Thorax - Mediastinum (1)

Question 1

A transverse line through which bony structures separates the superior mediastinum from the rest of the mediastinum?

Answer 1

Through the sternal angle and the intervertebral disc between T4 and T5.

Question 2

Describe the relationship between the Visceral pericardium and the Parietal pericardium.

Answer 2

The visceral pericardium and parietal pericardium are the two continuous layers lying closest to the myocardium, and between them is a potential space: the pericardial cavity. The visceral pericardium is also called the epicardium.

Question 3

Explain the nerve fibres and the sensation of pain involved in pericarditis.

Answer 3

It is the parietal layer, not the visceral layer, of the pericardium that is sensitive to pain. Pain impulses conducted from it by the somatic phrenic nerves result in referred pain sensations.

Question 4

Describe the relationship between the fibrous pericardium and the following structures:
The great vessels, The heart, The diaphragm.

Answer 4

The tough fibrous pericardium overlies the parietal pericardium. It is continuous superiorly with the tunica adventitia of the great vessels, and inferiorly with the central tendon of the diaphragm.

Question 5

What is the coronary sinus? Where is it?

Answer 5

This is the main vein that drains the myocardium. It enters the RA.

Question 6

What is the infundibulum of the heart? What is another name for it?

Answer 6

This is the outflow part of the right ventricle, close to the pulmonary valve. It is also called the conus arteriosus because it is the tapering of the ventricle into a cone-shape. It is smooth-walled, with no trabeculae carneae, unlike the rest of the ventricle.

Question 7

What are trabeculae carneae?

Answer 7

These are irregular muscular elevations / ridges lining the interior walls of each ventricle.

Question 8

Describe the structures that keep the tricuspid valve in place.

Answer 8

The tricuspid valve is surrounded by a fibrous ring which maintains the calibre of the orifice. Each cusp of the tricuspid valve have chordae tendinaea attached, which arise from papillary muscles, which arise from the muscular wall of the ventricle.

Question 9

What are the semilunar valves?

Answer 9

These are the pulmonary and aortic valves.

Question 10

What are the auricles in the heart?

Answer 10

The left and right auricles are ear-like projections of the left and right atria.

Question 11

What is the oval fossa?

Answer 11

This is a remnant of the fetal foramen ovale. It lies in the interatrial septum and is visible in both the left and right atria.

Question 12

What are pectinate muscles?

Answer 12

These are the rough muscle lining of the inner surfaces of the left and right atria. There are also smooth surfaces of both atria that do not contain pectinate muscles.

Question 13

How much thicker are the walls of the LV compared to the RV?

Answer 13

2-3 times.

Question 14

What is the name of the smooth non-muscular outflow part of the left ventricle?

Answer 14

The aortic vestibule.

Question 15

Does each cusp of the AV valves receive chordae tendinae from a specific papillary muscle?

Answer 15

No. Chordae tendinae from each papillary muscle lead to more than one cusp. There is overlap, so that the apparatus can function like a parachute.

Question 16

At what part of the cardiac cycle do the papillary muscles start to contract?

Answer 16

Just before and during systole. They need to pull the chordae tendinae taut before systole starts, to prevent retrograde flow of blood into the atria.

Question 17

What are some differences between semilunar cusps and the cusps of the AV valves?

Answer 17

Semilunar cusps do not have tendinous cords to support them. They are smaller in area.

Question 18

How do the semilunar valves close?

Answer 18

At the start of diastole, as the ventricles relax, blood starts to flow retrograde from the aorta (or pulmonary trunk) to the ventricles. As this happens, the blood is “caught” in the cusps which open up like pockets, and they expand onto each other to close the orifice.

Question 19

What are the aortic sinuses?

Answer 19

These are the mouths of the coronary arteries, right at the origin of the aorta, just after the aortic valve.

Question 20

Name the cusps of the mitral valve.

Answer 20

Two cusps: Anterior and posterior

Question 21

Mitral valve: Which cusp is the thickest and most rigid?

Answer 21

The anterior cusp is thicker and more rigid than the posterior cusp.

Question 22

Mitral valve: Where is it located in relation to the ribs?

Answer 22

The mitral valve is located posterior to the sternum at the level of the 4th costal cartilage.