Kidneys – What They Do, Their Structure, and Why They Are Important for Your Blood Pressure

You've heard about the kidneys many times, but have you ever considered that a pair of bean-shaped organs could be very important to your health? Kidneys perform many vital functions in your body: elimination of wastes from your body, balance of electrolytes and also control of your blood pressure.

What Is the Structure of the Kidneys?

The kidneys are located in the back of the abdominal cavity, one on the left and one on the right side of your spine. The left one is usually larger than the right, as the right kidney often shares space with the liver. Kidneys are covered with two thick layers of fat for protection and one thin layer of microfibers that create a renal capsule or covering. On the top of each kidney sits an adrenal gland that helps connect the kidneys to other organs.

Kidneys contain multiple lobes that are shaped in the form of small pyramids. Consequently, each lobe consists of its own renal cortex (outer section) and medulla (inner section). The space between these elements is filled with nephrons (smallest single unit of the kidneys) that are responsible for the creation of urine. The urine runs through thin tubes called the ureters to reach the bladder, while blood passes through the renal arteries and drains back to the renal veins.

What Are the Functions of the Kidneys?

Generally speaking, the kidneys are responsible for the maintenance of homeostasis in your body. Management of various processes that keep your entire body safe and sound depends heavily upon the following kidney functions:

1. Waste excretion
2. Acquisition and processing of nutrients
   
3.  Control of pH levels
   
4. Maintenance of osmolality
   
5. Production of calcitriol (activated vitamin D) important to healthy bones, and erythropoietin (a hormone) that helps make red blood cells
   
6. Balance of blood pressure

The latter function is particularly critical. Kidneys regulate blood pressure by changing the fluid levels outside of the cells that is defined as extracellular fluid. Changes of the extracellular fluid level affects production of angiotensin II, a substance that constricts the blood vessels. The kidneys also aid in the absorption of salt that results in extracellular fluid increase and therefore higher blood pressure. That is why any substances that affect blood pressure are usually harmful to kidney function. For example, nicotine/substance abuse, junk food and excessive alcohol use are the most typical causes of kidney function disruption.

Photo Credits: Robina Weermeijer