Bio 38.3 The Respiratory System

1. The Respiratory System Bio 38.3 The Respiratory System

2. Gas Exchange: A person can go without water for a week and without food for more than a week. But if a person stops breathing for more than a few minutes, he or she will die. Breathing is the means by which our body obtains needed gases (oxygen) and releases waste gases (carbon dioxide). Remember that in cellular respiration our cells use oxygen to break down the energy stored in glucose sugars to store it in ATP for later use. The waste product our cells produce in this process is carbon dioxide which our bodies need to get rid of. 38.3 The Respiratory System

3. Breathingis only one part of the gas exchange that takes place in our bodies. The gases must be transported to the cardiovascular system and than exchanged at the level of the cells. All of the organs and tissues that function in this exchange of gases make up the respiratory system. The Path of Air

4. A breath of air enters the respiratory system through the nose or the mouth. Air is made up of many gases. About 21% of air is the gas oxygen. Hairs in your nose filter dust and particles out of the air. Tissues that line the nasal cavity moisten and warm the air you breath in. The Path of Air

5. From the nose, air passes through a muscular tube in the upper throat called the pharynx, which serves as a passageway for air and food. The air continues on through a passageway of air; called the larynx, or voice box, located in the neck. A flap of tissue, the epiglottis, covers the opening to the larynx when you swallow food and liquids. This prevents food and liquid from passing into your lungs. The Path of Air

6. From the larynx, the air passes into the trachea, a long straight tube in the chest cavity. The trachea, or windpipe, divides into two smaller tubes, the bronchi, which lead to the lungs. The Path of Air

7. Within the lung, the bronchi divide into smaller and smaller tubes called bronchioles. The smallest bronchioles end in clusters of air sacs called alveoli where gases (oxygen and carbon dioxide) are exchanged. The Path of Air

8. Each the 300 million small alveoli is surrounded by a jacket of capillaries. Alveoli increase the surface area of your lungs to as much as 32 times the surface area of your body. The cells that line the bronchi and trachea secrete mucus that traps foreign particles in the air. The mucus is directed upward by cilia to the epiglottis, where mucus is swallowed and digested. Microbes in the mucus are destroyed by acids and enzymes in the stomach. The Path of Air

9. The lungs, which are among the largest organs in the body, are suspended in the chest cavity, bounded on the sides by ribs and on the bottom by the diaphragm. The diaphragm is a powerful muscle spanning the rib cage under the lungs, and it aids in respiration. A double membrane surrounds both lungs. The outermost membrane is attached to the wall of the thoracic cavity, and the inner membrane is attached to the surface of the lungs. Between both membranes is a small space filled with fluids. Lungs

10. Air is drawn into and pushed out of lungs by the mechanical process known as breathing. Breathing occurs because of air pressure differences between the lungs and the atmosphere. To draw air into the lungs, a process called inhalation, the rib muscles must first contract. This draws the rib cage up and out, the diaphragm contracts, moving downward. Breathing

11. When the diaphragm moves downward, the volume of the chest cavity increases, which reduces the air pressure in the chest cavity below that of the atmosphere outside the body. Since air always flows from a higher pressure to a lower pressure, air rushes into the lungs filling them. Exhalation (breathing out) now occurs when the rib cage and diaphragm muscles contract, returning to their resting position. Because the air pressure is now higher outside the body than inside it, the gas flows from the lungs to the outside as carbon dioxide is forced out of the lungs. Breathing

12. You took your first breath within moments of being born. Since than , you have repeated the process more than 200 million times. What controls how fast or slow you breath? Receptors in the brain and cardiovascular system continuously monitor the levels of oxygen and carbon dioxide within the blood. These receptors allow the body to automatically regulate oxygen and carbon dioxide concentrations by sending nerve signals to the brain. The brain than responds in turn by sending nerve signals back to the diaphragm and rib muscles telling the body to breath faster or slower. Breathing Rate

13. It may surprise you to know that carbon dioxide ratios have a greater effect on breathing than do oxygen levels. If the concentration of carbon dioxide in your blood increases, as during exercise, you respond by breathing more deeply. When the carbon dioxide level drops, your breathing slows. Factors such as stress, pain or fear also influence your breathing rate. Breathing Rate

14. The signals that travel from the breathing center of the brain are not subject to voluntary control. You can not simply decide to stop breathing indefinitely. You can hold your breath for awhile, but even if you loose consciousness, your respiratory control will take over and force your body to breath. Breathing Rate

15. Breathing is the first step to getting oxygen to the trillions of cells in your body. When oxygen molecules move from your lungs to the alveoli, their journey has just begun. As oxygen passes into the plasma of the bloodstream, it is picked up by the red blood cells that carry an iron-containing protein celled hemoglobin. Gas Transport

16. Each hemoglobin molecule contains four atoms of iron. The iron atoms in the hemoglobin give red blood cells their red color. The iron atoms bind temporarily with oxygen. Temporarily means that, at the appropriate time, the oxygen will be released elsewhere in the body and used by cells that need it to carry out cellular respiration. Oxygen Transport

17. Follow the steps listed to trace the path of oxygen and carbon dioxide as it travels through your body: 1: oxygen from outside the body is drawn into the lungs. 2: The oxygen travels to the alveoli in the lungs where it moves into pulmonary capillaries. In the pulmonary capillaries the oxygen gets drawn into the blood, binding to the iron molecules in the blood’s hemoglobin. Oxygen Transport

18. 3: The oxygen rich blood now travels to the heart. The heart in turn pumps this oxygen-rich blood to all the tissues of the body where it is needed for energy. Oxygen Transport

19. 4: As oxygen reaches the cells through the capillaries in the tissues throughout the body, the hemoglobin now releases the oxygen. The cells now draw it in, diffusing it in through the cell’s semipermeable membranes. Once in the cell, oxygen is the catalyst that allows cellular respiration to occur. Oxygen Transport

20. 5: In the tissues, the presence of carbon dioxide produced by cellular respiration makes the blood more acidic and causes the hemoglobin to take on a different shape, one that gives up oxygen more easily. The carbon dioxide diffuses from the cells to the blood. Oxygen Transport

21. 6: Most of the carbon dioxide now travels back to the heart in the form of bicarbonate atoms. 7: The heart pumps the now oxygen-depleted blood back to the lungs. Here, the carbon dioxide is now released through the capillaries back into the alveoli. 8: The carbon dioxide is now expelled from the lungs with every exhalation of breath Oxygen Transport

22. At the same time that the red blood cells are unloading oxygen to the tissues, they are also taking in carbon dioxide from the tissues. Carbon dioxide is carried by the blood in three forms. About 7% of the CO2 is dissolved in the blood plasma About 23% of the CO2 is attached to hemoglobin molecules inside red blood cells The major part, about 70%, is carried in the blood as bicarbonate atoms. Carbon Dioxide Transport

23. Respiratory diseases affect millions of Americans. A chronic pulmonary, lung, disease is one for which there is no cure. Asthma: Asthma is a chronic condition in which bronchioles of the lungs become inflamed because of their sensitivity to certain stimuli in the air. The bronchial walls tighten and extra mucus is produced, causing the airways to narrow and breathing to become difficult. In severe asthma attacks, the alveolie may swell enough to rupture. Respiratory Diseases

24. Stressful situations and strenuous exercise can trigger an asthma attack. Left untreated, asthma can be deadly. Fortunately, prescribing inhalant medicines may help to stop an asthma attack by expanding the bronchioles. Asthma can strike people of all ages. Asthma

25. Emphysema is a chronic pulmonary disease resulting from a chemical imbalance that destroys elastic fibers in the lungs. Normally, these elastic fibers allow the lungs to expand and contract. Emphysema begins with the destruction of alveolie. Damage to the alveolie is irreversible and results in constant fatigue and breathlessness. Severely affected individuals must breath from tanks of oxygen in order to live. Smoking is the cause of up to 90 percent of emphysema cases. Emphysema affects millions of lives annually. Emphysema

26. Lung cancer is one of the leading causes of death in the world today. Cancer is a disease characterized by abnormal uncontrolled cell growth. In the United States alone, about 28%, or 155,000, of all cancer deaths each year are attributed to lung cancer. Smoking is the major cause of lung cancer. Once cancer is detected, the affected lung is sometimes removed surgically. Even with such drastic measures, lung cancer is usually not curable. Only about 15% of lung cancer victims live more than 5 years after a diagnoses. Lung Cancer