Mammals A. A pair of kidneys, located in the lower abdomen, filter a variety of substances from the blood. The kidneys regulate the volume and solute concentrations of extracellular fluid. B. Kidney Structure 1. The outer coat of connective tissue is the renal capsule. Nephrons filter and retain water and solutes, leaving a concentrated urine to be collected in the central renal pelvis.
Kidney stones are deposits of uric acid that lodge in the ureters or the urethra.
C. Nephron Structure 1. Filtration occurs in the glomerulus-a ball of capillaries nestled in the Bowman's capsule. The capillaries exit the glomerulus, converge, then branch again around the nephron tubules where they participate in reclaiming water and essential solutes. Urine Formation A. Urine-Forming Processes 1. Blood cells, proteins, and other large solutes cannot pass the capillary wall into the capsule.