

Answer 13

Nerve: Long thoracic n.
O: ribs 1-8 or 1-9
I: medial border of the scapula

Question 14

Primary movements of Serratus anterior

Answer 14

Protracts scapula (scapular abduction) and its lower fibres can help to superiorly rotate scapula (lowkey abduct)

Question 15

Describe the general appearance of scapula

Answer 15

A flat triangular bone that covers the posterolateral surface of ribs 2-7, with 3 angles(corner), borders, protuberences and surfaces. Lateral end is the end of the 3 protuberences that allow the glenohumeral joint to articulate and acromioclavicular joint. Lateral end is stiff and thick to allow lots of muscles to attach

Question 16

Describe the 3 protuberences and therefore surfaces of the scapula with respect to 3 angles and borders

Answer 16

On the posterior surface of scapula is protuberence of spine which runs from medial border to lateral, ending in the corner of glenoid fossa (lateral angle). This divides the post. surf. of scapula into supraspinous fossa (closer to superior angle/border) and infraspinous fossa (closer to inferior angle/border).
The last surface is the anterior surface called subscapula fossa.
Protuberence of coracoid process is more anterior than acromion which is at the lateral end of the spine.

Question 17

Describe the inside of sternoclavicular joint

Answer 17

It is a saddle shaped synovial joint between medial end of clavicle and the manubrium of sternum. There is a a meniscus (intra articular fibrocartilagionous disc) that lies between the articulating surfaces of the two bones.

Question 18

Describe the 4 ligaments that strengthen the sternoclavicular joint

Answer 18

• Anterior + Posterior sternoclavicular ligament that is a thickening of the capsule of S.C joint (posterior one stronger).
• Interclavicular ligament which links across the jugular notch
• Costoclavicular ligament which is a fulcrum for upper clavicular movements and chief stabiliser of joint (follows subclavius).

Question 19

Describe the inside of the acromioclavicular joint

Answer 19

It is a synovial joint between the lateral end of the clavicle and the medial border of the acromion. There is a wedge shaped fibrocartilagenous intra articular disc between the articulating surfaces of the two bones.

Question 20

Describe the ligaments that support the acromioclavicular joint

Answer 20

The joint capsule itself is strengthened by the intrinsic acromioclavicular ligament.
The joint is supported by two parts of the coracoclavicular ligament-> conoid + trapezoid. these help to save energy to fight the pull of the trapezius muscle on the acromion.

Question 21

What are the 4 posterior muscles that originate from axial skeleton to pectoral girdle

Answer 21

Trapezius, levator scapulae and rhomboid major and minor

Question 22

What is the innervation, origin and insertion of the trapezius (all three parts)

Answer 22

N: accessory nerve (Cranial nerve 11)
Origin: external occipital proturberance, spinous processes of c7- T12
Insertion: anatomical horseshoe
Superior- clavicle, Middle: acromion Inferior: spine of scapula

Question 23

What are the primary movements of trapezius (all, sup, mid, inf, sup+inf only on the scapula

Answer 23

All together : Retract the scapula
Sup: elevates scapula (suspends neck)
Mid: retracts 
Lower: depresses
Sup + Inf: superior rotation

Question 24

What is the innervation, origin and insertion of levator scapulae

Answer 24

N: Dorsal scapular nerve (C3&C4)
Origin: cervical spinous processes 1-4
Insert: superior angle of the scapula

Question 25

Are levator scapulae and rhomboid maj+ minor superficial or deep to trapezius

Answer 25

deep

Question 26

What are the 1’ movements of levator scapulae

Answer 26

elevate scapula

Question 27

What is the innervation, origin and insertion of Rhomboid minor and major

Answer 27

N: Dorsal scapular nerve
Origin: Minor is spinous processes C7,T1. Major is T2 to T5
Insert: medial border of scapula, with minor inline with spine of scapula and major lower than that.

Question 28

What is the primary movement of rhomboid major and minor

Answer 28

retracts the scapula.

Question 29

What is the innervation, origin and insertion of Latissimus dorsi- which has a aponeurosis before the muscle belly

Answer 29

N: Thoracodorsal n
O: spinous processes of T7 to S5
I: floor of the intertubercular groove on the anterior of the humerus.

Question 30

What is the primary movement of latissimus dorsi

Answer 30

Adduct the humerus, internally rotates humerus and the lower fibres can depress scapula by pulling on the humerus