How our body works, Part 4- the urinary system
By Penelope A. Domogo, MD
In review, we have discussed 3 body systems and how they work. Part 1 discussed the digestive system and Part 2 discussed the respiratory system. These two systems are the natural entrances of our basic ingredients for life – air, water and food. The digestive system digests, absorbs and metabolizes our food and drink to convert it into the nutrients that we need. Although it is designed to recognize natural substances that are not good for us like some harmful bacteria, it cannot screen out fat, sugar, additives and some other harmful substances that we put in our mouth. So these harmful substances are absorbed into the blood and weaken not only our digestive system but all other body systems. Aside avoiding unhealthy food that weaken us, we need to strengthen our digestive system by eating fruit vegetables like squash, sayote, okra, etc. To strengthen our respiratory system, we need to eat beans often. We then tackled the circulatory system in Part 3. Here we explained how these nutrients and oxygen are circulated all over our body to enter each individual cell 24/7. It’s mind-boggling. And if we realize that this efficient distribution happens without any effort on our part, it’s humbling. This is all thanks and praise to our loving Creator who designed us and our environment. Now, do we respect his design?
Let us now proceed to the urinary system. The urinary system functions to clean the by-products of nutrient metabolism from our blood. You see, when we use something to create energy, there are by-products. For example, when we light wood to create fire to warm ourselves and cook our food, may naiiwan na ashes, charcoal and soot. Another example is when a car uses diesel oil to move the engine, there is also a by-product of that combustion- fumes and other wastes. Likewise, when our body metabolizes the oxygen and nutrients to fuel our body so that it will function, it creates by-products such as carbon dioxide, urea (ammonia), uric acid, creatinine, etc. which are all deposited in the bloodstream. These are not useful inside us so we usually call them “waste” but are useful for those in our environment so we need to excrete them. If we don’t excrete them, these become poison to us. For carbon dioxide, we discussed in Part 2 of this series that this is unloaded in the lungs and we excrete it by exhaling it out to the environment for our plants. In God’s design, everything has a good purpose and nothing goes to waste.
The urinary system is composed of 2 kidneys, 2 ureters, I urinary bladder and 1 urethra. Action takes place in the kidneys, filtering the blood and produces urine as the vehicle for excretion. Urine then flows through the ureters, collected in the bladder so that we don’t have to pee very often like a baby who has no control yet. In time we can train the bladder to hold urine before it is excreted through the urethra onto the plants. This system works in harmony with the other systems in our body to maintain a healthy internal environment for our cells and tissues to function well. We need at least one properly functioning kidney to survive so we thank God he gave us a spare.
Let us, then, dissect the kidney and appreciate its different parts and amazing technology. Each kidney is only about the size of your fist but it contains a very interesting mix of cells and tissues some of which are round cells, oblong cells, square cells, columns, calyces, and about one million convoluted tube systems called nephrons beautifully curled inside the kidneys. Can you imagine these? Side by side these nephrons are teeny weeny blood vessels. They are so tiny that you need a powerful microscope to see them.
These nephrons act as filters- fine mesh to filter your blood . The “holes” in these filters are so small that only water and small particles are able to get through and bigger particles (but still microscopic) like red blood cells and white blood cells stay in the bloodstream. Blood passes through the kidneys every five minutes – ensuring that waste materials don’t build up. This translates to about 180 liters of blood being processed daily by your amazing kidneys.
As blood passes through these nephrons, byproducts like urea, uric acid, creatinine and those not needed in the body like excess vitamins and minerals, other toxins and excess water are excreted out. Important substances like glucose are retained and needed water is reabsorbed. (Urea and uric acid are produced when protein is metabolized in the body and so high protein food like meat, eggs, milk will produce more urea and uric acid. Creatinine only comes from metabolism of animal protein.)
Aside from its intricate cleansing function, the kidneys also have an equally amazing regulating function. If you are impressed with the gadgets in a water refilling station, the kidneys are much more high tech than that. Without any effort from us, the kidneys are able to regulate the concentration of various components of the blood so that a normal pH is maintained. Wow! Good blood is slightly alkaline.
The kidneys also regulate how much urine is excreted – on a hot sweaty day, you will notice that less urine is produced so it’s more yellow because the waste matter is concentrated. More (and thus less yellow) urine is produced if you drink so much and on cold days. These are common sense.
One other important function of the kidneys is to produce hormones needed to produce red blood cells and help in bone formation, among other things so you understand that patients undergoing dialysis need to be transfused with blood as their kidneys are damaged.
Because our kidney is like a filter or a sieve, its function will be compromised if we abuse it. If your blood is too thick and heavy because of the MSG, excess sugar, salt and protein and fat, the “holes” will enlarge. Cooks will readily understand what this means. These microscopic filters can also be damaged by toxins like some chemicals in processed food, some medicines (that is why we always warn that there is no absolutely safe medicine.) Naturally, when these holes enlarge or destroyed, then bigger particles like red blood cells and white blood cells (also called pus cells) will pass through so the laboratory will see a lot of particles which should not be in your urine. These are warnings from your body- if you don’t heed them, these will result to more problems later, one of which is kidney failure. You don’t want that, neither do I.**
Psalm 66: 4 – “Come now and see the works of God, how wonderful he is in his doing toward all people.”