It is difficult to define the spaces, since there is great interplay between them. However, we can say that the epithelium bounding the spaces inside and outside the body.

Thus, through the skin or mucous membrane, a particle would be moving from the external environment to the internal environment, or vice versa.

Bacteria are often on our surfaces. They're on the epithelia. On the skin. On mucous membranes.

Bacteria form in these areas, colonies - biofilms.

Occasionally, a bacterium can cross the epithelial barrier and reach our internal environment - BT. From there you can even spread (spread) - metastatic dissemination.

This results in inflammatory immune response. Not even disregarding the epithelial surface has a lot to answer immuninflamatory, but secondary to passage of antigens or phagocytosis of bacteria by antigen presenting cells.

Following this logic, we could identify the light of the gastrointestinal tract, and URINARY TRACT, for example, as a means external to the body.

Thus, bacteria in the gut would not be in but outside the body.
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An interesting situation is occurring in true cysts, in which the material inside the cyst is enclosed, separated from the interstitium. There is a demarcation of the epithelium of the cyst. IE, the cyst fluid is compatible with a means external to the body.
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Now, the rationale for expanding the cellular level. We can check the status of mitochondria.
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Were they inside or outside the cell?
;-)