Origin: Medial two-thirds of the costal surface of the scapula (subscapular fossa)

Insertion: Lesser tubercle of the humerus

Innervation: Upper and lower subscapular nerves (C5, C6)

Action: Medially rotates the arm and assists extention of the arm

Description: A broad, flat process located at the lateral end of the scapular spine. It articulates with the clavicle through a synovial joint (acromioclavicular joint)

Functions:

Joints: The acromion forms the acromioclavicular joint with the clavicle, allowing for shoulder movement and stability

Muscle and Ligament Attachments: The deltoid, trapezius, acromioclavicular ligament, and coracoacromial ligament attach to the acromion

Subacromial Space: The acromion and coracoid process, along with the coracoacromial ligament, form the acromial arch, which contains the subacromial space where rotator cuff muscles and tendons pass

Description: A heavy ridge that runs from the medial border of the scapula to the acromion process

Functions: It supports the acromion process, divides the posterior surface of the scapula into a supraspinatous fossa and an infraspinatous fossa

Origin: Supraspinatous fossa

Insertion: Greater tubercle of the humerus (highest facet)

Innervation: Suprascapular nerve (C5, C6) from the superior trunk of the brachial plexus

Action: Abducts the arm (initiates abduction)

Origin: Infraspinatous fossa

Insertion: Greater tubercle of the humerus (middle facet)

Innervation: Suprascapular nerve

Action: Laterally rotates the arm

Description: It is a small depression on the superior border of the scapula and it forms a tunnel with the superior transverse scapular ligament

Description: The bone of the shoulder. A triangular-shaped bone located in the upper back, on the dorsal surface of the rib cage. It articulates with the axial skeleton through the clavicle at the coracoclavicular and acromioclavicular joints

Functions: The scapula plays a crucial role in shoulder movements, including abduction (raising the arm), flexion (bending the arm), and rotation. It also helps stabilize the shoulder joint and facilitates the movements of the upper arm

Description: The bone of the arm (brachium). It articulates proximally with the scapula at the glenoid fossa; it articulates distally with the radius and ulna at the elbow joint

Functions:

Joints: It forms the glenohumeral joint (shoulder joint) with the scapula and the elbow joint with the radius and ulna.

Muscles: Numerous muscles attach to the humerus, enabling arm movement and supporting the shoulder and elbow

Support: The humerus provides structural support for the arm and is crucial for carrying weight and performing daily activities

Description: It is a small depression on the superior border of the scapula and it forms a tunnel with the superior transverse scapular ligament

Description: An "S" shaped bone extends from the sternum (breastbone) to the scapula (shoulder blade)

Functions:

Supports the shoulder: Acts as a strut to hold the arm away from the trunk, allowing for free movement

Protects neurovascular structures: Lies above important nerves and blood vessels, providing a layer of protection

Transmits forces: Transfers forces from the upper limb to the axial skeleton

Description: A beak-like process that projects anteriorly from the lateral end of the superior border of the scapula

Functions: Attachment site for the short head of the biceps brachii muscle, the coracobrachialis muscle, the pectoralis minor muscle and the coracoacromial and coracoclavicular ligaments

Description: A cone-shaped ligament that connects the clavicle to the coracoid process of the scapula, forming part of the coracoclavicular ligament. It runs from the conoid tubercle on the clavicle to the base of the coracoid process

Functions: Works along with the trapezoid ligament, plays a crucial role in stabilizing the acromioclavicular joint, preventing the acromion from being driven inferiorly from the clavicle. It also helps to resist excessive rotation of the clavicle and scapula, while still allowing for retraction and protraction of the acromion

Description: Three important ligaments on the anterior side of the shoulder joint, connecting the scapula (shoulder blade) to the humerus (upper arm bone)

Functions: Play a crucial role in stabilizing the shoulder joint, particularly against anterior displacement

Superior Glenohumeral Ligament: Helps stabilize the joint in adduction and external rotation. It also contributes to suspending the humeral head, along with the coracohumeral ligament

Middle Glenohumeral Ligament: Stabilizes the joint in adduction and external rotation, and it also plays a role in limiting external rotation, especially in the range of abduction up to 45 degrees

Inferior Glenohumeral Ligament: Important for stabilizing the shoulder in the inferior direction and is composed of anterior and posterior bands, along with the axillary pouch

Description: Also known as the superior transverse scapular ligament, is a fibrous band that spans the suprascapular notch

Functions: The ligament acts as a roof for the suprascapular foramen, which allows the suprascapular nerve and artery to pass through

Description: A strong, triangular band of tissue connecting the acromion and coracoid process of the scapula, forming part of the coracoacromial arch

Functions:

Static Restraint: Acts as a primary static restraint to superior humeral head displacement, helping to stabilize the glenohumeral join

Load Distribution: It plays a role in transmitting forces from the surrounding muscles and helps distribute load across the shoulder girdle

Description: a broad, quadrilateral ligament that connects the coracoid process of the scapula (shoulder blade) to the trapezoid line on the inferior surface of the clavicle (collarbone)

Functions: The trapezoid ligament, along with the conoid ligament, helps to stabilize the coracoclavicular joint, which connects the clavicle to the scapula. It helps to prevent vertical displacement of the scapula towards the clavicle and allows for slight scapular rotation around the clavicle

Description: A capsular ligament of the glenohumeral joint, spanning the space between the greater and lesser tubercles of the humerus

Functions: Acts as a roof over the bicipital groove, converting it into a canal, which helps keep the long head of the biceps tendon and its synovial sheath within the groove during shoulder movements.

Description: A ligament connecting the acromion (part of the shoulder blade) and the clavicle (collarbone)

Functions:

Horizontal Stability: Providing horizontal stability to the acromioclavicular joint, helping to prevent the clavicle from shifting forward or backward

Joint Support: Together with thecoracoclavicular ligaments, helps to hold the clavicle in place relative to the acromion, preventing excessive movement and ensuring proper shoulder mechanics

Description: Fluid-filled sac located beneath the latissimus dorsi muscle and its tendon

Functions: Reduces friction between the muscle and tendon during movement, allowing for smooth shoulder joint action

Description: A fluid-filled sac in the shoulder joint that cushions and reduces friction between the rotator cuff tendons and the acromion, the top part of the shoulder blade

Functions: It acts as a cushion, allowing the rotator cuff to move smoothly and reducing friction between the tendons and the bone

Description: Located between the subscapularis muscle and the chest wall

Functions: It manage the friction of the superficial fibers against the scapular neck, the humeral head, and the coracoid process

Description: A fluid-filled sac, or bursa, located in the shoulder, specifically between the deltoid muscle and the glenohumeral joint capsule

Functions: Its primary function is to reduce friction between the deltoid muscle and the rotator cuff tendons as they move over the shoulder joint

Description: A small sac located in the anterior shoulder region, specifically beneath the coracoid process of the scapula

Functions: It helps reduce friction between these tendons and the bones, facilitating shoulder movement, particularly internal and external rotation

Description: This bursa is located between the distal biceps tendon and the radial tuberosity

Functions: The bursa's main role is to facilitate movement by reducing friction between the tendon and the bone as the forearm pronates (rotates palm down) and supinates (rotates palm up)