Shoulder Anatomy and Function Quiz

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Questions and Answers

What is the primary function of the subacromial bursa?

It absorbs shock during arm movements.

It stabilizes the shoulder joint.

It facilitates the movement of the supraspinatus tendon. (correct)

It supplies blood to the deltoid muscle.

Which muscles are primarily responsible for shoulder abduction above 90 degrees?

Subscapularis and teres minor

Pectoralis major and coracobrachialis

Latissimus dorsi and biceps brachii

Serratus anterior and trapezius (correct)

Which condition is characterized by pain during abduction of the arm between 50-130 degrees?

Frozen shoulder

Rotator cuff tear

Subacromial bursitis (correct)

Shoulder instability

Which nerve is NOT involved in the innervation of the glenohumeral joint?

Medial pectoral nerve Signup and view all the answers

What condition is most directly caused by tendons rubbing under the coracoacromial arch?

Rotator cuff problems Signup and view all the answers

Which ligament prevents upper displacement of the humerus?

Coracoacromial ligament Signup and view all the answers

What structure separates the tendon of the supraspinatus muscle from the coracoacromial arch?

Subacromial bursa Signup and view all the answers

Which extracapsular ligament holds the tendon of the long head of the biceps in place?

Transverse humeral ligament Signup and view all the answers

What function does the subscapular bursa serve?

It reduces friction between tendons and articulating surfaces Signup and view all the answers

Which ligament connects the base of the coracoid process to the anterior part of the greater tubercle of the humerus?

Coracohumeral ligament Signup and view all the answers

What type of joint is the shoulder joint classified as?

Ball and socket joint Signup and view all the answers

What contributes to the instability of the glenohumeral joint?

Disproportion of articular surfaces Signup and view all the answers

Which structure deepens the glenoid cavity of the scapula?

Glenoid labrum Signup and view all the answers

What type of capsule surrounds the shoulder joint?

Fibrous capsule Signup and view all the answers

Which ligaments provide support to the shoulder joint anteriorly?

Glenohumeral ligaments Signup and view all the answers

What is the function of the subscapular bursa in the shoulder joint?

Reduce friction between tendons Signup and view all the answers

Which tendon passes through the joint outside the synovial membrane?

Tendon of the long head of biceps brachii Signup and view all the answers

What separates the tendon of the subscapularis from other structures in the shoulder?

Subscapular bursa Signup and view all the answers

What condition can result from the painful arc/impingement syndrome during arm abduction?

Rotator cuff injury Signup and view all the answers

What anatomical feature increases the likelihood of supraspinatus tendon impingement?

Coraco acromial arch Signup and view all the answers

Why is the inferior aspect of the glenohumeral joint particularly vulnerable to dislocation?

It is least protected Signup and view all the answers

Which tendon, when injured, can lead to paralysis of the deltoid muscle and loss of shoulder abduction?

Axillary nerve Signup and view all the answers

What describes a common cause of rotator cuff injuries in older adults?

Avascularity of tendons Signup and view all the answers

Which ligament provides superior stability to the shoulder joint?

Coraco humeral ligament Signup and view all the answers

What is a consequence of a poorly healed rotator cuff tear?

Recurrent dislocation Signup and view all the answers

Which area indicates loss of sensation due to axillary nerve injury?

Regimental badge area Signup and view all the answers

Study Notes

Shoulder Joint Overview

The shoulder joint, also known as the glenohumeral joint, is a ball-and-socket synovial joint formed between the glenoid cavity of the scapula and the head of the humerus.
This structure allows for a wide range of movements in multiple planes.
Bone structure and movement range influence the joint's stability.
Shoulder movement occurs at both the glenohumeral and scapulothoracic joints.

Joint Structure and Stability

The joint is lined with synovium and enclosed in a fibrous capsule.
The glenoid cavity is deepened by a glenoid labrum, a rim of fibrocartilage, but despite this, the glenohumeral joint remains relatively unstable.
Instability arises due to the shallowness of the glenohumeral joint and the disproportion of the articular surfaces.
Stability is maintained by the capsule, various ligaments, and the rotator cuff muscles.

Capsule Structure

The capsule is attached to the glenoid labrum, the scapula, and the anatomical head of the humerus.
It bridges the intertubercular groove of the humerus and extends medially to the surgical neck of the humerus.
The capsule is tough but relatively lax to facilitate a broad range of movement.
Thickening of the capsule occurs in regions where it attaches to three glenohumeral ligaments and a coracohumeral ligament.

Bursae of the Shoulder

Subscapular bursa facilitates the movement of the subscapularis tendon over the scapula.
A bursa is a fluid-filled sac that reduces friction between articulating surfaces, reducing friction between the tendon and the surrounding structures (e.g., scapula).
The subscapular bursa connects to the synovium and the joint cavity, making movement smooth.
Subacromial bursa facilitates the movement of the supraspinatus tendon under the coracoacromial arch and over the deltoid muscle.
Inflammation of the bursa can result in subacromial bursitis, causing pain during arm abduction.

Ligaments of the Shoulder

Intracapsular ligaments: Three fibrous bands between the glenoid labrum and the humerus. These support the anterior capsule, including the superior, middle, and inferior glenohumeral ligaments.
Extracapsular ligaments:
- Coracoacromial ligament links the acromion and coracoid process
- Coracohumeral ligaments connect the coracoid process to the greater tubercle of the humerus.
- Transverse humeral ligament holds the tendon of the long head of the biceps in place during movement.

Coraco Acromial Arch

The coracoacromial arch is a strong osseoligamentous structure that provides a smooth undersurface over the acromion.
The coracoacromial ligament and coracoid process form this arch.
The arch overhangs the humeral head, preventing superior displacement of the humerus.
Within this space, there's a subacromial bursa and other rotator cuff tendons.

Movements of the Shoulder

Flexion: Primarily by the pectoralis major, anterior deltoid, coracobrachialis, and biceps brachii.
Extension: Primarily by the latissimus dorsi and posterior deltoid.
Abduction: Begins with the supraspinatus (15-20 degrees), then central deltoid (20-90 degrees), and finally scapula rotation by the trapezius and serratus anterior (above 90 degrees).

Neurovascular Supply

Blood supply via the anterior and posterior circumflex humeral arteries and the suprascapular artery.
Innervation by the suprascapular, axillary, and lateral pectoral nerves which originate from the brachial plexus (C5-C6).
Injuries to the brachial plexus can affect shoulder movement.

Clinical Applications

Axillary nerves and circumflex artery are vulnerable during intramuscular injections and shoulder dislocations.
Rotator cuff problems include tendon rubbing under the coraco-acromial arch and inflammation or wear of tendons.
Chronic inflammation can lead to problems like impingement syndrome, occurring between 70–120 degrees of abduction.

Shoulder Disorders

Rotator cuff problems: Tendon rubbing under the coraco-acromial arch causes irritation and inflammation; this can lead to bursitis, supraspinatus tendonitis, rotator cuff injury, and degeneration or rupture of the tendons.
Dislocation: The inferior aspect of the glenohumeral joint is the least protected, thus inferior displacement is common.
Axillary nerve injury: Injured during dislocation or intramuscular injections. Symptoms include deltoid paralysis, loss of abduction, and sensory loss.
Frozen shoulder: Adhesive fibrosis and scarring between the inflamed capsule, rotator cuff, subacromial bursa, and the deltoid. Often causes difficulty in abducting the arm.
Glenoid labrum tears: Common in athletes or those with shoulder instability or partial dislocation (subluxation) marked by pain and popping/snapping sensations.
Osteoarthritis: A less common cause due to degenerative changes in articular cartilage. Usually secondary to trauma, including previous dislocations, humeral head fractures, or large rotator cuff tendon tears.

Stability

Tendons of the rotator cuff (anterior, posterior, superior) provide stability
Glenohumeral intracapsular ligaments (anterior, inferior) provide stability
Coracohumeral ligaments (superior)
Coracoacromial arch (superior)
Deepening of the glenoid cavity by the glenoid labrum
Splinting effect of the long head of the biceps and triceps.

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Description

Test your knowledge of shoulder anatomy and its functions with this quiz. Explore key structures, ligaments, and conditions associated with the shoulder joint. Perfect for students of anatomy or anyone interested in human biomechanics.