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Clinical Anatomy Course > 9. Heart & Vascular System > Flashcards

9. Heart & Vascular System Flashcards

1
Q

What is the mediastinum?

A
  • The mediastinum is an anatomical region located centrally within the thorax, extending between the left and right lungs in the horizontal plane and between the neck and abdomen in the vertical plane.
  • The region may be subdivided into the anterior, middle, posterior and superior mediastinum.
  • The mediastinum contains all the thoracic viscera and structures except for the lungs.
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2
Q

What is the only structure that the mediastinum does not contain?

A

Lungs

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3
Q

Where is the anterior mediastinum and what is contained in it?

A
  • Between the thoracic plane and the diaphragm, anterior to the pericardium
  • Contents:
    • Thymus gland
    • Ectopic parathyroid gland
    • Thyroid tissue
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4
Q

Where is the middle mediastinum and what is contained in it?

A
  • Between the anterior and posterior margins of the pericardium, extending superiorly to the thoracic plane and inferiorly to the diaphragm
  • Contents:
    • Heart
    • Pericardium
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5
Q

Where is the posterior mediastinum and what is contained in it?

A
  • Between the thoracic plane and the diaphragm, posterior to the pericardium
  • Contents:
    • Descending aorta (and its branches)
    • Thoracic duct
    • Right lymphatic duct and associated nodes
    • Oesophagus
    • Sympathetic chain
    • Splanchnic nerves
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6
Q

Where is the superior mediastinum and what is contained in it?

A
  • Between the superior thoracic aperture to the thoracic plane
  • Contents:
    • Aortic arch and great vessels
    • Trachea
    • Oesophagus
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7
Q

What mnemonic can be used to remember the structure seen at the thoracic plane?

A

“RATPLANT”:

  • R = rib 2
  • A = aortic arch
  • T = tracheal bifurcation
  • P = pulmonary trunk
  • L = ligamentum arteriosum
  • A = azygos vein
  • N = nerves (loop of recurrent laryngeal)
  • T = thoracic duct
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8
Q

What are the main nerves seen in the mediastinum?

A
  • Phrenic
  • Vagus (CN 10)
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9
Q

What does the vagus nerve supply (in the mediastinum)?

A

Parasympathetic supply to:

  • Heart
  • Airways
  • Right and left recurrent laryngeal nerves
  • Abdomen (fore- and mid-gut derivatives)
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10
Q

Describe the path and branches of the vagus nerve in the mediastinum.

A
  • Enter the superior mediastinum via the posterior part of the carotid sheath
  • The right vagus nerve produces the right recurrent laryngeal nerve as it crosses the subclavian artery,
    • The right recurrent laryngeal nerve loops beneath the right subclavian artery and runs superiorly to supply the larynx.
  • The left vagus nerve produces the left recurrent laryngeal nerve as it crosses the aorta
    • The left recurrent laryngeal nerve loops beneath the ligamentum arteriosum and then ascends to supply the larynx.
  • The vagus nerves supply branches to the pulmonary and oesophageal plexuses before passing through the diaphragm.
  • Additionally, the vagus provides some parasympathetic innervation to the heart.
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11
Q

What do the phrenic nerves supply?

A
  • Motor to the diaphragm
  • Sensory to pleura, pericardium and peritoneum
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12
Q

What nerve roots form the phrenic nerve?

A

C3-C5

This can be remembered as “C3, C4, C5 keep the diaphragm alive”

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13
Q

What is the costodiaphragmatic recess and what is the significance?

A
  • These are the sharp angles created between the costal (thoracic wall) and diaphragmatic pleurae bilaterally, located at the bases of each pleural cavity.
  • These spaces may contain fluid in certain diseases such as heart failure, lung cancer and pneumonia.
  • This fluid causes a blunting of the normally sharp angles of the recesses, which is a characteristic sign of pathology.
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14
Q

What is the effect of damage to the phrenic nerve?

A
  • Injury to one phrenic nerve will cause paralysis of half of the diaphragm.
  • Paralysis of the diaphragm can be identified on radiographs, as when a patient is asked to take a breath in, instead of descending as the diaphragm would normally, the paralysed hemidiaphragm ascends due to the push from abdominal viscera below.
  • Conversely, the paralysed dome descends in expiration due to positive pressure within the lungs.
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15
Q

What is the effect of damage to the vagus nerve? How may this occur?

A
  • Distension of the aortic arch (e.g. in aortic aneurysms and dissections) may cause compression of the left recurrent laryngeal nerve as it loops around the ligamentum arteriosum.
  • This will result in paralysis of the laryngeal muscles on the left side, causing a hoarse voice.
  • Distally, damage to the vagus nerve will reduce parasympathetic innervation to the foregut and midgut structures, resulting in gastroparesis (failure of stomach motion).
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16
Q

What is thoracic inlet (a.k.a. outlet) syndrome?

A
  • Thoracic inlet syndrome involves obstructions impinging on this superior thoracic aperture can cause dysfunction of the structures emerging from the thorax.
  • Symptoms of this compression may be neurogenic (pain, upper limb motor weakness), venous (swelling, discolouration of the upper limbs) or arterial (pain, cold and pale upper limbs).
  • Possible causes of obstruction include tumours and cervical ribs.
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17
Q

What is the pericardium continuous with?

A
  • Superiorly: Tunica adventitia of the great vessels
  • Inferiorly: Diaphragm
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18
Q

What are the layers of the pericardium?

A
  • Fibrous pericardium (outermost) -> Consists of dense collagenous tissue interspersed with elastic fibrils.
  • Serous pericardium:
    • Parietal -> Simple squamous epithelium
    • Visceral -> Simple squamous epithelium
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19
Q

What is the function of the pericardium?

A
  • Fixation of the heart in position
  • Protection of the heart from bacterial/viral infection
  • Lubrication of heart movement
  • Resist over-distension of the heart
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20
Q

What is fluiod accumulation in the pericardial cavity called?

A
  • Pericardial effusion
  • When this impairs cardiac function, it is referred to as cardiac tamponade
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21
Q

Describe what is meant by the fibrous skeleton of the heart. What is the function?

A
  • The musculature and valves of the heart are built upon an underlying fibrous skeleton, formed from dense collagenous connective tissue.
  • The bases of the valvular cusps attach to the four rings of the fibrous skeleton, forming the two inflow and two outflow tracts of the cardiac ventricles.
  • In addition, the fibrous skeleton creates a non-conducting insulating band (anulus fibrosus) between the atria and the ventricles, ensuring the wave of depolarisation passes through the AV node to reach the ventricles.
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22
Q
A
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23
Q

What makes up most of the right border of the heart?

A

Right atrium

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24
Q

What does the right atrium drain?

A
  • Superior and inferior vena cava
  • Coronary sinus
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25
Q

Which of the atria has more notable internal features?

A

Right atrium

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26
Q

Describe the features of the interior of the atria.

A

Right atrium:

  • Anterior wall is trabeculated -> Formed of pectinate muscle
  • The pectinate muscle arises from the crista terminalis, which is a curved ridge that separates the trabeculated side from the smooth posterior side

Left atrium:

  • Predominantly smooth walled
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27
Q

What is the right atrial appendage/auricle?

A

The part of the right atrium that curves around the origin of the aorta, which increases the total volume of the right atrium.

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28
Q

Which surface side of the heart does the left atrium form?

A

Posterior

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29
Q

What is the clinical significance of the left atrial appendage/auricle?

A

Blood there is stagnant, so it is a commno site of thrombi.

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30
Q

Which surface side of the heart does the right ventricle make up?

A

Anterior

31
Q

Draw the heart chambers seen from the anterior side.

A
32
Q

Interpret what can be seen on this X-ray.

A
33
Q

Describe the features of the interior of the ventricles.

A

Left and right ventricles:

  • Inflow tract walls are lined with trabeculae carnae
  • Chordae tendinae attach to the valves and are connected to papillary muscles

(Trabeculae carnae are sort of like pectinate muscles in the atria)

34
Q

Name all of the heart valves.

A
  • Pulmonary (semilunar) valve
  • Aortic valve
  • Mitral/Bicuspid valve (left)
  • Tricuspid valve (right)
35
Q

What are the heart sounds and where is each best heard?

A
  • S1:
    • Closure of mitral and tricuspid valves at the end of diastole
    • Mitral valve -> Heard over the apex of the heart
    • Tricuspid valve -> Heard over the fourth intercostal space at the left sternal edge
  • S2:
    • Closure of the aortic and pulmonary valves at the end of systole
    • Aortic valve -> Heard at the second right intercostal space
    • Pulmonary valve -> Heard at the second left intercostal space.
36
Q

Where may be the mitral valve heart sound be heard?

A

Over the apex of the heart (5th left intercostal space)

37
Q

Where may be tricuspid valve heart sound be heard?

A

Over the fourth intercostal space at the left sternal edge

38
Q

Where may the aortic valve heart sound be heard?

A

Second right intercostal space

39
Q

Where may the pulmonary valve heart sound be heard?

A

Second left intercostal space

40
Q

Describe the location of the apex beat of the heart.

A

5th left intercostal space at the mid-clavicular line

41
Q

What can displacement of the apex beat of the heart indicate?

A

Cardiac hypertrophy

42
Q

Describe what makes up each of the borders of the heart.

A
  • Right border: Right atrium
  • Left border: Left ventricle, left atrium
  • Inferior border: Right ventricle
  • Superior border: Right and left atria
43
Q

Where is the SAN found?

A

Posterior wall of the right atrium just beneath the orifice of the superior vena cava.

44
Q

Where is the AVN found?

A

Septal wall of the right atrium just above the tricuspid valve orifice.

45
Q

Describe the position of the atrio-ventricular bundle.

A

From the atrioventricular node, the atrio-ventricular bundle (of His) passes down through the fibrous skeleton which separates and insulates the atria from the ventricles, the runs down on the interventricular septum dividing into right and left bundle branches.

46
Q

Draw the cardiac conducting system.

A
47
Q

Describe the autonomic supply to the heart.

A
  • Sympathetic postganglionic fibres largely from the cervical sympathetic ganglia, pass to the sino-atrial node, the atrio-ventricular node, and to the cardiac muscle.
  • Parasympathetic fibres from the vagus nerve are distributed almost entirely to the sinu-atrial node.
48
Q

Where do the coronary arteries originate from?

A

Right and left aortic sinuses, located just above and behind the aortic valve cusps.

49
Q

What are the main branches of the coronary arteries that you need to know?

A
  • Anterior and posterior interventricular branches
  • Marginal branches
  • Supply to AVN and SAN
50
Q

Describe the path and branches of the right and left coronary arteries.

A

Right coronary artery:

  • Passes from the right aortic sinus along the coronary sulcus (groove between atria and ventricles).
  • Within the groove, branches into:
    • SAN artery (in 60% of individuals)
    • AVN artery
    • Right marginal artery
    • Posterior interventricular artery (in 70% of individuals)

Left coronary artery:

  • Passes in the atrioventricular groove
  • Branches into:
    • Left anterior descending artery (passes in the anterior interventricular groove)
    • Circumflex artery (passes in atrioventricular groove to posterior heart)
    • Left marginal artery

Note: It helps to think of the heart as if it were not tilted.

51
Q

What two arteries supply the interventricular septum?

A

The left anterior descending artery supplies the anterior 2/3rds of the interventricular septum, whilst the posterior interventricular artery supplies the posterior 1/3rd.

52
Q

What artery supplies the SAN and AVN?

A
  • SAN -> Right coronary artery (in 60% of individuals)
  • AVN -> Right coronary artery
53
Q

Coronary arteries are … arteries.

A

Functional end

54
Q

When is there most perfusion through the coronary arteries?

A

During diastole

55
Q

What is the consequence of occlusion of the major coronary arteries?

A
  • Angina, radiating into the left arm and neck
  • This is because sensory fibres innervating the heart pass along the sympathetic nerves to terminate in the upper thoracic spinal cord. As such, ischaemic pain from the heart is referred to the dermatomes of T1-T5.
56
Q

What is coronary dominance?

A
  • Coronary dominance is determined by the coronary artery that gives rise to the posterior interventricular artery.
  • The right coronary artery is dominant in 70% of the population, whereas the left coronary artery is dominant in around 10% of the population.
  • Approximatively 20% of people have co-dominance, meaning that both the right coronary artery and the circumflex branch of the left coronary artery supply the posterior interventricular artery.
57
Q

What are the three main shunts that are present in the foetal circulation?

A
  • Foramen ovale -> Shunts highly oxygenated blood (from the umbilical veins) from the right atrium to the left atrium.
  • Ductus arteriosus -> Passes between the pulmonary trunk and the arch of the aorta. Functions to protect the developing lungs from circulatory overload and carries moderately oxygenated blood.
  • Ductus venosus (not in spec) -> Connects the umbilical vein to the inferior vena cava, therefore carries highly oxygenated blood.
58
Q

What drives changes in the foetal circulation at birth?

A

Air in the lungs

59
Q

What are the main changes in the foetal circulation that occur at birth?

A
  • The foramen ovale closes to form the fossa ovalis – this closure forces the entire right heart’s output to the lungs.
  • The ductus arteriosus constricts – this occurs when the blood PO2 exceeds 50mmHg, as the foetus takes its first breaths.
  • The umbilical vein constricts – this prevents blood loss via the umbilicus. The ductus venosus forms the ligamentum venosum, whilst the umbilical vein forms the ligamentum teres, the free edge of the falciform ligament of the liver.
60
Q
A
61
Q
A
62
Q
A
63
Q

Describe atrial septal defects.

A
  • Characterised by a defect within the inter-atrial septum, allowing blood to pass from the left atrium back into the right atrium.
  • These defects may result from a failure of adhesion between the flap valve of the foramen ovale and the septum secundum at birth, or due to a failure of fusion of the septum primum with the endocardial cushions.
  • Depending on the size of the shunt, this can lead to right sided overload, pulmonary hypertension and atrial arrhythmias.
64
Q

Describe ventricular septal defects.

A
  • Characterised by a defect in the interventricular septum, most commonly within the membranous portion of the septum.
  • Shunting of blood from the left ventricle to the right ventricle may lead to increased pulmonary blood flow, reduced cardiac output and raised pulmonary artery pressure.
65
Q
A
66
Q

What features can occur with heart defects?

A
  • Shunts
  • Cyanosis
67
Q

What is tetralogy of Fallot?

A
  • One of the most common cyanotic heart conditions, characterised by:
    • Large ventricular septal defect
    • Overriding aorta
    • Right ventricular outflow obstruction
    • Right ventricular hypertrophy.
  • Severe cyanosis may be present at birth.
  • Full surgical repair is required within the first year of life.
68
Q

What is coarction of the aorta?

A
  • A narrowing of the aorta, which typically occurs at the junction of the aortic arch and the descending aorta.
  • This constriction forces the heart to pump harder than usual, in order to propel blood beyond the stenosis.
  • This results in high blood pressure in the head, neck and upper limbs, and low blood pressure in the lower limbs.
  • Consequences of coarctation include premature heart disease, cerebral aneurysms, organ failure, arterial rupture and death.
69
Q

What is patent ductus arteriosus?

A
  • When the ductus arteriosus fails to close after birth
  • This allows a portion of oxygenated blood from the left heart to flow back to the lungs by flowing from the aorta, which has a higher pressure, to the pulmonary artery.
  • With time, an uncorrected PDA usually leads to pulmonary hypertension followed by right-sided heart failure.
70
Q

Label this radiograph.

A
  1. Ascending aorta
  2. Arch of aorta
  3. Descending aorta
  4. Heart
71
Q
A
72
Q
A
73
Q
A
  1. Right pulmonary vein entering left atrium
  2. Right atrium
  3. Right ventricle
  4. Infundibulum of left ventricle
  5. Left lung
  6. Descending aorta
  7. Oesophagus
  8. Azygous vein
74
Q
A

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