KIDNEY
Kidneys filter blood and produce urine. Unlike the human kidney which is multilobed (10 to 12 lobes) separated by renal columns (cortical tissue that extends alongside the margin of pyramids in the medulla), the monkey kidney is unilobular.

Cortex – darker outer region.
– Renal Corpuscles – spherical structures that form ultrafiltrate from blood.
– Cortical Labyrinths – regions between renal corpuscles and medullary rays that contain proximal and distal convoluted tubules.
– Medullary Rays – projections of tubules between the cortex and medulla that contains straight tubules and collecting ducts.

Medulla – lighter inner region.
– Pyramids – equal to the number of lobes and form conical structures whose base faces the cortex and their apex form the renal papilla. Urine passes through the minor calyx which is cup-shaped structure that is an extension of the renal pelvis.
– Renal Pelvis – funnel-shaped origin of the ureter.

Arcuate Arteries- branches of interlobular arteries that form an arcade over the pyramids at the junction of the cortex and medulla.

Hilum – concave surface with a deep fissure in which vessels enter and exit the kidney.

URETER
Ureter transport urine from the kidney to the bladder. It is lined with an epithelium that is impermeable to water and ions. Peristaltic contraction of the smooth muscle moves urine from the kidney to the bladder.

Cross-Section – composed of four concentric layers:

Transitional Epithelium (Urothelium) – consists of two to three cell layers in the upper ureter with up to ten cell layers near the bladder
– Umbrella Cells – upper layer of cells that change shape depending on the distention of the ureter (relaxed)

Lamina Propria – thick layer of dense irregular connective tissue rich in collagen and elastic fibers

Muscularis Externa – irregular arrangement of smooth muscle in two layers (inner longitudinal and outer circular) in the upper ureter or three layers (inner longitudinal, middle circular and outer longitudinal) near the bladder

Adventitia – loose connective tissue with blood vessels, nerves and adipose cells

BLADDER
The urinary bladder is a muscular sac that stores urine, allowing urination to be infrequent and voluntary. It is lined by transitional epithelium (urothelium), and has a thick layer of smooth muscle.

Bladder is an expandable vessel for the storage of urine. It is lined with an epithelium that is impermeable to water and ions.

Like the ureters, the bladder is composed of four concentric layers.

Transitional Epithelium (Urothelium) – consists of three to five cell layers.
– Umbrella Cells – the upper layer of cells that change shape depending on the distention of the bladder.

Lamina Propria – thick layer of dense irregular connective tissue rich in collagen and elastic fibers.

Muscularis Externa – irregular arranged smooth muscle that forms an inner longitudinal, middle circular and outer longitudinal layers.

Outer Layer of Connective Tissue – most of the bladder is covered externally by adventitia with parts of its superior surface covered by serosa of the peritoneum.
– Adventitia – loose connective tissue with blood vessels, nerves and adipose cells.
– Serosa – composed of a surface layer of mesothelium supported by loose irregular connective tissue.