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Block 2 > The Heart & Mediastinum > Flashcards

The Heart & Mediastinum Flashcards

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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
The left atrium of the heart is closely related to the oesophagus. What can this relationship be used for?
Transesophageal Echocardiogram (TOE) -> probe in oesophagus to image the heart
26
Where is the posterior mediastinum?
Behind the pericardial sac + anterior to the vertebral column
27
What structures are within the posterior mediastinum?
``` Oesophagus Vagal nerve plexus Descending aorta Thoracic duct Sympathetic chain Azygous system ```
28
What structures are within the middle mediastinum? What are they bound by?
Heart Pericardium Origins of great vessels (e.g. ascending aorta, pulmonary trunk + SVC) Phrenic nerves Bound by the pericardial sac
29
What is the fibrous pericardium bound to?
Central diaphragmatic tendon
30
Think of the heart shaped as a door wedge. What are its borders?
``` Diaphragmatic Left Right Base/posterior Apex (further corner away from base which is why it is also called the posterior surface) ```
31
The chambers of the heart tend to be named in a different direction to which they are facing. Why is this?
Heart is a midline structure that rotates left during development SO R sided structures sit anteriorly L sided structures sit posteriorly
32
What might form in the atrial appendages, especially in cases of atrial fibrillation?
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
What is the pericardium composed of?
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
What is between the hearts parietal + visceral layers?
Pericardial cavity containing small amounts of lubricating pericardial fluid
35
How might haemopericardium lead to a cardiac tamponade?
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
Where are the reflections of the pericardial sac formed in the developing heart?
At great vessels
37
What 2 structures are formed when the heart tube and pericardial sac are developing?
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
What can the transverse pericardial sinus be used for in surgery?
Can be used in surgery to clamp arterial outflow
39
Where is the atrioventricular valves (AV)? What do they do?
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
What so papillary muscles do?
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
What might happen after a myocardial infarction with damage to the papillary muscle?
Cannot contract -> AV valve incompetence = blood regurgitation from ventricle to atrium causing a cardiac murmur
42
What is the fibrous cardiac skeleton made from?
Dense fibrous connective tissue
43
What are the main functions of the fibrous cardiac skeleton?
- Mechanical stability - Electrical insulation (prevents free conduction of signal from atria -> ventricles) - Attachment point for cardiac muscle + valve cusps
44
What structure is the ONLY route for signal conduction from atria to ventricles?
AV node + then bundle
45
What is the structure of the aortic and pulmonary valves?
Semi-lunar with 3 cusps with pocket-like sinuses behind each valve cusp
46
What is the function of aortic and pulmonary valve cusps?
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
Why might aortic and pulmonary valve cusps have varying nomenclature?
Position alters from embryological -> adult position due to rotation of heart in development Aortic: posterior -> anterior Pulmonary: anterior -> posterior
48
How is the myocardium supplied with blood?
Coronary arteries arise from coronary sinus above aortic valve cusps -> main inflow during dyastole
49
What does the right coronary artery supply?
RA + RV SA node AV node Posterior IV septum (minority of septum)
50
What is a right coronary artery (RCA)/left coronary artery (LCA) dominant heart? How common are they?
The dominant artery gives rise to PIVA 60% of individuals = RCA 40% of individuals = LCA
51
What are the branches of the right coronary artery? What do they supply?
SAN artery (supplies SA node, R + L atria) Anterior ventricular arteries Marginal artery (reaches apex) PIVA (posterior 1/3 of septum)
52
What does the left coronary artery supply?
LA + LV AV bundle R + L bundle branches Anterior IV septum (majority of septum)
53
What are the branches of the left coronary artery? What do they supply?
``` 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
What artery is a common place for atherosclerotic plaque build up?
LAD
55
Why might you image heart vessels on a angiogram?
Check for stenosis or atherosclerotic plaques
56
What is the venous drainage of the heart?
Coronary veins drain blood from myocardium -> majority of venous blood drains into RA via coronary sinus (inc. SVC + IVC)
57
What are the 4 surface anatomical points that map out the heart?
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
Why is surface anatomy of the heart important?
Clinical examination Interpreting medical images Guiding surgical approach Predicting injury
59
What are the auscultation points of the 4 heart valves?
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
Why are valves listened to in a different place to their actual surface markings?
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
What is the main function of the right atrium?
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
What are the rough bits of the right atrium made from?
Pectinate muscle
63
What is the fossa ovalis?
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
What is the main function of the left atrium?
Receives highly oxygenated blood from lungs via 4 pulmonary veins Moderator band - component of electrical conduction system
65
What is the structure of the right ventricle?
Crescent-shaped + thinner wall than LV
66
Why is the left ventricular wall so much thicker than the right ventricular wall?
Must eject blood into aorta + then to rest of body so needs to be the most muscly
67
What are the rough parts of the left ventricle called?
Trabeculae carnae (embryological remnant)
68
What is the function of the conduction system of the heart?
Allows rapid coordinate delivery of cardiac impulse to atrial + ventricular muscles
69
Explain the electrical conduction system of the heart.
Originate in SA node (pacemaker) -> atria contract -> AV node -> ventricular septum -> R bundle branch -> purkinje fibres that contract ventricles -> atria + ventricles subsequently relax
70
What might be the consequence of a ventricular septal defect or infarct?
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
What is the parasympathetic supply to the heart?
Vagus nerve (CN X) - branches mainly arising in thorax Postganglionic fibres arise from ganglia on heart
72
What is the sympathetic supply to the heart?
Top of sympathetic chain (T1-4) descend through neck to heart Cardiac visceral sensory travel back to CNS with sympathetic nerves
73
What does the SNS and PNS do to the heart?
SNS: increases HR + contractility PNS: decreases HR
74
Why can you get referred cardiac pain?
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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