How does blood reach literally every cell in the body? There can’t be capillaries between every single cell when capillaries are also made of cells…. can there?

Question

How does this work?

In: 4868

Answer 1

As other people have said, charged concentrations will attempt to balance themselves out passively, and can also be forcibly reversed using an active transport system (think powered toll booths) located on the surfaces of all cells. There are also physical connective junctions between cells, which all substances to pass from cell to cell that are too large to be transported through the cell membrane otherwise. In other words, the equivalent of tunnels. Between these two mechanisms (and a couple of others for larger molecules and biochemical products), almost any substance, be it an ion, atom, or chemical construct, can move between cells without effort.

However, it also needs to be noted, that many of these system either require energy input to work, ionic gradients to work, or transport molecules. In the case of oxygen transport, for example, a major player is what is the enzyme known as cytochrome C oxidase. If this enzyme is inhibited, cells – and thus organisms – can actually die no mater how effectively they can take in oxygen via physical respiration. The reason cyanide is a poison that kills so effectively is that it actually binds to cytochrome C oxidase, and permanently deactivates it. If enough of it’s cytochrome C oxidase is deactivated, a cell cannot complete the steps needed to create energy using oxygen, and a lack of energy will kill any and all cells in minutes.