In the Ox and pig, numerous renal pyramids are present with the formation of minor and major calyces. In the horse, sheep and dog the apices of the pyramids do not appear separate and the inner part of medulla forms the renal crest (results of fusion of papillae in the embryo), which shows numerous openings the area cribrosa.
The renal crest projects into the renal pelvis the dilated origin ureter. No minor and major calyces are formed. In the cat the cells in the proximal convoluted tubules contain many fat droplets and a similar condition is also terminal portions of the tubule in the dog.
The excretory passages are renal calyces, pelvis, ureter, urinary bladder and urethra.
From the renal papillae urine passes into the renal pelvis of the renal pelvis of the kidney, hence it flows through the ureter into the urinary bladder and leaves the body by way of urethra.
