part in the main- tenance of body metabolism, by supplying oxygen to the tissues, and removing carbon dioxide from the tissues in the chemic interchange taking place between the air, the blood, and the tissues during the act of respiration, and circulation of the blood. Rate of Respiration. — The normal rate of respira- tion varies at different ages as follows: At birth and during the first year, 44 per minute; five years, 26 per minute; fifteen to twenty years, 20 per minute; twenty to twenty-five years, 18.7 per minute; thirty to fifty years, 18 per minute. Respiration is divided into: inspiration, an active process due to muscular activity, when air enters the lungs, due to atmospheric pressure being greater than the contained intrapulmonary; expiration, a quiet or passive process, due to the recoil of the elastic tissue of the lungs, the abdominal and thoracic walls; when the intrathoracic pressure becomes greater than the atmospheric air pressure it allows the contained air to escape until the intrapulmonary pressure equals the atmospheric air pressure, then inspiration occurs again, and the respiratory cycle is repeated. The Volumes of Air Breathed. — This is determined by an apparatus known as Hutchinson's spirometer. With this apparatus four volumes of air are deter- mined. (1) The tidal volume or the amount of air which flows into and ou^ of the lungs during an ordinary inspiration and expiration varies from 20 to 30 cubic inches. (2) The complemental volume or the amount of air taken into the lungs, in addition to the tidal volume, resulting from a forcible inspiration, which amounts to 110 cubic inches. (3) The reserve volume or the amount of air which flows out of the lungs, in addition to the tidal volume resulting from a forcible expiration, which amounts to 100 cubic inches. (4) The residual volume or amount of air remaining in the lungs, as a permanent volume, after the most forcible expiration. The vital capacity is the amount of air which can be expelled from the lungs after they are filled by the most forcible inspiration. This amounts to 230 cubic inches (3593 c.c). * Changes in the Composition of Inspired and Expired Air as a Result of Respiration. Inspired Air, 100 Volumes Oxygen 20.80 Carbon dioxide traces Nitrogen 79.20 Watery vapor variable Expired Air, 100 Volumes Oxygen 16.02 Carbon dioxide 4.38 Nitrogen 79.60 Water vapor saturated Organic matter (Brubaker) The above analyses show that the air under ordinary conditions loses oxygen to the extent of 4.37 per cent., and gains in carbon dioxide to the extent of 4.38 per cent.; it gains in nitrogen to the extent of 0.4 per cent., and watery vapor to the point of saturation, also organic matter. From experiments with the spirometric apparatus, and the taking of the percentage loss of oxygen and gain in carbon dioxide shown by the analysis of the respired air, it is possible to figure approximately the total amount of oxygen absorbed and carbon dioxide given off during respiration. The minimum daily volume of air breathed is assumed to be 10,800 liters and the maximum daily volume 12,240 liters. Thus the minimum daily yolume of oxygen absorbed is 510 liters, maximum 585 liters. Carbon dioxide is exhaled amounting to 473 liters, the minimum daily volume; 526 liters, the maximum daily volume. Thus one can readily understand how essential it is for human beings to obtain a fresh supply of air to breathe in order to maintain life and carry on its various activities. Since during every breath the external air loses oxygen and gains carbon dioxide, besides other waste products, the air in dwellings, offices, etc., should be frequently renewed in order to maintain a condition of health. If we take in at each inspiration 30 cubic feet of air, and breathe at the rate of 18 respirations a minute, then in twenty- four hours 450 cubic feet (12.8 cm.) will pass in and out of the lungs. Thus it is easy to understand how a person laboring, or sleeping, etc., in an unventilated room w^ould readily succumb, theoretically, by rebrea th- ing the poisoned air from his own lungs. The Changes in the Blood during Respiration.— The blood as it is forced from the right ventricle of the heart through the pulmonary artery to the lungs, is dark bluish red in color. On reaching the air cells of the lungs the blood becomes bright red in color and is carried through the pulmonary veins to the left auricle, then into the left ventricle of the heart, when it passes out through the large artery (aorta) to supply the body tissues. The blood is changed while flowing through the capillaries from fhe venous to the arterial state. When the dark bluish-red blood in the pulmonary arteries reaches the capillaries of the pulmonary system where they surround the air cells, and the thin membrane 248 THE RESPIRATORY APPARATUS separating the capillaries from the intrapulmonary air, the carbon dioxide is given off and the oxygen is taken up and combines chemically with the hemo- globin contained in the red cells, forming oxyhemo- globin, the blood in the arterial capillaries of the pulmonary veins immediately turns bright red as a result of the interchange. This bright red or arterial blood is carried to the tissues by the arteries and capillaries. Fig. 94 AIR THIN MUCOSA l-1-l-l-l'l'l-l- CAPILLARY BLOOD VESSEL (® ©(S>0©©©C2) O 03a©(20 O0G)© © <2© Diagram of the essentials of a respiratory apparatus. (F. H. G.) This power possessed by the blood of absorbing and giving up oxygen and carbon dioxide through the capillary walls from and to the air and tissues respec- tively is based on the well-known fact that liquids will absorb or dissolve at any constant pressure unequal volumes of different gases in accordance with their solubilities, and with variations in temperature (Brubaker) . The Relation of the Nerve System to Respiration. — The rhythmic movements of respiration are controlled by nerve impulses which arise in groups of nerve cells in the central nerve system, and are transmitted to the inspiratory and expiratory centres in the medulla oblongata, which are stimulated into activity. The inspiratory and expiratory centres are included under the term respiratory centre. The vagus nerve is the important nerve which transmits nerve impulses from the inspiratory centre in the medulla to the lungs. It contains excitor and inhibitor fibers; the former, when stimulated, increase the rate of inspiration and the latter decrease it. QUESTIONS 249 Respiration is believed to be due to a stimulus resulting from the alternate distention and collapse of the walls * of the pulmonary alveoli — a mechanic action. The inspiratory centre can be influenced directly by nerve impulses being transmitted from the brain in response to voluntary acts, or emotional states, sighing, etc., also indirectly by nerve impulses reflected to the centre from the surfaces of the skin and mucous membranes through afferent nerves; as cold applied to the skin, irritating gases to the nasal and bronchial mucous membranes, and collapse or distention of the pulmonary alveoli. QUESTIONS 1. Name the organs of respiration. 2. What effect has the nasal mucous membranes upon the air we breathe? 3. What is dyspnea? 4. What is the organ of the voice? 5. Give the relations of the larynx. 6. How many cartilages form the larynx? Name them. 7. Which cartilage forms the Adam's apple? 8. What is the rima glottidis? 9. Describe the true and false vocal cords. 10. Which muscles open the glottis? Close it? 11. Which muscles regulate the tension of the vocal cords? Relax them? 12. What do you understand by the term phonation? 13. How is articulate speech produced? 14. Name the number of rings in the trachea. 15. What variety of epithelium lines the trachea and what is its function? 16. Are there glands in the trachea, and to what variety do they belong? 17. Where do the bronchi enter the lungs? 18. Are the pleurae closed sacs? 19. What do you understand by the terms visceral and parietal pleura? 20. Where is the pleural cavity located? Does it contain fluid? 21. What membranes cover the lung? 22. Name the parts of each lung. 23. What structures form the root of the lung?* 24. How many lobes has the right lung? The left? 25. Give the microscopic structure of the lung. 26. What is a bronchiole? Lobule? 27. Where is the infundibulum in the lobules of the lungs? The air sacs? 28. Name the variety of epithelium lining the bronchi, bronchioles, alveoli, and air sacs. 29. What relation do the capillaries of the pulmonary artery and vein bear to the air sacs of the lobules? 30. What relation do the respiratory epithelium and capillaries bear to respiration? 31 Describe respiration. 32. Give the normal rate of respiration per minute at birth. Five years. Fifteen to twenty years. Twenty to twenty-five years. Thirty to fifty years. 33. Name the divisions of respiration. 34. What do you understand by the terms tidal volume? comple- mental volume? reserve volume? residual volume? in relation to respiration? 35. What is the average vital capacity of the lungs? What is meant by it? 36. Give the minimum and maximum daily volume of air breathed. 37. What gaseous interchange takes place during each respiration between the hemoglobin of the red cells and the air we breathe? 38. How is the color of the blood affected by respiration? 39. Where is the oxygen absorbed at each respiration carried to? Where does the carbon dioxide in the blood come from to be given off at each respiration? 40. What centre in the medulla controls inspiration and expira- tion?
Key Takeaways
- The normal rate of respiration varies by age, with newborns breathing about 44 times per minute.
- Respiration is divided into inspiration and expiration, both controlled by the central nervous system.
- The vital capacity of the lungs is approximately 230 cubic inches.
Practical Tips
- Monitor air quality in enclosed spaces to ensure proper ventilation and prevent buildup of carbon dioxide.
- Regularly check for respiratory symptoms that may indicate underlying issues, such as dyspnea or changes in breathing patterns.
- Understand the mechanics of respiration to better manage conditions like asthma or chronic obstructive pulmonary disease (COPD).
Warnings & Risks
- Avoid prolonged exposure to poorly ventilated areas where air quality can deteriorate rapidly.
- Be aware that respiratory infections can significantly impact lung function and oxygen exchange.
- Do not ignore persistent breathing difficulties, as they may indicate serious health issues.
Modern Application
While the historical techniques in this chapter provide foundational knowledge about respiration, modern survival preparedness emphasizes continuous monitoring of air quality, especially in enclosed spaces. Understanding these principles can help prevent respiratory issues and ensure better overall health during emergencies or prolonged periods indoors.
Frequently Asked Questions
Q: What is the normal rate of respiration for a newborn?
The normal rate of respiration for a newborn is about 44 breaths per minute.
Q: How does the respiratory system exchange oxygen and carbon dioxide with the blood?
During respiration, oxygen from the air diffuses into the blood through the capillaries surrounding the alveoli in the lungs. Simultaneously, carbon dioxide from the blood diffuses out of the capillaries and into the air sacs to be exhaled.
Q: What is the average vital capacity of the lungs?
The average vital capacity of the lungs is approximately 230 cubic inches (3593 c.c.).