In this section,

we will review the general features of the heart and the 

pericardium.

We will emphasize the microscopic and the light 

microscopic appearance of cardiac muscle and the 

conduction system.

Upon completion of this section,

you should be able to identify the structures listed in 

the study guide.

Most of these terms will appear on the screen 

as they are discussed.

You should be able to describe the morphology of the 

cardiac muscle by light microscopy.

You should also be able to describe the internal 

conduction system of the heart.

The bulk of the heart is composed of cardiac muscle 

and a small amount of cardiac muscle is also 

found.

The attachment point between the vena 

cava,

pulmonary vein and the heart.

Cardiac muscle is composed of individual 

branched cells with cross striations 

and nuclei.

In a central position cardiac 

muscle is under the control of the autonomic nervous 

system and is therefore considered to be 

an involuntary muscle.

This diagram shows the heart in place with 

lungs removed.

It shows the sack like covering of the heart known 

as the pericardium.

This para cardinal sack is essentially non 

dispensable pericardium is 

composed of a parietal layer and a visceral 

layer.

As shown here,

the parietal layer completely 

envelopes the heart.

In the next diagram,

the parietal layer has been cut away 

to reveal the reflection 

of this layer onto the surface 

of the heart as the visceral 

pericardium or the epic 

RD um 

examining the pericardium by low 

power light microscopy,

we can see that this parietal pericardium 

consists of two layers.

First there is a fibrous 

pericardium 

and a series 

pericardium.

The fibrous pericardium consists of 

dense connective tissue 

with blood vessels,

nerves and lymphatic 

vessels.

I'm changing Now to my 40 x.

objective.

We can now see the 

area of the serious 

pericardium 

with a small amount of 

underlying connective tissue and 

a covering meself idiom is indicated 

by the nucleus.

Now in this area 

of the diagram,

we can see that the visceral pericardium has 

been partially removed to expose 

the underlying muscle fibers 

within the myocardial.

The bundles of cells are 

arranged in a 

regular fashion,

and we will now examine a diagram of the heart 

with the visceral pericardium removed.

In this diagram we can see the general 

orientation of the bundles of 

cells as Early as 

1911 Franklin Pain.

Mall suggested that this arrangement of cells would 

be the most effective and squeezing blood 

from the heart during contraction.

The inter ventricular saugus 

has openings for the coronary 

vessels that supply 

the cardiac muscle.

Let's look at the internal structures of the 

heart shown when the anterior wall of the heart is 

removed.

The major landmarks of the heart include 

the right and left atria,

the right and left ventricles,

the inferior and 

superior vena cava,

pulmonary vein 

atrial ventricular valves.

The outer epic are ideal 

surface,

the middle mile cardi um 

and the innermost indoor cardio 

surface.

The heart muscle has its own ability to 

contract,

but the rate is controlled by a 

system of modified cardiac muscle 

cells within the substance of the heart 

called the conducting system nerve 

fibers from the 

autonomic nervous system terminate 

in a specialized area of the right atrium 

called the sino atrial 

node.

The S.

A node then controls the rate of 

heart contraction throughout the conduction system.

The modified cardiac muscle cells of the essay 

node spread throughout 

the atrial wall 

as the per kenji fibers 

and working myocardial 

cells.

These connect with the atrial 

ventricular node or the A.

V.

Node.

The A.

V cells are also 

modified cardiac muscle cells,

which become continuous with 

the atrial ventricular bundle 

for the common bundle of his.

The column bundle 

divides about 

into the right and left 

bundles and about halfway down the inter 

ventricular septum.

The cells within these bundles 

enlarge these enlarged cells 

are also known as the poor kenji fibers.

The rate of transmission of the impulse 

increases in the park in the fibers,

and these bundles of fibers continue to branch 

and eventually terminate in 

the a pickle portion of the ventricles.

The conduction system is insulated by 

connective tissue throughout its length.

Therefore myocardial excitation 

takes place only at the termination 

of the Perkins.

The fibers.

We'll now examine selected structures in a 

gross heart.

We have removed the anterior wall 

of the right atrium 

and the right ventricle.

As we move down from the right atrium 

we see the right atrial 

ventricular valve or the 

trike.

A spit valve.

The wall of the right ventricle 

is thicker in the wall of the right 

atrium.

As we move into the right ventricular 

wall,

we see ridges which are termed the 

Tribeca lee.

Carney bundles of 

muscle can be 

seen.

These are termed popularly muscles,

these attached to the cornea tendons 

which in turn attaches to the lips of the trike.

A spit valve at the 

base of the inter ventricular septum.

We can see the an 

electrode 

implanted in the mile 

cardi um through the end of 

cardio surface if the essay,

no,

does not function normally.

A pacemaker that uses electrodes like this one can 

supplement or control the rate of heart 

contraction.

Now,

let's see this section 

of the heart wall.

On a slide 

for general orientation.

We can point out certain landmarks on the microscope slide 

itself.

First note the general 

homogeneous appearance 

of the muscle within the myocardial.

There are some septal divisions 

due to the presence of the paramecium.

This section is taken at the junction of 

the atrium 

and the ventricle and shows 

portions of the atrial wall 

with its thickened and no cardio.

We can see the ventricular wall,

the atrial ventricular valve 

and the area of the 

Angeles.

Fibrosis.

The animus fibrosis is a connective tissue 

compensation to which both the atrial 

ventricular valves and the cardiac 

muscle cells attached.

A branch of the coronary artery is 

also seen in the 

sub epic Ardian 

coronary artery and its branches 

penetrates the myocardial.

We will now examine these areas on the light 

microscope,

we're now on our scan objective on the light 

microscope.

Looking at the atrial wall just 

being the atrial cavity.

We see as we look through the atrial wall,

starting from the outside the area 

of the epic Rd.

Um the 

myocardial 

and they thicker indo cardi um 

extending from here to here 

with its lining 

endothelial cells.

As we begin to move down the 

atrial wall toward the 

ventricle.

We see 

first the area of the Angeles 

fibrosis.

We see the atrial ventricular 

valve.

And as we move back we begin to see now 

the muscle within the 

myocardial um of the ventricular 

wall.

As we move through the 

ventricular wall 

we see again the branch of 

the coronary artery located in the 

sub epic are ideal connective 

tissue.

And we see 

the 

branching of the coronary 

artery into the 

connective tissue.

Septa the perry 

mycelium.

As we move down the wall,

we see the 

epic Rd um 

with its lining muzzle federal cells and 

the sub epic cardio.

A real or connective tissue.

Well now I'm moving back 

to this area within the Mile Cardi um 

showing both cross section 

and longitudinal section of Muscle.

We're changing now to our 10x.

objective.

We see 

first cross 

sections all of the cardiac muscle 

cells with their central 

nuclei.

Note the nuclear cytoplasmic 

ratio 

in this area.

We see longitudinal sections 

cardiac muscle cells.

With the brian jean 

and again 

central nuclei.

I'm now going to the oil immersion lens.

To examine this area in greater detail 

note the cylindrical shape.

All the cells within this longitudinal view.

Note the branching 

here and here of 

individual cells.

You can see the week 

cross banding 

and the positioning of the central 

nucleus.

As we move the area,

we can see a capillary 

located within the 

endometrium with 

the original sites located within the lumen.

This is the nucleus 

of the capillary lining,

sell the endothelial cell.

At this point 

we can see the 

presence of the irregular dense structures 

known as interconnected desks.

These served as 

junctions between individual cells 

and are presumed important for the attachment 

between cells and for the 

transmission of the deep polarization contraction 

wave.

This completes the light microscopic study of 

normal cardiac muscle cells.

Well now look at components of the conduction 

system in the heart.

We're on our 10 X.

Objective.

This is a sino atrial node with a 

try chrome stain.

There is an abundance of connective 

tissue and a small 

number of cells.

The essay cells seem to be distributed 

in a somewhat random fashion.

Note the presence of a nodal artery 

and branches of same,

which is a landmark for identifying 

the S.

A.

Node.

We'll now examine this area on the 

oil immersion objective.

We can see the small 

size of the fibers.

We can see there is a lighter stained area 

which does contain glycogen 

And may be responsible for some 

distortion of the mile five reels 

within the mono fiber.

The next part of the conduction system is 

the A.

V.

Node,

the A.

V.

Node and 

bundle are demonstrated by a try 

chrome stain.

Again,

note the prevalence or the connective 

tissue which serves to 

insulate the A.

V.

Node and bundle from the 

surrounding cardiac muscle 

cells.

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

objective.

Again,

the atrial ventricular node 

and the common bundle.

We can see again that the fibers 

are distributed in a 

somewhat random fashion.

Will now continue by examining 

the per kenji fibers.

This is on low power with a mallory 

stain to show first the 

Mackenzie fibers 

as compared with the normal fibers,

the increased size of the cells 

and the lighter steam as compared with the 

normal cardiac cells can be 

seen.

The lighter stain again is due in 

part to the increase in the amount of 

glycogen 

where now going to move 

from the endo cardio surface 

into the myocardial.

And again we see the presence 

of bundles of per kenji 

fibers or cells now 

located within the perry mycelium 

of the myocardial.

We're moving back now to the endo cardio surface 

and we'll be changing to our oil immersion objective 

on oil immersion.

Week again,

see the large 

Mackenzie cells,

the light staining characteristics 

and somewhat Randomly 

oriented mile five grills 

present within the for kenji 

fiber size of these 

cells and the light staining characteristic is compared 

with the normal cardiac muscle 

cell in this 

area.

Now,

for review,

let's look at the next diagram 

in summary,

this diagram shows certain key 

characteristics of cardiac muscle that can be 

seen on the light level.

These small elements 

represent collagen fibers in the connective 

tissue,

which would be considered as a part of the endometrium.

This represents a 

capillary within the endometrium.

The cardiac muscle cells,

or fibers are characterized 

by a cylindrical shape,

branching 

and with central nuclei 

and cross dry ations.

Cardiac muscle also has a dense line 

which is termed the inter collected 

desk.

These desks are the inter cellular 

junctions which serve to 

attach the cells together and 

transmit the electrical impulse from one cell to 

another,

brian jean,

and the presence of the interconnected desk 

are unique within cardiac muscle 

cells.

This concludes the section on light microscopy 

of cardiac muscle with a brief description 

of pericardium,

epic Rd,

um and endo cardi,

um