The shoulder

Question 1

Bones of the Shoulder

Answer 1

1. Clavicle: The collarbone connects the arm to the body and helps stabilize the shoulder.
2. Scapula: Also known as the shoulder blade, it has several important features:
   - Glenoid Cavity: The shallow socket that articulates with the head of the humerus.
   - Acromion: The bony process on the scapula that forms the highest point of the shoulder.
   - Coracoid Process: A hook-like structure that provides attachment for ligaments and muscles.
3. Humerus: The upper arm bone, which has a rounded head that fits into the glenoid cavity of the scapula

Question 2

Joints of the Shoulder

Answer 2

1. Glenohumeral Joint: The main joint of the shoulder, a ball-and-socket joint that allows for a wide range of motion including flexion, extension, abduction, adduction, internal rotation, and external rotation.
2. Acromioclavicular Joint: The joint between the acromion of the scapula and the clavicle, which allows for limited movement and stability.
3. Sternoclavicular Joint: The joint between the sternum and the clavicle, which connects the upper limb to the trunk and allows for movement of the clavicle.

Question 3

Ligaments of the Shoulder

Answer 3

1. Glenohumeral Ligaments: A group of ligaments that reinforce the shoulder joint capsule and help stabilize the joint.
2. Coracohumeral Ligament: Connects the coracoid process of the scapula to the humerus, providing additional stability.
3. Acromioclavicular Ligament: Connects the acromion to the clavicle and helps stabilize the acromioclavicular joint.
4. Coracoacromial Ligament: Spans between the coracoid process and the acromion, forming a protective arch over the shoulder joint.

Question 4

Muscles of the Shoulder

Answer 4

Rotator Cuff Muscles: A group of four muscles that stabilize the shoulder joint and allow for its movement:
- Supraspinatus: Abducts the arm.
- Infraspinatus: Externally rotates the arm.
- Teres Minor: Externally rotates the arm.
- Subscapularis: Internally rotates the arm.
2. Deltoid Muscle: The primary muscle responsible for shoulder abduction, as well as flexion and extension of the arm.
3. Pectoralis Major: A large muscle that aids in flexion, adduction, and internal rotation of the arm.
4. Latissimus Dorsi: A broad muscle that extends, adducts, and internally rotates the arm.
5. Teres Major: Assists in the internal rotation and adduction of the arm

Question 5

Blood Vessels of the Shoulder

Answer 5

1. Subclavian Artery: This artery is a major source of blood supply to the upper limb. It branches into several arteries that supply the shoulder region.
2. Axillary Artery: As the subclavian artery passes the first rib, it becomes the axillary artery. The axillary artery has several branches that supply the shoulder:
   - Superior Thoracic Artery: Supplies the upper part of the thorax.
   - Thoracoacromial Artery: Supplies the deltoid muscle and the pectoral region, branching into several smaller arteries.
   - Lateral Thoracic Artery: Supplies the serratus anterior and pectoral muscles.
   - Subscapular Artery: Supplies the subscapularis muscle and branches into the circumflex scapular artery, which supplies the scapula.
   - Anterior and Posterior Circumflex Humeral Arteries: These encircle the humerus and supply the deltoid muscle and shoulder joint.
3. Veins: The venous drainage of the shoulder region follows the arterial supply, primarily through:
   - Axillary Vein: Drains blood from the upper limb and is formed by the union of the brachial veins and basilic vein.
   - Cephalic Vein: A superficial vein that runs along the lateral side of the arm and drains into the axillary vein.
   - Basilic Vein: Runs along the medial side of the arm and drains into the brachial vein.

Question 6

Nerves of the Shoulder

Answer 6

1. Brachial Plexus: The primary nerve supply to the shoulder comes from the brachial plexus, which is formed by the anterior rami of spinal nerves C5 to T1. Key nerves include:
   - Axillary Nerve: Innervates the deltoid and teres minor muscles and provides sensory innervation to the skin overlying the deltoid muscle.
   - Musculocutaneous Nerve: Supplies the anterior compartment of the arm, including the biceps brachii and brachialis muscles.
   - Suprascapular Nerve: Innervates the supraspinatus and infraspinatus muscles, which are crucial for shoulder stability and movement.
   - Long Thoracic Nerve: Innervates the serratus anterior muscle, which is important for scapular movement and stabilization.
2. Cervical Nerves: The cervical nerves (C3-C4) also contribute to the innervation of the shoulder region, particularly through the supraclavicular nerves, which provide sensory innervation to the skin over the shoulder