The thesis contains three research papers studying the behavior of institutional players, such as corporations, investors and dealers, and their effects on the financial market structure. Chapter 1 studies how firms function like banks by issuing entrusted loans to other firms. I show that in a model with entrepreneurial moral hazard and bank moral hazard, entrusted loans arise endogenously when the banking sector is highly compétitive. Entrusted loans involve a lending chain in which high-capitalized firms channel bank loans into médium-capitalized firms. Moreover, I provide welfare implications that participating in entrusted loans can improve the total welfare of banks and firms, but destroy firms' value and harms real efficiency. Chapte...