Coracoacromial Arch Anatomy Notes
Coracoacromial Arch Introduction:
Table of Contents
The coracoacromial arch is an extrinsic, protective structure.
Coracoacromial Arch Formation:
It is formed by
- Acromion,
- Coracoacromial ligament, and
- Coracoid process.
Coracoacromial Arch Synonymous:
Secondary socket for the head of the humerus.
Read And Learn More: Anatomy Notes And Important Questions and Answers
Coracoacromial Arch Functions
- It adds stability to the joint, and
- Protects the head of the humerus.
- The subacromial bursa facilitates movement between the coracoacromial arch and the subjacent supraspinatus and shoulder joint. Thus, it functions as a secondary synovial articulation.
- It prevents upward dislocation of the shoulder.
Structures Deep To Coracoacromial Arch
- Supraspinatus muscle, and
- Subacromial bursa.
Coracoacromial Arch Applied anatomy
1. Osteoarthritis or thickening of the coracoacromial arch results in impingement syndrome or painful arc syndrome. This is characterised by pain in the abduction of the shoulder between 60° and 120°.
2. The coracoacromial arch is so strong that a forceful superior thrust of the humerus will not fracture it. Excessive pressure may fracture the humerus or clavicle but not the coracoacromial arch.
Question: Describe the shoulder joint or glenohumeral joint under the following heads
1. Glenohumeral Joint Classification,
2. Glenohumeral Joint Ligaments,
3. Glenohumeral Joint Movements,
4. Glenohumeral Joint Relations,
5. Glenohumeral Joint Blood supply,
6. Glenohumeral Joint Nerve supply,
7. Glenohumeral Joint Applied anatomy, and
8. Glenohumeral Joint Stability of shoulder joint
Answer:
Shoulder Joint or Glenohumeral Joint Classification
Structural: AB’S
Axis: Multiaxial
A number of bones: 2. Hence it is simple.
Shape: Ball and socket type of synovial joint
Functional: Diarthrosis.
Shoulder Joint or Glenohumeral Joint Ligaments
Capsule
1. Attachments to
- Humerus: It is attached to the anatomical neck of the humerus except medially.
- Scapula: It is attached to the peripheral margins of the glenoid cavity. It includes the supraglenoid tubercle but excludes the infraglenoid tubercle.
2. Deficient: It is deficient in the region of the bicipital groove for the passage of
- Tendon of the long head of biceps,
- Synovial sheath,
- Ascending branch of the anterior circumflex humeral artery.
3. Laxity: It is lax on the inferior side, 1 cm below the surgical neck of the humerus.
4. Strengthened: It is strengthened by the rotator cuff, i.e.
- Supraspinatus,
- Infraspinatus,
- Teres minor, and
- Subscapularis.
5. Capsule has two openings for
- The long head of biceps muscle, and
- Subscapular bursa.
Synovial membrane:
It lines the inner surface of the capsule and extends on the long head of the biceps, as a tubular extension. It communicates with the synovial membrane of the subscapular bursa.
Glenoid labrum:
Structurally it is fibrocartilage in nature and lar in cross-section. It is attached to the peripheral margin of the glenoid cavity.
- It deepens the cavity of the shoulder joint.
- It protects the edges of the articulating surfaces.
- It provides the cushion for the head of the humerus to roll as a ball bearing.
Glenohumeral ligament (It is a condensation of the anterior part of the capsule). It extends superiorly from the superomedial margin of the glenoid cavity.
Inferiorly, it is attached to three attachments:
- The superior band is attached to the upper end of the lesser tubercle.
- The middle band is attached to the lower end of the lesser tubercle.
- The inferior band is attached to the lower part of the anatomical neck.
Coracohumeral ligament:
It is a thick band in the upper part of the fibrous capsule. It extends from the root of the coracoid process to the neck of the humerus.
Transverse humeral ligament:
Bridges greater and lesser tubercles.
Shoulder Joint or Glenohumeral Joint Movements
1. Flexion
- Anterior fibres of deltoid, and
- Clavicular fibres of pectoralis major.
2. Extension
- Posterior fibres of deltoid with
- Latissimus dorsi.
3. Abduction
- For every 15° of abduction, 10° occurs at shoulder joint and 5° at shoulder girdle
- 1-15°: Supraspinatus
- 15–90°: Middle fibres of deltoid (acromial). Note: Supraspinatus and deltoid act between 0° and 90° (Gray’s 40th edition)
- 90°–120° by fibres of serratus anterior attached to the inferior angle of the scapula.
- 120°-180° is by serratus anterior through the shoulder girdle.
4. Adduction
Sternal fibres of pectoralis major, and
Latissimus dorsi.
5. Medial rotation:
Lady, soldier and majors are medial rotators, i.e. muscles forming posterior boundaries of the axilla, namely
- Latissimus dorsi,
- Subscapularis,
- 2 majors (pectoralis major and teres major), and
- Anterior fibres of deltoid.
6. Lateral rotation (TIP)
Teres minor,
Infraspinatus, and
Posterior fibres of the deltoid.
7. Circumduction (combination of movements): Abduction of the flexed joint.
shoulder joint or glenohumeral joint Relations
1. Superiorly
- Coracoacromial arch,
- Subacromial bursa,
- Supraspinatus, and
- Deltoid.
2. Inferiorly: Long head of triceps
3. Anteriorly:
- Subscapularis,
- Coracobrachialis,
- The short head of biceps, and
- Clavicular fibers of deltoid.
4. Posteriorly
- Posterior fibres of the deltoid,
- Infraspinatus, and
- Teres minor.
5. Intracapsular: Tendon of the long head of the biceps.
Shoulder Joint Or Glenohumeral Joint Blood Supply
- Anterior circumflex humeral artery,
- Posterior circumflex humeral artery, Branches of axillary artery
Subscapular artery, - Suprascapular artery: Branch of thyrocervical trunk-branch of 1st part of the subclavian artery.
shoulder joint or glenohumeral joint Nerve supply
1. It is mainly from the posterior cord of the brachial plexus through the subscapular nerve.
2. The capsule is supplied by
- Suprascapular nerve (posterior and superior part)
- Axillary nerve (anteroinferior part)
- Lateral pectoral nerve (anterosuperior part)
shoulder joint or glenohumeral joint Applied anatomy
1. The shoulder joint is the most frequently dislocating joint in the body. It is due to
- Disproportionate articular surfaces of the head of the humerus and the glenoid cavity of the scapula, and
- Laxity of capsule: The Capsule is lax inferiorly hence inferior dislocation is most common.
2. It usually occurs when the arm is forcefully abducted. The axillary nerve is usually injured.
3. Frozen shoulder (adhesive capsulitis):
It is a common condition due to adhesion between two layers of synovial membrane. It is scarring between the inflamed joint capsule of the glenohumeral joint, rotator cuff, subacromial bursa, and deltoid.
4. Shoulder tip pain: Irritation of the diaphragm causes referred pain to the shoulder tip.
The skin over the shoulder joint is supplied by the supraclavicular nerve. The diaphragm is supplied by the phrenic nerve. The root values of the phrenic nerve and supraclavicular nerve are the same, i.e. C3 and C4 of the spinal segment.
Therefore, the pain of the diaphragm is referred to as the tip of the shoulder.
Shoulder Joint Or Glenohumeral Joint Stability Of Shoulder Joint
The stability of the shoulder joint mainly depends upon surrounding muscles.
1. Rotator cuff
- Supraspinatus,
- Infraspinatus,
- Teres minor, and
- Subscapularis.
2. The long head of the biceps being intracapsular stabilizes the joint from inside the capsule.
3. Long muscles of the shoulder
- Deltoid laterally,
- The long head of the triceps medially,
- Pectoralis major anteriorly, and
- Latissimus dorsi posteriorly.
Question-5: Name The Flexors Of The Elbow Joint
Answer:
Flexors Of The Elbow Joint Main flexors
- Brachialis,
- Biceps brachii, and
- Brachioradialis
Flexors Of The Elbow Joint Other flexors
- Pronator teres,
- Flexor carpi radialis,
- Palmaris longus,
- Flexor digitorum superficialis, and
- Flexor digitorum profundus.
Anastomosis Around The Elbow Joint
Anastomosis Around The Elbow Joint Introduction:
It is an important communication between the brachial and the terminal branches of the brachial artery (radial and ulnar arteries).
Anastomosis Around The Elbow Joint Distribution: It supplies
- Ligaments,
- Bones of the elbow region,
- Elbow joint, and
- Superior radioulnar joint.
Anastomosis Around The Elbow Joint Division
1. In front of the lateral epicondyle of the humerus:
The anterior descending branch (radial collateral artery), a branch of profunda brachii, anastomoses with the radial recurrent artery, branch of the radial artery.
2. Behind the lateral epicondyle of the humerus:
The posterior descending artery, a branch of the profunda brachii artery, anastomoses with the interosseous recurrent artery, a branch of the posterior interosseous artery.
3. In front of the medial epicondyle of the humerus:
The inferior ulnar collateral branch of the brachial artery anastomoses with the anterior ulnar recurrent branch of the ulnar artery.
4. Behind the medial epicondyle of the humerus:
The superior ulnar collateral branch of the brachial artery anastomoses with the posterior ulnar recurrent branch of the ulnar artery.
5. Just above the olecranon fossa:
A branch from a posterior descending artery, a branch of the profunda brachii artery, anastomoses with the branch from the inferior ulnar collateral artery.
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