URINARY SYSTEM (Chap. 23)
Parts of the Urinary Tract
You drink, you pee. But urine is more than just that drink you had a few hours ago. The body produces pee as a way to get rid of waste and extra water that it doesn’t need. Before leaving your body, urine travels through the urinary tract.
The urinary tract is a pathway that includes the:
- kidneys: two bean-shaped organs that filter waste from the blood and produce urine
- ureters: two thin tubes that take pee from the kidney to the bladder
- bladder: a sac that holds pee until it’s time to go to the bathroom
- urethra: the tube that carries urine from the bladder out of the body when you pee
The kidneys are key players in the urinary tract. They do two important jobs — filter waste from the blood and produce pee to get rid of it. If they didn’t do this, toxins (bad stuff) would quickly build up in your body and make you sick. That’s why you hear about people getting kidney transplants sometimes. You need at least one working kidney to be healthy.
You might wonder how your body ends up with waste it needs to get rid of. Body processes such as digestion and metabolism (when the body turns food into energy) produce wastes, or byproducts. The body takes what it needs, but the waste has to go somewhere. Thanks to the kidneys and pee, it has a way to get out.
When you’re asked to give a urine sample during a doctor’s visit, the results reveal how well your two kidneys are working. For example, white blood cells in the urine can be a sign of an infection.
Pee also is a way for your body to keep the right amount of water. Did you ever notice that if you drink a lot, you pee more and the pee is pale yellow? That’s because your body is getting rid of extra water and your pee has more water in it than usual.
IMMUNITY
Inside your body there is an amazing protection mechanism called the immune system. It is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites that would love to invade your body. To understand the power of the immune system, all that you have to do is look at what happens to anything once it dies. That sounds gross, but it does show you something very important about your immune system.
Let’s start at the beginning. What does it mean when someone says “I feel sick today?” What is a disease? By understanding the different kinds of diseases it is possible to see what types of disease the immune system helps you handle.
When you “get sick”, your body is not able to work properly or at its full potential. There are many different ways for you to get sick — here are some of them:
- Mechanical damage - If you break a bone or tear a ligament you will be “sick” (your body will not be able to perform at its full potential). The cause of the problem is something that is easy to understand and visible.
- Vitamin or mineral deficiency - If you do not get enough vitamin D your body is not able to metabolize calcium properly and you get a disease known as rickets. People with rickets have weak bones (they break easily) and deformities because the bones do not grow properly. If you do not get enough vitamin C you get scurvy, which causes swollen and bleeding gums, swollen joints and bruising. If you do not get enough iron you get anemia, and so on.
- Organ degradation - In some cases an organ is damaged or weakened. For example, one form of “heart disease” is caused by obstructions in the blood vessels leading to the heart muscle, so that the heart does not get enough blood. One form of “liver disease”, known as Cirrhosis, is caused by damage to liver cells (drinking too much alcohol is one cause).
- Genetic disease - A genetic disease is caused by a coding error in the DNA. The coding error causes too much or too little of certain proteins to be made, and that causes problems at the cellular level. For example, albinism is caused by a lack of an enzyme called tyrosinase. That missing enzyme means that the body cannot manufacture melanin, the natural pigment that causes hair color, eye color and tanning. Because of the lack of melanin, people with this genetic problem are extremely sensitive to the UV rays in sunlight.
