Lecture 7 DA

Question 1

What are the consequences of parasympathetic innervation to the heart? What nerves does it involve?

Answer 1

Decreased heart rate & force of contraction.

It involves the vagus nerve and parasympathetic cardiac nerves.

Question 2

What anchors the valves (besides the chordae tendinae)?

Answer 2

The fibrous skeleton.

Question 3

What are the consequences of sympathetic innervation to the heart? What nerves does it involve?

Answer 3

Increased heart rate & force of contraction.
It involves:
Preganglionic nerves from T1-4 spinal cord segments.
Postganglionic nerves from the cervical and upper thoracic sympathetic ganglia.
Sympathetic cardiac nerves.
Cardiac plexus.

Question 4

Where is the cardiac plexus found in relation to the trachea/bronchi?

Answer 4

It is found anterior to the pulmonary bifurcation.

Question 5

Where is heart pain referred to, and what nerve does it involve?

Answer 5

It is referred to dermatomes T1-4 and involves the visceral sensory nerve.

Question 6

In referred pain, why is pain felt more over the left shoulder?

Answer 6

Visceral sensory nerves follow sympathetic nerves, and this occurs more over the left shoulder due to the plexus arrangement.

Question 7

Describe the layers of the pericardium and where they attach.

Answer 7

Visceral layer (also called epicardium)- layer attached directly to the heart.
Parietal layer - layer attached to the fibrous pericardium.
Serous pericardium - both visceral and parietal layers.
Fibrous pericardium - outermost layer of the pericardium.
There is a space between the visceral and parietal layers of the serous pericardium known as the pericardial space. It is filled with serous fluid.

Question 8

What nerve is the pericardium innervated by?

Answer 8

The phrenic nerve.

Question 9

Describe two pericardial sinuses and their clinical relevance.

Answer 9

The oblique sinus, found posterior to the heart and in between the left and right pulmonary veins. It is the deepest & inferior-most structure of the heart in the supine position.
The transverse sinus, found on the hearts exterior superiorly and superior to the oblique sinus. It is found posterior to the pulmonary trunk birfurcation, aorta, and superior vena cava. It is also between the superior left & right pulmonary veins. It allows one to tie and cut the great vessels during a heart operation (aortic/valve/partial/full caridac replacement).
They are possible sites of a hematoma (yes, i said hematoma and not haematoma, cuz muh freedom).

Question 10

Describe the coronary circulation.

Answer 10

There are two coronary arteries, left & right, the first branch off the base of the aortic arch.
The left coronary artery runs behind the pulmonary trunk & enters the left atrioventricular groove, giving off two branches as it does so:
-The left circumflex branch, which follows the left atrioventricular groove, gives off the left marginal artery at the left posterior border.
-The left marginal artery, runs down the left posterior border.
-The anterior interventricular branch, which runs through the anterior interventricular groove instead (also called left descending artery, probably by yankees).
The right coronary artery enters the right atrioventricular groove, branching as it reaches the right posterior border:
-The right marginal artery, found at the right posterior border of the heart.
-The right coronary artery follows the right atrioventricular groove. When it reaches the interventricular groove, it gives off the branch posterior interventricular atery, which follows the groove.
Anastamoses:
Circumflex artery and right coronary artery.
anterior and posterior inteventricular artery.

Question 11

Which artery is the SA node supplied by?

Answer 11

The right coronary artery, which should give off the appropriate branch before giving off the posterior interventricular artery.

Question 12

What kind of arteries are coronary arteries? What is the consequence of this?

Answer 12

They are functional end arteries. As a result, the can form anastamoses if gradually occluded. However, sudden occlusion causes myocardial infarction.

Question 13

What is angiography?

Answer 13

A catheter is inserted into the left or right coronary artery, which are then injected with an opaque dye, to image for blockages.

Question 14

What is angioplasty?

Answer 14

Balloons are inserted into the blockage, expanded to create an opening and then removed.

Question 15

What is coronary bypass?

Answer 15

When a blockage of the coronary artery is bypassed using another vessel, most often the saphenous vein, but also internal thoracic/mammary artery.

Question 16

Describe the drainage of the coronary circulation.

Answer 16

Coronary sinus - found posteriorly in the right atrioventricular groove (which overlies it), opening direct to the right atrium.
Small cardiac vein - drains inferiorly (follows right coronary artery).
Great cardiac vein - drains superiorly (follows anterior atrioventricular artery and left coronary artery).
Oblique cardiac vein of the left atrium - drains superiorly (found superior to the small cardiac vein)
Left marginal vein - drains laterally to the sinus, joins with the great cardiac vein before draining to the coronary sinus (follows the left marginal artery).
Right marginal vein - follows the right marginal artery.

Question 17

What does it mean if cardiac cells are intercalated?

Answer 17

It means the conduction for contraction is almost simultaneous throughout the cellls, allowing for a synchronised contraction.

Question 18

What structures allow syncronised contraction and prevents the entire heart from squeezing?

Answer 18

The fibrous skeleton seperates the muscles, preventing contraction.
The moderator band regulates contraction to the ventricles from the atria.

Question 19

Describe the moderator band (better known as septomarginal trabecula).

Answer 19

It begins in the SA node, allows atrial contraction. It then heads to the AV node, allowing ventricular contraction. Purkinje fibres extend throughout the ventricles, to ensure they contract from the bottom up. The anterior papillary muscles are reached by purkinje fibres.

Question 20

Which node is dominant? How is this clinically relevant?

Answer 20

The SA node is dominant, and sets the pace for heartbeat.
If damaged, the AV node can take over and set the pace however.
Blockage can damage both, and if so, a pacemaker is needed.