Capillaries are everywhere. It's the end point of the circulatory system everywhere, so there are beds of capillaries in basically any living tissue.

Probably the most well-known tissue with poor/limited blood supply is tendons/ligaments - these are connective tissues with a lot of intracellular matrix made up of collagen, and blood supply to these tissues is poor the further you get from the source blood vessel as there is often very little collateral circulation (what it's called when an area has multiple arteries that feed the capillary beds).

Capillaries are very small. We are talking of a scale where red blood cells might only fit through single file. At this microscale, diffusion/osmosis are what predominantly facilitates the movement of useful stuff out of the blood and into the extracellular fluid/cells, and waste back into the blood vessels to be taken away.

To add to the other answers. The process of oxygenation of the cells from the capillaries is called diffusion. Basically the capillary wall is thin enough, that it is leaking Oxygen molecules to the surrounding tissues. The rate of oxygenation depends on partial pressure of oxygen and carbon dioxide (and some other factors) in the surrounding tissues, but usually you can't diffuse farther then a few mm's in a living organism.

Diffusion is mostly used by insects as the main oxygenation process since they are small enough to just have some air filled pipes (tracheas) inside their bodies where the oxygen is directly absorbed from the air.

[removed]