Heart and Vessel Radiology and Histology

Question 1

What exits the pericardial sac superiorly? Inferiorly?

Answer 1

Superiorly: aorta, pulmonary artery, superior vena cava

Inferiorly: Inferior vena cava

Question 2

The apex of the heart is the. . .

Answer 2

. . . tip of the left ventricle

Question 3

Heart anterior view

Answer 3

Question 4

Heart posterior view

Answer 4

Question 5

Two ‘rules’ of normal cardiac anatomy

Answer 5

1. Right structures are slightly anterior of left structures
2. Atria are slightly right of their ventricles

Question 6

Cardiac skeleton

Answer 6

Fibrous connective tissue that forms the scaffold for cardiac muscle

Question 7

Endocardium

Answer 7

Single-cell-thick layer that covers the interior of the heart

Question 8

Myocardium

Answer 8

Thickest layer of the heart, where bundles of cardiac mucsle reside. Surrounded by connective tissue and adipose tissue through which vasculature runs.

Question 9

Epicardium

Answer 9

synonymous with visceral pericardium

Question 10

Right atrium and ventricle diagram

Answer 10

Question 11

trabeculae carneae

Answer 11

Irregular bridges covering all of the right atrium except for the inner wall of the outflow tract towards the pulmonary artery. Gives the ventricular wall a sponge-like appearance.

The moderator band is a large trabecula that crosses the ventricular cavity and carries part of the cardiac conduction system to ventricular muscle.

Question 12

Contraction of the papillary muscles prior to other regions of the ventricle. . .

Answer 12

. . .tightens the chordae tendineae, helping to align and restrain the leaflets of the tricuspid valve as they are forced closed. This action prevents blood from regurgitating into the right atrium during ventricular contraction.

Question 13

How is regurgitation prevented at each heart valve?

Answer 13

The atrioventricular valves utilize papillary muscles and chordae tendinae to increase the tension in the ligaments of the cusps, helping to align and restrain them as they are forced closed.

The semilunar valves utilize the distension of the valve cusps to repel fluid forced backwards by the elastic recoil of the pulmonary artery and aorta.

Question 14

Left atrium left ventricle diagram

Answer 14

Question 15

Interventricular Septum

Answer 15

Thick wall between the left and right ventricles. Composed of a muscular and a membranous part. The small, oval-shaped membranous part of the septum is thin and located just inferior to the cusps of the aortic valve. The large muscular portion of the septum bulges toward the right ventricle due to the greater hydrostatic pressure in the left ventricle.

Question 16

Conduction system view

Answer 16

Question 17

Source of the heart’s sympathetic innervation

Answer 17

Preganglionic sympathetic neurons, with cell bodies located within the upper five to six thoracic levels of the spinal cord, synapse with second-order neurons in the cervical sympathetic ganglia. Traveling within the cardiac nerves, these fibers terminate in the heart and great vessels.

Question 18

Source of the heart’s parasympathetic innervation

Answer 18

Preganglionic parasympathetic fibers originate in the dorsal motor nucleus of the medulla and pass as branches of the vagus nerve to the heart and great vessels. Here, the fibers synapse with second-order neurons located in ganglia within these structures.

Question 19

Most cardiac reflex loops are innervated by. . .

Answer 19

. . . the afferent vagus nerve.

Question 20

___ are the major sources of CNS input for the SA and AV nodes.

Answer 20

Efferent vagal fibres are the major sources of CNS input for the SA and AV nodes.

Question 21

The AV nodal-artery is a branch of the. . .

Answer 21

. . . right coronary artery

Question 22

Right dominant and left dominant coronary circulation

Answer 22

The posterior descending and AV nodal arteries arise from the RCA in 85% of the population, and in such people, the coronary circulation is termed right dominant.

In approximately 8%, the posterior descending artery arises from the circumflex artery instead, resulting in a left dominant circulation.

In the remaining population, the heart’s posterior blood supply is contributed to from branches of both the RCA and the circumflex, forming a codominant circulation.

Question 23

The SA nodal-artery is a branch of the. . .

Answer 23

. . . right coronary artery in 70% of people, circumflex 25% of the time, and tributaries from both 5% of the time.

Question 24

Muscle fibres located just beneath the endocardium are supplied by. . .

Answer 24

. . . either the terminal branches of the coronary arteries or directly from the ventricular cavity through tiny vascular channels, known as thebesian veins.

Question 25

Collateral connections between coronary arteries

Answer 25

Exist at the **subarteriolar** level. In the normal heart, few of these collateral vessels are visible. However, they **may become larger and functional when atherosclerotic disease obstructs a coronary artery,** thereby providing blood flow to distal portions of the vessel from a nonobstructed neighbor.

Question 26

Coronary veins

Answer 26

The coronary veins follow a distribution similar to that of the major coronary arteries. Return blood to the right atrium predominantly via the **coronary sinus.** The **major veins lie in the epicardial fat**, usually **superficial to their arterial counterparts.**

Question 27

Heart lymphatics

Answer 27

The heart lymph is drained by an extensive **plexus of valved vessels located in the subendocardial connective tissue of all four chambers.** This lymph drains into an **epicardial plexus** from which are derived several larger lymphatic vessels that follow the distribution of the coronary arteries and veins. Each of these larger vessels then **combines in the AV groove** to form a single lymphatic conduit, which **exits the heart to reach the mediastinal lymphatic plexus** and ultimately the thoracic duct.

Question 28

Intercalated disks on histology represent. . .

Answer 28

. . . **gap junction complexes between adjacent cardiomyocytes.**

Question 29

T tubules

Answer 29

Deep, fingerlike invaginations of the sarcolemma. The T tubule system **increases the surface area of the sarcolemma** in contact with the extracellular environment, **allowing the transmembrane ion transport** accompanying excitation and relaxation **to occur quickly and synchronously.** The sarcoplasmic reticulum abuts the T tubules at right angles in lateral calcium-storing sacs, called the **terminal cisternae**

Question 30

Silhouette Sign

Answer 30

If the intersection of two structures that are normally very different in opacity on an X-ray is blurred in some way, there may be something dense in between them.

Question 31

The portion of the right lung that abuts the heart is the. . .

Answer 31

. . . right middle lobe

Question 32

How might one distinguish a right lower lobe and right middle lobe abnormality?

Answer 32

If you can still see the cardiac border, then the middle lobe probably is not the problem. In this case it is more likely to be the lower lobe. If this border is obscured, but the costophrenic angle is preserved, this is more likely to be a middle lobe problem than a lower lobe problem.

Question 33

Generally lower lobe problems are best visualized on. . .

Answer 33

. . . lateral films

Question 34

On an X-ray, the heart span should not take up more than ___ of the width of the thoracic cavity.

Answer 34

On an X-ray, the heart span should not take up more than **50%** of the width of the thoracic cavity.

Question 35

The phrenic nerves pass. . .

Answer 35

. . . from the C3-C5 region downwards bordering the trachea and expanding outward to the border of the mediastinal and pleural spaces. They pass anterior to the hyla of the lungs and descend down the pericardium to the central ligament of the diaphragm, extending from there to innervate each hemidiaphragm.

Question 36

In general, veins lack \_\_\_, while arteries either have multiple layers.

Answer 36

In general, veins lack **significant elastic tissue**, while arteries either have multiple layers.

Question 37

Which ventricle generates more pressure? Which pumps more volume?

Answer 37

The LV generates more pressure because it must overcome a greater resistance in systemic circulation than the RV must overcome for pulmonary circulation. Both must pump out the **same volume**, as this is a closed system. If they are not, blood is pooling somewhere.

Question 38

Which chamber is which on this EKG?

Answer 38

Question 39

Which ventricle is more round?

Answer 39

The **left**. The right ventricle is more like a flat-ish bellows. This is important when it comes to approximating ejection fraction from an EKG, as you must know rough geometric properties to approximate volume from a 2d plane.

Question 40

Central venous catheters used to access the right atrium via the subclavian vein. Nowadays, they tend to use the jugular vein. This is because accessing through the subclavian vein was associated with high rates of iatrogenic \_\_\_.

Answer 40

Central venous catheters used to access the right atrium via the subclavian vein. Nowadays, they tend to use the jugular vein. This is because accessing through the subclavian vein was associated with high rates of iatrogenic **pneumothorax**. Access via the subclavian passes the apex of the right lung's pleura, and puncturing this from outside the body causes pneumothorax and lung collapse.

Question 41

Pulmonary stem cell diagram

Answer 41