Kidney - Excretory Portion

Collecting duct: 

As urine leaves the distal tubule, it enters the excretory portion of the uriniferous tubule, the collecting duct. 
The collecting ducts begin in the cortex as arched connecting tubules. (Some texts refer to these as the terminal part or "connecting segment" of the distal convoluted tubule, but histologically and embryologically they are part of the collecting duct.) 
These connecting tubules straighten out and join other connecting tubules at the medullary ray to form a collecting duct. 
The collecting ducts penetrate deep into the medulla.

The histological appearance of the collecting ducts is similar to the distal tubule: pale staining, low cuboidal cells. 
The nuclei are centrally located. In contrast to the distal tubule, though, the collecting duct has an extra cell type, the intercalated cell. 
This cell type is involved in acid-base balance, and it stains more darkly than the principal cells of the collecting duct. This micrograph of a medullary ray shows some differences:

Both the distal tubule and collecting duct are less acidophilic than the proximal tubule, but the nuclei of the collecting duct are more centrally located than the apically-bulging nuclei of the distal tubule. Intercalated cells are distinguishable in some normal preparations; however preparations such as this immunostain for ANF are often necessary to identify these cells.

Papillary Ducts: 

Also called the ducts of Bellini, these ducts are formed in the inner medulla where several collecting ducts merge. 

This cross-section shows that the cells of the papillary ducts are similar to those of the collecting duct, but somewhat taller. 

At the apex of a medullary pyramid (a renal papilla), several papillary ducts will open into a minor calyx.

Minor calyces: 

There are 7-10 minor calyces per kidney. These excretory passages are lined with transitional epithelium, as is evident in this micrograph.

Major calyces: 

Two or three minor calyces then merge as they move toward the hilum, forming a major calyx. 
There are 3-5 major calyces per kidney. 
These, too, are lined by transitional epithelium.

Renal pelvis: 

The system of minor calyces, major calyces, and the funnel-like passage leading to the ureter make up the renal pelvis. 
Covered by transitional epithelium, the renal pelvis is histologically almost identical to the ureter. 
The renal pelvis can be thought of as the dilated proximal end of the ureter.