Shoulder and Scapular Region

Write Origin, Insertion, Action, Nerve Supply & Applied Aspect of Deltoid Muscle.

 A. a. Deltoid muscle: It is a triangular (inverted delta) shaped muscle that forms the  rounded contour of  the shoulder. It is divided into three parts anterior, middle and posterior.

Origin:

• Anterior part: Anterior border of lateral 1/3^rd of  clavicle.
• Middle (acromial) part: Lateral border of the acromion process of scapula.
• Posterior part : Lower lip of the crest of spine of scapula

Insertion:  ‘V’ shaped deltoid tuberosity  on anterolateral surface of humerus. 

Actions:

• Anterior fibers: Flexion and medial rotation of arm.
• Middle fibers: Abduction of arm from 15 to 90.
•  Posterior fibers : Extension and lateral rotation of the arm.

Nerve supply : Axillary nerve (C5,C6) from  posterior cord of brachial plexus.

Applied Aspect

Write Origin, Insertion, Action & Nerve Supply of Muscles of Scapular Region.

Describe Briefly the Musculotendinous or Rotator Cuff.

Rotator cuff is formed by a group of four muscles that surround the  shoulder joint . As a group, they are  responsible for stabilizing the shoulder  joint. Individually, they rotate the shoulder joint. The  muscles that form rotator cuff are:

1. Supraspinatus
2. Infraspinatus
3. Teres minor
4. Subscapularis

• The muscles take origin from scapula and are inserted on lesser and greater tubercles of humerus.
• Their flattened tendons while crossing the shoulder joint blend with each other and with the capsule of the joint.
• Musculotendinous cuff provides support to  the capsule of the shoulder joint all around except  The joint is supported anteriorly by subscapularis, superiorly by supraspinatus and  posteriorly by infraspinatus and teres minor.As the joint is not protected inferiorly , the head of the humerus  is usually  dislocated inferiorly. The axillary nerve related to the surgical neck of humerus may get injured.
• Details of the muscles forming ‘Rotator cuff’ are as follows:

         *  The rotator cuff muscles can be easily remembered using the acronym SITS

 Describe Subacromial bursa.

• Is the largest bursa in the body. It is located inferior to the acromion arch and above the tendon of supraspinatus and greater tubercle of humerus.
• It is continuous with the subdeltoid bursa present beneath the deltoid muscle.
• It protects the supraspinatus tendon from friction against acromion during abduction of arm.
• Subacromial bursitis is a condition caused by inflammation of the bursa.

What are the Boundaries and Contents of Intermuscular Spaces in the Scapular Region.

Three intermuscular spaces are present in the  scapular region:

Quadrangular space

Boundaries 

• Superiorly – Subscapularis, capsule of shoulder joint, teres minor ( from front to back)
• Inferiorly – Teres major
• Laterally – surgical neck of humerus
• Medially – long head of triceps

 Contents

• Axillary nerve
• Posterior circumflex humeral vessels

Upper triangular space

    Boundaries

• Laterally – Long head of triceps
• Medially – Teres minor
• Inferiorly – Teres major

Contents

• Circumflex scapular artery

Lower triangular space

   Boundaries

• Superiorly – Teres major
• Laterally – Shaft of humerus
• Medially – Long head of triceps

  Contents

• Radial nerve and profunda brachii vessels

Draw  labeled diagram to show the anastomosis around scapula.

 Anastomosis around scapula  is between branches of first part of subclavian artery and branches of third part of axillary artery. It provides collateral circulation in case distal part of subclavian artery or proximal part of axillary artery is blocked.

Enumerate the movements possible at scapulothoracic joint (movement of scapula) and the muscles responsible for them.

Applied Aspect