Renal Medulla: Definition & Function

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  • 0:00 What Is the Renal Medulla?
  • 1:21 What Does the Renal…
  • 3:04 Lesson Summary
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Lesson Transcript
Instructor: Mary Ellen Ellis
The interior of your kidney is where all the action happens. In the renal medulla, your kidney gets to work filtering blood and balancing your body's fluids, a process that eventually leads to the release of urine. In this lesson, you'll learn about the different parts of the renal medulla and how they work.

What Is the Renal Medulla?

Did you ever wonder what the interior portion of a kidney is called? Well, maybe not, but you're about to find out. It's called the renal medulla. The word 'renal' comes from the Latin name for 'kidney' and can be used in both an anatomical or diagnostic sense. For instance, 'renal disease' means a disease of the kidneys. The word 'medulla' means 'middle' and comes from the Latin word for 'marrow,' the interior portion of bone. So, the renal medulla is found in the inside region of the kidney.

If you're lucky, you have two kidneys in your body. Each performs the same major functions, which include filtering out waste, eliminating and balancing fluids and controlling blood pressure. The main function of the kidneys, and the one that we experience several times a day as we go to the bathroom, is to filter out waste and produce urine to be eliminated from the body.

Much of this happens deep inside the kidney in the renal medulla. Here, blood enters through the branches of the renal artery, the main artery responsible for bringing oxygenated blood into the kidney. Once in the renal medulla, the blood is filtered through a million little filtration units. From there, the fluid moves through tubules, where water and other chemicals are added; it ultimately ends up in the bladder as urine to be excreted.

What Does the Renal Medulla Do?

If you've ever seen a kidney bean, you know what your kidneys look like. The outermost layer of the kidney is a tough, protective skin called the renal capsule. Under that is a layer filled with blood vessels and tubules called the renal cortex. Underneath the cortex, we find the center of the kidney, the renal medulla.

The main structures inside the medulla are pyramid-shaped; they're called the renal pyramids. The apex of each pyramid faces the center of the kidney and is connected to urine-collecting tubules. Each kidney's renal medulla has between 27 and 30 pyramids, and each of these is made up of tens of thousands of nephrons. Each kidney has around one million nephrons, the basic structural units of the kidney that are responsible for doing the bulk of the filtering work.

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