A textbook of physiology for nurses

Front matter

NATIONAL LIBRARY OF MEDICINE

SURGEON GENERAL'S OFFICE

LIBRARY.

Preface

It is presumed that the pupil nurse, for whom this book has been compiled, is familiar with the writer’s Anatomy for Nurses, and has a similar knowledge of physies and chemistry. Technical terms have been employed, without full explanation, upon this assumption. A brief appendix containing an outline of some physieal and chemical phenomena has been added for those who have not received a proper introduction to these subjects.

In the preparation of the work we have chiefly relied on the work of Luciana, Howell, Pearce-Macleod, Jones and Bunce, Mallet’s Syllabus of Chemistry, ~Ganot’s Physics, and Bliss and Olive’s Physics and Chenustry for Nurses. The work is an elementary one and has no claim to originality except in arrangement and treatment.

W. G. CHRISTIAN.

C. C. HASKELL.

Richmond, Va.

Appendix

APPENDIX

ILLUSTRATIONS

FIG. PAGE Profile of Skeleton Frontispiece 1. Simple tissues Be Soa tees Keke 18 2. White blood corpuscles from man 20 3. Diagram of entire circulation 22 4. Diagram of valves of the heart Bos Sern 25 5. Cross section of small artery and veins: A, artery; V, vein 27 6. The aorta and its branches Bye eee ae 28 7. Apparatus for measuring the Galeviat blood pressure in 10) | ee tana Manits cae 31 8. The position of the lungs in the ae cue O 9. Diagram of structure of lungs showing eee tanks bronchioles, and alveoli 36 10. Front view of organs. Semidiagrammatic 49 11. Diagram of the alimentary tube and its appendages 52 12. The stomach and duodenum opened 56 13. Schema of simple reflex are 58 14. Cross section of pancreatic tubule sos 60 15. Injected lacteal vessels in two villi of human intestine 3 16. The microscopic structure of the liver Cts 17. Portion of transverse section of human liver 78 18. Vertical section of human spleen 80 19. Longitudinal section through the kidney “oo 20. Diagrammatic representation of the course of the eS ous tubules and the kidney vessels 86 21. The thyroid gland 95 22. Schema of simple reflex are 100 25. Brain, lateral view 101 24. Cortical centers in man 103 25. Brain, mesial view SEN eke Prunes Utah nce er 104 26. Diagram of section of spinal cord, showing tracts 111

14 i ILLUSTRATIONS

FIG. , 27. The simplest reflex are in the spinal cord . . . . 28. Orbital muscles . . . ae ae ea a

29. Section through the iitaeiby partion of the eye . .) 4 a 30, Formation of image on reting . . . .. . . ss» % 31. Errors in refraction. .. PES Cee age 32. Tympanum of right side with the anions ‘icehedngs in place 33. Semidiagrammatic seetion through the right car... fs 54. Diagrammatic view of the organ of Corti . . . . . .

Chapter I

Just as anatomy is a study of form, physiology is a study of function. Anatomy studies the appearances of the bones, ligaments, muscles, vessels, nerves and viscera, by dissecting the dead body. Physiology explains that bones are supports and levers; ligaments, binding tissue ; muscles, moving agents; vessels, channels for circulating fluids; nerves, conducting agents; viscera, agents of secretion or excretion necessary for life and growth. Physiology can not be Jearned from the dead hody, though some of it can be guessed at, but must be discovered by observation of the living animal or plant. Examination and analysis of the cells of which bodies are composed may reveal their physical and chemical character, but the more thorough the analysis, the more complete the destruction of the cells and the more impossible it is to investigate their vital activities. Hence many vital phenomena are still unexplained, though the number is daily decreasing.

The most widely distributed of all the tissues of the body is the blood. It is the universal solvent for all material used in building other tissues, in keeping them in a state of health by carrying food to them and by removying worn out or injurious material from them. The funetions of the blood and the forces of the circulation make, aK

‘sanssly aydmig—] “3147

The blood consists of a liquid, plasma, and solid bodies, red corpuscles, or erythrocytes, blood platelets; and white corpuscles, which are of two kinds, leucocytes and lymphocytes.

The plasma is all of the liquid part of the blood as it exists in the living animal and is to be distinguished from ‘‘serum,’’ which is the liquid part after coagulation has occurred. Plasma consists chiefly of water, but contains other substances of the greatest importance. The inorganic salts, such as sodium chloride, calcium chloride, and potassium chloride, as well as compounds of these bases with other acid radicals, are of importance in regard to the phenomena of osmosis, as influencing the irritability of muscle and nerve, and are supposed to play an important role in the maintenance of the heart beat. Calcium salts cause an increased vigor of contraction and if present alone, cause the heart to stop tightly contracted; while the salts of potassium tend to cause relaxation. It is suggested that the presence of these salts in proper concentrations causes the alternate contraction and relaxation of the heart during life.

Among the organic constituents are proteins, which are known as fibrinogen, serum albumin, and serum globulin or paraglobulin. In addition, there are what may be designated as temporary constituents of the plasma, substances on their way from the digestive canal to the tissues, such as fat, sugar, the results of protein digestion; as well as waste products on their way to the organs of excretion; bodies known as hormones, which are produced at one part of the body and sent elsewhere to influence other structures; substances which are manufactured to enable the animal to overcome bacterial invasion; and certain substances which resemble ferments in their action. Among the latter may be mentioned prothrombin, which, as we shall see, is active, in causing bloodclotting or coagulation.

Of the formed elements of the blood, the red corpuscles or erythrocytes are the most numerous. There are about five million of these to the cubie millimeter of the blood of a healthy man; women are supposed to have about five hundred thousand less. They contain a substance known as hemoglobin, which, by virtue of its iron content, is capable of forming unions with gases, especially with oxygen, and to a less extent with earbon dioxide. These unions, as we shall find, are essen-

Fig. 2.—White blood-corpuscles from man. (Hill’s Histology.)

tial for the processes of respiration. The number of these corpuscles is reduced under certain pathologic condition, as in the various anemias; and may be increased when there is a great loss of fluid from the body, as in cholera or where there is a diminution in the amount of oxygen in the surrounding air, as in ascents to great heights.

The white cells serve an entirely different function in the body. There are from five to ten thousand to the cubie millimeter of blood on the average, but this number is subject to wide variations under altered conditions. The white cells are of assistance in the digestion of protein and in the transportation of fat in the blood, which probably explains the increase in their numbers following a meal. Cold baths and pregnancy are other ‘‘physiologic’’? causes of increased numbers of leucoeytes. A very important duty of the white cells 1s to combat bacterial invasion, and it is found that many infectious diseases are accompanied by an increase in the number of the leucocytes, this leucocytosis often being of value in the diagnosis. In pneumonia, for instance, the number not infrequently is increased to forty or titty thousand to the cubie millimeter. In the leucemias, there is often a still larger increase ; while in some other diseases, such as typhoid fever, there is a reduction ‘in the number, this being known as a leucopenia.

There are about three hundred thousand platelets to the cubic millimeter. These are small dise-shaped bodies when examined with proper care, but usually disintegrate and appear simply as detritus in the ordinary stained specimens of blood. Their functions are imperfectly understood; they appear to be of importance in the coagulation of the blood, and it is claimed that their number is reduced in the hemorrhagic diseases.

Lymph.—It must be understood that the tissue cells are not bathed direct in blood. The blood, carried in its system of vessels, has been likened to a wholesaler, and the part of the retailer, coming in intimate contact with the consuming tissue cells, is taken by the lymph. The lymph is derived from the blood by the processes of filtration and osmosis, and is poured out into the spaces surrounding the cells. Containing the nutritive substances derived from the blood, it turns these over to the cells and receives waste products from the latter. It is forced into special vessels, known as lymphatic channels, and finally is carried back into the blood stream through the right and left lymphatie ducts. Along th course of the lymphatic channels are found the lymphatie glands, which act as filters, attempting to prevent the entrance of bacteria or toxins into the circulation. The ‘‘waxen kernels’? are lymphatic glands that have become inflamed and swollen as the result of the action of some toxie agent.

Coagulation—The clotting or coagulation of the blood is nature’s way of stopping hemorrhage and where there is derangement of the process, serious or even fatal hemorrhage may occur from an apparently trivial wound. A substance known as prothrombin and salts of calcium is found in the blood. If calcium acts on prothrombin, it converts the latter into thrombin and thrombin causes fibrinogen, a soluble protein of the blood plasma, to assume an insoluble form, known as fibrin, this latter constituting the clot, enclosing the red corpuscles in its meshes. The white cells possess the power of movement, so they are not included in the clot to any considerable extent. That blood does not normally clot in the vessels, is explained by the presence of a substance known as antithrombin, which prevents the action of the calcium salts on the prothrombin. When tissues are wounded, another substance, known as kephalin or ‘‘thromboplastice’’ substance, neutralizes the antithrombin and allows the conversion of prothrombin into active thrombin. If blood is obtained by puncturing a vein and drawing the blood into a perfectly clean syringe, contact with wounded tissue is prevented and coagulation is delayed, because the thromboplastie substance is not derived from passing over wounded tissue. Clotting will oecur, however, because the platelets will gradually disintegrate and furnish the requisite thromboplastic material. The hemorrhagic diseases which have been mentioned, are accompanied by a marked inerease in the a cava soy ven Sag e ee right auricle LA ventricle ejuoe inferior vena cava

Jhepatic veins

» mh Owe ” systemic ©

Fig. 3.—Diagram of entire circulation.

coagulation time, so that individuals have bled to death after the extraction of a tooth or the production of similar small wounds.

The circulatory apparatus consists of a central pumping station, the heart; a set of vessels leading from the heart to all portions of the body, the arteries; an immense number of small thin-walled vessels, the capillaries, in which the arteries terminate; and a set of vessels, the veins, which return the blood to the heart. The schematic drawing shows that arteries constantly diminish in size as they get further from the heart, that the capillaries are the terminations of arteries and beginning of veins, and that the veins, by one vein joining another, increase in size as they approach the heart. The total area of capillaries is greater than that of the veins and much greater than that of the arteries. If the blood in the arteries differs from that in the veins, it is obvious that there must be a sort of midpoint in the capillary system where arterial changes to venous blood; and if this is true, it is apparent that the arteries carry something to the tissues which they need and that the veins take something away which is either useless or injurious. The object of the circulation of the blood is, there- _ fore, briefly, to feed or irrigate the tissues through the arteries and to drain them through the veins. But the veins can not pour out the blood so charged, because it would waste the blood which ean be purified; so the lungs have been provided to burn up the waste material and change venous back to arterial blood which is further cleansed by the liver.and kidneys. The course of the circulation is then from the heart through the arteries and capillaries to the tissues where arterial is changed to venous blood; through venous capillaries and veins to the heart and thence to the lungs where venous is changed to arterial blood and thence back to the heart to go over the same route as long as life lasts. The heart is, therefore, the main force of the cireulation. Anatomy has taught us that it is a four-chambered hollow muscle. The two thin-walled chambers at the base are called auricles, the two thick-walled chambers forming the apex, the ventricles. Both the left auricle and ventricle are thicker than the right, but the left ventricle is much thicker than any other part of the organ. The right half is concerned with venous blood and the pulmonary circulation. The blood from the upper extremities, head and neck is collected and poured into the right auricle through the superior vena cava; that from the lower part of the body enters the same cavity through the inferior vena cava. From the right auricle the course is into the right ventricle through the auwriculoventricular opening, thence through the pulmonary artery into the lungs whence it is collected by the four pulmonary veins and earried into the left auricle from which it flows through the left auriculoventricular opening into the left ventricle from which it is pumped through the aorta to all parts of the body.

The auriculoventricular openings are guarded by valves composed of triangular flaps, the right—tricuspid -—having three, and the left—bicuspid, or mitral—haying two. The two auricles fill at the same time. As the blood flows in through cave or pulmonary veins, it passes through the auriculoventricular openings into the eorresponding ventricle until that cavity is nearly full. As the blood rises in the ventricle it floats the valve flaps away from the walls of the ventricles and toward the opening. This action continues until there is but a slitlike aperture between the flaps. Just at this moment the auricle contracts, forees into the ventricle all the blood it will hold and presses the valves tightly across the opening into which it would project if the papillary muscles did not contract and hold the edges of the valve at just the right angle. This action of the auricles is called auricular systole (from a Greek word meaning to contract). With a barely perceptible pause ventricular systole begins, the blood is forced into the aorta and pulmonary artery, whose openings are guarded by three euplike folds called semilunar valves. As the blood rushes between these cups some of it gets into three lit-

_ Fig. 4—Diagram of valves of the heart. ‘The valves are supposed to be viewed from above, the auricles having been partially removed. A, aorta with semilunar valve; B, pulmonary artery and valve; C, tricuspid, and D, mitral valve; FE, right, and F, left coronary artery; G, wall of right, and H, = left auricle; 7, wall cf right, and J, of left ventricle. (Stewart’s Physiology.)

tle pockets, sinuses of Valsalva, between the valve folds and the arterial walls, so that when the foree from behind ceases the weight of the blood and the elastic recoil of the vessels force each flap towards the opening, and, the three flaps coming together, the return of blood to the heart is prevented. This completes the contractile or systolic period of the heart cycle and the period of rest, diastole, begins. A cardiac cycle, therefore, consists of two distinct parts; i.e., auricular systole, ventricular systole, and diastole, or rest. The closure of the auriculoventricular valves takes place at the same instant; that of the semilunar valves a little later. The sound of the first, dull and low pitched and confused with the sound made by contracting muscle, is called the first sound of the heart; the sharp, high, short click of the semilunar valves, make the second sound. Cardiac systole lasts about the tenth of a second, diastole about five tenths; so that the heart is at rest about sixty per cent of the time.

Exact closure of all the valves is necessary to prevent leakage. It follows, therefore, that if any valve is too short or too long, has a rough place on it either through the presence of a foreign body or a wound, it will not meet its fellows exactly and there will be a falling back of blood into the chamber which that valve guards. Or if the opening is too small from any cause, there will be greater difficulty in driving the blood through, or it would take a longer time. Either defect would cause a change in the heart sounds.

Various infectious processes are apt to cause such damage to the valves through the production of ‘‘endoearditis,’’? an acute inflammatory process involving the inner lining of the heart. When the inflammation subsides, scar tissue appears and, as is always the case with such tissue, contraction causes a distortion of the leaflets with a resultant leakage. Rheumatic fever, tonsillitis, chorea, and pneumonia are the commonest predisposing causes for endoearditis.

The heart is the chief, but not the only, force of the circulation. The arteries are lined by a thin ecoat—the intima—continuous with the lining membrane of the heart; but around this their walls are composed of fi-

CIRCULATION oT brous, muscular and elastic tissue. The latter is particularly important. If fluid is put into an iron pipe until it is full, no force will get any more of the liquid in; but if the same experiment is tried with a rubber tube, not only ean an additional amount be forced into the stretched tube, but, as soon as the power is withdrawn, the additional fluid will be squeezed out, even against vravity, by the elastic contraction of the tube. When the heart forces blood into the aorta, that tube expands. As soon as the heart ceases to contract, the elastic coat

Fig. 5.—Cross section of small artery and vein: A, artery; V, vein. (Hill’s Histology.)

of the artery contracts. If the semilunar valves hold, no blood ean return to the heart and the contraction of the elastic artery must drive the blood onward into the smaller arteries. The elastic recoil of the arteries themselves, is, therefore, the second great force of the cireulation and one which acts continuously. The heart acts only during systole, the recoil of the arteries continues during diastole. As the arteries diminish in size they offer greater resistance, partly by friction, to the passage of the blood; and as their distance from the heart inereases and their strength diminishes, the heart’s impact and the elastic recoil both lose power until, in minute arteries the blood flow approaches the character of a steady stream instead of the jet-like type of the larger arteries. In the arteries the blood leaps in jets; in the capillaries it oozes; in the veins it flows. It is like a swift torrent which spreads into a marsh where movement is barely perceptible until its outlet is found in a deep, dirty, sluggish stream.

The venous current is collected by the veins from the capillaries. The blood, through capillaries and veins, still receives an impulse from the heart, but not in sufficient strength to complete the return circulation. Certain accessory forces are, therefore, called into play. The first of these is the suction of the thorax caused by inspiration, and described under that head. A more widespread factor is that of the valves in the veins, particularly those so located that gravity habitually retards the flow. These valves are half cup shaped, concavity upward, very much like the semilunar valves, so arranged that the blood fiows easily over their free surface, but is caught in the hollow cup when it attempts to fall back. From this position it is forced on to the next valve partly by the push of the heart from behind, partly by suction of the thorax in front and largely by the massage-like action of the muscles which squeeze and compress the veins and drive the blood to the uext valve, where the same process is repeated.

Circulation Time.—The circulation time can not be definitely stated. The usual estimate is that from twenty-five to thirty beats of the heart are required to complete the circulation; i.e., to drive the blood throughout the body. About a fourth of this number completes the pulmonary circulation. The velocity through different vessels also varies as does the quantity supplied to each

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‘Osrerces tam organ. The latter has been determined by experiments which prove that in every minute each hundred grams of the leg receive 5 ¢.c. of blood; while the same weight of spleen would receive 58 ¢.c¢., of brain 136 ¢.c. and of the thyroid no less than 560 ¢.c. in the same time.

Circulation Velocity—Circulation velocity does not refer to the rapidity of flow through any given vessel, but to the time it takes for a given portion of blood to pass between two points as from one jugular vein through the heart, pulmonary artery, veins, left heart, aorta and capillaries of the head to the opposite jugular. This is determined by putting some methylene blue in one jugular and watching for its appearance in the other. This has been accurately determined in many lower animals and is estimated to be about thirty-two seconds in man. As the rate of flow is much more rapid in the largest than in the smallest-arteries, in the arteries than in the capillaries, and in the veins than in the eapillaries, it can not be calculated by simply watching the speed with which corpuscles pass through one of the vessels. Of course the velocity of the blood current will not be confounded with the rate of the pulse, which is an impact rather than a current.

The Pulse.—The pulse is seen and normally felt only in the arteries. The capillary and venous systems are so much wider than the arterial, that the force of the heartbeat is not displayed in the pulsatile or expansile manner so characteristic of the latter. The column of blood extending from the heart throughout the arteries may be compared to a series of balls suspended by strings and each touching the other. If the first of the series is struck sharply the power will be transmitted throughout the series, but it will visibly affect the last only. If fresh blood is pumped into the aorta, that particular blood will immediately flow but a short distance, but the force will be applied to every drop of blood in every artery. Each artery will expand and contract just as the aorta does and the expansion will be synchronous with the heartbeat; but that particular jet of blood will not reach the artery being felt for several seconds. It follows from this that the greater the power of the heartbeat the stronger will be the pulse; the more frequent the heartbeat, the more rapid the pulse, the more the capillaries are expanded, the less the resistance to the outflow, the more compressible the pulse and the lower the blood pressure.

In the lungs the blood circulates under the same general conditions as in other parts of the body. Pressure is less in the pulmonary vessels because the right ventricle is weaker than the left. Inspiration and expiration also affeet both the systemic and pulmonary circulation. In inspiration about one-twelfth of all the blood in the hody is in the lungs, while expiration reduces this to one-fifteenth or eighteenth.

Blood Pressure.—If liquid be pumped into an inelastic tube, the pressure will be exactly proportionate to the quantity of fluid and the foree of the pump. As soon as the pump ceases to act, the pressure falls to zero. If the same experiment be conducted with an elastic tube pressure will again be equal to force and quantity, but the elastic recoil of the tube will maintain some pressure after the pump ceases to act. If the tube be converted into two whose combined area is as great as that of the single tube, but with thinner walls, pressure will decrease because friction will be greater; and if the proecess of division be continued until each tube is of microscopie size, but their combined area is much greater than that of the original tube, pressure will be very greatly

CIRCULATION Bee diminished. If now several small tubes unite to form one, and this is joined by another formed in the same way and the process is repeated until there is but one tube, the pressure in that will be less than the pressure in the numerous microscopic tubes, and much lower than it was in the one large elastic tube because friction so

-————

Fig. 7.—Apparatus for measuring the arterial blood pressure in man. ‘The pressure in the cuff is raised by means of the syringe until the pulse can no longer be felt at the wrist. ‘This pressure is read off on the mercury manometer (systolic pressure). (Pearce-Macleod, Fundamentals of Human Physiology.)

retards the flow that the larger tube can never be filled.

The arteries, capillaries, and veins form such a set of tubes and blood pressure varies in these sets of vessels.

As ordinarily understood blood pressure means arterial pressure and is taken during systole, systolic pressure or, during diastole, diastolic pressure. The method of determining pressure is to encirele the arm (because there is but one bone and the muscles, when compressed, squeeze the arteries uniformly) with a long rubber sae, enclosed in leather, which is connected by tubing with a column of mercury and an air pump. When air is pumped into the sac until the blood ean no longer pass under it, as shown by disappearance of the radial pulse, the height of the column of mereury is read, This is systolic pressure and, in healthy young men, varies between 110 and 130 mm. of mercury.

Pressure Forces.—Pressure forces are three in number: i.e., the power of the heart, the resistance ot the vessels, and the quantity of blood. In normal animals, the two former change with changing conditions, so that a practically constant level of pressure is maintained the greater part of the time. Decrease in the volume of the blood tends to lower the pressure, but, within certain limits, this is compensated for by increase in the rate of the heart and a constriction of the vessels. Likewise, if fluid is introduced into the vessels, it does not cause a marked and persistent rise in the pressure, due to the same factors working in the opposite direction. The volume of the blood remaining the same, certain drugs are capable of causing vascular contraction, as epinephrine, which, uninterfered with, would cause an enormous rise in pressure. Injecting this drug into the circulation does cause a rise in the pressure, but when this reaches a certain level, the heart is slowed, in order to prevent an undue strain. On the other hand, when the vessels are caused to dilate by nitrites, the

CIRCULATION 33 heart beats more rapidly in the attempt to raise the pressure back to the normal level.

Occasionally, this compensatory action fails. Such is the case in fainting or syneope. Here, the vessels, especially in the abdominal region, dilate, and insufficient pressure is maintained to supply the brain properly with blood, so unconsciousness occurs. In moderate hemorrhage, the loss of blood is compensated for in the manner described, but when the loss has assumed very serious proportions, the pressure falls and unconsciousness results. It is obvious that this fall of pressure is conservative; if it did not take place, great difficulty wuuld oceur in regard to clotting. Therefore, it may be unwise to resort to measures aimed to raise the blood pressure before the bleeding point has been located and the hemorrhage checked.

Diseases which harden the walls of small vessels, converting them into inelastic tubes, have the effect of constricting vessels, increasing resistance and raising blood pressure. Many drugs affect blood pressure either, like digitalis, increasing the power of the heart, or, like the nitrites (amyl, sodium, ete.) by dilating peripheral vessels and causing a fall of blood pressure. Others act upon the nervous mechanism of the heart, which, roughly, consists of a set of sympathetic fibers which accelerate or augment the action of the heart and a set of vagus or pneumogastrie fibers which slow or inhibit its action. This subject will be discussed under the nervous system.

CHAPTER IT

RESPIRATION

The air which surrounds us is in the main composed of two gases, oxygen and nitrogen, thoroughly mixed but not chemically combined. Of these the nitrogen is inert while the oxygen is essential to animal life. The organ which enables us to bring this gas in contact with the blood is the lung, while its use in the animal economy is called respiration. But taking oxygen into the lungs, would be of no service if the process stopped there. It is, therefore, carried by the blood into all parts of the body where the oxygen is used and injurious matter taken up and removed. If two gases be placed one on either side of a wet membrane, like parchment, they will mix with each other by a process called osmosis. If, therefore, a liquid, hike blood, containing oxygen be brought in contact with tissues containing carbon dioxide, the two gases would interchange even if there were no chemical activity to promote the change. Blood going to all parts of the body earries oxygen in combination with hemoglobin. When in contact with live tissue this oxygen is given up to the tissue and earbon dioxide is taken up and earried by the venous blood to the lungs where, in the cells of those organs, a re-exchange is effected, the carbon dioxide being given up and oxygen, derived from the inspired air, takes its place. The last exchange is ealled the external and the first the internal respiration,