Srotas comprehends all channels- big and small, perceptible and imperceptible- that compose the internal transport system of the body. There are several synonyms used for the term Srotas viz. Srotamsi, Siras, Dhamanis, Rasayanis,Panthanas etc. These channels acquire the shape and color of the Dhatu that they transport. http://www.ayurvedinstitute.com/intro3.htm It is claimed that there are 9 in men and 11 in women.