Upper Limb: Shoulder and Axilla

Lower Limb > Neurovasculature > Study Aims
STUDY AIMS
At the end of your study, you should be able to:
Identify the different parts and surface markings of the clavicle and scapula
Describe the sternoclavicular, acromioclavicular, and glenohumeral joints, their movements, and supporting ligaments
Understand the organization of the scapular muscles
Know the origins, insertions, and actions of the intrinsic scapular muscles
Identify the boundaries of the axilla and describe its contents
Describe the organization of the deep fascia

Upper Limb > Neurovasculature > Guides
GUIDE

6-2: Upper Limb: Shoulder and Axilla
    Bones (Plate 419 through Plate 421)
  • Clavicle: with sternal and acromial ends
    • Double-curved long bone
    • Sternal end articulates with manubrium of sternum
    • Acromial end articulates with acromion
    • Osteological features:
      • Deltoid tubercle for attachment of the deltoid muscle
      • Conoid tubercle for attachment of conoid ligament
      • Subclavian groove for attachment of subclavius muscle
      • Trapezoid line where trapezoid ligament attaches
    • Serves as a strut suspending the scapula and limb with maximum freedom
  • Scapula: lying against posterolateral thorax
    • Triangular flat bone
    • Lies posterolateral on second through seventh ribs
    • Osteological features
      • Concave costal surface = subscapular fossa
      • Posterior surface divided by spine = transverse ridge of bone
      • Supraspinous fossa
      • Infraspinous fossa
      • Acromion = flattened lateral end of spine
      • Coracoid process = anterior projection above glenoid cavity
      • Glenoid cavity = socket for head of humerus
      • Suprascapular notch (scapular notch) = notch found on superior border, two thirds of the way along laterally
    • Capable of considerable movement over thoracic wall
    Joints
  • Sternoclavicular Joint (Plate 419)
    • Saddle-type, synovial joint
    • Divided into two compartments by an articular disc
    • Movements
      • Elevation with posterior rotation
      • Protraction
      • Depression
    • Articulation between concave facet of manubrium and concave facet of clavicle
    • Strengthened by anterior and posterior sternoclavicular, costoclavicular, and interclavicular ligaments
    • Blood supply: Branches of suprascapular and internal thoracic arteries
    • Nerve supply: Branches of the supraclavicular nerve, and nerve to subclavius
  • Acromioclavicular Joint (Plate 423)
    • Plane-type, synovial joint
    • No demonstrable movement; muscles moving the scapula cause the acromion to move on the clavicle
    • Articulation between concave facet of acromion and convex facet of clavicle
    • Strengthened by acromioclavicular and coracoclavicular (conoid and trapezoid) ligaments
    • Coracoclavicular
      • Unites coracoid process and clavicle
      • Has two component ligaments:
        • Conoid: vertical, in shape of inverted pyramid
        • Trapezoid: horizontal, extends laterally to inferior surface of clavicle
    • Blood supply: Branches of suprascapular and thoracoacromial arteries
    • Nerve supply: Branches of the supraclavicular, lateral pectoral and axillary nerves
  • Shoulder (Glenohumeral) Joint (Plate 422 and Plate 423) (Fig. 6-2-1)
    • Multiaxial, synovial ball-and-socket joint
    • Movements:
      • Flexion/extension
      • Abduction/adduction
      • Internal/external (medial/lateral) rotation
      • Circumduction
    • Articulation of head of humerus with the shallow glenoid cavity of the scapula
    • Joint socket deepened by glenoid labrum (fibrocartilaginous ring) and supported by the rotator cuff muscles (see below)
    • Loose fibrous capsule encloses and contains two apertures:
      • Between the tubercles of the humerus for passage of long head of biceps brachii, which attaches to supraglenoid tubercle within the joint
      • Anterior opening, inferior to coracoid process, for communication between subscapular bursa and synovial cavity of joint
    • Blood supply: Branches of anterior and posterior circumflex humeral arteries from the axillary and suprascapular artery from the subclavian
    • Nerve supply: Branches of suprascapular, axillary, and lateral pectoral nerves
  • Ligaments of glenohumeral joint ( Table 6-2-1):
    • Glenohumeral ligaments—strengthen capsule anteriorly
    • Coracohumeral ligament—strengthens joint superiorly
    • Transverse humeral ligament—bridges gap between greater and lesser tubercle and holds tendon of biceps brachii in place
    • Coracoacromial ligament—from acromion to coracoid process, prevents displacement of humeral head superiorly
    Bursa (Important ones)
  • Contain thin layer of synovial fluid
  • Located where tendons rub against bone, ligaments, or tendons and when skin moves over bone directly beneath
  • Subscapular bursa
    • Between tendon of subscapularis muscle and neck of scapula.
    • Communicates with cavity of the shoulder joint
  • Subacromial (subdeltoid) bursa
    • Between deltoid, supraspinatus tendon and glenohumeral capsule.
    • Does not communicate with cavity of shoulder.
    • Facilitates movement of deltoid over joint capsule and supraspinatus tendon under coracoacromial arch
    Muscles of the scapula (Plate 424 and Plate 425) ( Table 6-2-2)
  • Superficial extrinsic (Join axial skeleton to the appendicular skeleton)
    • Trapezius
    • Latissimus dorsi
  • Deep extrinsic
    • Levator scapulae
    • Rhomboid major and minor
  • Intrinsic
    • Deltoid: Gives shoulder its rounded appearance, abducts arm past 15 degrees
    • Teres major: Adducts and medially rotates arm
    • Teres minor: Hidden by deltoid, assists lateral rotation of arm and adduction
    • Supraspinatus: Initiates arm abduction
    • Infraspinatus: Laterally rotates arm
    • Subscapularis: Primary medial rotator of the arm, also adducts
  • Rotator cuff
    • Four of scapulohumeral muscles
      • Supraspinatus
      • Infraspinatus
      • Teres minor
      • Teres major
    • Form musculotendinous cuff around glenohumeral joint
    • Blend with articular capsule to reinforce it
    • Hold head of humerus in glenoid cavity
    Axilla: ( Plate 429 )
  • Pyramid-shaped area inferior to glenohumeral joint containing important neurovascular structures to the upper limb
  • Boundaries:
    • Base: skin of armpit and axillary fascia from arm to thoracic wall
    • Apex: bounded by the first rib, clavicle, and superior border of the scapula
    • Anterior wall (anterior axillary fold): pectoralis major and minor
    • Posterior wall (posterior fold): subscapularis, teres major, latissimus dorsi
    • Medial wall: ribs 1 through 4, serratus anterior, and intercostal muscles
    • Lateral wall: intertubercular groove of humerus
  • Contents (see Section 6-6: Upper Limb: Neurovasculature for details):
    • Axillary artery and branches
    • Axillary vein and tributaries
    • Axillary lymph nodes (five major collections)
    • Brachial plexus ( Plate 430)
  • Fascia (Plate 428)
    • Pectoral fascia
      • Attaches to clavicle and sternum
      • Invests the pectoralis major
      • Extends laterally as the axillary fascia
      • Continues inferiorly with fascia of abdominal wall
    • Clavipectoral fascia
      • Invests subclavius and pectoralis minor
      • Continues superiorly as the costocoracoid membrane (pierced by the lateral pectoral nerve)
    • Axillary sheath: invests axillary artery and brachial plexus
  • Axillary Lymph Nodes
    • Arranged in five main groups
    • Apical group
      • Along medial side of axillary vein and first part of axillary artery
      • Receives lymph from all other groups
      • Efferent lymphatic vessels from these nodes form subclavian lymphatic trunk
    • Pectoral (anterior) group
      • Medial wall of axilla
      • Receives lymph from breast, anterior thoracic wall
    • Subscapular group
      • Along posterior axillary fold
      • Receives lymph from posterior thoracic wall and scapula
    • Humeral (lateral) group
      • Along lateral wall of axilla
      • Receives lymph from upper limb
    • Central group
      • Deep to pectoralis minor
      • Receives lymph from pectoral, subscapular, and humeral groups
Upper Limb > Shoulder and Axilla > Figures
FIGURES
Plate 429: Upper Limb—Shoulder and Axilla—Axilla (Dissection): Anterior View
Plate 430: Upper Limb—Shoulder and Axilla—Brachial Plexus: Schema
Fig. 6-2-1: Computed Tomography (CT) Angiogram of the left shoulder and arm. (Image courtesy of Stephen W. Carmichael, Ph.D., D.Sc., Professor and Chair Emeritus, Department of Anatomy, Mayo Clinic, Rochester MN US)
Upper Limb > Shoulder and Axilla > Tables
TABLES

Table 6-2-1: Ligaments of the Glenohumeral Joint(author table)
LIGAMENT ATTACHMENTS COMMENT
Joint capsule Margin of glenoid cavity →anatomical neck of humerus Loose fibrous capsule
Weakest inferiorly
Glenohumeral Supraglenoid tubercle →blend with fibrous capsule (superior, middle and inferior bands) Reinforce anterior capsule
Coracohumeral Coracoid process →greater tubercle of humerus Strong
Transverse humeral Bridges intertubercular groove between greater and lesser tubercles Holds tendon of biceps brachii in intertubercular groove
Coracoacromial Coracoid process →acromion Completes coracoacromial arch protecting humeral head

Table 6-2-2: Scapular muscles*
Muscle Origin Insertion Innervation Action Blood Supply
Superficial extrinsic muscles
Trapezius Medial third of superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of CVII to TXII Lateral third of posterior clavicle, medial acromion, superior edge of spine of scapula Spinal root of accessory nerve [XI] and C3, C4 Elevates scapula (descending part), retracts scapula (transverse part), depresses scapula (ascending part); rotates scapula (descending and ascending parts acting together) Transverse cervical artery, dorsal scapular artery
Latissimus dorsi Spinous processes of TVII to TXII, thoracolumbar fascia, iliac crest, lower three to four ribs Floor of intertubercular sulcus of humeru Thoracodorsal nerve (C6,C7,C8) Extends, adducts and medially rotates arm, draws shoulder downwards and backward Thoracodorsal artery
Deep extrinsic muscles
Levator scapulae Posterior tubercles of transverse processes CI to CIV Medial border of scapula above base of spine of scapula Dorsal scapular nerve (C5) and C3 and C4 Elevates scapula medially, inferiorly rotates glenoid cavity Dorsal scapular artery, transverse cervical artery
Rhomboid minor Ligamentum nuchae, spinous processes of CVII and TI Medial border of scapula above base of spine of scapula Dorsal scapular nerve (C4,C5) Retracts and stabilizes the scapula Dorsal scapular artery
Rhomboid major Spinous processes of TII–TV Medial border of scapula below base of spine of scapula Dorsal scapular nerve (C4,C5) Retracts and rotates scapula to depress the glenoid cavity Dorsal scapular artery
Intrinsic muscles
Deltoid Lateral third of anterior clavicle, lateral acromion, inferior edge of spine of scapula Deltoid tuberosity of humerus Anterior and posterior branches of axillary nerve (C5,C6) Clavicular part –flexes and medially rotates arm; acromial part –abducts arm; spinal part –extends and laterally rotates arm Posterior circumflex humeral artery, deltoid branch of thoracoacromial artery
Supraspinatus Supraspinous fossa of scapula Superior facet of greater tubercle of humerus Suprascapular nerve (C4,C5,C6) Initiates arm abduction, acts with rotator cuff muscles Suprascapular artery
Infraspinatus Intraspinous fossa of scapula Middle facet of greater tubercle of humerus Suprascapular nerve (C5,C6) Lateral rotation of arm (with teres minor) Suprascapular artery
Teres minor Upper two thirds of posterior surface of lateral border of scapula Inferior facet of greater tubercle of humerus Posterior branch of axillary nerve (C5,C6) Lateral rotation of arm, adduction Circumflex scapular artery
Teres major Posterior surface of inferior angle of scapula Medial lip of intertubercular sulcus Inferior subscapular nerve (C6,C7) Adducts and medially rotates arm Circumflex scapular artery
Subscapularis Subscapular fossa Lesser tubercle of humerus Superior and inferior subscapular nerves (C5,C6,C7) Medially rotates arm and adducts it Subscapular artery, lateral thoracic arter
*main nerve root is indicated in bold
(From Moses KP, Banks JC, Nava PB, et al. Atlas of Clinical Gross Anatomy. Mosby, 2005. Page 190, Table 17.1)

Upper Limb > Shoulder and Axilla > Facts and Hints
FACTS & HINTS

PART A: HIGH-YIELD FACTS
Box 6-2-1: Clinical Points
Fracture of the Clavicle
  • Common, especially in children
  • Usually results from a fall on outstretched hand or direct trauma to the shoulder
  • Fractures of middle third are most frequently seen
  • Sternocleidomastoid muscle pulls the proximal fragment superiorly and the shoulder pulls the distal fragment inferiorly
  • Small lump may remain after the clavicle has healed
  • Box 6-2-2: Clinical Points
    Calcific Supraspinatus Tendonitis
  • Inflammation and calcification of the subacromial bursa resulting in pain, tenderness and limitation of movement of the shoulder joint
  • Calcium deposits frequently also seen in the supraspinatus tendon
  • Pain is especially severe with the arm abducted between 50 to 130 degrees (the painful arc) as the supraspinatus tendon is in contact with the inferior surface of the acromion here
  • Box 6-2-3: Clinical Points
    Shoulder Dislocation
  • High mobility and instability of the glenohumeral joint leads to frequent dislocation
  • 95% of dislocations are in interoinferior direction, caused by excessive extension and lateral rotation of humerus (e.g., in the throwing motion)
  • Humeral head places stress on joint capsule, which may be torn anteriorly, with elements of the rotator cuff
  • Axillary and musculocutaneous nerves may also be injured
  • Posterior dislocation is uncommon, but may occur during epileptic seizure or electrocution
  • Box 6-2-4: Clinical Points
    Rotator Cuff Injury
  • Musculotendinous rotator cuff may be damaged by trauma or degenerative disease
  • One or more of tendons may be torn when the arm is forcefully abducted, leading to pain in the anterosuperior aspect of the shoulder
  • Supraspinatus tendon is most commonly involved in degenerative tendonitis
  • Leads patient’s arm to drop suddenly at approximately 90-degree abduction, when instructed to lower it slowly from a fully abducted position

  • PART B: MNEMONICS
    Box 6-2-5: Memory Aids
    Rotator cuff muscles: SITS = Supraspinatus, Infraspinatus, Teres minor, Subscapularis

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