What is the term for a membranous wall that divides two cavities?

The term "septum" refers specifically to a membranous or muscular wall that divides two cavities within the body, such as the heart or nasal passages. In anatomy, septa are critical as they serve to separate different functional areas, allowing for distinct functions within each compartment. For example, the septum in the heart separates the right and left sides, ensuring that oxygenated and deoxygenated blood do not mix.

While the term "partition" may also imply a dividing structure, it is generally used in a broader context and does not specifically denote a biological structure. "Barrier" typically refers to an obstruction that prevents passage or contact, which doesn't capture the anatomical significance of a septum. Lastly, "fascia" is a connective tissue that surrounds muscles, organs, and other tissues, but does not describe a dividing wall between cavities. Thus, the specificity and biological context of "septum" makes it the correct term for a membranous wall that divides two cavities.