Pleural cavity in the context of "Respiratory disease"

In pharmacokinetics, a compartment is a defined volume of body fluids, typically of the human body, but also those of other animals with multiple organ systems. The meaning in this area of study is different from the concept of anatomic compartments, which are bounded by fasciae, the sheath of fibrous tissue that enclose mammalian organs. Instead, the concept focuses on broad types of fluidic systems. This analysis is used in attempts to mathematically describe distribution of small molecules throughout organisms with multiple compartments. Various multi-compartment models can be used in the areas of pharmacokinetics and pharmacology, in the support of efforts in drug discovery, and in environmental science.

In humans and related organisms, there are five major body compartments: the blood plasma, interstitial fluids, fat tissues, intracellular fluids, and transcellular fluids, the latter of which includes fluids in the pleural (peritoneal) cavity. The relative percents of body mass of these are included in the pie chart above.

The mesothelium is a membrane composed of simple squamous epithelial cells of mesodermal origin, which forms the lining of several body cavities: the pleura (pleural cavity around the lungs), peritoneum (abdominopelvic cavity including the mesentery, greater and lesser omentum, falciform ligament and the perimetrium) and pericardium (around the heart).

Mesothelial tissue also surrounds the male testis (as the tunica vaginalis) and occasionally the spermatic cord (in a patent processus vaginalis). Mesothelium that covers the internal organs is called visceral mesothelium, while one that covers the surrounding body walls is called the parietal mesothelium. The mesothelium that secretes serous fluid as a main function is also known as a serosa.

In anatomy, a potential space is a space between two adjacent structures that are normally pressed together (directly apposed). Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realization being dynamic according to physiologic or pathophysiologic events). In other words, they are like an empty plastic bag that has not been opened (two walls collapsed against each other; no interior volume until opened) or a balloon that has not been inflated. The pleural space, between the visceral and parietal pleura of the lung, is a potential space. Though it only contains a small amount of fluid normally, it can sometimes accumulate fluid or air that widens the space. The pericardial space is another potential space that may fill with fluid (effusion) in certain disease states (e.g. pericarditis; a large pericardial effusion may result in cardiac tamponade).