In this section we’ve outlined details about the kidney, including its location, functions, internal structure, and how they interact with complementary organs in your body. To learn about diseases that are treatable with transplant, please visit our "Kidney Diseases” section.
Location
We have two kidneys: the left and right kidney. The bean-shaped organs are approximately 11-14cm tall, 6cm wide, and 4cm thick: about the dimensions of a computer mouse. They are located within the abdominal cavity, resting against the back inner wall and behind most organs, including the liver, instestines, and colon. They are within the ribcage, positioned just above the lowest rib.
Functions
The kidneys’ main function is to remove toxins from our blood, which is why they receive 20% of the heart’s output. Secondary functions include regulating blood pressure, and balancing blood acidity level. The kidneys also secrete a variety of hormones, helping with the production of red blood cells, intestinal absorption of calcium, and several other functions.
Internal Structure
The renal artery brings blood into the kidney and delivers it to the renal cortex (located alongside the outer wall) for initial filtration from pollutants. Decontaminated blood returns to the heart through the renal vein, while the remaining product proceeds through the renal medulla for further filtration and reabsorption of useful substances. Once the filtration process is complete, the waste –urine– is deposited into the minor calyx, drains into the renal pelvis, and down the ureter. Both left and right ureters lead to the urinary bladder, which gives the sensation of needing to urinate once full.
Supplementary Organs
The descending aorta supplies blood from the heart down to the organs below it, including abdominal organs, and the legs. The kidneys get their blood from the aorta through the renal arteries. This blood is then returned to the renal veins, which flows into the inferior vena cava, then back to the heart. The toxic waste from the kidneys, known as urea, is deposited into the urinary bladder via the ureters. Once full, the bladder gives the sensation of needing to urinate, subsequently expelling its waste through the urethra.