both visceral and parietal membranes are part of
Serous membrane In anatomy, serous membrane (or serosa) is a smooth tissue membrane consisting of two layers of mesothelium, which secrete serous fluid. The inner layer that covers organs (viscera) in body cavities is called the visceral membrane. A second layer of epithelial cells of the serous membrane, called the parietal layer, lines the body wall. Between the two layers is a potential space, mostly empty except for a few milliliters of lubricating serous fluid that is secreted by the two serous membranes.[1]
Membrane models Evert Gorter and FranÃ§ois Grendel (Dutch physiologists) approached the discovery of our present model of the plasma membrane structure as a lipid bi-layer. They simply hypothesized that if the plasma membrane is a bi-layer, then the surface area of the mono-layer of lipids measured would be double the surface area of the plasma membrane. To examine their hypothesis, they performed an experiment in which they extracted lipids from a known number of red blood cells (erythrocytes) of different mammalian sources, such as humans, goats, sheep, etc. and then spreading the lipids as a mono-layer in a Langmuir-Blodgett trough. They measured the total surface area of the plasma membrane of red blood cells, and using Langmuir's method, they measured the area of the mono-layer of lipids. In comparing the two, they calculated an estimated ratio of 2:1 Mono-layer of lipids:Plasma membrane. This supported their hypothesis, which led to the conclusion that cell membranes are composed of two apposing molecular layers.[1] The two scientists proposed a structure for this bi-layer, with the polar hydrophilic heads facing outwards towards the aqueous environment and the hydrophobic tails facing inwards away from the aqueous surroundings on both sides of the membrane. Although they arrived at the right conclusions, some of the experimental data were incorrect such as the miscalculation of the area and pressure of the lipid mono-layer and the incompleteness of lipid extraction. They also failed to describe membrane function, and had false assumptions such as that of plasma membranes consisting of mostly lipids. However, on the whole, this envisioning of the lipid bi-layer structure became the basic underlying assumption for each successive refinement in modern understanding of membrane function.[2]