Fibrous capsule

The fibrous capsule of the kidney is a thin, tough layer of dense connective tissue that envelops the external surface of the kidney.

This capsule serves as a protective barrier, maintaining the structural integrity of the organ and providing resistance against trauma and infection. It is composed primarily of collagen fibers and contains a population of mesenchymal stromal cells that are functionally distinct from those found in the renal cortex, contributing to the three-dimensional organization of the kidney and playing a role in homeostatic processes such as pressure natriuresis.