Lungs and thoracic walls Flashcards
What is the composition of the thoracic walls?
- Posterior: 12 thoracic vertebrae
- Lateral: 12 ribs and 11 intercostal spaces and all of their contents
- Anterior: Sternum and costal cartilages
What are the contents of the intercostal spaces?
- External intercostal muscles (fibres running forwards and downwards) and becomes membranous sheath between costal cartilages
- Internal intercostal muscles (fibres running backwards and upwards) and become posterior intercostal membranes posteriorly
- Innermost intercostal muscles (fibres running backwards and upwards)
- Subcostalis (posterior, spanning multiple ribs and in the same plane as innermost)
- Transversus thoracis (Arises from posterior sternum, crosses 2 or more ribs and attaches to 3rd-6th costal cartilages)
- Intercostal neurovascular bundle
What are the contents of the intercostal neurovascular bundle (from superior to inferior)?
VAN:
- Intercostal Veins: Draining into the internal thoracic veins (anterior) and azygos/hemiazygos veins (posterior).
- Intercostal Arteries: Originating from the internal thoracic artery (anterior) and the descending aorta (posterior).
- Intercostal Nerves (arising from associated spinal levels separately).
Where is the intercostal neurovascular bundle?
Between internal and innermost intercostal muscles
What is the structure of a rib?
Posterior-anterior:
- Head
- Neck
- Tubercle
- Angle
- Costal groove (inferior)
- Body
- Shaft
What is significant about the structure of a rib?
The angle is the most vulnerable point on a rib.
What is the general structure of the chondrosternal joint?
- The ribs articulate with their costal cartilage via a primary cartilaginous joint.
- The costal cartilages usually articulate with the sternum via synovial joint (atypical as contains fibrocartilage).
What are the types of ribs in the thoracic wall?
- First 7 ribs are ‘true’ ribs as they articulate with the sternum individually.
- The last 5 ribs are false ribs:
1. Ribs 8-10 have costal cartilages fused with the one above (forming costal margin)
2. Ribs 11 and 12 don’t articulate with the sternum, so are floating ribs.
What is significant about rib 1, 11 and 12?
They articulate with their own vertebral bodies only, whereas other ribs articulate with their own vertebral bodies of the vertebrae above. The 11th and 12th rib are tethered to transverse processes of own vertebrae but don’t form joints.
What are the movements associated with the thoracic wall?
- Pump handle movement: Upper 7 ribs rotate about the vertebral joints superiorly, leading to anterior expansion of the thoracic cavity.
- Bucket handle movement: Ribs 7-10 lifted laterally by diaphragm, leading to lateral expansion of the thoracic cavity.
- Ribs 5-9 able to carry out combination of both types of movements.
What are the accessory inspiratory muscles?
- Sternocleidomastoid
- Pectoralis major
- Pectoralis minor
- Scalenes
- External intercostal muscles
What are the accessory expiratory muscles?
- Latissimus dorsi
- Anterior abdominal wall muscles
What is the structure of the pleura?
- The pleura consists of 2 layers:
1. Parietal pleura
2. Visceral pleura - Between the parietal pleura and the visceral pleura is the pleural cavity, containing small amount of serous fluid.
- The 2 layers are continuous with each other at the hila of the lungs.
What structures are lined by parietal pleura?
- Cervical part: Covers the apex of the lungs (beyond thoracic inlet)
- Costal part: Covers inside of thoracic wall
- Mediastinal part: Covers the fibrous pericardium
- Diaphragmatic part: Covers superior surface of diaphragm
What structures are lined by the visceral pleura?
External surface of the lungs