Part 1 - Pectoral Girdle & Breast

• Clavicle


  • Connects upper limb to trunk
  • Shaft has double curve (S-shaped) in the horizontal plane
  • Medial 1/3 of shaft convex anteriorly, lateral 2/3 concave anteriorly
  • Sternal end enlarged and triangular, articulates with manubrium of sternum at sternoclavicular joint
  • Acromial end flat, articulates with acromion of scapula at acromioclavicular joint
  • Serves as moveable, crane-like strut from which scapula and free limb are suspended
  • Allows scapula to move on thoracic wall at scapulothoracic joint, increasing range of motion of limb
  • Forms one of bony boundaries of cervico-axillary canal, protecting neurovascular bundles
  • Transmits shocks from upper limb to axial skeleton
  • Long bone with no medullary cavity, consists of trabecular bone with shell of compact bone
  • Superior surface smooth, lies just deep to skin and platysma muscle
  • Inferior surface rough due to strong ligaments

  
• Scapula


  • Triangular, flat bone
  • Lies in posterolateral aspect of thorax, overlying 2nd to 7th ribs
  • Posterior surface convex, unevenly divided by spine into supraspinous and infraspinous fossae
  • Costal surface concave, forms large subscapular fossa
  • Fossae provide attachment for muscles
  • Body thin, triangular, translucent superior and inferior to spine
  • Borders thicker, especially lateral border
  • Acromion flat, expanded lateral continuation of spine, forms subcutaneous point of shoulder
  • Deltoid tubercle medial attachment of deltoid muscle on scapular spine
  • Spine and acromion serve as lever for trapezius muscle
  • Glenoid cavity shallow, concave, oval fossa receiving head of humerus
  • Coracoid process beak-like, superior to glenoid cavity, provides inferior attachment of coracoclavicular ligament
  • Medial, lateral and superior borders, superior, lateral and inferior angles
  • Lateral border thick bar preventing buckling, terminates in truncated lateral angle
  • Superior border thinnest, marked by suprascapular notch
  • Provides base from which upper limb operates and moves freely

  
• Physiological joint


  Movement occurs between musculoskeletal structures
• Anatomical joint


  Movement occurs between directly articulating skeletal elements
• Sternoclavicular (SC) joint

  • Saddle type synovial joint
  • Articular disc divides joint into 2 compartments
  • Disc attached by ligaments, serves as shock absorber
  • Only articulation between upper limb and axial skeleton
  • Sternal end of clavicle articulates with manubrium and 1st costal cartilage
  • Joint capsule surrounds joint including epiphysis, synovial membrane lines internal surface
  • Ligaments: anterior/posterior sternoclavicular, interclavicular, costoclavicular
  • Movement: elevation to 60°, anterior/posterior 25-30°, circumduction possible
  • Supplied by internal thoracic and suprascapular arteries, innervated by medial supraclavicular and subclavius nerves

  
• Acromioclavicular (AC) joint


  • Plane type synovial joint
  • Acromial end of clavicle articulates with acromion of scapula
  • Articular surfaces separated by incomplete wedge-shaped disc
  • Joint capsule loose, fibrous layer, strengthened superiorly by trapezius
  • Ligaments: acromioclavicular, coracoclavicular (conoid and trapezoid)
  • Supplied by suprascapular and thoraco-acromial arteries, innervated by lateral pectoral and axillary nerves

  
• Pectoralis major


  • Clavicular head originates on anterior surface of medial half of clavicle, sternocostal head on anterior surface of sternum and superior 6 costal cartilages
  • Inserts on lateral lip of intertubercular sulcus of humerus
  • Innervated by lateral and medial pectoral nerves
  • Adducts humerus, medially rotates humerus, draws scapula anteriorly and inferiorly
  • Clavicular head flexes humerus, sternocostal head extends humerus from flexed position

  
• Pectoralis minor


  • Originates on upper margins and outer surfaces of 3rd-5th ribs near their costal cartilages
  • Inserts on medial border and superior surface of coracoid process of scapula
  • Innervated by medial pectoral nerve
  • Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall

  
• Subclavius


  • Originates at junction of 1st rib and its costal cartilage
  • Inserts on inferior surface of clavicle
  • Innervated by nerve to subclavius
  • Depresses and steadies clavicle

  
• Perpendicular muscles


  • Pectoralis major
  • Pectoralis minor
  • Subclavius
  • Serratus anterior

  
• Muscle


  • Origin
  • Insertion
  • Innervation
  • Main Action
• Pectoralis major


  • Clavicular head flexes humerus
  • Sternocostal head extends humerus from flexed position

  
• Pectoralis minor


  • Stabilizes scapula by drawing it inferiorly and anteriorly against the thoracic wall
• Subclavius


  • Anchors and depresses clavicle
• Serratus anterior


  • Protracts scapula
  • Rotates scapula
• Clavipectoral Fascia (costocoracoid membrane)

  • Extent- clavicle superiorly to axillary fascia inferiorly
  • Enclosed structures- subclavius and pectoralis minor
  • Piercing structures- Medial and lateral pectoral nerves, Pectoral branch of thoraco-acromial artery, Cephalic vein

  
• Breast


  • Modified sweat gland
  • Secretes milk
  • Exists in both males and females
• Breast in females


  • Underdeveloped before puberty but undergoes growth after puberty and pregnancy
• Mammary papilla (Nipple)


  • Conical
  • 4th intercostal space in nulliparous females
  • Variable in multiparous females
  • Pink or light brown in colour
• Areola


  • Base of nipple
  • Pigmented area of skin
  • Size increase and darkening with 1st pregnancy (3 months) and never returns to original colour
  • Contains areolar (sebaceous) glands of Montgomery which are tiny swellings (secretions are moistening and antibacterial)
• Structure of the breast

  • Entire gland in superficial fascia (retromammary space)
  • Lactiferous ducts give rise to buds that develop into 15-20 separate lobes of glandular tissue
  • Tubulo-alveolar type
  • Each separated from its neighbour by fibrous connective tissue
  • Suspensory ligaments of cooper compartmentalizes the lobes and supports glandular lobes

  
• Arterial supply of the breast

  • Perforating branches of internal thoracic a. at 2nd to 4th interspaces
  • Perforating branches of 3rd to 5th intercostal aa.
  • Pectoral branches of the thoraco-acromial artery
  • Branches of lateral thoracic artery
  • Branches of subscapular a.

  
• Venous drainage of the breast

  Anastomotic circle around nipples (circulus venosus) into axillary and internal thoracic vv. via intercostal vv.

  
• Lymph drainage of the breast

  • Axillary group (drains 75%)
  • Parasternal group (drains 20%)
  • Intercostal group (drains 5%)
  • Sappey's plexus
  • Abdominal lymph nodes

  
• Nerve supply of the breast

  • Anterior and lateral cutaneous branches of 3rd to 6th intercostal nerves
  • Nervous plexus around nipple helps signaling suckling
  • Nerves vulnerable during mastectomy: Intercostal brachial n., Medial brachial cutaneous n., Long thoracic n., Thoracodorsal n., Medial pectoral n.
• Applied anatomy of the breast

  • Lymph flow is important clinically as it is the primary route of metastasis of breast cancer and for performing and interpreting a node biopsy
  • Cyst (galactocele) may develop with blockage of lactiferous ducts

  
• Breast conditions


  • Peau D'orange
  • Amastia
  • Polymastia
  • Polythelia
  • Gynaecomastia
• Bones of the shoulder region

  • Humerus

  
• Humerus


  • Articulates with the scapula at the glenohumeral joint proximally, and with the radius and ulna at the elbow joint distally
  • Proximal end has head, anatomical neck, surgical neck, greater tubercle, lesser tubercle, intertubercular sulcus
  • Shaft has deltoid tuberosity and oblique radial groove
  • Distal end has condyle with capitellum and trochlea, coronoid fossa, olecranon fossa, and radial fossa

  
• Glenohumeral joint


  • Ball and socket type synovial joint
  • Articulating surfaces are large round humeral head and shallow glenoid cavity
  • Joint capsule is loose fibrous layer attached medially to glenoid cavity and laterally to anatomical neck of humerus, deficient inferiorly

  
• Glenohumeral joint


  • Ball and socket type synovial joint
  • Multiaxial spheroidal
• Articulating surfaces of glenohumeral joint

  • Large round humeral head articulates with the shallow glenoid cavity of the scapula
  • Shallow glenoid cavity slightly deepened by the ring-like fibrocartilaginous glenoid labrum
  • Both articular surfaces covered with hyaline cartilage
• Glenohumeral joint capsule


  • Loose fibrous layer surrounds the joint and is attached medially to the margin of the glenoid cavity and laterally to the anatomical neck of the humerus
  • Deficient inferiorly
  • Superiorly, the fibrous layer encloses the proximal end of the long head of the biceps brachii to the supraglenoid tubercle of the scapula within the joint
  • Has 2 apertures - an opening between the tubercles of the humerus for the tendon of the long head of the biceps brachii, and an opening anteriorly and inferior to the coracoid process that allows communication between the Subtendinous bursa of subscapularis and the synovial cavity of the joint

  
• Ligaments of glenohumeral joint

  • Glenohumeral - 3 fibrous bands that reinforce the anterior aspect of the joint capsule
  • Coracohumeral - strong broad band that passes from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus
  • Transverse humeral ligament - broad fibrous band that runs obliquely from the greater to the lesser tubercle of the humerus, bridging over the intertubercular sulcus
  • Coracoacromial ligament - spans between the inferior surface of the acromion and the lateral border of coracoid process, forming a protective arch that overlies the humeral head

  
• Bursae of glenohumeral joint

  • Subtendinous bursa of subscapularis - located between tendon of subscapularis and neck of scapula, protects the tendon
  • Subacromial (subdeltoid) - large bursa located under coracoacromial ligament and deltoid muscle

  
• Blood supply of glenohumeral joint

  • Anterior and posterior circumflex humeral arteries
  • Branches of the suprascapular artery

  
• Innervation of glenohumeral joint

  • Suprascapular, axillary and lateral pectoral nerves
• Glenoid cavity accepts a little more than a third of the humeral head and is held in the cavity by the rotator cuff muscles (SITS)
• Muscles involved in movement of the glenohumeral joint

  • Abduction: Deltoid, (supraspinatus initiates movement)
  • Adduction: Pectoralis major, latissimus dorsi, (teres major, long head of triceps brachii)
  • Flexion: Clavicular head of pectoralis major, anterior deltoid , (coracobrachialis)
  • Extension: Posterior deltoid, (teres major, latissimus dorsi, long head of triceps brachii)
  • Medial rotation: Subscapularis, (pectoralis major, deltoid, latissimus dorsi, teres major)
  • Lateral rotation: Infraspinatus, (teres minor, deltoid)

  
• Factors for stability of the glenohumeral joint

  • Glenoid labrum- increases concavity
  • Coracoacromial arch- prevents upward dislocation
  • Tendon of long head of biceps- superior support
  • Long head of triceps- inferior support during abduction
  • Ligaments
  • Rotator cuff muscles- strong lateral stability, stabilizes head of humerus in glenoid cavity (supraspinatus, infraspinatus, teres minor, subscapularis)