What does the term 'body cavities' describe in anatomy?

The term 'body cavities' refers to hollow spaces within the body that house and protect organs. These cavities provide a framework that allows organs to function effectively while also enabling movement and expansion. Key examples of body cavities include the thoracic cavity, which contains the heart and lungs, and the abdominal cavity, which houses digestive organs. By offering a supportive environment, body cavities are vital for maintaining homeostasis and allowing for efficient physiological processes. The other choices do not appropriately define body cavities; regions for muscle attachment pertain to areas where muscles connect to bones, parts of the nervous system refer to components related to nerve function, and fluid-filled sacs generally describe structures like bursae or cysts, which are distinct from the concept of body cavities.