01 / Location & anatomical relationships
Toward the back of the upper abdomen, on either side of the spine.
02 / Structure & organization
The cortex and medulla contain nephrons and collecting pathways. Filtration begins at glomeruli, followed by selective tubular reabsorption and secretion. Urine drains through calyces into the renal pelvis and ureter.
03 / Function
They remove wastes and help balance water and salts in your body.
04 / Mechanism
Microscopic units called nephrons first filter small substances and water from blood. Their tubules then return much of what the body needs to the blood. The remaining fluid becomes urine. This careful sorting helps regulate water, salts and acid balance.
Working together: urinary system
Kidneys make urine, ureters carry it to the bladder, and the urethra provides the path out during urination.
Meet this body system →FOR DEEPER STUDY
Connect structure with function
Urine formation is not simple sieving. Kidneys regulate acid-base balance and blood pressure and contribute endocrine functions through renin, erythropoietin and vitamin D activation.
Check your understanding
Locate the kidneys in relation to its neighbors. Explain how the structural features described above support its function, then distinguish it from a nearby structure with a different role.
Keep learning
Further reading: NIDDK: Your Kidneys & How They Work.
Continue with OpenStax Anatomy and Physiology for system-level study. This atlas is educational and has not undergone independent medical peer review.