UNIT 4: The heart

Question 1

Give an overview of the position and sections of the mediastinum.

Answer 1

Located between the two pleural cavities within the thoracic cage.
Starts at the thoracic inlet and ends at the diaphragm.
T4/5 divides into the superior and inferior mediastinum
THe inferior can then be split into the anterior, middle and posterior, with the middle consisting of other pericardial sac and the heart.

Question 2

What is the largest section of the mediastinum?

Answer 2

The middle.

Question 3

What is the pericardium?

Answer 3

Found within the mediastinum.
Is the covering of the heart.
Consists of the viseceral and parietal serous membrane, and an outer fibrous pericardium.

Question 4

What does the fibrous pericardium attach to?

Answer 4

Fuses superiorly with the roots of the great vessels, fuses inferiorly with the diaphragm.
Anteriorly is connected to by the sternopericardial ligaments.

Question 5

What two layers is the pericardial cavity between?

Answer 5

Is a small cavity containing fluid, located between the parietal and visceral pericardium.

Question 6

WHat are pericardial sinsues?
Where are they located?
What causes them to form?

Answer 6

Pericardial sinuses are potential spaces within the pericardium.
The visceral and parietal pericardium layers are often separate but a points they fuse together such as around the great arteries then again around the great veins.
Sinuses are the cavities created between these fusions.
The transverse sinus is between the the great arteries and the great veins.
The oblique sinus is found posterior and superiorly to the apex of the heart, as is holding the heart from the back.

Question 7

What is pericarditis?

Answer 7

Inflammation of the pericardium

Question 8

What is cardiac tamponande?

Answer 8

When fluid builds up in the pericardial cavity, exerts pressure on the myocardium.
Fbrous pericardium is unable to expand to cope with the extra fluid.
Symptoms include decreased cardiac output, hypotension and tachycardia, may also have difficulty breathing.

Question 9

What are the different great vessels?

Answer 9

Inferior vena cava
Superior vena cava (L+R brochicephalic, jugular and subclavian)
Pulmonary veins (4)
Pulmonary trunk
Ascending aorta and its arch (gives of the brachiocephalic, left common carotid and left subclavian).

Question 10

What does the brachiocephalic artery trunk bifuracte into?

Answer 10

The right common carotid and the right subclavian artery.

Question 11

What is the ligamentum arteriosum?

Answer 11

Ligament connecting the pulmonary trunk to the arch of the aorta.
Left over from a foetal feature doctus arteriosum which allowed blood to bypass the lungs during foetal development as blood was oxygenated by the mother.

Question 12

What is the coronary sinus?

Answer 12

A collection of cardiac veins on the posterior surface of the heart, mainly made from the widening of the great cardiac vein.

Question 13

How can doexygenated blood enter the right atrium?

Answer 13

Superior vena cava
Inferior vena cava
The coranry sinus.

Question 14

What are the internal features of the right atrium?

Answer 14

Derived from two different embryological structures, the boundary between these features is shown in adults as a thick muscular ridge known as the crista terminalis.
Anterior to this are walls of muscular ridges known as musculi pectinati.
Posterior to this are smooth walls, contains the fossa ovali.

Question 15

What is the fossa ovalis?

Answer 15

Marks the embryological location of the foramen ovale, allowed blood to bypass the lungs.
The fossa is found in the adults rights atrium
The valve is found in the adults left atrium

Question 16

What are trabeculae carnea?

Answer 16

Means fleshy beams
Are muscular ridges found in the ventricular walls.

Question 17

Explain the features of valves related to the ventricles.

Answer 17

Bicuspid (mitrial valve) has two cusps (LV)
Tricuspid valve has three cusps (RV)
The aortic and pulmonary semilunar valves have three cusps
The AV valve cusps each attach to chordae tendinae which then each attach to two papillary muscles.

Question 18

How does the left ventricular wall compare to the right?

Answer 18

The left wall has longer and thicker myocardium, gives a stronger force of contraction, needed to pump blood a greater distance.

Question 19

What are the different borders of the heart?

Answer 19

Right
Left
Inferior
Superior.

Question 20

What are the different surfaces of the heart?

Answer 20

Diaphragmatic (inferior)
base (posterior)
Sternocostal (anterior)
Left and right pulmonary surfaces.

Question 21

What are the different surface anatomy landmarks of the different heart valves?

Answer 21

Aortic valve: just to the right of the sternum in the 2nd intercostal space
Pulmonary valve: just to the left of the sternum in the 2nd intercostal space.
Tricupsid valve: just to the left of the sternum in the fifth intercostal space
Bicuspid valve:Left 5th intercostal space in the midclavicular line.

Question 22

What is the septomarginal trabecula?

Answer 22

Part of the conductive circuit of the heart, connects the right bundle in the septum to the anterior wall of the right ventricle

Question 23

What is the fibrous cardiac skeleton?

Answer 23

Four inteconnected fibrous rings that surround the valves of the heart.
Are connected by the right and left fibrous trigone, the left trigone contains the AVN.

Question 24

What is the function of the fibrous cardiac skeleton?

Answer 24

Electrical insulation between heart chambers
Point of attachment for cusps
Maintains integrity/openess.
Structure for muscle to contract against.

Question 25

What is the aortic sinus and what does it give rise to?

Answer 25

When the arotic valve closes, pressure temporarly drops in the aort causing a small backflow in blood to collect just superior to the valve, this blood can then enter and flow out of the first branches from the aorta the left and right coronary arteries.

Question 26

What are the different branches of the right coronary artery?

Answer 26

The sinatrial branch - posterior to the SVC then swings round to run down the right atrium The marginal branch- the right border of the heart The posterior descending branch - diaphragmatic surface between the two ventricles.

Question 27

What are the branches of the left coronary artery?

Answer 27

The left circumflex artery - posterior to the pulmonary trunk, then warps around the anterior margin between the left atriuam and ventricle towards the posterior surface of the heart. The left anterior descending artery - the anterior section between the two ventricles Left marginal branch - branches off the circumflex to supply the left boundary Diagonal branch - branches off LAD to supply the left ventricle

Question 28

Explain the venous drainage of the heart?

Answer 28

All veins are tributaries of the coronary sinus which is found on the base of the heart just below the left atrium. Great vein - travels round the left atrium and becomes the anterior descending vein. Small cardiac vein - travels right to the right atrium boundary with the ventricle to becomes the right marginal vein. Anterior veins of the right ventricle Middle cardiac vein - branches from the sinus between the left and right ventricles on the diaphragmatic surface of the heart.

Question 29

What is a cardiac arrest?

Answer 29

A breif loss in heart function, loss of electrical activity. Causes no heart activity, stop breathing and loss of consciousness.

Question 30

What is coronary artery disease?

Answer 30

A reudction of blood supply to the heart muscle (myocardium) often due to plaque formation from atherosclerosis in the coronary arteries. Includes angina and myocardial infarction.

Question 31

What arteries are most commonly blocked during a myocardial infarction?

Answer 31

The left anterior descending (40-60%) - also known as the widow maker. Right circumflex artery - 30-40% Left circumflex branch - 15-20%.

Question 32

What is a percutaneous transluminal coronary angioplasty?

Answer 32

Local anesthetic given to the groin area Incision made in the femoral artery and guide wire inserted. Introducer is used to insert a guide wire and diagnostic catheter into the coranary artey (guide wire is then removed) X-ray and dye are used to identify a blockage Cather is then replaced by a guiding catheter and a thinner wire. A balloon catheter is guided to the blockage site, balloon is inflated to widen the artery. The balloon is removed and a stent put in place to keep the artery open. An x-ray is once again used to check the arteries. All catheters and guide wires are removed.

Question 33

What is cardiac referred pain?

Answer 33

Pain felt at a site that is not where the stimulus originated. Cardiac pain is often felt in the left jaw, neck shoulder and arm. This is due to multiple sensory nerves converging on the same spinal segment. Brain assumes what area of the body is most likely to be feeling this pain.

Question 34

What is a dermatome?

Answer 34

An area of skin innervated by a single spinal segment. Note nerve innervation is variable and regions may overlap.