WEBVTT 00:06.900 --> 00:12.733 [Wonder Engine of the Body (The Human Heart)] 00:12.733 --> 00:21.266 [Produced with the cooperation of the American Heart Association by The Bray Studios, Inc.] 00:21.266 --> 00:26.966 [Narrator:] The heart is a pumping engine which, from its earliest appearance in the embryo to the end of our life, 00:26.966 --> 00:34.166 keeps our blood in circulation so that all our organs may grow and perform their appointed tasks. 00:34.166 --> 00:40.166 Few people realize the amount of work required of this small mass of muscle 00:40.166 --> 00:44.899 no larger than a man's fist. 00:44.900 --> 00:50.800 Considered an engine, the heart is rated as having only about 1/240th of a horsepower, 00:50.800 --> 00:58.833 but it is an engine which sometimes remains in motion for 60, 80, or more years without layups, repairs, or replacements. 00:58.833 --> 01:03.799 You will say that a motor of only 1/240th horsepower is not very strong. 01:03.800 --> 01:14.266 But the work done by the heart beating 70 times per minute could in one hour raise the weight of four tons over a distance of one foot. 01:14.266 --> 01:18.999 The energy expended by the heart in the course of a whole day could, if he were not in a hurry, 01:19.000 --> 01:26.633 lift a person weighing 150 pounds to the very top of the Empire State Building. 01:26.633 --> 01:35.466 Or it could, in one day, fill a tank holding 2,500 gallons or about ten tons of fluid. 01:35.466 --> 01:38.332 The heart beats by contracting rhythmically. 01:38.333 --> 01:41.666 Normally, it contracts about 70 times per minute. 01:41.666 --> 01:48.999 This amounts to about 100,000 beats in the course of 24 hours and nearly 36 million times in a year. 01:49.000 --> 01:58.266 Could you, without tiring, perform a similar task with your hands more than 100,000 times in one day? 01:58.266 --> 02:05.632 How then can the heart, without ceasing and without fatigue, perform its big task over the years of a lifetime? 02:05.633 --> 02:09.133 The answer is that the heart takes a short rest between each beat, 02:09.133 --> 02:13.533 and the rest amounts to about 12 hours in the course of 24. 02:13.533 --> 02:17.233 During these rest periods, the heart recovers for the next beat. 02:17.233 --> 02:22.233 It teaches the lesson that periods of rest are necessary for sustained efficiency. 02:22.233 --> 02:30.066 Without these rest periods, the heart could not execute the 36 million pump strokes which are required to keep us alive for one year. 02:30.066 --> 02:34.299 [...] 02:34.300 --> 02:37.933 The whole amount of blood in the body is from 5 to 6 quarts, 02:37.933 --> 02:42.166 and the heart is the circulating pump which keeps these five to six quarts 02:42.166 --> 02:47.199 constantly coursing through the body by way of two circuits of blood vessels: 02:47.200 --> 02:51.566 a larger one, which leaves the left half of the heart by way of the aorta 02:51.566 --> 02:54.232 and passes to every part of the body, 02:54.233 --> 02:58.099 [...] 02:58.100 --> 03:06.000 returning to the right half of the heart by way of the superior and the inferior vena cava, 03:06.000 --> 03:11.533 and a smaller circuit, which leaves the right half of the heart by way of the pulmonary arteries, 03:11.533 --> 03:14.533 to enter the lungs, where the blood takes up oxygen, 03:14.533 --> 03:18.999 [...] 03:19.000 --> 03:25.900 and then flows back to the left half of the heart, which it enters by way of the pulmonary veins. 03:25.900 --> 03:29.066 Both of these circuits are working simultaneously. 03:29.066 --> 03:34.332 In their course, the vessels of both circuits divide into smaller and smaller branches. 03:34.333 --> 03:38.999 The smallest branches are called capillaries and are of microscopic size, 03:39.000 --> 03:44.533 so small that the tiny blood corpuscles must pass through them single file. 03:44.533 --> 03:47.799 [...] 03:47.800 --> 03:52.766 So enormous is their number that if all the blood vessels of the body were laid end to end, 03:52.766 --> 03:55.599 they would encircle the globe four times. 03:55.600 --> 03:58.300 But their enormous number also accounts for the fact 03:58.300 --> 04:04.300 that it takes about a half a minute for a given portion of the blood to complete its course through the two circuits. 04:04.300 --> 04:10.233 Thus, a single blood cell may make almost 3,000 round trips in the course of a single day. 04:10.233 --> 04:17.799 [...] 04:17.800 --> 04:21.366 The normal heart beats 70 times per minute on the average. 04:21.366 --> 04:25.766 The physician, feeling the pulse, can count its frequency and, within limits, 04:25.766 --> 04:31.699 can draw some conclusions as to the state of the heart. 04:31.700 --> 04:35.533 Normally also, the pulse rate varies within fairly large limits. 04:35.533 --> 04:38.499 It may drop to 60 or even lower during sleep, 04:38.500 --> 04:42.133 may rise to 90 during the morning shower, 04:42.133 --> 04:46.899 remain near 70 during the larger part of the day, 04:46.900 --> 04:51.433 go up above 100 while taking some recreational exercise, 04:51.433 --> 04:55.433 and drop back to below 70 while relaxing therefrom. 04:55.433 --> 05:01.866 Such temporary variations are perfectly normal and to be expected. 05:01.866 --> 05:06.032 Temporary variations of the heartbeat may also be due to other causes, 05:06.033 --> 05:11.799 such as various forms of excitement, pleasant or unpleasant. 05:11.800 --> 05:15.100 Such variations may be very noticeable and even alarming, 05:15.100 --> 05:20.366 but they do not indicate an unhealthy condition of the heart, nor need they be a cause for worry. 05:20.366 --> 05:23.832 Yet, if such occurrences are too frequent or too persistent, 05:23.833 --> 05:26.099 a physical examination is called for. 05:26.100 --> 05:29.566 [...] 05:29.566 --> 05:33.266 One of the methods available to the physician for judging the condition of the heart 05:33.266 --> 05:36.466 is by listening to its rhythmic movements by means of the stethoscope. 05:36.466 --> 05:39.299 The sounds are represented by a subdued lub-dub, 05:39.300 --> 05:42.466 with a pause of about a half a second between each double sound. 05:42.466 --> 05:47.199 [...] 05:47.200 --> 05:52.800 Another method of envisioning the condition of this hidden motor is by the use of the electrocardiogram, 05:52.800 --> 05:58.733 a sensitive instrument which records the electrical changes which occur in the heart muscle during each beat. 05:58.733 --> 06:01.999 These records are called electrocardiograms. 06:02.000 --> 06:04.633 By a knowledge of the records of normal hearts, 06:04.633 --> 06:11.099 a physician draws useful information as to the condition of the heart muscle and the rhythm of the beat. 06:11.100 --> 06:15.000 [...] 06:15.000 --> 06:17.733 This is a record of a normal heartbeat. 06:17.733 --> 06:20.699 [...] 06:20.700 --> 06:22.833 This is one of an abnormal beat. 06:22.833 --> 06:25.866 [...] 06:25.866 --> 06:31.132 Every time the heart contracts, it forces a volume of blood into the elastic arteries. 06:31.133 --> 06:34.066 The increased pressure causes their brief distension. 06:34.066 --> 06:37.032 This is noticed as the pulse, as you have seen. 06:37.033 --> 06:39.899 Between heart contractions and its rest periods, 06:39.900 --> 06:45.233 the arteries relax and blood pressure within decreases. 06:45.233 --> 06:51.666 The blood pressure is measured by means of an apparatus known as the sphygmomanometer. 06:51.666 --> 06:54.266 It is recorded in two phases of the heart cycle: 06:54.266 --> 06:59.166 one when the heart is contracted, systole, 06:59.166 --> 07:05.066 and one when the heart is relaxed, diastole. 07:05.066 --> 07:08.499 Normal limits of pressure have been established for both phases. 07:08.500 --> 07:16.200 But, like the pulse rate, blood pressure may vary without indicating a condition dangerous to health. 07:16.200 --> 07:18.500 The heart is the strongest organ of our body. 07:18.500 --> 07:23.700 Yet, statistics show that heart disease has become the most frequent cause of death. 07:23.700 --> 07:26.900 One reason for this is that more people live to an age 07:26.900 --> 07:32.500 where the effects of wear and tear on the heart is one of the natural incidents of life. 07:32.500 --> 07:35.066 [...] 07:35.066 --> 07:37.699 A normal artery, when cut in half lengthwise, 07:37.700 --> 07:40.266 shows the normal thickness of its walls. 07:40.266 --> 07:46.766 In arteriosclerosis, there occurs a gradual thickening of the walls, narrowing the channel of the flow. 07:46.766 --> 07:53.666 The narrowing of the channels may extend to the blood vessels supplying the heart itself. 07:53.666 --> 08:00.466 The heart does not lie free in the chest cavity but is enclosed within a sac-like covering, the pericardium. 08:00.466 --> 08:06.632 If this sac is removed, we see the heart itself and the blood vessels that enter and emerge from it. 08:06.633 --> 08:09.166 This large vessel is called the aorta. 08:09.166 --> 08:12.099 Branching from the aorta, where it emerges from the heart, 08:12.100 --> 08:19.333 are two vessels call the coronary arteries because of their fancied resemblance to a crown. 08:19.333 --> 08:21.466 In a sectional view of the heart wall, 08:21.466 --> 08:25.999 the coronary arteries are seen branching into many thousands of small vessels. 08:26.000 --> 08:30.466 They supply the heart muscle with its necessary food, for, strange to say, 08:30.466 --> 08:36.999 the blood passing through the chambers of the heart does not enter the surrounding muscular structure. 08:37.000 --> 08:42.400 A sclerotic narrowing may occur progressively in the arteries of any area of the heart. 08:42.400 --> 08:46.500 Here, the coronary arteries are seen in an enlarged sectional view. 08:46.500 --> 08:50.166 These vessels show coronary sclerosis. 08:50.166 --> 08:54.832 This heart area supplied by these blood vessels may not receive enough nourishment, 08:54.833 --> 08:57.566 and this may result in a heart attack so-called. 08:57.566 --> 09:02.699 In this greatly enlarged cross-section of the heart muscle, we see a part of the affected area. 09:02.700 --> 09:07.866 The lessening of the blood supply caused by coronary sclerosis causes the muscle to weaken 09:07.866 --> 09:11.299 and, by a gradual process, to be replaced by scar tissue. 09:11.300 --> 09:14.300 [...] 09:14.300 --> 09:18.533 Through a number of causes, unforeseen or due to some disease condition, 09:18.533 --> 09:24.533 a blood clot within a coronary artery may cause a complete and sudden stoppage of the blood supply, 09:24.533 --> 09:28.899 causing a sudden and complete stoppage of function in this part of the heart muscle. 09:28.900 --> 09:31.266 This is called coronary thrombosis. 09:31.266 --> 09:38.166 While it may kill the patient suddenly, like the blow of an ax, more frequently he recovers. 09:38.166 --> 09:42.866 Recovery from coronary thrombosis is enhanced by a period of complete rest, 09:42.866 --> 09:48.766 the chief treatment, during which absence of strain permits the healing process to proceed. 09:48.766 --> 09:54.332 This healing process consists in the establishment of so-called collateral circulation. 09:54.333 --> 09:57.199 [...] 09:57.200 --> 10:01.266 Here we see a section of the heart muscle which has been incapacitated. 10:01.266 --> 10:06.299 During the rest period, branches from adjoining unaffected arteries become larger, 10:06.300 --> 10:13.733 and spreading through the affected area, restore it to a greater or lesser degree of functional capacity. 10:13.733 --> 10:16.199 There are other general facts to be considered. 10:16.200 --> 10:20.366 Overweight, for instance, definitely throws additional work upon the heart. 10:20.366 --> 10:22.966 Its cure and prevention are possible. 10:22.966 --> 10:25.832 An excessive secretion of the thyroid gland 10:25.833 --> 10:28.333 overstimulates the heart and the circulation. 10:28.333 --> 10:34.033 This is called hypothyroidism and may be cured or its progress at least controlled. 10:34.033 --> 10:37.299 [...] 10:37.300 --> 10:40.400 Syphilis is avoidable, preventable, and curable. 10:40.400 --> 10:43.900 It affects the cardiovascular system years after the onset, 10:43.900 --> 10:48.200 causing a disease condition of the wall of the aorta. 10:48.200 --> 10:52.333 Infections in any part of the body, such as the kidneys, 10:52.333 --> 10:55.199 the lungs, the nose and throat, 10:55.200 --> 10:57.700 throw additional work upon the heart. 10:57.700 --> 11:00.733 While all of these are not preventable or curable, 11:00.733 --> 11:04.699 prompt and adequate treatment will diminish their effects on the heart. 11:04.700 --> 11:07.933 Luckily, your heart is the strongest organ of your body. 11:07.933 --> 11:10.033 It has a tremendous task to perform. 11:10.033 --> 11:15.533 It daily pumps nine to ten tons of blood through miles of blood vessels to keep your body functioning. 11:15.533 --> 11:18.699 Help it function properly by following the rules of good health 11:18.700 --> 11:24.000 and the advice of your family doctor. 11:24.000 --> 11:33.066 [The End] [A Bray Studios Production] 11:33.066 --> 11:37.332 [from the film library of The American Medical Association]