Breast, Pectoral Region and Axilla

Question 1

Body Wall Layers of Thorax

Answer 1

Superficial to Deep:

• Skin
• Superficial Fascia
• Muscles of Upper Limb
• Intercostal mm. and ribs
  
  • External intercostals
  • Internal intercostals
  • Innermost intercostals and Transversus Thoracis
• Endothoracic fascia (areolar CT)
• Parietal Pleura
• Thoracic Cavity

Question 2

Composition of The Breast

Answer 2

• Glandular tissue
• Adipose tissue
• Suspensory ligaments

Question 3

Lymphatic Drainage of Breast

Answer 3

75% of Lymphatic Drainage goes to Axillary Lymph Nodes

• Pectoral: drains most of breast (initial breast cancer metastasis)
  
  • Cancerous lymph nodes feel hard, enlarged, non-tender (infection would be enlarged and tender)
• Subscapular
• Humeral (lateral)
• Central
• Apical

Remaining 25% drains to parasternal lymph nodes (next to sternum)

Question 4

Pectoralis Major

Answer 4

Innervation:

• Medial and Lateral Pectoral nn.

Insertion:

• Intertubercular sulcus of humerus

Action:

• Flexes, aDducts and medially rotates arm

Blood Supply:

• Thoracoacromial a.

Question 5

Pectoralis Minor

Answer 5

Innervation:

• Medial pectoral n.

Insertion:

• Coracoid Process of Scapula

Action:

• Protracts and depresses scapula

Blood Supply:

• Thoracoacromial a.

Question 6

Serratus Anterior

Answer 6

Innervation:

• Long thoracic n.

Insertion:

• Medial border of scapula

Action:

• Protracts and depresses scapula

Blood Supply:

• Lateral thoracic a.

Question 7

What is a winged scapula?

Answer 7

• Clincal condition that arises from paralyzed serratus anterior
  
  • Usually a result of clipping the long thoracic nerve during a radial mastectomy
  • Back mm. working unopposed to retract and elevate scapula

Question 8

Intercostal Spaces

Answer 8

• Space between two ribs
  
  • 11 spaces on one side of the body

Question 9

External Intercostal Muscles

Answer 9

• Fibers directed inferiomedially (“hands in pockets”)
  
  • Posterior rib to beginning of costal cartilage
  • Anterior Intercostal Membrane: aponeurosis of external intercostals from costal cartilage to sternum

Question 10

Internal Intercostal Muscles

Answer 10

• Fibers run inferolaterally (“Hands on boobs”)
  
  • From sternum to angles of rib
  • Posterior Intercostal Membrane: aponeurosis of internal intercostal mm. from angles of rib to vertebrae

Question 11

Innermost Intercostal Muscles

Answer 11

• Deep to internal intercostals
  
  • ​Fibers run in same direction as internal intercostals
  • Neurovascular bundle runs between
• Lateral sides of the thoracic wall

Question 12

Contents of Intercostal Space

Answer 12

• From superior to inferior (VAN):
  
  • Vein
  • Artery
  • Nerve
• Main vessel and nerve branches run in costal groove (inferior part of rib)
  
  • Collateraly branches run supeior to rib
• To remove fluid from thoracic cavity, needle should be inserted SUPERIOR to rib (collaterals not as important)

Question 13

Bony Architecture of Sternum

Answer 13

3 Specific Parts:

• Manubrium
• Body
• Xiphoid Process (often cartilaginous until 40s)

Sternal Angle

• Junction between manubrium and body
• Location of costal cartilages of 2nd ribs

Location of sternal puncture (bone marrow harvest)

Question 14

Define Axilla and Borders

Answer 14

Pyramidal space at junction of arm and thorax

Borders:

• Apex: clavicle, scapula, 1st rib
• Medial: thoracic cage, serratus anterior
• Lateral: intertubercular groove of humerus and nearby muscles
• Base: skin and fascia

Question 15

Anterior Axillary Fold

Answer 15

Formed by pectoralis major

Question 16

Posterior Axillary Fold

Answer 16

Formed by latissimus dorsi and teres major

Question 17

Contents of Axilla Neurovascular Bundle

Answer 17

• Axillary Artery
• Axillary Vein
• Brachial Plexus

All covered by axillary sheath

Question 18

Axillary Artery Major Divisions

Answer 18

• Begins at lateral border of 1st rib (continuous with subclavian a.)
• Becomes brachial a. at inferior border of teres major

Divided Into 3 Parts:

1. Proximal to Pectoralis Minor:
   
   • Highest thoracic a. (supreme/superior)
2. Deep to Pectoralis Minor:
   
   • Thoracoacromial a.
   • Lateral thoracic a.
3. Distal to Pectoralis Minor
   
   • Subscapular a.
     
     • ​thoracodorsal a.
     • circumflex scapular a.
       
       • ​anastomoses with suprascapular a. and dorsal scapular a. (from subclavian a.)
   • Anterior humeral circumflex a.
   • Posterior humeral circumflex a.

Question 19

Axillary Lymph Nodes

Answer 19

• Superficial Lymphatics: follow superficial veins and drain into deep lymphatics:
  
  • ​Subscapular: drains posterior thoracic wall/scapular region
  • Pectoral: drains anterior thoracic wall/breast
  • Lateral: drains upper limb

Central: receives lymph from above three

Apical: receives lymph from central lymphatics

Question 20

Prefixed Plexus

Answer 20

• C4-C8

Question 21

Postfixed Plexus

Answer 21

• C6-T2

Question 22

Roots of Brachial Plexus

Answer 22

• Anterior rami of C5-T1
• Found between anterior and middle scalenes