L4 The Thoracic Wall

Question 1

Name the structures

Answer 1

1. Functions
   
   • Protection (Lungs, heart, …)
   • Support and structure
2. Borders
   
   • Sternum (anterior)
   • Thoracic spine (T1-T12)
   • Ribs (I-XII)
   • Superior thoracic aperture (Thoracic inlet)
     
     • Top of sternum, T1 and Rib I
   • Inferior thoracic aperture (Thoracic outlet)
     
     • Infrasternal angle (Inferior – sternum)

Question 2

What are the three types of ribs?

Answer 2

• True ribs (I-VII)
  
  • Direct insertion onto sternum via costal cartilage
• False ribs (VIII-X)
  
  • Indirect insertion onto sternum via costal margin
  • Costal margin merges with costal cartilage of Rib VII
  • Infrasternal angle
• Floating ribs (XI-XII)
  
  • No anterior attachment (only posterior onto thoracic vertebrae)

Question 3

What are the typical features on the rib?

Answer 3

• Head of the rib (posterior)
  
  • Crest
  • Neck
  • Tubercle (most posterior)
    
    • Articulates with vertebral column
• Costal angle and body
  
  • Costal groove (neurovascular supply)
• Costal cartilage (anterior)
• 3 articular surfaces

1. Costal cartilage (ant.)
2. Head (post.)
3. Tubercle (post.)

Question 4

What are the facets of the vertebra that articulates with the rib?

Answer 4

1. Demi facets (superior, inferior)
   
   • On the body
2. Costal facets
   
   • On the transverse processes

Question 5

What are the joints connecting the rib and the vertebra?

Answer 5

1. Costovertebral joint
   
   • Two separate synovial joints (movement during respiration)
     
     • Plane/Gliding
   • Head of the rib (costo-) – Body of the vertebral bone – Own level AND vertebra above
   • Two demi facets – Two vertebral bone
   • Ie. Rib IV – T4 and T3
2. Costotransverse joint
   
   • Tubercle of the rib (costo-) – Costal facet on transverse process of thoracic vertebra at own level

Question 6

What are the different types of ribs?

Answer 6

1. True ribs (I-VII)
   
   • Direct insertion onto sternum via costal cartilage
2. False ribs (VIII-X)
   
   • Indirect insertion onto sternum via costal margin
   • Costal margin merges with costal cartilage of Rib VII
   • Infrasternal angle
3. Floating ribs (XI-XII)
   
   • No anterior attachment (only posterior onto thoracic vertebrae)

Question 7

What are the anterior joints of the thoracic cage?

Answer 7

1. Costochondral (rib-cartilage) – Solid synchondrosis joint (cartilage)
2. Sternocostal (sternum-rib) – Synovial, plane/gliding

Exception: 1^st rib – Synchondrosis

Should be called sterno-chondral

1. Interchondral (between-cartilage) – Between costal cartilages of false ribs

Question 8

Name the different parts of the sternum. Which vertebrae level correspond to the jugular notch and the xiphoid process?

Answer 8

Question 9

Identify the two superficial muscles of the thoracic wall

Answer 9

1^st layer

1. External intercostal muscles ( \ )
   
   • Anterior, inferior (hands in pockets)

2^nd layer

1. Internal intercostal membrane
2. Internal intercostal muscles ( / )
   
   • Anterior, superior (thumb in armpit palm interior)

1.

Question 10

What are the muscles composing the third layer of anterior thoracic wall muscles?

Answer 10

3^rd layer

1. Innermost intercostal muscles ( \ )
2. Transversus Thoracis
   
   1. “Christmas tree”
   2. Body of sternum / Xiphoid process – Ribs 2-6

Question 11

The top of the diaphragm corresponds with which rib? Which side is higher? Why?

Answer 11

1. Right and left dome
   
   • Central tendon
   • Right side higher than left
     
     • Liver under right dome
   • Rib 5

Question 12

Which spinal nerves innervate the diaphragm? Where do the neruovascular structures travel in regards to their corresponding rib?

Answer 12

“C3, C4, C5 – Keeps the diaphragm alive!”

1. Right and left Phrenic nerve
2. Innervated by two nerves (collateral)

“VAN”

1. Intercostal Vein, Artery and Nerve superiorly,
2. Between 2^nd and 3^rd layer (Internal and innermost intercostal muscles)
3. Protected by costal groove
4. In case of lung failure and fluid inside thoracic cavity, insert chest tube placement ABOVE rib
5. NAV located inferiorly for collateral

Question 13

Describe the arterial system of the thoracic wall

Answer 13

• Anterior

Aorta

• sublcavian artries
• internal thoracic arteries
• anterior/posterior intercostal arteries (linked via anastomosis)
• musculophrenic artery/superior epigastric artery

+ Subcostal arteries (rib 11/12), directly from the aorta

Question 14

Describe the venal system of the thoracic wall

Answer 14

Anterior

1. Superior epigastric + Musculophrenic
2. Internal thoracic veins
   
   1. Anterior intercostal veins
3. Brachiocephalic trunk
4. SVC

Posterior

1. Left posterior intercostal vein
2. Hemiazygos vein
3. Bridge
4. Azygos vein
   
   1. • Right posterior intercostal vein
5. SVC

Question 15

Nervous system of the thoracic wall?

Answer 15

1. Ventral rami
2. Intercostal nerve
3. Lateral cutaneous nerve
4. Anterior cutaneous nerve