Within multicellular organisms, tissues are organized communities of cells that work together to carry out a specific function. The exact role of a tissue in an organism depends on what types of cells ...

Capillaries are very tiny blood vessels — so small that a single red blood cell can barely fit through them. They help to connect your arteries and veins in addition to facilitating the exchange of ...

Your autonomic nervous system (ANS) is the part of your central nervous system (CNS) that controls unconscious activities like breathing and digestion. This system is always working, whether or not ...

Your brain ventricles are four fluid-filled chambers that produce cerebrospinal fluid. This fluid helps nourish your brain and protect it from injury. It would be easy to argue that your brain is the ...