Thoracic Wall 2

Question 1

What is the retromammary space?

Answer 1

✓ Layer of loose connective tissue between the deep layer of superficial fascia and the deep fascia
– Provides some degree of movement over underlying structures

Question 2

Where does the vascular supply of the breast come from?

Answer 2

Internal thoracic artery
(Mammary branches and Anterior intercostal arteries)

Axillary artery
(lateral thoracic artery and thoracic-acromial artery)

Question 3

Where does the vascular drainage of the breast come from?

Answer 3

Veins follow the arteries and drain mainly to axillary and internal thoracic veins

Question 4

How is lymph drainage of the breast organised?

Answer 4

in 5 sections; the areola and 4 quadrants around the areola.

Question 5

Describe lymph drainage of the breast

Answer 5

✓ Areola + Lateral quadrants →Axillary lymph nodes

✓ Medial quadrants →parasternal lymph nodes
→Opposite breast

✓ Inferior quadrants
→Inferior phrenic lymph nodes

Question 6

Describe the intercostal spaces

Answer 6

✓ 11 pairs of Intercostal Spaces,
✓ Each filled with 3 layers of muscles
and membranes

Question 7

What are the three muscles found in intercostal spaces?

Answer 7

External intercostal muscles
Internal intercostal muscles
Innermost intercostal muscles

Question 8

Describe the external intercostal muscles

Answer 8

✓ Extend from the inferior edge of the rib above, to superior edge of the rib below
✓ Anteriorly, muscle fibres are replaced by external intercostal membrane
✓ Raise ribs → inspiration, prevent indrawing during inspiration

Question 9

Describe the internal intercostal muscles

Answer 9

✓ Extend from the lateral edge of costal groove of the rib above, to superior edge of the rib below
✓ Posteriorly, muscle fibres are replaced by internal intercostal membrane
✓ Prevent indrawing during inspiration; Aids elastic recoil by moving ribs inferiorly in expiration

Question 10

Other than the intercostal muscles, what muscles can be found on the ribcage?

Answer 10

Transversus thoracis
✓ Lies posterior to sternum
✓ Internal aspect of ribs and costal cartilages 3 to 6, to sternum, xiphisternum and costal margin

Subcostalis
✓ Lies on posterior wall
✓ Lower ribs, internal surface, near angle down to inner surface of 2 to 3 ribs below

Question 11

Where does the spinal nerve pass through to enter the thoracic cavity?

Answer 11

✓Intervertebral foramen: between pedicle, articular processes; vertebral body and IV disc

Question 12

Why is it important to know about the location of the emergence of the spinal nerve

Answer 12

✓Spinal (intercostal) nerve may be at risk of compression by arthritis, fracture, disc prolapse
✓Osteoporotic fractures (collapse) of the vertebral body and facet joint arthritis may cause local and spinal (intercostal) nerve pain

Question 13

Describe the intercostal nerves

Answer 13

✓ Intercostal nerves, together with the intercostal vein and artery (the order is VAN) lie in the costal groove at the inferior edge of the rib, between the internal and innermost intercostal muscles

Question 14

Do the anterior rami of the thoracic spinal nerves form nerve plexus?

Answer 14

✓ Anterior rami of the thoracic spinal nerves do not form nerve plexus and maintain their segmental orientation and become intercostal nerves
– Except T1 and lateral cutaneous branch of T2 (Brachial plexus)

Question 15

Describe the pathway of the intercostal nerves

Answer 15

✓ First gives off lateral cutaneous branch
✓ Travels in the costal groove
✓ Becomes superficial parasternally, named anterior cutaneous branch

Question 16

What nerves other than the thoracic nerves supply the anterior thoracic wall?

Answer 16

Supraclavicular nerves (C3-4) descend over the clavicle as far as the 2nd costal cartilage

Question 17

What is unique about T1 dermatome compared to the rest of the thoracic nerves?

Answer 17

✓T1 has no cutaneous distribution over the anterior thoracic wall

• Joins the brachial plexus, supplying the medial arm and forearm
• (May be distributed only in a small region on the back)

Question 18

What thoracic nerve supplies both the thoracic wall and other regions in regards to its dermatome?

Answer 18

T2 gives a large lateral cutaneous branch (the Intercostobrachial nerve) that supplies thorax wall in axilla and upper, medial part of upper limb – (at risk in breast surgery)

Question 19

Summarise intercostal nerves

Answer 19

✓ Mixed spinal nerves (sensory and motor
✓ The ventral ramus of T1 joins the Brachial Plexus (inferior
trunk) to supply
– the small muscles of the hand
– the skin of the medial aspect of the arm and forearm – muscles of the 1st intercostal space
✓ Ventral rami of T2 – T11
– provide motor fibres to intercostal muscles, abdominal
muscles
– sensory supply to the skin and parietal pleura

Question 20

What are the two main arteries that supply the thoracic wall?

Answer 20

Thoracic aorta

Subclavian artery

Question 21

What are the branches of the subclavian artery that supply the thoracic wall?

Answer 21

✓ vertebral artery
✓ thyrocervical trunk
✓ costocervical trunk (to supreme intercostal)
✓ Internal thoracic artery

Question 22

What are the branches of the thoracic aorta that supply the thoracic wall?

Answer 22

✓ Parietal branches

– 3rd - 11th posterior intercostal arteries
– Subcostal artery (inferior to 12th rib, supply posterior abdominal wall)
– Superior phrenic artery (diaphragm)

Question 23

Describe the anterior intercostal arteries

Answer 23

– 2 per space in spaces 1-6
– 7th -10th Anterior intercostal arteries are branches of the musculophrenic artery
– 11th intercostal space and subcostal area have no anterior supply

Question 24

Describe the posterior intercostal arteries

Answer 24

✓ 1st-2nd posterior intercostal arteries (from supreme intercostal branch of costocervical trunk)
✓ 3rd-11th posterior intercostal arteries (from Thoracic aorta)
– 2 per space
✓ Anterior and posterior intercostals anastomose.
– This anastomosis may form a collateral circulation in Coarctation of the Aorta

Question 25

Describe venous drainage of the thoracic wall

Answer 25

✓ Anterior intercostal veins drain to the internal thoracic vein →brachiocephalic vein
✓ Posterior intercostal veins drain either to the brachiocephalic vein or to the superior vena cava via azygos system

Question 26

What the fuck is the azygos system?

Answer 26

Oh lord
so it’s a bunch of tubes that feed into a bigger tube that feeds into the big one, however it is asymmetrical

Basically:
POSTERIOR INTERCOSTAL VEINS
RIGHT (R)
1*
R brachiocephalic vein
2, 3, 4
R superior intercostal vein → Azygos
5 - 11
Ayzgos

LEFT (L)
1*
L brachiocephalic vein
2, 3, 4
L superior intercostal vein→ L Brachiocephalic vein
5 - 8
Accessory hemiazygos→ Azygos
9 - 11
Hemiazygos → Azygos

Question 27

Describe the function of the azygos system

Answer 27

✓ Drains the posterior wall of the thorax and part of the posterior abdominal wall
✓ Begins from lumbar and subcostal veins and/or direct branch of the inferior vena cava
✓ Passes behind the diaphragm, with the aorta and thoracic duct
✓ Ascends in the posterior mediastinum, passes posterior to the right lung hilum, arches and opens into the superior vena cava
− Connects superior and inferior vena cava

Question 28

what is the hemiazygos?

Answer 28

✓ =Inferior hemiazygos vein
✓ Has connections with the left renal vein
✓ Passes through or behind the left crus of the diaphragm
✓ Crosses to the right at approximately T9 and joins the azygos

Question 29

What is the accessory hemiazygos?

Answer 29

✓ =Superior hemiazygos
✓ Descends from 4th intercostal space, crosses to the right at approximately T8
✓ Can open into
• Azygos
• Hemiazygos 
• Both

Question 30

Describe the lymph drainage of the thoracic wall anteriorly?

Answer 30

Anteriorly
→parasternal nodes
– alongside internal thoracic (mammary) artery
→bronchomediastinal trunks

Question 31

Describe the lymph drainage of the thoracic wall posteriorly?

Answer 31

Posteriorly
→intercostal nodes
→thoracic duct (inferiorly) or bronchomediastinal trunks (superiorly)

Question 32

Describe common pathologies of rib fracture

Answer 32

✓ Fractures of the ribs are relatively common, and most frequently occur between ribs 3 and 10.

✓ Little can be done to assist the healing of broken ribs other than binding them tightly to limit movement.

✓ Can cause hemothorax, pneumothorax with or without pulmonary injury, splenic injury