Here's why:

* Blood is a fluid connective tissue that circulates throughout the body.

* It contains plasma, which is a liquid that carries dissolved nutrients, like glucose, amino acids, and vitamins.

* Blood also contains red blood cells, which are responsible for transporting oxygen to the cells.

* Nutrients are absorbed from the digestive system and enter the bloodstream.

* The blood then delivers these nutrients to all the cells in the body.

So, while other systems play a role in digestion and absorption, it's the blood that ultimately carries the vital nutrients to where they are needed.