Lecture 22: Heart Macro and Micro

Question 1

what artery and vein run parallel to the phrenic nerve

Answer 1

the pericardicophrenic artery and vein

Question 2

pericardium compositin

Answer 2

outer fibrous sac and inner serous sac, inner serous sac further divides into parietal layer (fused to fibrous sac) and visceral layer (intimate with heart). The parietal layer and visceral layer are separated by the pericardial cavity.

Question 3

part of the wall of the heart, outer to inner

Answer 3

epicardium, myocardium (cardiac muscle), and endocardium

Question 4

Sulci, types, appearance, contents

Answer 4

Sulci separate the superficial borders between atria and ventricles, There is the coronary sulci that runs around the heart between atria and ventricles and there are the posterior and anterior atrioventricular sulci that run between the right and left sides of the heart. They are surrounded by pericardial fat, and contain the coronary arteries and cardiac veins
There is also a sulcus terminalis that separates the right atria from the connections to superior vena cava.

Question 5

Branches of right coronary artery

Answer 5

Sino-atrial (SA) nodal branch, marginal branch, atrioventricular (AV) nodal branch, posterior interventricular branch

Question 6

Branches of left coronary artery

Answer 6

anterior interventricular branch (LAD= left anterior descending), circumflex branch

Question 7

anastomoses of coronary artery branches

Answer 7

circumflex branch of left artery with posterior right coronary artery
posterior interventricular branch (off of right coronary) with anterior interventricular branch (LAD=left anterior descending)

Question 8

what does right coronary artery distribute blood to

Answer 8

Right atria and ventricle, posterior part of left ventricle, posterior part of interventricular septum

Question 9

what does left coronary artery distribute blood

Answer 9

left atria and ventricle, variable amount of right ventricle, most of interventricular septum

Question 10

right coronary dominance vs left coronary dominance

Answer 10

in 70% of hearts RCA is dominance, it gives rise to posterior ventricular branch
but in 15% of hearts LCA is dominant, it gives rise to posterior ventricular branch

Question 11

what feeds into atrioventricular nodal branch?

Answer 11

80% from RCA, 20% from LAD

Question 12

cardiac veins of heart

Answer 12

coronary sinus, great cardiac vein, middle cardiac vein, small cardiac vein, anterior cardiac veins, venae cordis minimae

Question 13

where does coronary sinus run?

Answer 13

in the coronary sulcus

Question 14

where does the great cardiac vein run?

Answer 14

in the anterior IV sulcus

Question 15

where does middle cardiac vein run?

Answer 15

in the posterior IV sulcus

Question 16

end arteries, what happens during occlusion

Answer 16

arteries that do not anastomose but end in capillaries, occlusion of end arteries leads to necrosis of the supplied tissue, classic example is the central artery of the retina

Question 17

functional end artery, example, alternate name

Answer 17

arteries that do anastomose, but the resulting collateral circulation is not robust enough to support the supplied tissue, so functionally these are end arteries. Example is the branches of the coronary arteries. An alternate name for functional end arteries is physiologic end arteries.

Question 18

What does coronary occlusion lead to?

Answer 18

Myocardial Infarction, which is necrosis of the myocardium.

Heart Attack.

Question 19

What would coronary Insufficiency lead to?

Answer 19

Myocardial Ischemia, which is cell starvation due to lack of oxygen, can lead to myocardial infarction once a critical level is reached. 
Angina Pectoris (Cardiac Pain/Chest Pain)

Question 20

Cardiac Pain, where is pain felt

Answer 20

Is a referred pain that is when damage to the heart is felt in the T1-T5 dermatomes. The most typical pattern is behind the sternum (substernal), upper left chest, and medial aspect of left arm.

Question 21

relative thickness of chamber walls

Answer 21

left ventricle > right ventricle > atria

Question 22

Contents of epicardium

Answer 22

The epicardium is the upper most layer on the heart. Fat cells, fibroelastic tissue, coronary vessels, lymphatics, and nerves. The vessels and lymphatics both run through the sulci. It’s externally covered by one layer of mesothelium (epithelium).

Question 23

endocardium

Answer 23

Bottom most layer. Contains connective tissue (CT) with collagen and elastic fibers, fibroblasts and a few SM cells. It is thicker on the atria wall.

Question 24

Subendocardium

Answer 24

found in some parts of the ventricle, contains the same types of tissue as are found in the endocardium

Question 25

Types of cells found in the myocardium

Answer 25

All of the cells are cardiac muscle cells (myocytes), but they are differentiated to have different functions. There are contractile cells, (myo) endocrine cells (these myocytes are found in atria), and conducting cells (nodal cells, purkinje fibers, bundle branches)

Question 26

How do cardiac muscle cells run?

Answer 26

Run in different directions, spirally around the ventricles and aorta. Is reflected in a histology cross section, all of the myocytes are cut at different angles and orientations in the same transverse cross section, which reflects the complex spiraling pattern.

Question 27

Qualities of cardiac myocyte seen in histology

Answer 27

Striations are caused by myosin-actin filament patterns, central nucleii, branching, and intercalating disks (ICD).

Question 28

What surrounds the cardiac myocyte

Answer 28

Real space, not potential space. And many capillaries per cell, because cells are very metabolically active.

Question 29

What happens to cardiac myocytes in old age

Answer 29

They acquire lipofuscin pigment, yellow-brown, from wear and tear. they do not have the ability to regenerate.

Question 30

What are intercalated disks

Answer 30

Specialized inter-cellular junctions that join adjacent myocytes together so that they can organize contractile motion

Question 31

What are intercalated disks made of

Answer 31

desmosomes, fascia adherentes (similar to zonula adherentes but more extensive), gap junctions. Fascia adherentes allow for muscle cells to transfer force between each other. Gap junctions allow for chemical signals to be transferred between each other so they can contract synchronically

Question 32

Components of hearts extracellular matrix, and their purpose

Answer 32

Basal Lamina forms a weave around the cardiac cell.
Elastin fiber bundles loops around the cardiac cell.
Collagen fibrils insert into the basal lamina weave, connecting them to collagen struts
Collagen struts are made of collagen fibril bundles, connect adjacent cardiocytes.

Question 33

atrial myocyte vs ventricular myocyte

Answer 33

the atrial myocytes are smaller, have fewer transverse tubules, and have granules

Question 34

What hormone do atrial myocytes create, and how is it stored

Answer 34

They make ANP (atrial natriuretic peptide) and store it in granules

Question 35

When is ANP released by the heart?

Answer 35

In response to atrial wall stretching (due to high blood volume), secreted through exocytosis, triggers urinal release and blocks sodium reabsorption in renal tubules which promotes sodium excretion.

Question 36

Is the cardiac conductive tissue nerves? What are these cells functions?

Answer 36

No, differentiated myocytes. They initiate a normal heart rhythm, conduct impulses quickly through heart tissue, and coordinate the contraction of the four chambers of the heart

Question 37

What is the pathway of electrical conduction in the heart?

Answer 37

SA node –> AV node –> AV bundle/bundle of His –>down either right bundle branch or left bundle branch –> Purkinje fibers

Question 38

Where is the SA node found

Answer 38

Where the christae terminalis meets the opening to the superior vena cava in the right atrium.

Question 39

SA node histological structure

Answer 39

The atrial myocytes are modified, smaller, no ICDs, fewer myofibrils, less organized striations, no fascia adherentes, autonomic nerves and blood vessels present, embedded in fibrous tissue

Question 40

Where are the purkinje fibers found, and what is their function

Answer 40

Subendocardium tissue only, located in the ventricular walls. Serve to coordinate tissue contraction of the ventricles.

Question 41

Purkinje fibers histological structure

Answer 41

larger in size, lots of glycogen, fewer fibrils, lack T-tubules, no typical ICD, no fascia adherentes

Question 42

Heart valve structure

Answer 42

Covered on both sides by endothelium. On the ventricular side there is a dense plate of collagenous tissue called lamina fibrosa and towards the atrial side there are elastic fibers. The valve receives no blood vessels.