Anatomy Lecture 3 (notebook LM)

Bones of the pectoral girdle (shoulder complex)

Sternum, clavicle, scapula, and humerus

The only bony joint connecting the upper limb to the thorax

Sternoclavicular joint

Classification of the Acromioclavicular joint

Plane joint

Classification of the Glenohumeral joint

Ball-and-socket joint

Primary mechanical function of the clavicle

Acts as a strut to keep the limb away from the thorax

The two distinct ends of the clavicle

Acromial end (lateral) and Sternal end (medial)

Most common mechanism for a clavicular fracture

A direct fall on the shoulder or indirect force via an outstretched hand

Definition: Ligament

A tough fibrous band of tissue connecting the articular extremities of bones. Bone to bone connection

Definition: Tendon

A tough cord or band of dense white fibrous tissue uniting a muscle with a bone

Definition: Joint Capsule

A sac-like envelope that forms a sleeve around a synovial joint

Definition: Bursae

Lubricated fluid-filled thin sacs that reduce friction between bone and soft tissue

Definition: Labrum

A rim of fibrocartilage that deepens the socket of a ball and socket joint to increase stability

Specific function of the glenoid labrum

Deepens the glenohumeral joint

Bursa most often implicated in rotator cuff injuries

Subacromial (subdeltoid) bursa

General characteristics of synovial fluid

Thick and slippery (like egg whites) and contains hyaluronic acid

Function: Acromioclavicular (AC) ligament

Stabilizes the AC joint and prevents sliding between the acromion and clavicle

Function: Coracoacromial ligament

Connects the coracoid to the acromion and prevents the humerus from moving too far superiorly

The two components of the coracoclavicular ligament

Trapezoid ligament and Conoid ligament

Function: Coracoclavicular ligament

Prevents superior displacement of the clavicle and provides weight-bearing support

Function: Coracohumeral ligament

Connects the coracoid process to the humeral head and supports the superior capsule

Role of the Glenohumeral ligaments

Superior, middle, and inferior bands that support the joint capsule

Function: Transverse humeral ligament

Overlies the tendon of the long head of the biceps brachii

Structures forming the coracoacromial arch

Coracoid process, coracoacromial ligament, and the acromion

Description of Grade I shoulder separation

A sprain of the acromioclavicular ligament

Description of Grade II shoulder separation

A tear of the acromioclavicular ligament

Description of Grade III shoulder separation

Tears of both AC and coracoclavicular (CC) ligaments; scapula separates from clavicle

Most common direction for a shoulder (GH) dislocation

Anterior-inferior (95% of cases)

Typical mechanism for an anterior shoulder dislocation

Abducted and laterally rotated arm receives a posterior blow to the proximal humerus or anterior blow to distal humerus

“shoulder separation” is another way to describe

Acromioclavicular Dislocation

The "Triple E" mechanism for posterior shoulder dislocations (rare 5% of all dislocations)

Epileptic seizure, Electric shock, or Extreme trauma

What structure prevents there from being a superior way to dislocate the shoulder

Coracoacromial arch

Nerve most likely injured during an anterior-inferior shoulder dislocation

Axillary nerve

axio-appendicular/ extrinsic shoulder muscles

Scapulothoracic joint and pectoral

Scapulohumeral/ intrinsic shoulder muscles

glenohumeral joint

Nerve supply to the Trapezius

Spinal accessory nerve (CN XI) and C3-C4 anterior rami

Primary actions of the Trapezius

Scapular elevation, retraction, depression, and rotation

Innervation of the Levator scapulae

Dorsal scapular nerve (C5) and C3-C4 anterior rami

Primary actions of the Levator scapulae

Scapular elevation and downward rotation

Innervation of the Rhomboid major and minor

Dorsal scapular nerve (C5)

Primary actions of the Rhomboid major and minor

Scapular retraction, fixation to the thoracic wall, and downward rotation

Innervation of the Latissimus dorsi

Thoracodorsal nerve (C6-C8)

Primary actions of the Latissimus dorsi

Humeral extension, internal rotation, and adduction

Innervation of the Deltoid

Axillary nerve (C5-C6)

List the intrinsic muscles of the shoulder

Deltoid, Teres minor and major, supraspinous, infraspinous, and subscapularis

The subscapularis is only seen from what anatomical view

anterior

Specific action of the anterior fibers of the Deltoid

Flexion and medial rotation of the arm

Specific action of the posterior fibers of the Deltoid

Extension and lateral rotation of the arm

Innervation of the Teres major

Lower subscapular nerve (C5-C6)

Primary actions of the Teres major

Humeral adduction and medial rotation

Acronym to remember the muscles of the rotator cuff

SITS- supraspinous, infraspinous, teres minor, subscapularis

Primary functional role of the rotator cuff muscles

To stabilize the shoulder joint during arm movements

Common innervation for Supraspinatus and Infraspinatus

Suprascapular nerve (C5-C6)

Primary action of the Supraspinatus

Initiates arm abduction and assists the deltoid

what is the primary arterial supply for the supraspinous and infraspinous muscles

suprascapular artery

Primary action of the Infraspinatus

Laterally rotates the arm

"Army over the bridge, Navy under the bridge" mnemonic

Army (suprascapular artery) goes over and Navy (suprascapular nerve) goes under the superior transverse scapular ligament in the supraspinous fossa only

Innervation of the Teres minor

Axillary nerve (C5-C6)

Primary action of the Teres minor

Laterally rotates the arm

Innervation of the Subscapularis

Upper and lower subscapular nerves (C5-C6)

Primary action of the Subscapularis

Medially rotates and adducts the arm

The most common rotator cuff muscle injured in tears

Supraspinatus

Common causes of rotator cuff tears

Sudden or chronic strain, anterior dislocations, or degenerative tendinopathy (age related and overuse)

Muscles of the pectoral region acting on the shoulder

pectoralis major, pectoralis minor, subclavius, serratus anterior

Innervation of the clavicular head of the Pectoralis major

Lateral pectoral (C5-C7)

Innervation of the sternocostal head of the Pectoralis major

Medial pectoral (C8-T1)

Innervation of the the Pectoralis major

Lateral and Medial pectoral nerves

Primary actions of the Pectoralis major (both heads)

Humeral adduction, internal rotation

Primary actions of the Pectoralis major (clavicular head)

Humeral flexion

Primary actions of the Pectoralis major (sternal head)

humeral extension of flexed arm

Innervation of the Pectoralis minor

Medial pectoral nerve (C8-T1)

Primary action of the Pectoralis minor

Stabilizes the scapula by pulling it inferiorly and anteriorly

Innervation of the Subclavius

Nerve to subclavius (C5-C6)

Primary action of the Subclavius

Draws the clavicle medially to pull the acromion anteriorly

Innervation of the Serratus anterior

Long thoracic nerve (C5-C7)

Primary actions of the Serratus anterior

Protracts the scapula and upwardly rotates the glenoid fossa

Contents of the Triangular Space

Circumflex scapular artery

What forms the superior, inferior, and lateral border of the Triangular space

Teres minor, Teres major, long head of the triceps brachii

Contents of the Quadrangular Space

Posterior circumflex humeral artery and the axillary nerve

What forms the superior, inferior, medial and lateral border of the Quadrangular space

teres major, teres minor, long head of triceps brachii, and the surgical neck of the humerus

Contents of the Triangular Interval

Profunda brachii artery (deep artery of the arm) and the radial nerve

What forms the superior, medial, and lateral border of the Triangular interval

teres major, long head of triceps brachi, lateral head of triceps brachii

Definition of the Scapulohumeral Rhythm ratio

2:1 ratio (2° of GH joint movement for every 1° of scapulothoracic movement)

The glenoid humeral joint can move alone for the forst 30 degrees of abduction, but has to work together with the _______________ joint for full range of motion

Scapulothoracic

What are the two superficial veins

cephallic and basilic

what are the two deep veins

Brachial and Axillary