A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition) by Calvin Cutter (lightweight ebook reader txt) 📖
- Author: Calvin Cutter
- Performer: -
Book online «A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition) by Calvin Cutter (lightweight ebook reader txt) 📖». Author Calvin Cutter
475–494. Give the physiology of the respiratory organs. 475. What is respiration? What is the principal object in breathing? 476. How are the useless atoms of matter conveyed into the veins of the systemic circulation? How may the principal elementary substances be separated from the blood? 477. How may an ordinary inspiration be accomplished?
Fig. 95.
Fig. 95. 6, Four of the vertebræ, to which are attached three ribs, (7, 7, 7,) with their intercostal muscles, (8, 8.) These ribs, in their natural position, have their anterior cartilaginous extremity at 4, while the posterior extremity is attached to the vertebræ, (6,) which are neither elevated nor depressed in respiration. 1, 1, and 2, 2, parallel lines, within which the ribs lie in their natural position. If the anterior extremity of the ribs is elevated from 4 to 5, they will not lie within the line 2, 2, but will reach the line 3, 3. If two hands extend from 1, 1, to 2, 2, they will effectually prevent the elevation of the ribs from 4 to 5, as the line 2, 2, cannot be moved to 3, 3.
What effect has a full inspiration on the ribs and diaphragm? How is the chest enlarged between the spinal column and sternum? What is said of the lateral diameter of the chest? Explain fig. 95.
478. The central portion of the ribs is raised by the action of intercostal muscles. The first, or upper rib, has but little movement; the second has more motion than the first, while 219 the third has still more than the second. The second rib is elevated by the contraction of the muscles between it and the first. The third rib is raised by the action of two sets of muscles; one lies between the first and second ribs, the other between the second and third. The motion of each succeeding rib is increased, because it is not only acted upon by the muscles that move the ribs above, but by an additional intercostal; so that the movement of the twelfth rib is very free, as it is elevated by the contraction of eleven muscles.
479. The tenth rib is raised eight times as much as the second rib, and the lateral diameter of the lower portion of the chest is increased in a corresponding degree. At the same time, the muscular margin of the diaphragm contracts, which depresses its central portion; and in this way, the chest is enlarged forward, laterally, and downward, simultaneously with the relaxation of the walls of the abdomen.
480. The lungs follow the variations of capacity in the chest, expanding their air-cells when the latter is enlarged, and contracting when the chest is diminished. Thus, when the chest is expanded, the lungs follow, and consequently a vacuum is produced in their air-cells. The air then rushes through the mouth and nose into the trachea and its branches, and fills the vacuum as fast as it is made. This mechanical process constitutes inspiration.
481. After the expansion of the chest, the muscles that elevated the ribs relax, together with the diaphragm. The elasticity of the cartilages of the ribs depresses them, and the cavity of the chest is diminished, attended by the expulsion of a portion of the air from the lungs. At the same time, the muscles that form the front walls of the 220 abdominal cavity, contract, and press the alimentary canal, stomach, and liver, upward against the diaphragm; this, being relaxed, yields to the pressure, rises upward, and presses upon the lungs, which retreat before it, and another portion of air is expelled from these organs. This process is called expiration.
478. Describe the action of the intercostal muscles upon the ribs. 479. How does the elevation of the tenth rib compare with the second? What effect has this elevation upon the lateral diameter of the chest? 480. Describe the process of inspiration. 481. Describe the process by which the air is forced out of the lungs.
Fig. 96.
Fig. 96. A front view of the chest and abdomen in respiration. 1, 1, The position of the walls of the chest in inspiration. 2, 2, 2, The position of the diaphragm in inspiration. 3, 3, The position of the walls of the chest in expiration. 4, 4, 4, The position of the diaphragm in expiration. 5, 5, The position of the walls of the abdomen in inspiration. 6, 6, The position of the abdominal walls in expiration.
482. Thus it is obvious that the enlargement of the chest, or inspiration, is produced in two ways: 1st. By the depression of the convex portion of the diaphragm; 2d. By the elevation of the ribs. On the contrary, the contraction of the 221 chest, or expiration, is produced by the depression of the ribs, and elevation of the central part of the diaphragm. These movements are successive during life, and constitute respiration.
Explain fig. 96. 482. In how many ways may the chest be enlarged, and how is it accomplished? How is the contraction of the chest effected?
Fig. 97.
Fig. 97. A side view of the chest and abdomen in respiration. 1, The cavity of the chest. 2, The cavity of the abdomen. 3, The line of direction for the diaphragm when relaxed in expiration. 4, The line of direction for the diaphragm when contracted in inspiration. 5, 6, The position of the front walls of the chest and abdomen in inspiration. 7, 8, The position of the front walls of the abdomen and chest in expiration.
Experiment. Place the ear upon the chest of a person, and a murmuring sound will be heard, somewhat like the soft sighings of the wind through forest trees. This sound is 222 caused by the air rushing in and out of the lungs, and is peculiarly distinct in the child.
Explain fig. 97. How may the murmur of respiration be heard?
483. It is not easy to decide how much air is taken into the lungs at each inspiration. The quantity, however, must vary in different individuals, from the difference in the condition and expansion of the lungs, together with the size of the chest. From numerous experiments, the quantity, at an ordinary inspiration, of a common-sized man, is fixed at forty cubic inches. It has been estimated that one hundred and seventy cubic inches can be thrown out of the lungs by a forcible expiration, and that there remain in the lungs two hundred and twenty cubic inches; so that these organs, in their quiescent state, may be considered as containing about three hundred and ninety cubic inches of air, or more than a gallon.
484. Respiration is more frequent in females and children than in adult men. In diseases, particularly those of the lungs, it is more increased in frequency than the action of the heart. In health, the smallest number of inspirations in a minute by an adult, is not less than fourteen, and they rarely exceed twenty-five. Eighteen may be considered an average number. The quantity of oxygen taken into the lungs at each inspiration is about eight cubic inches, one half of which disappears in every act of respiration.
Observation. Under different circumstances, however, the consumption of oxygen varies. It is greater when the temperature is low, than when it is high; and during digestion the consumption has been found one half greater than when the stomach was empty.
483. Can it be ascertained with accuracy how much air is taken into the lungs at each inspiration? Why not? What is the probable quantity that an ordinary sized man inspires? How much can be thrown out of the lungs at a forcible expiration, and how much remains in the lungs? From these calculations, how much may they contain in their quiescent state? 484. In whom is respiration most frequent? How in disease? How in health? How many may be considered an average number? When is the consumption of oxygen the greatest?
223485. Dr. Southwood Smith has lately performed a series of very interesting experiments, from which he deduces the following general results: “1st. The volume of air ordinarily present in the lungs is about twelve pints. 2d. The volume of air received by the lungs at an ordinary inspiration is one pint. 3d. The volume of air expelled from the lungs at an ordinary expiration, is a little less than one pint. 4th. Of the volume of air received by the lungs at one inspiration, only one fourth part is decomposed at one action of the heart. 5th. The quantity of blood that flows to the lungs, to be acted upon by the air at one action of the heart, is two ounces, and this is acted on in less than one second of time. 6th. The quantity of blood in the whole body of the human adult, is twenty-five pounds avoirdupois, or twenty pints. 7th. In the mutual action that takes place between the air and blood, every twenty-four hours, the air loses thirty-seven ounces of oxygen, and the blood fourteen ounces of carbon.”
486. Apparently, atmospheric air is a simple element. But chemical analysis shows its composition to be oxygen and nitrogen, in the proportion of twenty-one parts of the former, and about seventy-nine of the latter. In addition, there is a small amount of vapor of water and carbonic acid. The pressure of this invisible, elastic fluid upon the body of an ordinary sized adult, is estimated to equal thirty-five thousand pounds.
487. The principal substance of a vitiated character in the dark-colored blood is carbonic acid. And since there is no chemical affinity between the oxygen and nitrogen of the air, the former readily unites with some of the elements of the blood. Hence, whenever blood is presented to the 224 air in the lungs, the oxygen leaves the nitrogen, and becomes mixed with the circulating fluid. (Appendix J.)
485. State the 1st, 2d, 3d, and 4th deductions from the experiments of Dr. Southwood Smith. The 5th, 6th, and 7th. 486. Of what is atmospheric air composed? What is the weight of air upon a common sized man? 487. What is the principal substance of a vitiated character in the dark-colored blood? What is said of the chemical affinity between oxygen and nitrogen?
488. Again, carbonic acid and water have a stronger affinity for atmospheric air than for the other elements of the blood. Consequently, when they are brought into contact with the air in the lungs, the carbonic acid and water leave the other constituents of the blood, and unite with the air. In this way the bluish, or impure blood is relieved of its impurities, and becomes the red, or pure blood, which contains the principles so essential to life. (Appendix K.)
489. The formation of carbonic acid and water, eliminated from the system through the lungs and skin, is explained by the following theory: In the lungs and upon the skin the oxygen separates from the nitrogen and unites with the blood in the capillary vessels of these organs. The oxygen is conveyed with the blood to the capillary arteries and veins of the different tissues of the system. In these membranes there is a chemical union of the oxygen with the carbon and hydrogen contained in the blood and waste atoms of the system. This combustion, or union of oxygen with carbon and hydrogen, is attended with the disengagement of heat, and the formation of carbonic acid and water. (Appendix L.)
490. The following experiment will illustrate the passage of fluids through membranes, and the different affinity of gases for each other. Put
Comments (0)