WEBVTT

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*This machine-generated transcript may have errors. If remediation or a manually-generated transcript is needed, please contact NLM Support at https://support.nlm.nih.gov.*

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In this section,

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we will review the general features of the heart and the

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pericardium.

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We will emphasize the microscopic and the light

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microscopic appearance of cardiac muscle and the

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conduction system.

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Upon completion of this section,

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you should be able to identify the structures listed in

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the study guide.

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Most of these terms will appear on the screen

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as they are discussed.

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You should be able to describe the morphology of the

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cardiac muscle by light microscopy.

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You should also be able to describe the internal

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conduction system of the heart.

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The bulk of the heart is composed of cardiac muscle

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and a small amount of cardiac muscle is also

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found.

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The attachment point between the vena

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cava,

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pulmonary vein and the heart.

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Cardiac muscle is composed of individual

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branched cells with cross striations

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and nuclei.

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In a central position cardiac

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muscle is under the control of the autonomic nervous

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system and is therefore considered to be

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an involuntary muscle.

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This diagram shows the heart in place with

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lungs removed.

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It shows the sack like covering of the heart known

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as the pericardium.

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This para cardinal sack is essentially non

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dispensable pericardium is

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composed of a parietal layer and a visceral

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layer.

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As shown here,

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the parietal layer completely

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envelopes the heart.

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In the next diagram,

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the parietal layer has been cut away

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to reveal the reflection

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of this layer onto the surface

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of the heart as the visceral

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pericardium or the epic

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RD um

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examining the pericardium by low

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power light microscopy,

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we can see that this parietal pericardium

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consists of two layers.

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First there is a fibrous

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pericardium

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and a series

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pericardium.

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The fibrous pericardium consists of

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dense connective tissue

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with blood vessels,

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nerves and lymphatic

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vessels.

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I'm changing Now to my 40 x.

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objective.

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We can now see the

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area of the serious

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pericardium

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with a small amount of

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underlying connective tissue and

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a covering meself idiom is indicated

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by the nucleus.

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Now in this area

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of the diagram,

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we can see that the visceral pericardium has

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been partially removed to expose

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the underlying muscle fibers

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within the myocardial.

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The bundles of cells are

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arranged in a

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regular fashion,

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and we will now examine a diagram of the heart

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with the visceral pericardium removed.

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In this diagram we can see the general

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orientation of the bundles of

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cells as Early as

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1911 Franklin Pain.

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Mall suggested that this arrangement of cells would

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be the most effective and squeezing blood

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from the heart during contraction.

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The inter ventricular saugus

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has openings for the coronary

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vessels that supply

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the cardiac muscle.

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Let's look at the internal structures of the

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heart shown when the anterior wall of the heart is

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removed.

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The major landmarks of the heart include

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the right and left atria,

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the right and left ventricles,

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the inferior and

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superior vena cava,

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pulmonary vein

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atrial ventricular valves.

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The outer epic are ideal

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surface,

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the middle mile cardi um

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and the innermost indoor cardio

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surface.

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The heart muscle has its own ability to

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contract,

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but the rate is controlled by a

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system of modified cardiac muscle

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cells within the substance of the heart

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called the conducting system nerve

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fibers from the

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autonomic nervous system terminate

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in a specialized area of the right atrium

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called the sino atrial

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node.

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The S.

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A node then controls the rate of

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heart contraction throughout the conduction system.

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The modified cardiac muscle cells of the essay

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node spread throughout

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the atrial wall

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as the per kenji fibers

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and working myocardial

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cells.

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These connect with the atrial

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ventricular node or the A.

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V.

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Node.

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The A.

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V cells are also

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modified cardiac muscle cells,

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which become continuous with

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the atrial ventricular bundle

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for the common bundle of his.

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The column bundle

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divides about

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into the right and left

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bundles and about halfway down the inter

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ventricular septum.

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The cells within these bundles

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enlarge these enlarged cells

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are also known as the poor kenji fibers.

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The rate of transmission of the impulse

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increases in the park in the fibers,

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and these bundles of fibers continue to branch

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and eventually terminate in

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the a pickle portion of the ventricles.

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The conduction system is insulated by

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connective tissue throughout its length.

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Therefore myocardial excitation

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takes place only at the termination

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of the Perkins.

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The fibers.

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We'll now examine selected structures in a

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gross heart.

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We have removed the anterior wall

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of the right atrium

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and the right ventricle.

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As we move down from the right atrium

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we see the right atrial

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ventricular valve or the

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trike.

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A spit valve.

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The wall of the right ventricle

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is thicker in the wall of the right

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atrium.

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As we move into the right ventricular

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wall,

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we see ridges which are termed the

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Tribeca lee.

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Carney bundles of

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muscle can be

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seen.

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These are termed popularly muscles,

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these attached to the cornea tendons

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which in turn attaches to the lips of the trike.

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A spit valve at the

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base of the inter ventricular septum.

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We can see the an

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electrode

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implanted in the mile

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cardi um through the end of

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cardio surface if the essay,

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no,

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does not function normally.

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A pacemaker that uses electrodes like this one can

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supplement or control the rate of heart

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contraction.

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Now,

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let's see this section

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of the heart wall.

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On a slide

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for general orientation.

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We can point out certain landmarks on the microscope slide

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itself.

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First note the general

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homogeneous appearance

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of the muscle within the myocardial.

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There are some septal divisions

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due to the presence of the paramecium.

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This section is taken at the junction of

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the atrium

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and the ventricle and shows

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portions of the atrial wall

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with its thickened and no cardio.

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We can see the ventricular wall,

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the atrial ventricular valve

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and the area of the

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Angeles.

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Fibrosis.

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The animus fibrosis is a connective tissue

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compensation to which both the atrial

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ventricular valves and the cardiac

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muscle cells attached.

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A branch of the coronary artery is

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also seen in the

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sub epic Ardian

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coronary artery and its branches

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penetrates the myocardial.

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We will now examine these areas on the light

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microscope,

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we're now on our scan objective on the light

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microscope.

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Looking at the atrial wall just

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being the atrial cavity.

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We see as we look through the atrial wall,

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starting from the outside the area

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of the epic Rd.

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Um the

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myocardial

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and they thicker indo cardi um

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extending from here to here

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with its lining

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endothelial cells.

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As we begin to move down the

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atrial wall toward the

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ventricle.

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We see

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first the area of the Angeles

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fibrosis.

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We see the atrial ventricular

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valve.

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And as we move back we begin to see now

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the muscle within the

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myocardial um of the ventricular

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wall.

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As we move through the

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ventricular wall

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we see again the branch of

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the coronary artery located in the

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sub epic are ideal connective

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tissue.

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And we see

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the

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branching of the coronary

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artery into the

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connective tissue.

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Septa the perry

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mycelium.

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As we move down the wall,

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we see the

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epic Rd um

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with its lining muzzle federal cells and

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the sub epic cardio.

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A real or connective tissue.

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Well now I'm moving back

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to this area within the Mile Cardi um

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showing both cross section

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and longitudinal section of Muscle.

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We're changing now to our 10x.

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objective.

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We see

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first cross

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sections all of the cardiac muscle

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cells with their central

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nuclei.

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Note the nuclear cytoplasmic

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ratio

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in this area.

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We see longitudinal sections

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cardiac muscle cells.

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With the brian jean

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and again

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central nuclei.

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I'm now going to the oil immersion lens.

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To examine this area in greater detail

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note the cylindrical shape.

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All the cells within this longitudinal view.

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Note the branching

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here and here of

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individual cells.

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You can see the week

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cross banding

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and the positioning of the central

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nucleus.

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As we move the area,

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we can see a capillary

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located within the

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endometrium with

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the original sites located within the lumen.

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This is the nucleus

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of the capillary lining,

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sell the endothelial cell.

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At this point

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we can see the

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presence of the irregular dense structures

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known as interconnected desks.

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These served as

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junctions between individual cells

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and are presumed important for the attachment

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between cells and for the

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transmission of the deep polarization contraction

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wave.

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This completes the light microscopic study of

15:46.130 --> 15:47.890
normal cardiac muscle cells.

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Well now look at components of the conduction

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system in the heart.

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We're on our 10 X.

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Objective.

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This is a sino atrial node with a

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try chrome stain.

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There is an abundance of connective

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tissue and a small

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number of cells.

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The essay cells seem to be distributed

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in a somewhat random fashion.

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Note the presence of a nodal artery

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and branches of same,

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which is a landmark for identifying

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the S.

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A.

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Node.

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We'll now examine this area on the

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oil immersion objective.

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We can see the small

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size of the fibers.

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We can see there is a lighter stained area

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which does contain glycogen

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And may be responsible for some

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distortion of the mile five reels

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within the mono fiber.

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The next part of the conduction system is

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the A.

17:02.770 --> 17:03.230
V.

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Node,

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the A.

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V.

17:08.440 --> 17:11.300
Node and

17:11.300 --> 17:14.300
bundle are demonstrated by a try

17:14.300 --> 17:15.270
chrome stain.

17:16.740 --> 17:17.360
Again,

17:17.840 --> 17:20.510
note the prevalence or the connective

17:20.510 --> 17:23.050
tissue which serves to

17:23.060 --> 17:24.840
insulate the A.

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V.

17:25.070 --> 17:27.830
Node and bundle from the

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surrounding cardiac muscle

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cells.

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I'm going to change Now to the 10 x.

17:36.470 --> 17:37.170
objective.

17:43.640 --> 17:44.360
Again,

17:46.040 --> 17:48.460
the atrial ventricular node

17:49.240 --> 17:51.680
and the common bundle.

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We can see again that the fibers

17:56.440 --> 17:58.840
are distributed in a

17:58.840 --> 18:00.850
somewhat random fashion.

18:03.620 --> 18:06.270
Will now continue by examining

18:06.840 --> 18:08.550
the per kenji fibers.

18:11.990 --> 18:14.390
This is on low power with a mallory

18:14.390 --> 18:16.940
stain to show first the

18:17.040 --> 18:18.200
Mackenzie fibers

18:20.140 --> 18:22.110
as compared with the normal fibers,

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the increased size of the cells

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and the lighter steam as compared with the

18:30.240 --> 18:33.010
normal cardiac cells can be

18:33.010 --> 18:33.560
seen.

18:34.930 --> 18:37.740
The lighter stain again is due in

18:37.740 --> 18:40.220
part to the increase in the amount of

18:40.220 --> 18:40.860
glycogen

18:45.340 --> 18:48.050
where now going to move

18:48.050 --> 18:50.610
from the endo cardio surface

18:52.610 --> 18:53.940
into the myocardial.

18:56.940 --> 18:59.770
And again we see the presence

18:59.780 --> 19:01.970
of bundles of per kenji

19:02.220 --> 19:04.980
fibers or cells now

19:04.980 --> 19:07.950
located within the perry mycelium

19:08.740 --> 19:09.980
of the myocardial.

19:11.340 --> 19:14.290
We're moving back now to the endo cardio surface

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and we'll be changing to our oil immersion objective

19:20.640 --> 19:21.660
on oil immersion.

19:21.790 --> 19:22.560
Week again,

19:22.560 --> 19:24.860
see the large

19:25.190 --> 19:26.450
Mackenzie cells,

19:27.690 --> 19:29.450
the light staining characteristics

19:31.640 --> 19:34.200
and somewhat Randomly

19:34.200 --> 19:36.500
oriented mile five grills

19:37.240 --> 19:39.970
present within the for kenji

19:39.970 --> 19:42.860
fiber size of these

19:42.860 --> 19:45.830
cells and the light staining characteristic is compared

19:45.830 --> 19:48.730
with the normal cardiac muscle

19:48.730 --> 19:51.380
cell in this

19:51.380 --> 19:51.860
area.

19:55.320 --> 19:55.820
Now,

19:55.940 --> 19:56.860
for review,

19:57.600 --> 19:59.160
let's look at the next diagram

20:02.140 --> 20:02.960
in summary,

20:03.690 --> 20:05.640
this diagram shows certain key

20:05.640 --> 20:08.470
characteristics of cardiac muscle that can be

20:08.470 --> 20:09.960
seen on the light level.

20:11.340 --> 20:13.130
These small elements

20:15.040 --> 20:17.580
represent collagen fibers in the connective

20:17.590 --> 20:18.290
tissue,

20:18.630 --> 20:21.460
which would be considered as a part of the endometrium.

20:23.320 --> 20:25.770
This represents a

20:25.770 --> 20:28.050
capillary within the endometrium.

20:30.030 --> 20:32.160
The cardiac muscle cells,

20:32.540 --> 20:35.420
or fibers are characterized

20:35.430 --> 20:37.170
by a cylindrical shape,

20:40.540 --> 20:41.350
branching

20:44.640 --> 20:46.460
and with central nuclei

20:49.040 --> 20:50.800
and cross dry ations.

20:53.140 --> 20:56.050
Cardiac muscle also has a dense line

20:57.340 --> 20:59.610
which is termed the inter collected

20:59.750 --> 21:00.360
desk.

21:03.150 --> 21:05.910
These desks are the inter cellular

21:05.910 --> 21:08.400
junctions which serve to

21:08.400 --> 21:11.000
attach the cells together and

21:11.000 --> 21:13.940
transmit the electrical impulse from one cell to

21:13.940 --> 21:14.370
another,

21:16.740 --> 21:17.460
brian jean,

21:19.240 --> 21:21.850
and the presence of the interconnected desk

21:23.240 --> 21:26.210
are unique within cardiac muscle

21:26.210 --> 21:26.900
cells.

21:28.340 --> 21:31.290
This concludes the section on light microscopy

21:31.290 --> 21:34.160
of cardiac muscle with a brief description

21:34.640 --> 21:35.670
of pericardium,

21:36.120 --> 21:36.780
epic Rd,

21:36.780 --> 21:38.060
um and endo cardi,

21:38.060 --> 21:38.260
um