Lecture 22: Heart Macro and Micro Flashcards
what artery and vein run parallel to the phrenic nerve
the pericardicophrenic artery and vein
pericardium compositin
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.
part of the wall of the heart, outer to inner
epicardium, myocardium (cardiac muscle), and endocardium
Sulci, types, appearance, contents
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.
Branches of right coronary artery
Sino-atrial (SA) nodal branch, marginal branch, atrioventricular (AV) nodal branch, posterior interventricular branch
Branches of left coronary artery
anterior interventricular branch (LAD= left anterior descending), circumflex branch
anastomoses of coronary artery branches
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)
what does right coronary artery distribute blood to
Right atria and ventricle, posterior part of left ventricle, posterior part of interventricular septum
what does left coronary artery distribute blood
left atria and ventricle, variable amount of right ventricle, most of interventricular septum
right coronary dominance vs left coronary dominance
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
what feeds into atrioventricular nodal branch?
80% from RCA, 20% from LAD
cardiac veins of heart
coronary sinus, great cardiac vein, middle cardiac vein, small cardiac vein, anterior cardiac veins, venae cordis minimae
where does coronary sinus run?
in the coronary sulcus
where does the great cardiac vein run?
in the anterior IV sulcus
where does middle cardiac vein run?
in the posterior IV sulcus
end arteries, what happens during occlusion
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
functional end artery, example, alternate name
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.
What does coronary occlusion lead to?
Myocardial Infarction, which is necrosis of the myocardium.
Heart Attack.
What would coronary Insufficiency lead to?
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)
Cardiac Pain, where is pain felt
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.
relative thickness of chamber walls
left ventricle > right ventricle > atria
Contents of epicardium
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).
endocardium
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.
Subendocardium
found in some parts of the ventricle, contains the same types of tissue as are found in the endocardium
Types of cells found in the myocardium
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)
How do cardiac muscle cells run?
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.
Qualities of cardiac myocyte seen in histology
Striations are caused by myosin-actin filament patterns, central nucleii, branching, and intercalating disks (ICD).
What surrounds the cardiac myocyte
Real space, not potential space. And many capillaries per cell, because cells are very metabolically active.
What happens to cardiac myocytes in old age
They acquire lipofuscin pigment, yellow-brown, from wear and tear. they do not have the ability to regenerate.
What are intercalated disks
Specialized inter-cellular junctions that join adjacent myocytes together so that they can organize contractile motion
What are intercalated disks made of
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
Components of hearts extracellular matrix, and their purpose
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.
atrial myocyte vs ventricular myocyte
the atrial myocytes are smaller, have fewer transverse tubules, and have granules
What hormone do atrial myocytes create, and how is it stored
They make ANP (atrial natriuretic peptide) and store it in granules
When is ANP released by the heart?
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.
Is the cardiac conductive tissue nerves? What are these cells functions?
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
What is the pathway of electrical conduction in the heart?
SA node –> AV node –> AV bundle/bundle of His –>down either right bundle branch or left bundle branch –> Purkinje fibers
Where is the SA node found
Where the christae terminalis meets the opening to the superior vena cava in the right atrium.
SA node histological structure
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
Where are the purkinje fibers found, and what is their function
Subendocardium tissue only, located in the ventricular walls. Serve to coordinate tissue contraction of the ventricles.
Purkinje fibers histological structure
larger in size, lots of glycogen, fewer fibrils, lack T-tubules, no typical ICD, no fascia adherentes
Heart valve structure
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.
