文档介绍：Pleural Effusion
The pleural space is not really a space but rather a potential space between the lung and chest wall.
It is a crucial feature of the breathing apparatus since pleurae serves as a coupling system between the lung and chest wall.
There is normally a very thin layer of fluid (from 2 to 10 um thick) between the two pleural surfaces, the parietal pleura and visceral pleura. The pleural space and the fluid within it are not under static conditions.
During each respiratory cycle the pleural pressures and the geometry of the pleural space fluctuate widely. Fluid constantly enters and leaves the pleural space.
Introduction
The serous membrane covering the lung parenchyma is called the visceral pleura. The remainder of the lining of the pleural cavity is designated the parietal pleura.
The parietal pleura receives its blood supply from the systemic capillaries. The visceral pleura is supplied predominantly by branches of the bronchial artery in humans.
The lymphatic vessels in the parietal pleura are in munication with the pleural space by means of stomas. These stomas are the only route through which cells and large particles can leave the pleural space.
Although there are abundant lymphatics in the visceral pleura, these lymphatics do not appear to participate in the removal of particulate matter from the pleural space.
Anatomy Of the Pleural Space
Figure 1. Anatomy of the pleural space SC: Systemic capillaries PC: Pulmonary capillaries
The passage of protein-free liquid across the pleural membranes is dependent on the hydrostatic and oncotic pressures across them.
When the capillaries in the parietal pleura are considered, it can be seen that hydrostatic pressure favoring the movement of fluid from these capillaries to the pleural space is the systemic capillary pressure (30cm H2O) minus the negative pleural pressure (-5cm H2O) or 35cm H2O.
Opposing this is the oncotic pressure in the blood (34cm H2O) minus the oncotic pressure in the p