Anatomy Lecture 4: Pectoral and Shoulder

Sternum

A bone of the thorax that forms part of the pectoral girdle (shoulder complex).

Clavicle

A lateral bone of the shoulder complex that acts as a mechanical strut and consists of an acromial end and a sternal end.

manubrium

top part of the sternum

xiphoid process

bottom tip of the sternum

conoid tubercle

part of the clavicle that is superior to the coracoid process of the scapula

Coracoid Process

A hook-like projection on the anterior scapula that serves as a key attachment site for ligaments and muscles.

supraglenoid tubercle

superior part of the scapula around the glenoid fossa

infraglenoid tubercle

inferior part of the scapula around the glenoid fossa

Acromioclavicular Joint

A plane joint formed by the articulation between the acromion of the scapula and the clavicle.

Glenohumeral Joint

A ball-and-socket joint ("shoulder joint") formed by the head of the humerus and the glenoid cavity of the scapula.

Sternoclavicular Joint

The only bony joint connecting the upper limb to the thorax, formed by the clavicle and the manubrium of the sternum.

Ligament

A tough fibrous band of tissue connecting the articular extremities of bones or supporting an organ in place.

Tendon

A tough cord or band of dense white fibrous connective tissue that unites a muscle with another part (such as a bone) and transmits muscle force.

Joint Capsule

A sac-like envelope enclosing the synovial joint cavity and forming a sleeve around it.

Bursae

Lubricated fluid-filled thin sacs located between bones, soft tissues, tendons, or muscles around joints to reduce friction.

Labrum

A rim (lip) of soft tissue or fibrocartilage surrounding the socket of a ball-and-socket joint to increase stability.

Glenohumeral Joint capsule

a loose, fibrous sheath that completely encloses the shoulder joint; runs from the rim of the glenoid fossa on the scapula to the anatomical neck of the humerus, providing a fluid-filled space that allows for extreme arm mobility while relying on surrounding ligaments and muscles for stability

Glenoid Labrum

A fibrocartilaginous rim that specifically deepens the glenohumeral joint socket.

subacromial bursae

a synovial fluid-filled sac between tendon/bone that is often implicated in rotator cuff injuries

Synovial Fluid

A thick, slippery joint fluid made from plasma containing proteins, enzymes, and hyaluronic acid.

Subacromial Bursa

A fluid-filled synovial bursa located between tendon and bone, commonly implicated in rotator cuff injuries.

Acromioclavicular (AC) Ligament

A ligament that stabilizes the AC joint and prevents sliding between the acromion and clavicle.

Coracoacromial Ligament

A ligament connecting the coracoid process to the acromion that prevents superior displacement of the humerus.

Coracoclavicular Ligament

A strong ligament consisting of the trapezoid and conoid ligaments that prevents superior displacement of the clavicle and provides weight-bearing support.

Coracohumeral Ligament

A ligament connecting the coracoid process to the humeral head that supports the superior aspect of the joint capsule.

Glenohumeral Ligaments

A set of superior, middle, and inferior ligaments that support and reinforce the glenohumeral joint capsule.

Transverse Humeral Ligament

A ligament that overlies the tendon of the long head of the biceps brachii muscle.

Superior Transverse Scapular Ligament

A ligament forming a "bridge" over the suprascapular notch, under which the suprascapular nerve travels and the the suprascapular artery goes over

Deltoid

Main abductor of the arm; anterior fibers flex and medially rotate, while posterior fibers extend and laterally rotate the arm.

intrinsic muscles of the shoulder

deltoid, supraspinatous, infraspinatous, teres major, teres minor, subscapularis

Teres Major

Humeral internal rotation and adduction of the arm.

Supraspinatus

Stabilizes the shoulder joint and assists the deltoid by initiating arm abduction.

Rotator cuff

SITS: supraspinatus, infraspinatus, teres minor, and subscapularis; all do humerus stabilization as part of their function

Infraspinatus

Stabilizes the shoulder joint and laterally (externally) rotates the arm.

Teres Minor

Stabilizes the shoulder joint and laterally (externally) rotates the arm.

Subscapularis

Stabilizes the shoulder joint, adducts the arm, and medially (internally) rotates the arm.

Pectoralis Major

Humeral adduction and internal rotation

sternocostal head

part of Pectoralis Major that extends the flexed arm

clavicular head

part of Pectoralis Major that flexes the arm

Pectoralis Minor

Stabilizes the scapula by pulling it inferiorly and anteriorly.

Subclavius

Pulls the acromion anteriorly by drawing the clavicle medially.

Serratus Anterior

Protracts the scapula, stabilizes the scapula, and upwardly rotates the glenoid fossa.

Axillary nerve (C5–C6)

Deltoid and Teres Minor nerve

Lower subscapular nerve (C5–C6)

Teres Major nerve

Suprascapular nerve (C5–C6)

Supraspinatus and Infraspinatus nerve

Upper and lower subscapular nerves (C5–C6).

Subscapularis (Innervation)

Lateral pectoral nerve (C5–C7)

Pectoralis Major clavicular head nerve

medial pectoral nerve (C8–T1)

Pectoralis Major sternocostal head and Pectoralis Minor nerve

Nerve to subclavius (C5–C6)

Subclavius nerve

Long thoracic nerve (C5–C7)

Serratus Anterior nerve

Suprascapular artery

Supraspinatus and Infraspinatus artery

Coracoacromial Arch

A protective arch formed by the coracoid process, the coracoacromial ligament, and the acromion.

Triangular Space Borders

Intermuscular space bordered by the teres minor (superior), teres major (inferior), and the long head of triceps brachii (lateral).

Circumflex scapular artery

Triangular Space Contents

Quadrangular Space Borders

Intermuscular space bordered by the teres minor (superior), teres major (inferior), long head of triceps brachii (medial), and surgical neck of humerus (lateral).

Axillary nerve (C5–C6) and posterior circumflex humeral artery

Quadrangular Space Contents

Triangular Interval Borders

Intermuscular space bordered by the teres major (superior), long head of triceps brachii (medial), and lateral head of triceps brachii (lateral)

Radial nerve (C5–T1) and profunda brachii artery

Triangular Interval Contents

Clavicular Fracture

An injury of the clavicle typically caused by a direct fall on the shoulder or an indirect force transmitted through the forearm or arm via an outstretched hand; treatment is severity dependent but can do surgery, immobilization, &/or PT

Acromioclavicular Dislocation ("Shoulder Separation")

Dislocation of the clavicle from scapula (specifically the acromion), typically caused by a hard fall on the shoulder or an outstretched upper limb; treatment is severity dependent but can do immobilization, inflammation/pain control, PT &/or surgery

Grade I Shoulder Separation

A injury grade of acromioclavicular dislocation involving a sprain of the AC ligament.

Grade II Shoulder Separation

An injury grade of acromioclavicular dislocation characterized by a tear of the AC ligament.

Grade III Shoulder Separation

A severe acromioclavicular dislocation characterized by a tear of both the AC and coracoclavicular (CC) ligaments, leaving the scapula completely separated from the clavicle.

Glenohumeral Joint Dislocation ("Shoulder Dislocation")

A joint dislocation occurring most commonly in the anterior direction (95%), often caused by the arm being abducted and laterally rotated and then receiving a posterior blow to the proximal humerus or anterior blow to the distal humerus; About 5% are in the posterior direction and typically occur by the “triple e”: epileptic seizure (muscle spasms), electric shock (muscle spasms), and extreme trauma (anterior blow to proximal humerus); treatment is reduction, immobilization, control of inflammation/pain, PT, &/or surgery

Anterior Shoulder Dislocation

The most common joint dislocation in the body (accounting for 95% of shoulder dislocations) that often occurs when the arm is abducted and laterally rotated during a posterior blow to the proximal humerus or an anterior blow to the distal humerus.

Posterior Shoulder Dislocation

A rare joint dislocation (accounting for 5% of shoulder dislocations) that typically occurs with epileptic seizures, electric shocks, or extreme trauma.

Rotator Cuff Tears

Muscle or tendon tears caused by sudden or chronic strain, anterior shoulder dislocations, or age-related/overuse degenerative tendinopathy.

supraspinatus muscle

Most Commonly Injured Rotator Cuff Muscle

suprascapular notch

divot between the coracoid process and superior border of the scapula where the suprascapular artery and nerve travel through; top of arch connected by the superior transverse scapular ligament