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What are the three joints that make up the shoulder girdle?
- sternoclavicular joint
- acromial clavicular joint
- glenohumeral joint
True or flase: there are two bony articulations between the upper limb and the trunk. Provide the correct information if the answer is false.
FALSE. There is only one bony articulation between the upper limb and the trunk: the articulation between the medial end of the clavicle, the 1st costal cartilage and the 1st rib.
True or false: the upper limb is far more interesting and useful than the lower limb
Describe the relationship between the suprascapular nerve, artery and the superior transverse ligament
the suprascapular nerve travels under the superior transverse ligament while the suprascapular artery travels over the ligament.
List the structures that reinforce the sternoclavicular joint capsule. Include which side or portion of the capsule each structure supports.
- Anterior support: anterior sternoclavicular ligament
- Posterior support: posterior sternoclavicular ligament
- Interclavicular support: interclavicular ligament
- Support between the medial clavicle, 1st rib and 1st costal cartilage: costoclavicular ligament
List the muscles that directly act on the acromialclavicular joint.
No muscles directly act on the acromialclavicular joint.
The range of motion allowed at the acromionclavicular joint is:
(A) 1-15 degrees
(B) 15-25 degrees
(C) 10-15 degrees
(D) 15-20 degrees
(E) no motion is allowed at the acromialclavicular joint.
D: 15-20 degrees
At the glenohumeral joint, what is sacrificed at the expense of mobility?
True or false: stability of the shallow glenoid cavity is reinforced by a tight fibrous joint capsule. Explain your answer if false
FALSE. The joint capsule and fibrous membrane are very lax, particularly inferiorly, to facilitate movement of the humeral head within the gelnoid cavity. Stability is gained through the musculotendinous collar created by the rotator cuff tendons and the glenohumeral ligaments, the coracoacromial ligament, the coracohumeral ligament and the bony arch created by the acromion and coracoid processes
Describe the insertion locations of the rotator cuff muscles relative to one another on the greater tubercle of the humerus.
- Superior facet: supraspinatus
- middle facet: infraspinatus
- lower facet: teres minor
Describe the anatomical difference(s) between the anatomical neck of the humerus and the surgical neck, as well as the clinical significance of this difference. Include a discussion of which structures are particularly in danger due to these differences and why they are in danger.
The anatomical neck is immediately inferior to the head of the humerus. The surgical neck is inferior to the anatomical neck and lies approximately at the location where the wide head begins to taper into a narrower shaft. This tapering renders the surgical neck more susceptible to breaking. Breaks at this point on the humerus place the posterior circumflex humeral artery and the axillary nerve in danger b/c they pass into the posterior arm at the level of the surgical neck.
List the structures that connect to the coracoid process.
- 1) conoid ligament of the coracoclavicular ligament
- 2) trapezoid ligament of the coracoclavicular ligament
- 3) pectoralis minor
- 4) superior transverse scapular ligament
- 5) coracohrachialis muscle
- 6) short head of biceps brachii
- 7) coraco-acromial ligament
- 8) coracohumeral ligament
True or false: the tendon of the short head of biceps brachii passes through the glenohumeral joint capsule. Provide the correct infomation if the answer is false.
FALSE: the tendon of the long head of biceps brachii passes through the glenohumeral joint capsule. The tendon of the short head originates from the coracoid process.
What is the functional significance of the inferior fold in the synovial membrane and fibrous joint capsule of the glenohumeral joint?
Facilitates humeral abduction, but also renders the GH joint particularly unstable from the inferior direction.
Describe the movements during arm abduction at the three joints that make up the shoulder girdle. Include the muscles involved in the movements and their specific actions.
- Glenohumeral joint: humerus moves through the arc of abduction, which is orthogonal to the plane of flexion/extension, with 10-degrees of humeral abduction for every 5-degrees of scapular lateral rotation.
- clavicle rotates inferiorly at the sternoclavicular joint and superiorly at the acromioclavicular joint and the scapula moves superiorly and rotates laterally.
- 1) Supraspinatus initiates humeral abduction
- 2) deltoid is active early on and then takes over after about 15 degrees
- 3) Trapezius acts to elevate and laterally rotate scapula during abduction
- 4) levator scapulae and the rhomboids may act to assist trapezius with scapular elevation
- 5) serratus anterior assists with lateral scapular rotation and to hold the scapula against the thorax during rotation
What is the glenohumeral rhythm?
During arm abduction there is 1 degree of lateral scapular rotation for every 2 degrees of humeral abduction rotation. Hence, movement of the AC and SC joints increases our range of motion during abduction by 1/3.
C5 and C6 of both the posterior cord are non-functional. Will the arm still be able to medially rotate? Answer why or why not in the context of every muscle associated with medial humeral rotation.
- Yes, the arm will be able to medially rotate, though it will be weaker in doing so b/c some of the muscle fibers that participate will not be active.
- The effects are as follows on the medial humeral rotators:
- 1) teres major (lower subscapular from the posterior cord, C5, C6, C7). It remains functional b/c of the C7
- 2) latissimus dorsi (thoracodorsal nerve from the posterior cord, C6, C7, C8). It remains functional b/c of C7 and C8.
- 3) pec major (lateral pectoral nerve, C5 and C6 to clavicular head, lateral pectoral nerve C6 and C7 to sternocostal head and medial pectoral nerve C8 and T1). It remains entirely functional b/c it has a ton of functional spinal levels and none of them are from the posterior cord
- 4) anterior fibers of deltoid are completely non-functional b/c it is innervated by C5 and C6 from axillary which is from the posterior cord
- 5) subscapularis is functional b/c it still has C7, though C5 and C6 from upper and lower subscapular nerves are out b/c they are from the posterior cord
- 6) Serratus anterior remains fully capable of scapular protraction b/c it is innervated by C5, C6 and C7 of long thoracic, directly from the roots of the brachial plexus
- 7) pectoralis minor remains fully active b/c it is innervated by medial pectoral (directly) and lateral pectoral (indirectly), receiving C5-T1, but none of them are from the posterior cord
True or false: the quadrangular space communicates the radial nerve and the posterior circumflex humeral artery from the anterior arm to the posterior arm. Provide the correct information if the answer is false.
FALSE: the quadrangular space communicates the axillary nerve and the posterior circumflex humeral artery.
True or false (if false, provide the correct information): the accessory nerve is CN XI and the motor component originates from spinal levels C1-C5, travels up into the skull via the jugular foramen and returns to its target muscles by passing back through the jugular foramen.
FALSE. It enters the skull via the foramen magnus and exits via the jugular foramen.
List the nerves that contribute to motor function of the shoulder and rotator cuff muscles that are NOT derived from the brachial plexus.
- 1) accessory nerve
- 2) Anterior ramus of C3
- 3) Anterior ramus of C4
True or false: C4 contributes fibers to the innervation of rhomboid major, but not to rhomboid minor. Provide the correction information if false.
FALSE. C4 contributes to both rhomboid major and minor. The difference is that both C4 and C5 are primary for major and neither is primary for minor.
Name the nerve that provides motor innervation to the deltoid muscle and trace it to its origin within the spinal cord. Indicate the starting point for the impulse.
- Axillary nerve:
- Deltoid (ending point) / Axillary nerve / posterior cord / posterior division / superior trunk / roots (AKA rami) C5 & C6 (C5 is primary) / spinal nerves of C5 & C6 / anterior roots of C5 & C6 / anterior white columns of C5 & C6 / Anterior grey horns of C5 & C6 (this is the starting point)
Name the nerve that innervates the infraspinatus muscle and trace it back to its spinal origins, designating the primary.
suprascapular nerve: suprascapular nerve/superior trunk/ roots C5, C6, C5 is primary
List all of the muscles in the shoulder region and rotator cuff that receive spinal contribution from C7.
Derive the path of the primary blood supply for the middle portion of trapezius on the left side of the body back to the arch of the aorta. Provide all relevant landmarks, parts, and communicating regions.
superficial cervical artery / transverse cervical artery (divides deep to levator scapulae) / thyro-cervical trunk / 1st part of subclavian (the first part is the portion from the origin of the artery to the medial border of the anterior scalene muscle) / arch of the aorta
True or false: there is one branch off of the first part of the axillary artery, two off of the second and three off of the third. Provide the correct information if the answer is false.
If the posterior division of the middle trunk had a lesion on it rendering the fibers non-functional, which muscles in the shoulder/rotator cuff region would lose some or all of their nerve supply, and which fibers would be lost?
- Subscapularis would lose C7 fibers
- Teres major would also lose C7
What is the difference between the ligamentum nuchae and the supraspinous ligament?
The ligament nuchae runs from the external occipital protuberance on the occipital bone down to the spinous process of C7. It send fibers anteriorly between these landmarks that attach to the spinous processes of the cervical vertebrae and along the base of the occipital bone. The supraspinous ligament is the inferior continuation of the ligamentum nuchae. It is a ligament cord that attaches to the remaining spinous processes, all the way along the vertebral column.
Change one thing about the position (i.e., origin, insertion or path) of teres major to enable it to participate in flexion of the arm at the glenohumeral joint:
It would have to originate somewhere on the anterior body, perhaps the clavicle like the clavicular portion of pec major or the ribs like pec minor. Then it would be able to flex the extended arm.