Schematic diagram of the concept of membrane anatomy. a Diagram of a coronal cross section through the anatomical structure of the urinary system and the ureteric sheath (left kidney). 1, Renal arteries; 2, aorta; 3, vena cava; 4, ovarian/testicular arteries; 5, common iliac arteries; 6, internal iliac artery; 7, perirenal fat; 8, pararenal fat; 9, UPJ; 10, renal hilar fat; 11, ureter; 12, ureteral feeding vessel; 13, ureteric sheath. b Diagram of an axial cross section of the embryonic fascia or fusion fascia that surrounds and separates the ureter. Transverse sections are indicated by an arrow in a. 1, descending colon; 2, prerenal fusion fascia; 3, parietal peritoneum; 4, transversalis fascia; 5, posterior renal fascia; 6, ureter; 7, ureteric sheath; 8, psoas; 9, quadratus lumborum. UPJ, ureteropelvic junction.