Shoulder Joint - Glenohumeral Joint - 3D Anatomy Tutorial

Summary

This tutorial provides a detailed explanation of the glenohumeral joint, which connects the humerus to the scapula. The joint is a synovial ball-and-socket type, offering great mobility but also instability due to the large humeral head and shallow glenoid cavity. The video covers key movements like flexion, extension, abduction, adduction, rotation, and circumduction. Muscles such as the deltoid, rotator cuff, and pectoralis major contribute to stability, while ligaments like the glenohumeral and coracohumeral ligaments support the joint. Additionally, bursae and joint capsules help cushion and reduce friction in this highly dynamic and mobile joint.

Takeaways

• 😀 The glenohumeral joint is a ball-and-socket joint between the humerus and scapula, known for its mobility but also instability.
• 😀 This joint allows a wide range of movements, including flexion, extension, abduction, adduction, internal and external rotation, and circumduction.
• 😀 The shallow glenoid cavity and the large head of the humerus contribute to the joint's mobility but make it relatively unstable.
• 😀 Several muscles, such as the deltoid, pectoralis major, and rotator cuff muscles, provide stability to the glenohumeral joint.
• 😀 The joint capsule consists of a fibrous membrane and a synovial membrane, which helps reduce friction and cushion the joint.
• 😀 Ligaments supporting the joint include the three glenohumeral ligaments, the transverse humeral ligament, and the coracohumeral ligament.
• 😀 The glenoid cavity is surrounded by the glenoid labrum, a fibrocartilaginous structure that adds depth to the joint and improves stability.
• 😀 The long head of the biceps tendon is attached to the supraglenoid tubercle and works with the glenoid labrum to stabilize the joint.
• 😀 Bursae such as the subacromial, subdeltoid, and subscapularis bursae reduce friction and cushion the glenohumeral joint during movement.
• 😀 The stability of the shoulder joint is a balance between the mobility of its structures and the support provided by muscles, ligaments, and bony processes.

Q & A

What is the glenohumeral joint, and what bones does it involve?

The glenohumeral joint is a synovial ball-and-socket joint between the head of the humerus and the glenoid cavity of the scapula.

Why is the glenohumeral joint considered unstable?

The glenohumeral joint is unstable because the humeral head is relatively large, while the glenoid cavity of the scapula is quite shallow, making the joint highly mobile.

What movements are possible at the glenohumeral joint?

The glenohumeral joint allows for flexion, extension, abduction, adduction, internal (medial) rotation, external rotation, and circumduction.

What role do muscles play in stabilizing the glenohumeral joint?

Muscles such as the deltoid, pectoralis major, rotator cuff muscles, long head of the biceps, long head of the triceps, teres major, and latissimus dorsi contribute to the stability of the glenohumeral joint.

How does the glenoid labrum contribute to joint stability?

The glenoid labrum is a fibrocartilaginous collar that surrounds the glenoid cavity, adding depth and improving the stability of the joint.

What is the function of the biceps tendon at the glenohumeral joint?

The long head of the biceps tendon passes over the glenohumeral joint and is continuous with the glenoid labrum, contributing to joint stability.

What is the role of the joint capsule in the glenohumeral joint?

The joint capsule surrounds the glenohumeral joint and consists of a fibrous membrane and a synovial membrane. The fibrous membrane encloses the joint, while the synovial membrane produces fluid to reduce friction and cushion the joint.

What are bursae, and why are they important in the shoulder joint?

Bursae are fluid-filled sacs that reduce friction and cushion the joint. They are formed by the protrusion of the synovial membrane through the fibrous membrane. Inflamed bursae can cause shoulder pain.

Can you name some of the bursae around the glenohumeral joint?

Some of the important bursae in the shoulder joint include the subtendinous bursa of the subscapularis, the subacromial and subdeltoid bursae, and bursae associated with the rotator cuff muscles.

What are the five main ligaments of the glenohumeral joint?

The five main ligaments are the three glenohumeral ligaments (superior, middle, and inferior), the transverse humeral ligament, and the coracohumeral ligament.