Lines of pleural reflection are lines along which the parietal pleura changes directions from one wall to another.
The sternal line of pleural reflection is the sharp line along which the costal pleura becomes the mediastinal pleura
The costal line of pleural reflection is the sharp line along which the costal pleura becomes the diaphragmatic pleura
The vertebral line of pleural reflection is a smooth reflection of the costal pleura onto the vertebrae posteriorly.
The lines of pleural reflection on the left side can be remembered as 4-6-8-10-12.
The line of pleural reflection on the left descends in the midline of the sternum to the 4th costal cartilage, where it deviates to the left
margin of the sternum at the 6th costal cartilage to accommodate the pericardium and the heart (cardiac notch).
This line then deviates to cross the 8th rib at the midclavicular line.
It crosses the 10th rib at the midaxillary line
It then crosses the 12th rib at approximately the neck.
On the right side, the line of pleural reflection descends at the midline of the sternum to the xiphoid process, and then deviates 8-10-12.
The lungs do not fully occupy the pleural cavities during expiration
There are peripheral areas where the diaphragmatic and costal pleura come in contact and these are called the costodiaphragmatic
recesses.
There are areas posterior to the sternum where the costal and mediastinal pleura come in contact with each other, and these are called
costomediastinal recesses.
The costomediastinal recess is larger on the left, because of the cardiac notch.
During expiration, the lower limit of the lungs is two costal spaces above the line of pleural reflection:
6-8-10: the sixth rib at the midclavicular line, the 8th rib at the midaxillary line, and the 10th rib at the neck.
Thus the costodiaphragmatic recess is approximately two costal spaces deep.Lungs
[Plate 193, Lungs: Medial Views]Organs of respiration
Light, soft and elastic
The right lung is larger than the left and has three lobes:
Superior or upper
Middle
Inferior or lower
The left lung has two lobes
Superior or upper
Inferior or lower