What do cavities refer to in the anatomical context?

In anatomical terminology, cavities refer to spaces within the body that are filled with or contain organs, connecting structures, and fluids. This perspective includes various body cavities such as the thoracic cavity, which houses the lungs and heart, and the abdominal cavity, which contains digestive organs. These cavities serve vital functions, providing protection and support to the organs they contain and allowing for the necessary movement and interaction between different systems within the body.

While the other options mention air-filled spaces or skeletal and muscular systems, they do not accurately describe the comprehensive nature of anatomical cavities, which involve not just empty spaces but also important biological structures and fluids that are critical for bodily functions. The definition reinforces the idea that anatomical cavities are integral to understanding human biology and physiology.