Excretion System – The Kidneys

The kidneys main function is filter our blood. Kidney called as excretion organ because it excretes (remove) waste in the form of urine. So blood comes into the kidney, waste gets removed, and salt, water, and minerals are adjusted, if needed. The filtered blood goes back into the body. Waste gets turned into urine. [1] 

Every day, the two kidneys filter about 120 (113 L) to 150 quarts (141 L) of blood to produce about 1 to 2 quarts (0,9 L) of urine, composed of wastes and extra fluid. [2]

Why is it important that the kidney filters the blood?

Wastes build up from cell activity and from digestion and it will take by blood. If these wastes are not removed, our cells can stop working, and we can get very sick [3]. Kidneys do excretion to prevent the buildup of wastes and extra fluid in the body.

How do the kidney work?

Okey, firstly, we will see the structure of kidney. Look at the Figure 1. This is our kidney. Kidney composed by three major regions, such as 1) Renal cortex, 2) Renal medulla and 3) Renal pelvis.

 Source : [3]

1) Renal Cortex

Is a layer of tissue that are located deeper within the kidney, within the renal pyramids of the medulla.

2) Renal Medulla

Inner region of of the kidney The medulla consists of renal pyramids, which are contain nephrons.

3) Renal Pelvis

The renal pelvis contains the hilium. The hilum is the concave part of the bean-shape where blood vessels and nerves enter and exit the kidney; it is also the point of exit for the ureters. The renal pelvis connects the kidney to the rest of the body [4].

The simple way to explain steps of kidney excretions process is :

Blood (contain waste) comes into kidney through renal artery (in renal pelvis region) → then blood goes some process: filtering, reabsorbing and augmentating (in medulla region, especially in nephrons of renal pyramid) → Blood (clean) get out from kidney through renal vein.

The “washing” process of blood by kidney consists of three steps, they are filtration, reabsorption and augmentation. These process occurs in nephrons. Nephrons is filtering units that located in renal pyramid in medula region. Look at Figure 2. Nephrons itself has three major parts, they are capsula bowman (contain glomerulus), loop henle and collecting tubule.

  

To know further about process of filtration, reabsorption and augmentation, please check this video

Lets find out, how if we doesn’t have kidney? Can we survive? How if filtration, reabsorption and augmentation doesn’t occur? Can you imagine that? We will discuss this topic in the next meeting.