1. What is the main function of the respiratory system?
To bring oxygen into the body and eliminate carbon dioxide from the body.
2. Trace the pathway of air from the outside of the body into the body.
Air enters the nose through the external nares. Then the air passes through the nasal cavity, pharynx, larynx, trachea, primary bronchus, and into the lungs.
3-4. Describe the location of the visceral and parietal pleura.
Visceral pleura covers the surface of the lungs. Parietal lines the mediastinum, the diaphragm, and the thoracic wall.
5. What is the function of pleural fluid?
Assists in breathing movements by acting as a lubricant.
6. Trace the pathway of air from the trachea to the respiratory zone.
Trachea, to primary bronchi, to secondary bronchi, to tertiary bronchi, to smaller bronchi, to bronchioles, to terminal bronchioles, to respiratory zone.
7. Describe the difference between bronchi and bronchioles in terms of smooth muscle and cartilage.
Bronchi have rings of cartilage that keep them open. Bronchioles have no cartilage, but they do have smooth muscle in their walls.
8. What is the function of the smooth muscle of the bronchioles?
To allow airflow regulation by altering the diameter of the bronchioles.
9. Where is the conducting zone and what is its function?
The conducting zone is the airway from the nasal cavity through the terminal bronchioles. Its function is to moisten, warm, and filter the air.
10. Where are three places alveoli are found?
(1) In respiratory bronchioles where they are scattered in the walls. (2) In alveolar ducts, which are completely lined by alveoli. (3) In alveolar sacs, where they are found in clusters.
11. What are the names of the blood vessels that carry blood to the lungs?
The pulmonary arteries and branches of the pulmonary arteries.
12. What are the names of the blood vessels that carry blood away from the lungs?
The pulmonary veins and branches of the pulmonary veins.
13. Which contain blood that is higher in oxygen, the pulmonary arteries or the pulmonary veins?
The pulmonary veins.
14. Where are the pulmonary capillaries found within the lung?
They surround each alveolus.
15. What three cell types are found within alveoli?
(1) simple squamous epithelium, (2) alveolar macrophages, (3) surfactant-secreting cells
16. What is the function of the alveolar macrophages, or dust cells, within alveoli?
They creep along the inner surface of the alveoli, removing debris and microbes.
17. What is the function of the surfactant-secreting, or Type II cells, within alveoli?
They secrete surfactant.
18. What is present on the inside surface of alveoli?
Alveolar fluid, which is composed of water and surfactant.
19. What would happen if there were no surfactant in alveolar fluid?
The alveoli would collapse due to the surface tension of the water.
20. Why is there no interstitial fluid in between the two layers of simple squamous epithelium in the respiratory membrane?
Because pulmonary blood pressure is so low that little fluid filters out of the capillaries into the interstitial space.
21. What two important gases diffuse across the respiratory membrane? In which direction does each gas flow?
Oxygen gas diffuses from the alveoli to the pulmonary capillaries. Carbon dioxide diffuses from the pulmonary capillaries to the alveoli.
Control of Respiration
22. What controls the basic rhythm of breathing?
Respiratory centers located in the brainstem.
23. What monitors changes in arterial PCO2, PO2 and pH?
Sensory receptors called chemoreceptors.
24. Explain how the inspiratory center initiates inspiration.
The inspiratory center sends nerve impulses along the phrenic nerve to the diaphragm and along the intercostal nerves to the external intercostal muscles which continue for a period of about 2 seconds. This stimulates the inspiratory muscles to contract, initiating inspiration.
25. Explain how the inspiratory center initiates expiration
The inspiratory center causes the phrenic nerve to stop firing for about 3 seconds, which allows the muscles of respiration to relax. The elastic recoil of the lungs and chest wall leads to expiration.
26-35. In each of these blanks, put "increase(s)" or "decrease(s)":
If the arterial PCO2 increases, there is a(an) a. __increase__ in the PCO2 in the fourth ventricle. This causes a(an) b. __ increase___ in hydrogen ions in the cerebrospinal fluid, which c. _decreases_ the pH of the cerebrospinal fluid. The hydrogen ions stimulate the central chemoreceptors to d. _ increase__ their rate of firing, which e. _ increases_ the nerve impulses to the respiratory centers. This f. _ increases_ the rate of nerve impulses to the respiratory muscles, resulting in a(an) g. _ increase _ in breathing rate and depth. As a result, there is a(an) h. __ increase __ in carbon dioxide exhalation which i. _ decreases_ the blood PCO2 to normal levels.
36. Do peripheral chemoreceptors directly respond to changes in the arterial blood, venous blood, or cerebrospinal fluid?
37-41. In each of these blanks, put "increase(s)" or "decrease(s)":
An increase in carbon dioxide levels in the arterial blood result in a(an) a. __ decrease __ in blood pH. There is a(an) b. _ increase __ in the rate of firing of the peripheral chemoreceptors, which c, __ increases__ the rate of respiration. As a result there is a(an) d. __ increase__ in carbon dioxide exhalation, which drives the chemical reaction to the left and e. _ decreases__ PCO2 and pH returns to normal levels.
42-50. In each of these blanks, put "increase(s)" or "decrease(s)": The peripheral chemoreceptors also respond to acids such as lactic acid, which a. _ increases _ during strenuous exercise. The lactic acid enters the blood and b. _ increases _ the concentration of hydrogen ions which c. _ decreases _ the pH which d. _ increases _ the firing rate of the peripheral chemoreceptors. There is a(an) e. __ increase_ in nerve impulses to the respiratory centers, which f. _ increases _ the breathing rate and depth. There is a(an) g. _ increases_ in carbon dioxide is exhalation which h. __ decreases __ the PCO2 in blood, driving the chemical reaction to the left, and i. _ decreases _ hydrogen ion levels.
51. What is the Hering-Breuer reflex?
Stretch receptors in the visceral pleura and large airways send inhibitory signals to the inspiratory center during very deep inspirations, protecting against excessive stretching of the lungs.
52. Do changes in PCO2 and PO2 play a significant role in stimulating increased ventilation due to exercise?
No they do not play a significant role.
53. What are the factors that stimulate increased ventilation during exercise?
Learned responses, Neural input from the motor cortex, Receptors in muscles and joints, Increased body temperature, Circulating epinephrine and norepinephrine and pH changes due to lactic acid.
54. How is the volume of the thoracic cavity changed?
By muscle contraction and relaxation.
55. What two muscles contract during quiet inspiration? What is the effect of their contraction?
The diaphragm and the external intercostals. As a result the thoracic cavity enlarges in all dimensions.
56. What happens to pressure when we increase the volume within the thoracic cavity and the lungs?
57. Explain what happens in quiet expiration.
The diaphragm and the external intercostal muscles relax, and the elastic lungs and thoracic wall recoil inward.
58. What effect does quiet expiration have on the volume of the thoracic cavity? How does this effect the pressure within the cavity?
The volume is decreased and therefore the pressure increases within the thoracic cavity.
59-61. What three factors cause the intrapleural pressure to be less than intrapulmonary (alveolar) pressure?
(1) The surface tension of the alveolar fluid. (2) The elasticity of the lungs. (3) The elasticity of the thoracic wall.
62. Why does a lung collapse if you cut into the pleural cavity?
Because the pressure of the intrapleural cavity becomes equal to atmospheric pressure. There is no longer less pressure in the intrapleural cavity compared to within the alveoli so the lung collapses.
63. If a pneumothorax occurs in one lung, why doesn't it also occur in the other lung?
Each lung has its own pleural cavity and pleural membranes so that changes in the intrapleural pressure of one lung do not affect the other lung.
64. Does histamine constrict or dilate bronchioles?
65. Does epinephrine constrict or dilate bronchioles?
66. What two factors is lung compliance dependent upon?
(1) The stretchability of the elastic fibers within the lungs. (2) The surface tension within the alveoli.