Shoulder, pectoral girdle and arm Flashcards
Location of the shoulder region
-Proximal end/attachment of the upper limb
-Overlaps with: thorax, upper back, lower lateral neck
-Anterior: pectoral region
-Lateral: deltoid region
-Posterior: scapular region
Bones and joints of the pectoral girdle
- Manubrium sterni
- Clavicle (collarbone)
- Scapula (shoulderblade)
- Humerus
A. Sterno-clavicular (SC) joint
B. Acromio-clavicular (AC) joint
C. Scapulo-thoracic “joint”
D. Gleno-humeral joint
Structure of the clavicle
- Sternal facet
- Acromial facet
- Trapezoid line
- Conoid tubercle
- Subclavian groove
Features of the clavicle
-No medullary cavity – trabecular (cancellous, spongy) bone surrounded by compact shell
-First bone to begin ossification in embryo, but also last bone to finish (males: 18-20 yrs; females: 21-25 yrs)
-Great variation in shape (left/right; sex)
Structure of the clavicle
- Glenoid cavity
- Subscapular fossa
- Supraspinous fossa
- Infraspinous fossa
- Spine
- Acromion process
- Coracoid process
Sterno-claviculalar joint
-Synovial joint
-Saddle-shaped, but functionally
a ball-and-socket joint
-Only articulation between axial
skeleton and pectoral
girdle/upper limb
Acromio-clavicular joint
-Synovial joint
-Incomplete articular disc
-No muscles bridging the joint
-AC joint injury = separated
shoulder
Movement of the scapulo-thoracic joint
Gleno-humeral joint
-Synovial joint
-Ball-and-socket
-Extremely mobile
Ligaments of the gleno-humeral joint
-Most dislocations are anterior
-Risk of injury to axillary and radial nerves
Pectoralis major muscle
-Flexes, adducts and medially rotates the arm at the glenohumeral joint
-Congenital hypoplasia of
pectoralis major: Poland’s
syndrome
Pectoralis minor
-Originates at 3rd-5th rib
-Inserts into coracoid process of scapula
-Pulls tip of shoulder down, protracts scapula
Subclavius muscle
-Originates at 1st rib
-Inserts into inferior surface of scapula
-Pulls tip of shoulder down, stabilises SC joint
-May cushion blood vessels and nerves that pass through axillary inlet
Deep posterior axio-appendicular muscles
-Elevate, retract and rotate scapula
-Serratus anterior: protracts the scapula (‘big swing muscle’)
Superficial posterior axio-appendicular muscles
Trapezius:
-Superior - elevates scapula
-Middle - retracts scapula
-Inferior - depresses scapula
Latissimus dorsi:
-Extends, adducts and
medially rotates arm at
gleno-humeral joint
Deltoid muscle
-Abducts and assists in flexing,
extending the arm at the glenohumeral joint
-First 10-15 degrees of
abduction by supraspinatus muscle
Deep intrinsic shoulder muscles
Supraspinatus
-Initiates abduction of arm at glenohumeral joint
Infraspinatus
-Laterally rotates arm
Teres minor
-Laterally rotates arm
Teres major
-Medially rotates arm
Subscapularis
-Medially rotates arm
Rotator cuff muscles
Typical sports injuries:
-Tears
-Tendinosis
-Inflammation
-Fibrosis
Humerus
Biceps brachii
-Supinator, then flexor of forearm at elbow joint
-Stabilises shoulder
-Forearm pronated → biceps functions as a supinator
-Elbow at 90 degrees and forearm supinated → biceps is a flexor
-In 10% of people: 3rd head originating from
superomedial part of brachialis
Anterior compartment muscles vs Posterior compartment muscles
Anterior compartment muscles = flexion
Posterior compartment muscles = extension
Brachialis
-Main flexor (‘workhorse’) of the forearm at the elbow joint
Coracobrachialis
-Adducts and flexes arm at shoulder joint
-Stabilises shoulder
Triceps brachii
-Main extensor of the forearm at the elbow joint
-Long head: adduction and
extension of arm at shoulder joint
Anconeus
-Assists triceps brachii as extensor
of forearm
-Tenses capsule of elbow joint
-May abduct ulna during pronation
of forearm
Origin, course and branches of the axillary artery
Anastomoses around the scapula
Arteries of the arm
