Musculo-neuro-vascular Systems of the Arm, Rotator Cuff, and Glenohumeral Joint

Flashcards testing detailed anatomical knowledge of the arm, rotator cuff, shoulder region, neurovascular structures, and relevant clinical syndromes based on lecture notes.

Which nerve innervates the latissimus dorsi muscle?

Thoracodorsal Nerve

What movement of the scapula is produced by the levator scapulae?

Downwards rotation

Where is the weakest point on the clavicle located?

The junction between Medial $\frac{2}{3}$ and Lateral $\frac{1}{3}$

How does the clavicle articulate medially and laterally?

Sternum medially & acromion laterally

What type of joint is the glenohumeral joint?

Ball & Socket Synovial joint

Which structure passively stabilises the glenohumeral joint?

Glenoid Labrum

From which cord of the brachial plexus does the medial pectoral nerve arise?

Medial Cord

Which branch of the axillary artery has the largest diameter?

Subscapular Branch

Which nerve innervates the serratus anterior muscle?

Long Thoracic Nerve

Winging of the scapula is caused by palsy of which nerve and nerve roots?

Long Thoracic Nerve (C5,6,7) Palsy

Which four muscles comprise the rotator cuff (SITS)?

Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis

Where do the tendons of the rotator cuff muscles insert on the humerus?

Proximal humerus at the greater & lesser tubercles

What is the origin of the supraspinatus muscle?

Supraspinous Fossa of scapula

What is the insertion of the supraspinatus muscle?

Greater Tubercle of Humerus (superior facet)

Which nerve innervates the supraspinatus muscle?

Suprascapular Nerve (C5,6)

What are the primary actions of the supraspinatus muscle?

Abducts arm $0\text{--}15^\circ$ and assists Deltoid with abduction from $15\text{--}90^\circ$

What is the origin of the infraspinatus muscle?

Infraspinous Fossa of scapula

What is the insertion of the infraspinatus muscle?

Greater Tubercle of Humerus (middle facet)

What is the primary action of the infraspinatus muscle at the GH joint?

Externally rotates arm at GH joint

What is the anatomical course of the suprascapular nerve through the scapular region?

Arises from superior trunk of brachial plexus, passes inferiorly through scapular notch into supraspinous fossa, and curves around the spinoglenoid notch into the infraspinous fossa

What is the origin of the teres minor muscle?

Infraspinous fossa (inferolateral to infraspinatus)

What is the insertion of the teres minor muscle?

Greater Tubercle of Humerus (inferior facet)

Which nerve innervates the teres minor muscle?

Axillary Nerve C5

What are the actions of the teres minor muscle at the GH joint?

External rotation of humerus at GH joint and adduction of the GH joint

What are the four borders of the quadrangular space?

Teres Minor, Surgical Neck (Humerus), Teres Major, and Long head of triceps

Which nerve passes laterally through the quadrangular space to reach the posterior surgical neck?

Axillary Nerve

What is the origin of the subscapularis muscle?

Subscapular Fossa of scapula

What is the insertion of the subscapularis muscle?

Lesser Tubercle of Humerus (anterior)

Which nerves innervate the subscapularis muscle, and from which cord do they originate?

Upper & Lower Subscapular Nerves from posterior cord

What functional deficit results from a subscapularis tendon tear?

Weak internal rotation of the humerus

Which rotator cuff tendon is most frequently injured?

Supraspinatus tendon

What are the origins of the deltoid muscle?

Lateral $\frac{1}{3}$ clavicle, Acromion, and Lateral $\frac{1}{3}$ Spine of scapula

Which nerve innervates the deltoid muscle?

Axillary Nerve (C5,6)

What are the actions of the anterior, middle, and posterior fibres of the deltoid muscle?

Anterior Fibres: GH Flexion; Middle Fibres: GH Abduction; Posterior Fibres: GH Extension

What is the origin of the teres major muscle?

Inferior $\frac{1}{3}$ of lateral border of scapula

What is the insertion of the teres major muscle?

Medial lip of bicipital groove

Which nerve innervates the teres major muscle?

Lower Subscapular Nerve (C5,6)

What clinical manifestations are seen in Quadrangular Space Syndrome?

Shoulder pain, paraesthesia in distribution of axillary nerve, and weakness of muscles innervated by axillary nerve

What causes shoulder impingement during glenohumeral abduction?

Compression of the supraspinatus tendon or overlying subacromial bursa between the head of the humerus and the inferior surface of the acromion

In Painful Arc Syndrome, within what range of shoulder abduction is pain experienced?

Between $60\text{--}120^\circ$

Why does pain ease beyond $120^\circ$ of abduction in Painful Arc Syndrome?

The greater tubercle rotates clear of the acromion, easing compression within the subacromial space

Which two veins unite to form the axillary vein at the lower border of teres major?

Basilic vein and brachial vein

What connective tissue partitions separate the anterior and posterior compartments of the arm inside the brachial fascia?

Medial and Lateral Intermuscular Septa

What are the origins of the long head and short head of the biceps brachii muscle?

Long Head: Supraglenoid Tubercle; Short Head: Coracoid Process of Scapula

What nerve innervates the biceps brachii, and what are its main actions?

Musculocutaneous Nerve (C5-7); Flexes elbow joint and supinates forearm (Radioulnar Joint)

Which structure forms a roof over the bicipital groove for the long head of biceps tendon?

Transverse Humeral Ligament

What muscle is the main flexor of the elbow joint and lies deep to the biceps brachii?

Brachialis

In $20\%$ of people, which second nerve provides motor input to the brachialis muscle?

Radial Nerve (C5,6)

What are the origin, insertion, and innervation of the coracobrachialis muscle?

Origin: Coracoid Process of Scapula; Insertion: Antero-medial aspect of humeral midshaft; Innervation: Musculocutaneous Nerve (C5-7)

Which muscle of the anterior compartment of the arm is pierced by the musculocutaneous nerve?

Coracobrachialis

As what cutaneous nerve does the musculocutaneous nerve terminate in the forearm?

Lateral Cutaneous Nerve of the Forearm

What are the origins of the three heads of the triceps brachii muscle?

Long Head: infraglenoid tubercle; Lateral Head: posterior humerus (superior to radial groove); Medial Head: posterior humerus (inferior to radial groove)

What is the insertion and primary action of the triceps brachii muscle?

Insertion: Olecranon process of ulna & fascia of forearm; Action: Extends elbow joint

What is the special action of the anconeus muscle during elbow extension?

Tenses the elbow joint capsule so that it is not pinched by the olecranon in the olecranon fossa

What are the borders of the triangular interval?

Humeral shaft, Teres major, and Long head of triceps

Which two neurovascular structures course through the triangular interval?

Radial Nerve and Profunda Brachii (Deep Brachial Artery)

How do the clinical effects of radial nerve injury differ between an axillary level and a humeral mid-shaft fracture?

Axillary injury denervates triceps (weak/absent extension) and causes wrist drop; mid-shaft injury leaves triceps mostly functional, but still results in wrist drop

How does the median nerve relate to the brachial artery as it descends the arm?

Crosses the brachial artery from lateral to medial

Which landmark on the humerus does the ulnar nerve pass posterior to at the elbow joint?

Medial epicondyle of humerus

Where does the cephalic vein run in the shoulder, and where does it drain?

Courses proximally in the deltopectoral groove, pierces clavipectoral fascia in the clavipectoral triangle, and drains into the axillary vein