READ: Body Systems Continued

READ: Body Systems Continued

5. Excretory System

The Excretory System

Lesson Objectives

  • Identify the functions of the excretory system.
  • List the organs of the excretory system.
  • Describe the parts of urinary system.

Vocabulary

&\mathbf{excretion} & &\mathbf{excretory \ system} & &\mathbf{kidney} \\ &\mathbf{kidney \ dialysis} & &\mathbf{kidney \ failure} & &\mathbf{nephron} \\ &\mathbf{urinary \ bladder} & &\mathbf{urinary \ system} & &\mathbf{urinary \ tract \ infection \ (UTI)} \\ &\mathbf{urination} & &\mathbf{urine}

The Excretory System

One of the most important ways your body maintains homeostasis is by keeping the right amount of water and salts inside your body. If you have too much water in your body, your cells can swell and burst. If you have too little water in your body, your cells can shrivel up like an old apple. Either extreme can cause illness and death of cells, tissues, and organs. The organs of your excretory system help to keep the correct balance of water and salts within your body.

Your body also needs to remove the wastes that build up from cell activity and from digestion. These wastes include carbon dioxide, urea, and certain plant materials. If these wastes are not removed, your cells can stop working and you can get very sick. The excretory system can also help to release wastes from the body. Excretion is the process of removing wastes from the body.

The organs of the excretory system are also parts of other organ systems. For example, your lungs are part of the respiratory system. Your lungs remove carbon dioxide from your body, so they are also part of the excretory system. More organs of the excretory system are listed in Table below.

Organs of the Excretory System
Organ(s) Function Other Organ System of which it is Part
Lungs Remove carbon dioxide Respiratory system
Skin Sweat glands remove water, salts, and other wastes Integumentary system
Large intestine Removes solid waste and some water in the form of feces Digestive system
Kidneys Remove urea, salts, and excess water from the blood Urinary system

Table 19.4: Organs of the Excretory System

Functions of the Excretory System

The excretory system controls the levels of water and salts in your body by removing wastes. This means the excretory system has an important role in maintaining homeostasis. Your body takes nutrients from food and uses them for energy, growth, and repair. After your body has taken what it needs from the food, waste products are left behind in the blood and in the large intestine. These waste products need to be removed from the body. The kidneys work with the lungs, skin, and intestines to keep the correct balance of nutrients, salts and water in your body.

The Urinary System

Sometimes, the urinary system is called the excretory system. But the urinary system is only one part of the excretory system. Recall that the excretory system is made up of the skin, lungs, and large intestine as well as the kidneys. The urinary system is the organ system that makes, stores, and gets rid of urine. It includes:

  • Two kidneys.
  • Two ureters.
  • One bladder.
  • One urethra.


The urinary system is shown in Figure below.


The kidneys filter the blood that passes through them and the urinary bladder stores the urine until it is released from the body.


Organs of the Urinary System

  1. As you can see from Figure above, the kidneys are two bean-shaped organs. Kidneys filter and clean the blood and form urine. They are about the size of your fists and are found near the middle of the back, just below your rib cage.
  2. Ureters are tube-shaped and bring urine from the kidneys to the urinary bladder.
  3. The urinary bladder is a hollow and muscular organ. It is shaped a little like a balloon. It is the organ that collects urine.
  4. Urine leaves the body through the urethra.


Lesson Summary

  • The excretory system controls the chemical make-up of liquids found in the body.
  • The organs of the excretory system remove wastes. They also maintain the proper levels of water, salts, and nutrients in the body.
  • The lungs, skin, kidneys, and large intestine are all organs in the excretory system.
  • The urinary system is made up of the kidneys, the ureters, the bladder, and the urethra

Review Questions

1. What is the main function of the excretory system?

2. List the organs that make up the excretory system.

3. What is the purpose of the urinary bladder?

4. What connects the kidneys to the urinary bladder?

5. What is the difference between the urinary system and the excretory system?


CK-12 Foundation, Biology. http://creativecommons.org/licenses/by-nc-sa/3.0/