Respiration and excretion
Human Biology - Grade 8
Respiration and excretion
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Study Guide Respiration and excretion Human Biology - Grade 8
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RESPIRATION AND EXCRETION Respiratory System Functions The respiratory system is the process of taking oxygen from the air and bringing it into the body and removing carbon dioxide from the body. In order to get energy from glucose, the cells of the body require oxygen. As we learned in Topic 4, respiration is a process that cells use to get energy by breaking down food molecules and releasing the energy that the food holds. The process of respiration in the body creates the waste materials of carbon dioxide and water. The carbon dioxide and some of the water is eliminated from the body through the lungs. Key Body Systems Support Respiration The process of respiration would not be able to take place without the respiratory, digestive and circulatory systems. Oxygen is gained by the respiratory system and glucose is gained from the digestive system. Both the oxygen and glucose are transported around the body by the circulatory system. With every breath, we pull oxygen out of the atmosphere. The atmosphere consists of 78% nitrogen, 21% oxygen, and 1% other gases, so the air that we breathe is not all taken into the body. There are many filters throughout the respiratory system that trap and eliminate pathogens and other materials. The system’s structures also help to warm and moisten the air in the body. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Structures of Respiratory System Air travels through the nose, pharynx, trachea, and the bronchi within the lungs. Nose: The air starts its journey to the lungs through one of the two nostrils of the nose. The nasal cavity is lined with cilia and mucus that trap and eliminate particles. Blood vessels in the nose begin to warm the air entering the body and the mucus moistens the air. The air then enters the throat or pharynx. Pharynx: The pharynx is an organ that is shared with the digestive system. Once through the pharynx, the air enters the trachea. Trachea: The trachea is the airway that leads from the pharynx to the lungs and is also called the windpipe. The trachea has rings of cartilage that help it to stay open and are lined with cilia and mucus to trap invading particles. If the lining of the trachea is irritated, you will cough causing the invading particles to be ejected from the body. The epiglottis seals off the opening to the trachea so that food does not enter. Bronchi: The air then enters the bronchi, which are two passages that lead into the lungs. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The lungs are the key organs of the respiratory system. The left bronchus leads into the left lung and the right bronchus leads into the right lung. The bronchi branch off into smaller and smaller passageways. At the very end of each branched passageway in the lungs is a structure called alveoli. The alveoli are small sacs within the lungs that specialize in the exchange of gases between blood and air. Lesson Checkpoint: What is the role of the alveoli in the respiration process? Process of Respiration On average, a person will take around 20,000 breaths a day! Here is what happens with each breath: When air enters the nose, passing through the pharynx, trachea, and bronchi to get to the alveoli, oxygen will pass through the walls of the alveoli and then the walls of the capillaries (yes, there are blood vessels in your lungs) and into the blood. Carbon dioxide will pass from the blood, through the capillary walls and into the alveoli. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
As a red blood cell passes through a capillary, it is loaded with carbon dioxide until it reaches the alveoli. Once the cell is next to the alveoli, the carbon dioxide quickly unloads while oxygen attaches to the hemoglobin. This is the process of gas exchange. If you were to open every surface within the lungs, the surface area would be the size of an average classroom! This large amount of surface area allows the alveoli to exchange a large amount of gases. Muscles in the respiratory process Every breath that you take is controlled by muscles. Muscles attached to the ribs and the diaphragm are used when you breathe. The diaphragm plays an important role in the breathing process. When a person inhales, the rib muscles contract, causing the chest to move up and out. The diaphragm also contracts moving downward. This allows the lungs to expand and take in air. When a person exhales, the diaphragm and rib muscles relax. This decreases the size of the chest and lungs, and forces the air to exit the lungs. Your voice The voice box, or larynx, is located at the top of the trachea just below the epiglottis. There are two vocal cords made of connective tissue that stretch across the larynx that produce the voice. The vocal cords are attached to muscles that contract and relax. This causes the vocal cords to vibrate and produces a voice. The Excretory System Waste products are created by respiration and need to be eliminated out of the body. The system of collecting the wastes produced by the body and eliminating them is the job of the excretory system. The actual process of waste removal is called excretion. If wastes were not eliminated from the body, they would begin to poison the body and cause you to get sick or even die. This system is another important system in your body! Excretion eliminates potentially harmful materials from the body and helps to maintain homeostasis. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
As we learned in Topic 16, kidneys are organs that eliminate wastes produced by the cells. The waste products are carbon dioxide, excess water, and urea. Urea is a chemical that is produced when the body breaks down proteins. All of the waste materials produced by the two kidneys are combined in a fluid called urine. The kidneys act like filters, removing wastes that are in the blood. Lesson Checkpoint: What is the waste product from the processing of proteins? Each of the two kidneys contains a million structures called nephrons that filter the blood. After entering the kidneys, blood flows through smaller and smaller arteries until it reaches capillaries in a nephron. Materials such as water, glucose, urea and other wastes are filtered out of the blood. The filtered materials then move through a capsule of the nephron. Blood and other materials stay within the capillaries. The filtered materials form urine and run through tubes. Some of the materials that were filtered are needed by the body, so they are reabsorbed into the blood. Waste products remain in the tubes and flow through the tubes out of the body by the following path. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Path of Urine Removal • The wastes produced by the kidneys run through tubes called ureters. • The ureters carry urine to a structure called the urinary bladder. When this structure is full, it pushes on nerves that let the body know that the urinary bladder must be emptied. • The urine leaves the body through a structure called the urethra. Lesson Checkpoint: How does your body know your bladder is full and needs emptying? Excretion and Homeostasis The kidneys are involved in maintaining the level of water that is in the body. The amount of water that is reabsorbed into the body depends on the conditions inside and outside the body. If the temperature is hot outside the body, the kidneys will allow more water to reabsorb than if it were cold. It is important to keep the kidneys working the best they are able by bringing in at least two liters of water into your body everyday. This ensures that a water balance within your body is maintained. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
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