The connective tissue skeleton in the mammalian kidney and its innervation

A special reticular basket-like system of connective tissue strips (called connective tissue skeleton – CTS) was found between the cortex and medulla in the kidney of various mammals. It enlarges the wall of the renal calyx (or pelvis) into the parenchyma. The main component of this system is collagen. A small amount of smooth muscle cells was found in one part of CTS strips situated around the papilla (the levator fornicis muscle). A dense monoaminergic and scanty cholinergic innervation was found in the whole system of the CTS. The functional importance of this system is discussed: (i) a tightly linked connection between the urine-discharging system and the kidney, (ii) ‘milking’ and similar effects in the papilla as well as perception of intrapelvic and intrarenal pressure, (iii) penetration of infection into the kidney and (iv) liberation of the monoaminergic transmitter.