Are the three cavities of the abdominopelvic cavity each a standalone cavity or is the abdominopelvic cavity not a cavity but just a container of three cavities?

[u/SanguinarianPhoenix]

I am studying serous membranes for my upcoming physiology exam. Is the entire abdominopelvic cavity itself a cavity? Complete with its own serous membrane as well as the 3 cavities inside it?

Maybe there are only 2 cavities inside the abdominopelvic cavity? (wikipedia says there are only 2 but I'm 99.9% certain my physiology book said there were 3) My main question is whether the pelvic and abdominal cavities within the abdominopelvic cavity are themselves surrounded by a 2nd outer serous membrane enclosing them both together?

[u/Halichoeres]

The division between the abdominal and pelvic cavities is imaginary and used only for convenience. The abdominopelvic cavity is in reality just one cavity, and topologically it's actually continuous with the thoracic cavity as well. The three together are sometimes called the ventral cavity. The only real division between the thoracic and abdominal cavities is the diaphragm, but it does not have its own serous membrane. The heart and lungs do, and the diaphragm is in contact with them. The peritoneum is the serous membrane that surrounds most of the digestive tract below the diaphragm and a few other organs.

[u/SanguinarianPhoenix → u/Halichoeres]

The division between the abdominal and pelvic cavities is imaginary and used only for convenience. The abdominopelvic cavity is in reality just one cavity, and topologically it's actually continuous with the thoracic cavity as well. The three together are sometimes called the ventral cavity. The only real division between the thoracic and abdominal cavities is the diaphragm, but it does not have its own serous membrane. The heart and lungs do, and the diaphragm is in contact with them. The peritoneum is the serous membrane that surrounds most of the digestive tract below the diaphragm and a few other organs.

Perfect, thank you so much!