In Ayurveda , Srotas refers to the thirteen internal channels of circulation in the human body. The doshas of the body, Vata, pitta and kapha move from one part of the body to another via channels called srotamsi (pleural). The largest srotas (singular) or channel is the Maha Srotas or gastrointestinal tract (Maha – large or great). The smallest srotamsi can be found in single cells in the body that under the microscope reveal that they are porous. Through these porous channels or srotamsi oxygen and nutrients can be absorbed and waste products like carbon dioxide can be expelled. So the srotamsi or channels in the body act like paths or roadways transporting blood and sensory information, absorbing nutrients and expelling waste products from the body. Each srotas has a sroto mula (root), a sroto marga (passage) and sroto mukha (mouth or opening).