Shoulder arthrology (wk7)

Question 1

Explain how the pectoral girdle and pelvic girdle structures differ in relation to their function

Answer 1

-Upper limb (pectoral girdle) -> Relatively mobile dexterity and a use of the hand or place of the hand in a space. A full circular area is not formed by the pectoral girdle, but muscles form part of the structure, allowing for greater mobility. Scapula -> acromion -> clavicle -> articulate with the sternum -> articulate with opposite clavicle -> acromion -> scapula. Gap between scapula is not a true joint and the rhomboid muscles will provide the closing of the girdle. The medial border of the scapula is attached to the spinal prothesis through the rhomboid muscles.
-Lower limb (pelvic girdle) -> The lower limb is more related with functions such as locomotion or weight bearing. Bones of the pelvis form a circular area which provide stability.

Question 2

Identify the bones that make up the pectoral girdle

Answer 2

-Two bones are primarily involved in the movement of the shoulder girdle -> scapula (irregular bone) and clavicle (flat bone)
-Their only bony link to the axial skeleton is provided by the clavicle’s articulation with the sternum

Question 3

Identify the 5 joints and the articulation’s that make up the pectoral girdle

Answer 3

-Three true joints:
* Sternoclavicular joint (SCJ)
* Acromioclavicular joint (ACJ)
* Glenohumeral joint (GJ)
-Two others:
* Scapulothoracic articulation
* Subacromial articulation

Question 4

Describe the main bony features that make up the clavicle

Answer 4

-Clavicle -> Extended ‘S’ shape. Important for the ability to perform certain movements and allows the ability to reach 180-degrees in lateral abduction. Sternal façade of the clavicle (medial surface) -> this surface will articulate with the sternum. Inferior surface of sternal façade of clavicle (proximal surface) -> Impression for Costco clavicle and ligament. In-between is the clavius muscle.

Question 5

Describe the main bony features that make up the scapula
-Manubrium, Coracoid process and acromion process

Answer 5

-Manubrium -> The thickest and strongest portion of the sternum. It’s broad and thick along its superior margin and narrows towards it inferior articulation with the mesosternum.
-Coracoid process (scapula) -> An osseous projection that projects from the upper margin of the scapula. This process is directed anterolaterally and positioned directly inferior to the lateral aspect of the clavicle.
-Acromion process (scapula) -> Extends from the spine of the scapula towards the front of the body. It functions to stabilize the shoulder joint and is attached by ligaments to the clavicle and coracoid process of the scapula.

Question 6

Identify the main bony features that make up the scapula
-Glenoid fossa, Lateral border and inferior angle

Answer 6

-Glenoid fossa (scapula) -> A shallow, pyriform articular surface, which is located on the lateral angle of the scapula.
-Lateral border (scapula) -> Thickest of the 3 borders of the scapula. It begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle.
-Inferior angle (scapula) -> Is thick and rough and is formed by the union of the vertebral and axillary borders.

Question 7

Identify the main bony features that make up the scapula
-Medial border, superior angle and spine of the scapula

Answer 7

-Medial border (scapula) -> Longest of the 3 borders and serves as the insertion point for 4 muscles connecting the scapula to the axial skeleton.
-Superior angle (scapula) -> Covered by the trapezius muscles and located at the approximate level of the second thoracic vertebra.
-Spine of the scapula (scapula) -> Shelf-like projection that separates the posterior surface of the scapula into 2 parts: the superior supraspinous fossa and the inferior infraspinous fossa.

Question 8

Describe the ligaments that provide stability to the Scapuloclavicular joint
-Sternoclavicular joint (SCJ)
(Functional classification, Structural classification, Articular surfaces, Articular disc, Ligaments, Movements)

Answer 8

• Functional classification -> Diarthrosis
• Structural classification -> Fibrocartilage, plane/ gliding style joint
• Articular surfaces -> Saddle-shaped clavicle, disc, manubrium
• Articular disc -> Increases congruence and shock absorber
• Ligaments -> Anterior and posterior sternoclavicular, interclavicular, costoclavicular
• Movements -> 3 axes + gliding of disc between clavicle mainly

Question 9

Describe the ligaments that provide stability to the Acromioclavicular joint
(Functional classification, Structural classification, Articular surfaces, Articular disc, Ligaments, Movements)

Answer 9

• Functional classification -> Diarthrosis
• Structural classification -> Synovial, plane/ gliding style joint
• Articular surfaces -> Lateral end of clavicle and acromion of scapula
• Articular disc -> Increases congruence and shock absorber
• Ligaments -> Coracoclavicular ligament: Conoid (medial) and Trapezoid (lateral) ligament, Acromioclavicular ligament
• Movements -> 3 axes + axial rotation, anterior/ posterior glide, superior/ inferior glide

Question 9

Describe the Glenohumeral Joint (GHJ)
(Functional classification, Structural classification, Articular surfaces, Articular disc, Ligaments, Movements)

Answer 9

• Functional classification -> Diarthrosis
• Structural classification -> Synovial, ball and socket
• Articular surfaces -> Glenoid of scapula and head of humerus
• Movements -> 3 axes + flexion/ extension, abduction/ adduction, lateral/ medial rotation

Question 9

Describe the connective tissue structures surrounding the GHJ

Answer 9

-The glenohumeral ligaments are composed of a superior, middle and inferior ligament, these 3 ligaments combine to form the glenohumeral joint capsule connecting the glenoid fossa to the humerus.
* Superior glenohumeral ligament -> Limits external rotation and inferior translation of the humeral head.
* Middle glenohumeral head -> Limits external rotation and anterior translation of the humeral head
* Inferior glenohumeral head -> Limits external rotation and anterior translation of the human head
* Coracohumeral ligament -> Split into anterior and posterior divisions by the biceps tendon. Helps to support the weight of the resting arm against gravity
-Labrum -> Serves to deepen the glenoid fossa by around 50%, allowing for more contact area between the surface of the glenoid and the humeral head. The increase in contact area also enhances joint stability.