Kidney
This is a low power view of a cross section through the kidney. The kidney is composed of an outer cortex and inner medulla. Note the inner medullary tissue surrounded by the outer cortical tissue. The tissue type of kidney is simple cuboidal epithelium and the cell type is cuboidal. The epithelium of the kidney aids in covering and secretion.

Proximal Convoluted Tubule
The proximal convoluted tubule is the site where majority (65%) of ions and water in the urinary space is reabsorbed back into the body. The cells of the proximal convoluted tubule have a deeply stained, eosinophilic cytoplasm. The cells are large so that in cross section not every nucleus will be visible, making it appear that the proximal convoluted tubule has fewer nuclei than other tubules. The cells also have an apical brush border to increase their surface area.

Distal Convoluted Tubule
The cells of the distal convoluted tubule are smaller and more lightly stained than those of the proximal convoluted tubule. Consequently, more nuclei are apparent in a cross section of distal convoluted tubule compared to proximal convoluted tubule. Distal convoluted tubules also lack a brush border on their apical surface. Note that in any given section of the kidney cortex, much less space is occupied by distal convoluted tubules as compared to proximal convoluted tubules. This is simply because the distal convoluted tubule is shorter and less convoluted

Collecting Ducts
The terminal portion of the distal tubule empties through collecting tubules into a straight collecting duct in the medullary ray. Collecting ducts can be differentiated from other tubules by the prominent lateral borders of the epithelial cells. The collecting duct system is under the control of antidiuretic hormone (ADH). When ADH is present, the collecting duct becomes permeable to water. The high osmotic pressure in the medulla then draws out water from the renal tubule.