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Phase 1 Cardio > Session 2: The superior mediastinum and the Heart > Flashcards

Session 2: The superior mediastinum and the Heart Flashcards

1
Q

What is the mediastinum?

A

The mediastinum is the part of the thoracic cavity that lies between the lungs. It contains all the thoracic viscera apart from the lungs.

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2
Q

What does the mediastinum contain?

A

• The heart and pericardium
• The great vessels
• The veins that drain the chest wall
• The trachea and main bronchi
• The oesophagus
• Nerves (somatic and autonomic)
• Lymphatics
• The thymus gland

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3
Q

What is the mediastinum divided into?

A

Super and inferior

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4
Q

What is the inferior mediastinum further divided into?

A

• anterior mediastinum
- narrow space
- contains the thymus gland in children and its remnant in adults

• middle mediastinum contains the heart inside the pericardial sac, the pulmonary trunk, and the ascending aorta

• posterior mediastinum

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5
Q

What does the superior mediastinum contain?

A

The main contents of the superior mediastinum are the:
• arch of the aorta and its three branches
• superior vena cava and its tributaries - the left and right brachiocephalic veins
• trachea
• oesophagus
• phrenic nerves (left and right) and vagus nerves (left and right)
• thoracic duct
• thymus gland

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6
Q

What does the aorta do?

A

The aorta leaves the left ventricle and carries oxygenated blood to the systemic circulation.

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7
Q

What does the arch of the aorta give rise to?

A

in the superior mediastinum it gives rise to three major branches that supply the upper body

  1. the brachiocephalic trunk.
    - bifurcates into right common carotid artery - right side of the head and neck, including the brain
    - right subclavian artery which supplies the right upper limb.
  2. the left common carotid artery, which supplies the left side of the head, neck, and brain.
  3. the left subclavian artery, which supplies the left upper limb.
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8
Q

What does the arch of the aorta contain?

A

contains the aortic bodies where chemoreceptors are located

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9
Q

What is the ligamentum arteriosum?

A

The ligamentum arteriosum is a fibrous, cord-like connection between the pulmonary trunk and the arch of the aorta.

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10
Q

What enters the right atrium?

A

Two large veins carrying deoxygenated blood enter the right atrium: the superior vena cava and the inferior vena cava.

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11
Q

Why is the trachea semi-rigid?

A

due to C-shaped, incomplete rings of cartilage in its walls.

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12
Q

What is the oesophagus like?

A

The oesophagus is a muscular tube that extends from the pharynx in the midline of the neck to the stomach.

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13
Q

What are the phrenic nerves formed by?

A

The left and right phrenic nerves, formed by fibres from the C3, C4 and C5 spinal nerves, innervate the diaphragm.

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14
Q

What is the vagus nerve from?

A

arise from the brainstem

contain somatic sensory, somatic motor and parasympathetic fibres.

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15
Q

What course does the vagus nerve take?

A

They descend through the neck alongside the internal carotid artery and internal jugular vein and enter the thorax via the superior thoracic aperture.

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16
Q

What is the thoracic duct?

A

major channel for lymphatic drainage from most regions of the body

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17
Q

What is the thymus gland?

A

The thymus is a lymphoid organ. It lies anteriorly in the superior mediastinum. It is important in children, but atrophies with age, eventually becoming fatty..

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18
Q

What is the pericardium?

A

The pericardium is a tough, fibrous sac that encloses the heart; it is loose to allow for the movement of the heart within it.

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19
Q

What is the space between the two layers of pericardium?

A

narrow space is the pericardial cavity.

It contains a small amount of pericardial fluid that lubricates the serous membranes and allows them to slide over each other with movements of the heart.

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20
Q

What are the surfaces of the heart?

A

• Base / posterior surface = left atrium, part of the right atrium
• Inferior / diaphragmatic surface = left ventricle, part of the right ventricle
• Anterior / sternocostal surface = right ventricle
• Left pulmonary surface = left ventricle
• Right pulmonary surface = right atrium

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21
Q

What is the apex formed by?

A
  • the left ventricle.
  • left 5th intercostal space in the midclavicular line
  • apex beat is palpable here.
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22
Q

What are the borders of the heart?

A

• Right border = right atrium
• Left border = left ventricle
• Inferior border = right ventricle and part of the left ventricle

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23
Q

What is the patent ductus arteriosus (PDA)?

A

type of congenital cardiac anomaly

The ductus arteriosus usually closes immediately after birth. In some infants, the ductus arteriosus does not close and remains open (patent).

  • After birth, the pressure in the aorta exceeds the pressure in the pulmonary trunk
  • hence blood flows through a patent ductus arteriosus from the aorta into the pulmonary trunk
  • Over time, increased flow through the pulmonary vessels can lead to pulmonary hypertension (high pressure in the vessels of the lungs) which strains the right side of the heart.
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24
Q

What is the hoarseness of the voice caused by?

A

Cancer at apex of the lung - recurrent laryngeal nerve (RLN) supplies most of the muscles of the larynx.

Hoarseness results as the patient can no longer fully adduct their vocal cords.

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25
Q

What is pericardial effusion?

A

Pericardial effusion is an increase in fluid volume in the pericardial space.

Pericardial effusion may result from inflammation of the pericardium (a condition called pericarditis) or an accumulation of blood (due to trauma).

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26
Q

What does the RCA supply?

A

supply parts of the conducting system of the heart, the right atrium, right ventricle, part of the left ventricle, and part of the interventricular septum.

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27
Q

What are the main branches of the RCA?

A

• The right marginal artery supplies the inferior border of the heart.

• The posterior interventricular artery (PIV) runs in the posterior interventricular sulcus and supplies both ventricles.

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28
Q

What does the LCA supply?

A

the left atrium, most of the left ventricle, part of the right ventricle, and part of the interventricular septum.

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29
Q

What are the branches for the LCA?

A

left main stem (‘LMS’).
The two terminal branches of the left coronary artery are the:
• Anterior interventricular artery (or the left anterior descending; ‘LAD’).
• Circumflex artery (abbreviated to ‘Cx’).

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30
Q

What are the main branches and course of the LCA?

A

• LAD runs in the anterior interventricular sulcus towards the apex.
• One or two diagonal branches arise from the LAD.
• The circumflex artery runs on the inferior / diaphragmatic surface.
• The left marginal artery arises from the circumflex and supplies the left ventricle.

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31
Q

Where does the posterior inter-venticular artery supply?

A

supplies a significant portion of the left ventricle
may arise from the right or left coronary artery.

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32
Q

What are the circulations of the PIV?

A

Most people have a right dominant circulation; the PIV arises from the right coronary. In these people, both the right and left coronary arteries supply the left ventricle.

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33
Q

What does the right atrium receive?

A

The right atrium receives deoxygenated blood from the body via the superior and inferior venae cavae, and from the heart via the coronary sinus.

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34
Q

What is the fossa ovalis?

A

– a depression in the interatrial septum.
- It is the remnant of the foetal foramen ovale
- In the foetus the foramen ovale shunts oxygenated blood from the right atrium to the left atrium, hence bypassing the lungs.

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35
Q

What is the Crista terminalis?

A

a muscular ridge that separates the smooth-walled posterior part of the atrium from the anterior part, which has a ridged, muscular wall.

The ridges are pectinate muscles and extend into the right auricle. The parts of the right atrium on either side of the crista have different embryological origins.

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36
Q

What is the blood flow in the RA?

A

From the right atrium, blood flows into the right ventricle via the right atrioventricular valve, also called the tricuspid valve.

The flow of blood is mostly passive, but the right atrium does contract to empty fully.

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37
Q

What does the RV do?

A

The right ventricle pumps the deoxygenated blood from the right atrium into the pulmonary trunk, which bifurcates into a left and right pulmonary artery.

38
Q

What is in the RV?

A

Internally features of the right ventricle are the:

• interventricular septum
• trabeculae carneae
• papillary muscles
• chordae tendineae
• moderator band

39
Q

What does the LA do?

A

The left atrium receives oxygenated blood from the lungs via the pulmonary veins (two from each lung).

From the left atrium, blood flows into the left ventricle via the left atrioventricular valve, also called the mitral valve.

The flow of blood is mostly passive, but the left atrium does contract to empty fully.

40
Q

What does the LV do?

A

The left ventricle pumps the oxygenated into the aorta.

The first branches from the aorta are the coronary arteries.

41
Q

What does the LV contain?

A

• trabeculae carneae
• papillary muscles; two
• chordae tendineae

42
Q

What happens in the AV valves?

A

Ventricular systole:

The tricuspid and mitral valves close during ventricular contraction and prevent regurgitation of blood back into the atria, ensuring that blood can only flow out the ventricles via the great vessels (the pulmonary trunk and aorta).

43
Q

What are the semi lunar valves?

A

The aortic and pulmonary valves are called semilunar valves, as their cusps are semi-circular (half-moon) shaped.

They prevent the backflow of blood from the aorta and pulmonary trunk into the left and right ventricles, respectively, that would otherwise occur at the end of ventricular contraction.

44
Q

What are the auscultations areas for valves?

A

• Aortic = 2nd intercostal space, just to the right of the sternum.
• Pulmonary = 2nd intercostal space, just to the left of the sternum.
• Tricuspid = 5th intercostal space, just to the left of the sternum.
• Mitral = 5th intercostal space, left midclavicular line.

45
Q

What conducts electrical impulses that stimulate myocardial contraction?

A

• Cells in the sinoatrial (SA) node spontaneously generate electrical impulses
- it is the ‘pacemaker’ of the heart
- It is located at the superior end of the crista terminalis.
• The SA node generates impulses at a rate of approximately 70 per minute.

46
Q

What supplies the SA node and AV node?

A

• The SA node is supplied by the RCA in approximately 60% of people and by the LCA in approximately 40% of people.
• The AV node is usually supplied by the posterior interventricular artery. In most people, the PIV arises from the RCA.
• In most people, the LCA supplies the Bundle of His.

47
Q

What is the innervation for the heart?

A
  • sympathetic and parasympathetic fibres.
  • acts on SA node and changes rate and force of myocardial contraction.

The heart is also innervated by visceral afferent fibres

48
Q

What do visceral afferent fibres do if myocardium is ischeaemic?

A

However, if the myocardium is ischaemic, this visceral sensory information is relayed back to our conscious perception and may be perceived as pain, burning, tightness or pressure in the chest.

Typically, the pain cannot be pinpointed, but is felt generally in the chest, the left side of the neck and / or the left arm. This is called referred pain.

49
Q

What is MI?

A

This is the death of a region of myocardium secondary to occlusion (blockage) of the coronary vessel that supplies it.

50
Q

What are congenital cardiac anomalies?

A

Openings can also occur in the interventricular septum. Ventricular septal defects (VSDs) allow blood to flow from the left to the right ventricle.

The severity of these defects largely depends on the size of the opening between the chambers.

51
Q

What is valve dysfunction?

A

The AV and semilunar valves may become narrowed (stenosis) or incompetent.

  • regurgitation
  • turbulent blood flow
  • murmurs on auscultation

Valve dysfunction - congenital or acquired.

For example, an AV valve may become dysfunctional if a myocardial infarct involves the associated papillary muscles.

52
Q

What are cardiomyopathies?

A

Cardiomyopathies are diseases of myocardium, and most are inherited.

This affects the heart’s ability to pump efficiently and can lead to heart failure.

53
Q

When does heart failure occur?

A

Heart failure occurs when the heart does not pump efficiently.

Signs and symptoms of heart failure include tiredness, shortness of breath and leg swelling.

54
Q

What is cardiac arrest?

A

cessation of cardiac contraction.

Sometimes there is still detectable electrical activity, but the heart does not contract in response.

55
Q

What do the aortic bodies do?

A

Contain chemoreceptors.
- constantly monitor arterial oxygen and carbon dioxide
- This visceral sensory information travels back to the CNS along the path of the vagus nerve
- results in reflex responses that regulate ventilation

56
Q

What is the ligamentum arteriosus a remnant of?

A

It is the remnant of the ductus arteriosus, a foetal circulatory shunt.

57
Q

What is the superior cava formed by?

A

• The SVC is formed by the union of the left and right brachiocephalic veins (brachium = arm; cephalic = head).

• Each brachiocephalic vein (left and right) is formed by the union of the internal jugular vein (which drains the head and neck) and the subclavian vein (which drains the upper limb).

58
Q

What is peristalsis?

A

‘Waves’ of contractions of smooth muscle in the oesophageal wall move swallowed food and fluid distally (peristalsis).

59
Q

What does the vagus nerve give rise to?

A
  • They each give rise to a recurrent laryngeal nerve (RLN), which ascend back up into the neck to innervate the muscles of the larynx.
60
Q

What innervates the pericardium?

A

The left and right phrenic nerves give rise to sensory branches that innervate the fibrous pericardium.

61
Q

What is cardiac tamponade?

A

Rapid fluid accumulation in the pericardial space

heart is compressed and unable to fill properly - a condition called cardiac tamponade.

62
Q

What does a left dominant circulation mean?

A

• In those with a left-dominant circulation, the PIV arises from the circumflex artery; the left coronary artery supplies the entire left ventricle.

63
Q

Why is determine left or right circulation important?

A

This is important in clinical practice. In someone with a right-dominant circulation, occlusion of the left main stem would impair blood flow to part of, but not the entire left ventricle. In someone with a left-dominant coronary circulation, blockage of the left main stem occludes blood flow to the entire left ventricle.

64
Q

What is the structure of the left atrium?

A

Like right atrium, thinner wall compared to the ventricles

  • internally has a smooth-walled posterior part and an anterior part bearing pectinate muscles
  • this reflects the left atrium’s development from two different embryological structures.
65
Q

What is the importance of the papillary muscle and the chords teedineae?

A
  • allow the closed valves to resist the pressure generated inside the ventricles during contraction and prevent them from being forced open.
66
Q

What is the structure of semi-lunar valves?

A

Each semilunar valve - three semi-circular cusps
- att. to inner wall of the vessel, free edge that projects into the vessel lumen
- forms a pocket, or sinus, between free edge and vessel wall.

67
Q

What does the AV bundle give rise to?

A

• bundle of his
- the right and left bundle branches.
• Purkinje fibres that enter the myocardium of the left and right ventricles, respectively, and stimulate contraction.

68
Q

What are the different parts of the aorta?

A

There are three ‘parts’ in the thorax:

  1. The ascending aorta gives rise to the coronary arteries, which supply the myocardium.
  2. The arch of the aorta - lies in the superior mediastinum.
  3. The descending (thoracic) aorta descends through the posterior mediastinum into the abdomen
69
Q

Where does the trachea extend from?

A
  • from the larynx in the midline of the neck into the superior mediastinum
  • palpable just superior to the suprasternal notch.
70
Q

Where does the mediastinum extend from?

A

The mediastinum extends from the:
• superior thoracic aperture superiorly to the diaphragm inferiorly
• sternum anteriorly to the thoracic vertebrae posteriorly.

71
Q

What separates the mediastinum?

A

The ‘line’ between these compartments runs from the sternal angle anteriorly to the T4/T5 junction posteriorly.

72
Q

Where does the oesophagus lie?

A

In the superior mediastinum, the oesophagus lies in the midline of the thorax, posterior to the trachea. It descends into the posterior mediastinum.

73
Q

What type of innervation do the phrenic nerves have?

A
  • somatic nerves
  • contain motor and sensory fibres
74
Q

What course do the phrenic nerves take?

A

They descend through the neck and enter the thorax through the superior thoracic aperture. They course over the pericardium and pierce the diaphragm.

75
Q

Where do the large veins of the heart return blood from?

A

• The superior vena cava (SVC) returns blood to the heart from the head, neck, and upper limbs.

• The inferior vena cava (IVC) returns blood to the heart from all regions inferior to the diaphragm (abdomen, pelvis, and lower limbs).

76
Q

What does the vagus nerve supply?

A

• They contribute parasympathetic fibres to the heart, lungs, and oesophagus.
• They traverse the diaphragm and convey parasympathetic fibres to most of the abdominal viscera.

77
Q

What course does the thoracic duct take?

A

It ascends through the posterior mediastinum and into the superior mediastinum, where it empties into the venous system at the union of the left internal jugular vein and left subclavian vein.

78
Q

What does the pericardial space allow?

A

The pericardial space allows the heart to move within the pericardial sac with each contraction.

79
Q

What is the PIV a branch of?

A

is the continuation of the right coronary artery on the inferior (diaphragmatic) surface of the heart

80
Q

What does the left circumflex artery supply?

A

It supplies the left atrium, part of the right ventricle and the left ventricle.

81
Q

What does the origin of PIV determine?

A

The origin of the posterior interventricular artery determines if an individual has a right dominant or a left dominant coronary circulation.

82
Q

What is in the RA?

A

Internally, its main features are the:
• interatrial septum which separates it from the left atrium
• fossa ovalis
• crista terminalis

83
Q

Where is the pulmonary valve?

A

At the entrance of the pulmonary trunk
Prevents backflow of blood into RV

RV wall thicker than RA - contraction propels blood into PT

84
Q

Where is the aortic valve?

A

At the entrance to the aorta
Prevents backflow of blood into LV

LV wall thicker than RV

85
Q

When/How do papillary muscles work?

A

P rises in the ventricles - valve cusps, which project into the ventricle, start to close passively.

Ventricles contract, the papillary muscles also contract.

The papillary muscles tense the cords, which in turn ‘pull’ on the valve cusps and prevent them everting into the atria.

86
Q

What causes MI?

A

Most commonly, atherosclerosis within the coronary arteries.

A fatty plaque in a coronary artery may grow until it causes stenosis and severely restricts blood flowing through it.

A fatty plaque may shear from the vessel wall, causing a clot to form in the lumen, which occludes blood flow.

87
Q

Do all cardiomyopathies have symptoms?

A

Unfortunately, some cardiomyopathies have no obvious symptoms and are a cause of sudden cardiac death in otherwise healthy, young people.

88
Q

What occurs with SL valves in VS?

A
  • ventricular systole, valve cusps are ‘flattened’ and blood flows through the valve
  • End of VS, pressure in the ventricles drops. Pressure in Ventricles<vessel (aorta or PT), blood in the vessel starts to flow back towards the heart.
89
Q

How do SL valves work?

A
  • Blood is immediately ‘caught’ in the valve cusps.
  • The sinuses rapidly fill with blood and the cusps balloon out into the lumen.
  • The free edges of the three valve cusps contact each other in the lumen and close the valve orifice.
90
Q

How do SL valves work?

A
  • Blood is immediately ‘caught’ in the valve cusps.
  • The sinuses rapidly fill with blood and the cusps balloon out into the lumen.
  • The free edges of the three valve cusps contact each other in the lumen and close the valve orifice.
91
Q

What is the foetal circulation of gas exchange?

A

In the foetus, gas exchange occurs at the placenta, not in the lungs.

The ductus arteriosus diverts most of the blood entering the PT directly to the aortic arch.

(only a small amount of blood circulates through the foetal lungs; enough for them to develop).

When a baby starts to use their lungs at birth, the ductus arteriosus closes, and blood in the pulmonary trunk enters the lungs.

92
Q

What are the effects of autonomic NS on the heart?

A

• Sympathetic stimulation increases the heart rate and force of contraction.
• Parasympathetic stimulation slows the heart rate and force of contraction.

Phase 1 Cardio (9 decks)

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