Breathing+HW+NLL

//**Breathing Mechanism of Breathing pp. 174-176**//

1. Define inspiration, expiration Inspiration is the active phase of ventilation because this is the phase in which the diaphragm and the external intercosal muscles contract. In its relaxed state, the diaphragm is dome-shaped, during inspiration; it contracts and become a flattened sheet of muscle. The process of inspiration, also called inhalation, moves air into the lungs, and the process of expiration, also called exhalation, moves air out of the lungs.

2. Where are the intercostals muscles? The intercostals muscles lie between the ribs.

3. Where is the diaphragm muscle? The diaphragm and connective tissue form the floor of the thoracic activity. The diaphragm is also located in the rib cage.

4. The lungs are in a "sealed" off thoracic cavity. Describe this cavity. Why is it considered "sealed"? The lungs lie within the sealed off thoracic cavity. The rib cage, consisting of the ribs joined to the vertebral column posterior and to the sternum interiorly, forms the top and sides of the thoracic activity. The lungs adhere to the thoracic wall by way of the pleura. Any space between the two pleurae is minimal due to the surface tension of the fluid between them.

5. Describe the diaphragm and intercostals muscles during inspiration. Following contraction of the diaphragm and the external intercostals muscles, the volume of the thoracic cavity will be larger than it was before. As the thoracic volume increases, the lungs increase in volume as well because the lung adheres to the wall of the thoracic activity. As the lung volume increases, the air passage within the alveoli decreases, creating a partial vacuum. In other words, alveolar pressure is now less than atmospheric pressure. Because a continuous column of air reaches into the lungs, air will naturally flow from outside the body into the respiratory passages and into the alveolu.

6. Air does NOT force open the lungs. So why does air enter the lungs? It is important to realize that air comes into the lungs because they have already opened air; air does not force the lungs to open. This is why it is sometimes said that humans inhale by negative pressure. The creation of a partial vacuum in the alveoli causes air to enter the lungs. While inspiration is the active phase of breathing, the actual flow of air into the alveoli is passive. Just as with bellows that are used to fan a fire, when the handles of the bellows are pulled apart, air automatically flows into the bellows.

7. Passive Recoil occurs during expiration. What does that mean? The presence of surfactant lowers the surface tension within the alveoli. Also, as the lungs recoil, the pressure between the pleura decrease, and this tends to make the alveoli stay open.

8. Why is air pushed out during expiration? Contraction of the internal intercostals muscles can force the rib cage to move downward and inward. Also, when the abdominal wall muscles contract, they push on the viscera, which push against the diaphragm, and the increased pressure in the thoracic cavity helps expel air.

9. How can you achieve maximum inspiratory effort? Maximum inspiratory effort involves muscles of the back, chest, and neck, which increases the size of the thoracic cavity larger than normal, this allowing maximum expansion of the lungs.

10. How can you force expiration, which is usually passive? While inspiration is always the active phase of breathing, expiration is usually passive—that is, the diaphragm and external intercostals muscles are simply allowed to relax, the lungs recoil, and expiration occurs. However expiration can also be forced. Forced expiration accompanies the maximum inspiratory efforts of heavy exercise. Forced expiration is also necessary to sing, blow air into a trumpet, or blow out birthday candles.

11. Do you use your total lung capacity when you breathe? What do you use? No we don’t use our total capacity when we breathe, we use about a quarter of air.

12. Why are the nasal cavities, trachea, bronchi, and bronchioles considered "dead air space"? It is a curious fact that some of the inhaled air never reaches the lungs; instead, it fills the nasal cavities, trachea, bronchi, and bronchioles. These passages are not used for gas exchange, and therefore, they are said to contain dead air space. To ensure that newly inhaled air reaches the lungs, it is better to breathe slowly and deeply.

13. How should you breathe to get the freshest air to your alveoli? Why? It is possible to increase the amount of air inhaled, and therefore the amount exhaled, by deep breathing. The maximum volume of air that can be moved in plus the maximum amount that can be moved out during a single breath is called vital capacity. It is called vital capacity because your life depends on breathing, and the more air you can move, the better off you are.