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Acland's DVD Atlas of Human Anatomy Transcript for Volume 6

© 2007 Robert D Acland

This free downloadable pdf file is to be used for individual study only. It is not to be reproduced in any form without the author's express permission.



PART 1 THE THORACIC ORGANS This tape shows the internal organs of the thorax and of the abdomen,and the male and female reproductive organs. In this first section we'll look at the organs of the thorax: first the heart, then the lungs. We'll also look briefly at the esophagus. The thorax itself, the upper part of the trunk which contains the heart and lungs, is shown in Tape 3 of this atlas. Here, we're looking at the contents.



THE HEART: INTRODUCTION Tounderstand the heart we'll begin by seeing where it is. We tend to put the heart here in our imagination, but in reality it's much closer to the mid-line. Seen from in front, the heart is here. It lies behind the sternum, and directly above the diaphragm. Seen from the side, the heart is here, occupying almost all the space between the vertebral bodies behind, and the sternum in front. When the diaphragmmoves, the heart moves with it. To get our first look at the heart, we'll start by removing the upper extremities, and all the shoulder muscles that surround the upper thorax, so as to leave just the thorax itself, enclosed by the ribs and intercostal muscles. Then we'll remove this part of the rib cage on each side, revealing the lungs, which are fully inflated here. When we let the lungs deflatewe can see the heart behind the sternum, contained within its protective jacket of pericardium. To see it better we'll take the lungs, the sternum and the pericardium out of the picture.
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This is the heart. This is the diaphragm. The major blood vessels that lead into and out of the heart take up almost as much space as the heart itself. Now that we've seen wherethe heart is we'll take a detailed look at it. We'll look at its four chambers, and its four valves; then we'll look at the great vessels that enter and leave the heart, and lastly we'll look at the coronary arteries.



Because we so often see simplified diagrams of the heart like this, we tend to think the atria, the inlet chambers, are above, and the ventricles, the pumpingchambers, are below. It's perhaps surprising to see that in reality the atria aren't above the ventricles, they're behind them. Here's the heart in isolation. Here are the ventricles in front, here are the atria behind. This generous coating of epicardial fat makes it hard to see the four chambers distinctly.

To see them more clearly, we'll go to a heart in which almost all the fat hasbeen removed. In this specimen all four chambers have been distended with equal pressure, making the atria somewhat larger than normal. This is a directly posterior view of the heart, this is a directly anterior view. The massive thick walled left


ACLAND'S DVD ATLAS OF HUMAN ANATOMY VOL 6 PART 1 ventricle projects forward and to the left. The thinner walled right ventricle is partiallywrapped round the left one.



ATRIA AND INLET VALVES We'll see the ventricles by themselves in a minute. For now, let's go round to the back, and look at the two atria. This the left atrium, this is the right atrium. Blood coming from the upper part of the body enters the right atrium by way of the superior vena cava. Blood coming from the lower part of the body enters it by way ofthe much larger inferior vena cava. In a more intact dissection, here's the inferior vena cava, coming through the diaphragm and almost immediately entering the right atrium.


In addition to the two venae cavae, blood from the heart itself enters the right atrium under here, by way of the coronary sinus, which we'll see later. From the upper part of the right atrium this blind...
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