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Block 2 > The Heart & Mediastinum > Flashcards

The Heart & Mediastinum Flashcards

1
Q

What is the mediastinum?

A

Broad central region that separates the two laterally placed pleural cavities extending from the sternum to the vertebrae bodies & from the superior thoracic aperture/inlet to the diaphragm (T1 -> T12)

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2
Q

Why is adipose tissue commonly found within the pericardium surrounding the heart?

A

Helps provide a cushion for the heart

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3
Q

How can you tell if an X-ray has been taken on inspiration?

A

Flattening of diaphragm

Corners of costodiaphragmatic recess

Can see middle rib sections

Lung fields sizeable

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4
Q

What 3 structures can you see directly above the heart on an X-ray?

A

Aortic notch
Pulmonary trunk
Lung hilum

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5
Q

What is the sternal plane?

A

Plane at sternal angle at rib 2 CC + ~ T4/5

Divides mediastinum into superior + inferior regions

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6
Q

How is the inferior region of the mediastinum further subdivided?

A

Anterior
Middle
Posterior

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7
Q

What can collect in the costodiaphragmatic recess?

A

Pleural effusion

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8
Q

Where is the posterior mediastinum?

A

Extends inferiorly to the 12th thoracic vertebrae

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9
Q

What must you be careful of if you are trying to access the costodiaphragmatic recess?

A

Liver

Kidneys

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10
Q

Where is the anterior mediastinum?

A

Narrow area between sternum + anterior pericardial sac

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11
Q

What is contained within the anterior mediastinum?

A

Internal thoracic vessels
Fat
Connective tissue
Some thymus (maybe)

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12
Q

What can the internal thoracic arteries be used for?

A

Coronary Artery Bypass Graft (CABG)

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13
Q

Where is the thymus?

A

In superior + sometimes anterior mediastinum

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14
Q

What happens to the thymus with age?

A

Relatively large in children causing a thymic sail sign on a CXR (looks like pathology) -> shrinks with age

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15
Q

What structures are contained within the superior mediastinum?

A 
Arch of aorta
Great vessels 
Trachea
Oesophagus
Thoracic duct
Phrenic nerve
Vagus nerve
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16
Q

What are the great vessels?

A 
Subclavian veins
Internal jugular veins
Brachiocephalic veins
Brachiocephalic trunk
SVC
Subclavian arteries
Common carotid arteries
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17
Q

Veins sit ___ to the arteries.

A

Anterior

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18
Q

What is the ligamentum arteriosum a remnant of? What happens if it stays open?

A

Ductus arteriosis

Helps you bypass lungs in utero so should fuse shut but if it stays open you will have a mix of oxygenated + deoxygenated blood in systemic circulation

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19
Q

What is the cysterna chili?

A

Dilated sac in lower abdominal area that drains most lymphatics from most of body + major route into circulation

Branches off to form thoracic duct

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20
Q

Where is the SVC formed?

A

1st rib CC

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21
Q

Where does the phrenic nerve pass through the mediastinum?

A

Anterior

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22
Q

How does the vagus nerve travel from the mediastinum to the abdomen?

A

Posterior to hilum of lung + anterior to subclavian vessels descending through the mediastinum

Forms a plexus around trachea + oesophagus when oesophagus is immediately posterior to the LA of heart

L vagus travels through diaphragm anteriorly + R vagus travels through posterior surfaces of oesophagus to innervate the abdomen

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23
Q

What does the recurrent laryngeal nerve (RLN) do? What fibre type foes it carry?

A

Sensory fibres below vocal chords

Motor fibres to every muscle in the larynx apart from the cricothyroid

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24
Q

On what side would a hilar lymph node enlargement cause a hoarse voice?

A

Left because RLN can be compressed underneath the aortic arch

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25
Q

The left atrium of the heart is closely related to the oesophagus. What can this relationship be used for?

A

Transesophageal Echocardiogram (TOE) -> probe in oesophagus to image the heart

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26
Q

Where is the posterior mediastinum?

A

Behind the pericardial sac + anterior to the vertebral column

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27
Q

What structures are within the posterior mediastinum?

A 
Oesophagus
Vagal nerve plexus
Descending aorta
Thoracic duct 
Sympathetic chain
Azygous system
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28
Q

What structures are within the middle mediastinum? What are they bound by?

A

Heart
Pericardium
Origins of great vessels (e.g. ascending aorta, pulmonary trunk + SVC)
Phrenic nerves

Bound by the pericardial sac

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29
Q

What is the fibrous pericardium bound to?

A

Central diaphragmatic tendon

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30
Q

Think of the heart shaped as a door wedge. What are its borders?

A 
Diaphragmatic
Left
Right
Base/posterior 
Apex (further corner away from base which is why it is also called the posterior surface)
31
Q

The chambers of the heart tend to be named in a different direction to which they are facing. Why is this?

A

Heart is a midline structure that rotates left during development SO

R sided structures sit anteriorly
L sided structures sit posteriorly

32
Q

What might form in the atrial appendages, especially in cases of atrial fibrillation?

A

Atrial appendages are dead ends of internal heart tissue so clots may form here + move to other parts of the body inc. head + neck - this is why AF can be so dangerous

33
Q

What is the pericardium composed of?

A
  1. Fibrous pericardium: tough outer connective tissue layer
  2. Serous pericardium:
    - Visceral (lines outside of heart forming epicardium) + parietal (lines inside of fibrous pericardium) layers
34
Q

What is between the hearts parietal + visceral layers?

A

Pericardial cavity containing small amounts of lubricating pericardial fluid

35
Q

How might haemopericardium lead to a cardiac tamponade?

A

Blood build up within tough fibrous pericardium reducing the heart’s ability to refill with blood from extremities + to contract due to high pressure -> impedes hearts ability to beat = irregular heart beats

36
Q

Where are the reflections of the pericardial sac formed in the developing heart?

A

At great vessels

37
Q

What 2 structures are formed when the heart tube and pericardial sac are developing?

A
  1. Transverse pericardial sinus: passageway between arterial outflows + venous inflow
  2. Oblique pericardial sinus: reflection of serous layer creating a blind ended sac posterior to heart behind LA
38
Q

What can the transverse pericardial sinus be used for in surgery?

A

Can be used in surgery to clamp arterial outflow

39
Q

Where is the atrioventricular valves (AV)? What do they do?

A

Valve formed by flap-like cusps anchored to the ventricle wall by tendons called chordae tendinae

Lie between atria + ventricles allowing for unidirectional flow of blood

40
Q

What so papillary muscles do?

A

Extensions of ventricular wall that do not contract to open valves (this is passive) but contact to prevent cusps from being blown back into atria during ventricular systole

41
Q

What might happen after a myocardial infarction with damage to the papillary muscle?

A

Cannot contract -> AV valve incompetence = blood regurgitation from ventricle to atrium causing a cardiac murmur

42
Q

What is the fibrous cardiac skeleton made from?

A

Dense fibrous connective tissue

43
Q

What are the main functions of the fibrous cardiac skeleton?

A
  • Mechanical stability
  • Electrical insulation (prevents free conduction of signal from atria -> ventricles)
  • Attachment point for cardiac muscle + valve cusps
44
Q

What structure is the ONLY route for signal conduction from atria to ventricles?

A

AV node + then bundle

45
Q

What is the structure of the aortic and pulmonary valves?

A

Semi-lunar with 3 cusps with pocket-like sinuses behind each valve cusp

46
Q

What is the function of aortic and pulmonary valve cusps?

A

Reverse flowing blood catches in the sinuses during ventricular diastole closing them - blood used to reperfuse myocardium itself

Cusps pushed toward vessel walls + open during ventricular systole

47
Q

Why might aortic and pulmonary valve cusps have varying nomenclature?

A

Position alters from embryological -> adult position due to rotation of heart in development

Aortic: posterior -> anterior

Pulmonary: anterior -> posterior

48
Q

How is the myocardium supplied with blood?

A

Coronary arteries arise from coronary sinus above aortic valve cusps -> main inflow during dyastole

49
Q

What does the right coronary artery supply?

A

RA + RV
SA node
AV node
Posterior IV septum (minority of septum)

50
Q

What is a right coronary artery (RCA)/left coronary artery (LCA) dominant heart? How common are they?

A

The dominant artery gives rise to PIVA

60% of individuals = RCA
40% of individuals = LCA

51
Q

What are the branches of the right coronary artery? What do they supply?

A

SAN artery (supplies SA node, R + L atria)
Anterior ventricular arteries
Marginal artery (reaches apex)
PIVA (posterior 1/3 of septum)

52
Q

What does the left coronary artery supply?

A

LA + LV
AV bundle
R + L bundle branches
Anterior IV septum (majority of septum)

53
Q

What are the branches of the left coronary artery? What do they supply?

A 
SAN artery (R + LA)
PIVA
Marginal artery (L ventricle to apex)
LAD (R + LV + anterior 2/3rd of septum)
Circumflex artery (LA + LV - continues as PIVA in 40% people)
54
Q

What artery is a common place for atherosclerotic plaque build up?

A

LAD

55
Q

Why might you image heart vessels on a angiogram?

A

Check for stenosis or atherosclerotic plaques

56
Q

What is the venous drainage of the heart?

A

Coronary veins drain blood from myocardium -> majority of venous blood drains into RA via coronary sinus (inc. SVC + IVC)

57
Q

What are the 4 surface anatomical points that map out the heart?

A
  1. 2rd R CC 1cm lateral to sternum (RA + SVC)
  2. 6th R CC 1cm lateral to sternum (RA + IVC)
  3. 2nd L CC 1cm lateral to sternum (auricle LA + PT)
  4. 5th L ICS medial to MCL(apex + LV)
58
Q

Why is surface anatomy of the heart important?

A

Clinical examination
Interpreting medical images
Guiding surgical approach
Predicting injury

59
Q

What are the auscultation points of the 4 heart valves?

A
  1. Pulmonary: 2nd L ICS lateral to sternum
  2. Aortic: 2nd 2 ICS lateral to sternum
  3. Mitral: 5th L ICS MCL
  4. Tricuspid: 4/5th ICS lateral to sternum
60
Q

Why are valves listened to in a different place to their actual surface markings?

A

Listened to just downstream from surface marking as you want to hear how blood goes through the valve to see if its operating properly

61
Q

What is the main function of the right atrium?

A

Receives venous blood from upper/lower body + the heart

Important for electrical conduction system of heart - SA + AV node initiate + continue conduction into ventricles

62
Q

What are the rough bits of the right atrium made from?

A

Pectinate muscle

63
Q

What is the fossa ovalis?

A

Shallow depression that is an embryological remnant of a hole called the foramen ovale from RA to LA that allowed blood to shunt avoiding the lungs as they are not functioning in utero -> when baby takes first birth as pressure changes in heart + lungs closing it

64
Q

What is the main function of the left atrium?

A

Receives highly oxygenated blood from lungs via 4 pulmonary veins

Moderator band - component of electrical conduction system

65
Q

What is the structure of the right ventricle?

A

Crescent-shaped + thinner wall than LV

66
Q

Why is the left ventricular wall so much thicker than the right ventricular wall?

A

Must eject blood into aorta + then to rest of body so needs to be the most muscly

67
Q

What are the rough parts of the left ventricle called?

A

Trabeculae carnae (embryological remnant)

68
Q

What is the function of the conduction system of the heart?

A

Allows rapid coordinate delivery of cardiac impulse to atrial + ventricular muscles

69
Q

Explain the electrical conduction system of the heart.

A

Originate in SA node (pacemaker) -> atria contract -> AV node -> ventricular septum -> R bundle branch -> purkinje fibres that contract ventricles -> atria + ventricles subsequently relax

70
Q

What might be the consequence of a ventricular septal defect or infarct?

A

Hole: bundle branches impacted in trajectory or ability to send signal down one side of heart disrupted electrical signals

RCA infarct: necrotic heart tissue along diaphragmatic edge killing the purkinje fibres stopping electrical signal conduction

71
Q

What is the parasympathetic supply to the heart?

A

Vagus nerve (CN X) - branches mainly arising in thorax

Postganglionic fibres arise from ganglia on heart

72
Q

What is the sympathetic supply to the heart?

A

Top of sympathetic chain (T1-4) descend through neck to heart

Cardiac visceral sensory travel back to CNS with sympathetic nerves

73
Q

What does the SNS and PNS do to the heart?

A

SNS: increases HR + contractility

PNS: decreases HR

74
Q

Why can you get referred cardiac pain?

A

Cardiac sympathetic signals travel back to T1-4 spinal cord at same time as somatic sensory fibres from periphery causing signals to get crossed

Somatic sensory fibres come back to T1-4 from arm for e.g. causing arm pain in an MI

Block 2 (45 decks)

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