Basics

• Kidneys are a pair of organs located in the abdominal cavity whose primary function is the regulation of the urinary system. Shaped like beans that weigh about 150 grams on average, the organ's location is symmetrical, meaning the kidneys appear facing each other on the opposite sides of the abdominal cavity, partially protected by the ribcage. The left kidney is usually a little bigger than the right, which is so the liver may be housed comfortably.
  
  

Exterior Anatomy

• Shaped like a thick bean, the kidney has two distinct surfaces. The concave surface, where it bends inward, is called the renal hilum. The renal hilum provides the entrance and exit points to the kidney; the renal artery enters while the renal vein and ureter leave. The convex surface, which essentially encompasses the inner workings of the kidney, is called the renal capsule and is a thick, tough, fibrous tissue that itself is layered with various fats. The top of the capsule is known as the superior, the bottom is known as the inferior.
  
  

Interior Anatomy

• The usable parts of a kidney can be separated into two major factions. The renal cortex is the outer portion of the kidney, and it contains blood vessels and cortical collecting ducts. The deeper portion of the kidney, where most of the functions take place, is the renal medulla. Inside are eight to 18 structures known as renal lobes that surround striped structures known as renal pyramids. All of the pyramids point toward the center of kidney's interior, with their tips, known as papilla, empty urine through the major and minor calyces and eventually into the renal pelvis, which acts as a funnel for urine to the ureter.
  
  

Primary Function

• Urine production is the chief responsibility of the kidney. Blood is delivered via the renal arteries and is filtered through the kidneys, where harmful waste products are removed, notably ammonia and urea. The urine is concentrated, and what results is a solution that is carried to and stored within the bladder prior to excretion.
  
  

Secondary Functions

• Urine production is not the kidney's only function; it's also vital in maintaining homeostasis within the body through the regulation of electrolytes, pH balance and blood pressure. They also reabsorb excess glucose and amino acids for use later. Last, kidneys also play an important role in the production of vitamin D, eyrthroprotein and rennin.