Lecture Tuesday August 21: Anatomy of the Thorax

Sternal angle (angle of Louis) is an important landmark.
- attachment of the second rib
Intercostal spaces are numbered according to the rib above (ie 2nd intercostal space is below the second rib)
Auscultation of the heart valves. Here is a good image to know.




Intercostal nerve, artery, vein of a given intercostal space run below the rib above. Small accessory branches run along the top of the rib below.
The visceral pleura of the lungs and parietal pleura of the thorax are attached to one another by a thin film of pleural fluid. When the diaphragm flattens and thoracic wall expands the visceral pleura (attached to the parenchyma of the lung) is pulled outward with the parietal pleura and the lung expands.
Air into pleural space (from either through the thoracic wall or through the lung itself) causes lung to collapse = pneumothorax
Blood into pleural space = Hemothorax
Excess fluid in the pleural space = hydrothorax
Parietal pleura highly innervated with stretch and pain receptors. Only stretch receptors (no pain) associated with the innervation of the visceral pleura.
Understand the concept of lung segments. DO NOT memorize the individual lung segments!
Phrenic nerve (C3, C4, C5): motor to the diaphragm and sensory from the parietal pleura of the diaphragm and pericardial sac
Referred pain from the heart-
Visceral sensory fibers from the heart, stimulated by ischemia to the heart muscle, travel back to the spinal cord along the pathway of the sympathetics to the heart (T1-T5. Review autonomic nervous system handout). Pain is partially sensed in the T1-T5 dermatomes because the brain cannot distinguish if the pain is coming from the skin or from the heart.
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