Kidneys are two bean-shaped organs in the renal system. They help the body to pass waste as urine. They also help filter blood before sending it back to the heart . Nephrons are the most important part of each kidney. They take in blood, metabolize nutrients, and help pass out waste products from filtered blood. Each kidney has about 1 million nephrons. Each has its own internal set of structures.
The kidneys perform many crucial functions, including:
- maintaining overall fluid balance
- regulating and filtering minerals from blood
- filtering waste materials from food, medications, and toxic substances
- creating hormones that help produce red blood cells, promote bone health, and regulate blood pressure
After blood enters a nephron, it goes into the renal corpuscle, also called a Malpighian body. The renal corpuscle contains two additional structures: glomerulus which is a cluster of capillaries that absorb protein from blood traveling through the renal corpuscle & Bowman capsule where remaining fluid, called capsular urine, passes through into the renal tubules.
The renal tubules are a series of tubes that begin after the Bowman capsule and end at collecting ducts.Each tubule has several parts:
- Proximal convoluted tubule. This section absorbs water, sodium, and glucose back into the blood.
- Loop of Henle. This section further absorbs potassium, chloride, and sodium into the blood.
- Distal convoluted tubule. This section absorbs more sodium into the blood and takes in potassium and acid.
By the time fluid reaches the end of the tubule, it’s diluted and filled with urea. Urea is byproduct of protein metabolism that’s released in urine.The renal cortex is the outer part of the kidney. It contains the glomerulus and convoluted tubules.The renal cortex is surrounded on its outer edges by the renal capsule, a layer of fatty tissue. Together, the renal cortex and capsule house and protect the inner structures of the kidney.There’s a collecting duct at the end of each nephron in the renal medulla. This is where filtered fluids exit the nephrons.
Once in the collecting duct, the fluid moves on to its final stops in the renal pelvis.The renal pelvis is a funnel-shaped space in the innermost part of the kidney. It functions as a pathway for fluid on its way to the bladder .The hilum is a small opening located on the inner edge of the kidney, where it curves inward to create its distinct beanlike shape. The renal pelvis passes through it, as well as the:
- Renal artery. This brings oxygenated blood from the heart to the kidney for filtration.
- Renal vein. This carries filtered blood from the kidneys back to the heart.
The ureter is a tube of muscle that pushes urine into the bladder, where it collects and exits the body.High blood pressure is a known risk factor for chronic kidney disease. Regular exercise, even for just 20 minutes a day, can help reduce blood pressure.