Physiology and Hygiene for Secondary Schools

to distribute heat, it is necessary to keep it moving, or circulating, in all parts of the body. So closely related to the

n 1628 he published a treatise in Latin on the circulation. The chief arguments advanced in support of his views were the presence of valves in the heart and veins, the continuous moveme

of the nature and purpose of the circulation was the necessary first step in understanding the plan of the b

for holding the blood and for keeping it in motion through the body. The heart, which is the chief organ for propelling the blood, acts as a force pump, while the arteries and veins serve

c cavity. Dotted lines show positin

e lungs. It is cone-shaped and is so suspended that the small end hangs downward, forward, and a little to the left. When from excitement, or other cause, one becomes conscious of the movements of the heart, th

, but its relation to this space is like that of the hand to the inside of an empty sack which is laid around it (Fig. 14). The inner layer of the pericardium is closely attached to the heart muscle, forming for it an outside covering. The outer layer hangs loosely around the heart and is

y the heart. B. Space inside of pericardial sac. a. Inner layer of pericardium and ou

e. On each side are two cavities, the one being directly above the other. The upper cavities are called auricles and the lower ones ventricles. To distinguish these cavities further, they are named from their positions the right auricle and the left auricle, and the right ventricle and t

e. 4. Right auricle. 5. Left auricle. 6. Right ventricle. 7. Left ventricle. 8. Chord? tendine?. 9

ovements. They consist of tough, inelastic sheets of connective tissue, and are so placed that pressure on one side causes them to come together and shut up the passageway, while pressure

6). It consists of three parts, as its name implies, which are thrown together in closing the opening. Joined to the free edges of this valve are many small, tendinous cords which connect at their lower ends with muscular pillar

icle,[pg 044] with the free margins extending into the ventricle. It is exactly similar in structure and a

s and valves. B. Right semilunar valve. The tricuspid

ssue which hang loosely from the walls when there is no pressure from above; but upon receiving pressure, the pockets fill and project into the opening, closing it c

auricles, while the walls of the left ventricle are two or three times thicker than those of the right. A less marked but similar difference exists between the auricles and also between the valves on the

ht ventricle forces the blood through the lungs and into the left auricle. The left ventricle forces bl

f the circulatory system, it makes actual connection with only a few of the blood tubes. These en

superior vena cava receives blood from the head and the upper extremities; the inferior vena

nary veins. These receive blood from the

. This receives blood from the heart and by its b

a receives blood from the heart and through its

walls. During contraction the cavities are closed and the blood is forced out of them. During relaxation the cavities open and are

which correspond to its different cavities. These connect with each other and with the blood

illustrating the

contraction of both the auricles and the ventricles.19 On account of the work which they perform, the auricles have been called the "feed pumps" of the heart; and the ventricles, the "force pumps."20 It is the function of the auricles to collect the blood from the veins, to let this run slowly into the vent

d and the two are fairly imitated by the words "lūbb, d?p." While the cause of the first sound is not fully understood, most authorities believe it to be due to the contraction of the heart muscle and the sudden tension on the va

the capillaries. The veins receive the blood from the capillaries and return it to the heart. The arteries and veins are similar in structure, both having the form of

layer of connective tissue. The inner coat is continuous with the lining of the he

voluntary, muscular fibers. This coat is quite thin in th

nnective[pg 048] tissue and is also much thicke

dissected to

tubes stand open when empty, whereas the veins collapse. The arteries also are highly elastic, while the veins are but slightly elastic. On the other hand, many of the veins contain valves, formed by folds in the inner coat (Fig

plit open to s

om bursting when the blood is forced into them from the ventricles, and it is a means of supplying pressure to

Then while the ventricles are resting and filling, the stretched arteries press upon the blood to keep it[pg 049] flowing in

places in the body, such as the wrist. This expansion, known as the "pulse," is the chief

ample, close the small veins in its vicinity and diminish the capacity of the larger ones. The natural tendency of such pressure is to empty the veins in two directions-one in the same direction as the regular movement of the blood, but the other in the opposite direction. The valves by closing cause the contracting muscle to push t

keeps the capacity of the blood vessels equal to the volume of the blood. Since the blood vessels are capable of holding more blood than may be[pg 050] present at a given time in the body, there is a liability of empty spaces occurring in these

stion. To increase the blood supply, the muscular coat relaxes. The arteries are then dilated by the blood pressure from within so as to let through a larger quantity of blood. To diminish the supply, the muscle contracts

ry small vein. Shading indicates the change of color of the blood as it passes

r of less than one two-thousandth of an inch (12 μ) and an average length of less than one twenty-fifth of an inch (1 millimeter). Their walls consist of a single [pg 051] coat which is continuous with the linin

hly magnified, showing its coat

he thinness of their walls, the capillaries a

aterials into t

pass from the blood vessels

f the work of the capillaries is apparent. To serve its purpose as a carrier, there must be places where the blood can load up w

g the blood out and of bringing it very near the i

of capillaries to another. Since pressure is necessary for moving the blood, these tubes must connect with the source of the pressure, which is the heart. In the arteries and veins the blood neither receives

his heart. The two divisions are known as the pulmonary and the systemic circulations. By the former the blood passes from the right ventricle through the l

ght auricle, tricuspid valve, right ventricle, right semilunar valve, pulmonary artery and its branches, capillaries of the lungs, pulmonary veins, left auricle, mitral valve,

nging from a dark red to a bright red color. In the systemic capillaries it gives up ox

the liver is called the portal circulation, and another in the kidneys is termed the renal circulation. To some extent t

kes on and gives off materials. 1. Body in general. 2. Lungs. 3. Kidneys. 4.

ly high pressure is maintained in the arteries nearest the heart.21 This pressure diminishes rapidly in the[pg 054] small arteries, becomes comparatively slight in the capillaries, and falls practically to nothing in the veins. Near t

ugh the capillaries is accounted for by the fact that their united area is many times greater than that of the arteries which supply, or the veins which relieve, them. This allows th

entricles are in a state of relaxation. It is also aided by the muscles and elastic tissue in all of the blood vessels. These, by keeping the blood vessels in a state of "tone," or so contracted that their capacity just equals the volume of the blood, enable pressure from the heart to be transmitted to all parts of the blood stream. A further aid to t

g

OF THE C

trengthened by a moderate increase in its usual work.23 It may even be subjected to great exertion without danger, if it be trained by gradually incr

f the amateur athlete, bicyclist, or mountain climber is frequently injured by attempting more than the previous training warrants. The new wo

eats, and pains in the heart region frequently arise from this cause. It is through their effect upon the nervous system that worry, overstudy, undue excitement, and dissipation cause disturbanc

ohol is a disturbing factor in the circulation. It increases the rate of the heart beat and dilates the capillaries. Its effect upon the capillaries is shown by the "bloodshot" eye and the "red nose" of the hard drinker. Another bad effect from the use of much alcohol is the weakening of t

co is begun in early life, it interferes with the growth of the heart, leading to its weakness in the adult. 2. When used in c

the proper control of the heart. In some individuals the taking of a very small amount of either tea or coffee is sufficient to

ered defective and, to perform its[pg 057] function in the body, must work harder than if it were in a normal condition. Rheumatic attacks of the heart do most harm when they occur in early life-the period when the valves are the most easi

e normal muscular "tone" of the blood vessels is a problem of great importance. Though the muscles of the blood vessels cannot be exercised in the same manner as the voluntary muscles, they may be called actively into play through all the conditions that induce changes in the blood supply to different parts of the body. The usual forms of physical exercise necessitate such changes and indirectly exercise the muscular coat. The exposure of the body to cold for

t cotton, sold in small packages at drug stores, is excellent for this purpose and should be kept in every home. A simple method of checking "nosebleed" is that of drawing air through the bleeding nostril, while the other nostril is compressed with the finger.24 Another method is to "press with the fing

ightly bandaged on the side of the wound nearest the heart; if a vein, on the side farthest from the heart. In addition to this, the edges of the wound should be closed and covered with cotton fiber and the limb should be placed on a support above the level of the rest of the body. A large handkerchief makes a convenient bandage if properly applied. This should be folded [pg 059]diagonally and a knot tied in the middle. Opp

onditions which enable materials both to enter and to leave the blood stream. The heart is the chief factor in propelling the blood, although the muscles and the elastic tissue in the walls of the arteries and the valves in t

n the study of the body was the disco

ty for a circulating

ng and naming the essential parts. Show also the connectio

endine? to that served by doorstops (the stri

what class of pumps does it belong? What spec

at use are the valves in

contracting muscles in different parts of

ge is the elastici

ed from the capillar

fference in structure betwee

complete circulation, naming all the divisions of

n of the heart be as long as the period of contraction, how

capillaries. Show how their str

the heart? What forms of exercise tend to injure it?

heumatism inj

ng the flow of blood from smal

TICA

the class is limited, the practical work may be confined to the study of the heart model, diagrams of the heart and the circulation, and a few

. To insure the specimen against mutilation, the lungs and the diaphragm must be left attached to the

phragm, and large blood vessels. Inflate the lungs and o

opening thus made until it is large enough to slip the heart out through it. Then slide back the pericardium until its connection with the large bl

s are to be distinguished by their thick walls. The heart may now be severed from the lungs by cutting t

for demonstrat

d portions are the auricles. The thicker and denser side lies toward the left of the animal's body and is called the left side of

s groove and cut toward the base of the heart until the pulmonary artery is laid open. Then, following within half an inch of the groove, cut down and around the right side of the heart. The wall of the right ventricle may now be raised and the cavity exposed. Observe the extent of the cavity, its shape,

it open for [pg 062]observation. Observe the openings into the auricle, there being one each for the vena cava superio

he cavity to the apex; it will also show the thickness of the walls and the shape of the cavity. Split u

find the places of entrance of the pulmonary veins. Examine the mitra

insure the semilunar valve's being left in good condition. After tying or plugging up the holes in the sides of the artery, pour water into the small end and observ

containing water. By alternately compressing and releasing the bulb, water is pumped from one vessel into the other. The bulb may be taken to represent one of the ventricles.

rating elastic

er tube three or four feet in length and having rather thin walls. In the opposite end of the rubber tube insert a sh

water is forced into it. (This is best ob

al when no pressure is being applied from the bulb. Compare with the ac

rubber tube. (In fitting the glass tube to the bulb use a very short rubber tube.) Ob

er (by sucking) to within about six inches of the end. Lay on the table with the glass tubes secured in an upright position (Fig. 26). Now compress the tube with the hand,

tus for showing advant

ssing with the hand some portion of the tube on the table. Observe in this instance that the water is all pushed in the same direc

on its surface. With a finger, stroke one of the veins toward the heart, noting that, as the blood is pushed along on one side of the finger the blood follows

eats during a period of one minute under the following conditions: (a) when sitting; (b) when standing; (c) after active exercise, a

e [pg 064]right hand and arm, clenching and unclenching the fist and flexing the arm at the elbow. Place the hands again side by

the degree to which the large veins are filled. Repeat the experiment, reversing the position of the hands. What results are observed? In what parts of the body does gravity aid in the return of the blood

attached to a thin board which has an opening in one end over which the web of the foot may be stretched. Threads should extend from two of the toes to pins driven into the board to secure the necessary tension of the web, and the foot and lower leg should be kept moist. Using a two-thirds-inch objective, observe the branching of the small arteries into the capillaries

refully wrapped with strips of wet cloth and securely tied to the board. The wrappi

g