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Semester 2 > CVS Session 2 > Flashcards

CVS Session 2 Flashcards

0
Q

Which are the two outflow valves of the heart?

A

Aortic (left)

Pulmonary (right)

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1
Q

What is the function of capacitance vessels?

A

Allow a store of blood so cardiac output is variable

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2
Q

Which are the inflow valves of the heart?

A

Mitral (left)

Tricuspid (right)

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3
Q

Describe the specialised form of cardiac muscle.

A

Discrete cells
Tightly connected
Electrically connected

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4
Q

How is force generated in cardiac muscle cells?

A

Electrical event in cell membrane –> increase calcium –> actin and myosin sliding filaments interact

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5
Q

What is the unique feature of electrical signals in cardiac muscle cells?

A

1 electrical signal = 1 contraction

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6
Q

How long is the contraction of a cardiac muscle cell?

A

280 Ms

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7
Q

What does a cell in systole do to its neighbour?

A

Trigger it to enter systole

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8
Q

What produces a coordinated contraction across the whole heart?

A

An AP generated in a small group of pacemaker cells

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9
Q

Describe the generation of action potentials by pacemaker cells.

A

Spontaneous at regular intervals

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10
Q

Briefly describe the spread of excitation across the heart.

A

SAN –> atrial systole –> AVN 120 ms delay –> Bundle of His –> endocardial to epicardial –> apex up to ventricle

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11
Q

What prevents tearing of the cardiac muscle during pumping?

A

Relaxation takes place outside to inside (opp. direction to excitation)

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12
Q

Why is the SAN not overridden as the ‘master node’ of the heart?

A

It is quick and powerful to fire

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13
Q

In a normal heart what is the only route for atrial to ventricular excitation spread?

A

Via the AVN

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14
Q

How is the arrangement of muscle in the ventricle used to maximise expulsion?

A

Figure of 8 arrangement

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15
Q

In which direction does the spread of excitation from the apex upwards force the blood to flow?

A

Towards the outflow valves

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16
Q

What is the Bundle of His?

A

Specialised cardiac tissue to accelerate AP conduction

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17
Q

What allows the heart to work as a reciprocating pump?

A

Regular alternating systole and diastole

Inflow and outflow valves

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18
Q

What occurs during diastole?

A

Ventricles fill from the veins

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19
Q

What occurs during systole?

A

Ventricles pump blood into arteries

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20
Q

What allows blood into the left ventricle from the atrium?

A

Mitral inflow valve

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21
Q

What closes the mitral valve?

A

Ventricular pressure > atrial pressure

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22
Q

What allows blood to flow from the left ventricle to the aorta?

A

Aortic outflow valve

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23
Q

What opens the aortic valve?

A

Intra-ventricular pressure > aortic pressure

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24
Q

How are cardiac valves arranged?

A

Flaps lying over each other or against wall

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25
Q

What is needed to close cardiac valves?

A

Regurgitation to lift valve flaps

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26
Q

How do inflow and outflow valves differ?

A

They are configured in opposite directions

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27
Q

At rest, how often does the SAN generate and AP?

A

About once a second

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28
Q

Is the length of ventricular systole variable?

A

Not really, always ~280 ms

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29
Q

How long is diastole at rest?

A

~700 ms

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30
Q

What is the variable portion of HR?

A

Length of diastole

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31
Q

Describe the end of ventricular systole.

A 
Ventricles contracted
IV pressure high
Outflow valves open
p(ventricular) > p(atrial)
Atrioventricular valves closed
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32
Q

What happens as the ventricles start to relax after ventricular systole?

A 
p(IV) < p(atrial)
Brief backflow closes outflow valves
All valves closed
Isovolumetric relaxation
Atria fill
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33
Q

What occurs in atrial systole?

A

Small amount of blood is pumped into ventricle to limit loss of regurgitation

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34
Q

Is limiting loss of regurgitation during atrial systole necessary?

A

Nope

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35
Q

What happens in ventricular systole?

A

p(IV) increases rapidly
After brief backflow A/V valve closes –> all valves closed
Isovolumetric contraction - blood trapped

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36
Q

What opens outflow valves?

A

p(IV) > p(atrial)

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37
Q

What halogens when the outflow valves open?

A

Rapid ejection phase
Blood moves to arteries
Arterial pressure rises rapidly

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38
Q

What happens during systole?

A 
Blood returns to atria
Eventually p(atria) > p(IV)
A/V valves are open
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39
Q

What is the rapid filling phase?

A

A/V valves are open so ventricles fill rapidly with most filling occurring in the 200-300 ms it lasts

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40
Q

When does ventricular filling stop?

A

When p(IV) = p(atrial)

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41
Q

What is diastasis?

A

Occurs halfway through diastole

Ventricular filling decreases as the ventricles are already full when the atria contract

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42
Q

What happens at the end of systole?

A

Rate of ejection decreases due to elastic walls of arteries
Arterial and intra ventricular pressure peak
Outflow ceases w/ blood in ventricle

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43
Q

What causes the first heart sound?

A

Closure of the A/V valves

44
Q

When is the first heart sound heard?

A

Onset of ventricular systole

45
Q

What causes the second heart sound?

A

Closure of outflow valves

46
Q

When is the second heart sound heard?

A

End of ventricular systole

47
Q

What is the time interval of the first and second heart sounds at rest?

A

280 ms (systole)

48
Q

What is the time interval of the second and first heart sounds at rest?

A

700 ms (diastole)

49
Q

What might alter the quality of heart sounds?

A

Altered valves e.g. calcification

50
Q

What might cause splitting of heart sounds?

A

If left and right heart valves do not close at the same time

51
Q

What causes a 3rd heart sound?

A

Rapid expansion of ventricle in early diastole during rapid filing phase

52
Q

When is a 3rd heart sound more commonly heard?

A

In thinner people

53
Q

What causes a 4th heart sound?

A

Atrial systole in children

54
Q

What causes heart murmurs?

A

Turbulent blood flow

55
Q

What may cause turbulent blood flow?

A

Valve stenosis
Valve incompetence
Aortic stenosis

56
Q

When do heart murmurs occur?

A

When blood flow is highest e.g. rapid ejection phase in aortic stenosis

57
Q

What is the typical stroke volume ejected per beat in an adult?

A

80 ml

58
Q

How is cardiac output calculated?

A

Stroke volume x heart rate

59
Q

At rest, what is the cardiac output for an average adult?

A

80 ml x 60 bpm = 5 l per minute

60
Q

In the fourth week of development, what is just beginning to differentiate into primitive blood cells and capillaries?

A

Primary heart fields w/ blood islands

61
Q

Is the cardiogenic field of the composite bilaminar and trilaminar embryo relatively differentiated?

A

No

62
Q

What is the progenitor to cardiac tissues?

A

Cardiogenic field

63
Q

What forms the primitive heart tube?

A

Lateral folding

64
Q

Briefly outline the formation of the primitive heart tube by lateral folding.

A

2 large BV come together to form one large BV that has arisen from the cardiogenic area

65
Q

Around which days does the CVS develop?

A

25

66
Q

Why does the CVS develop so early?

A

It is needed by the foetus

67
Q

What brings the primitive heart tube into the thoracic region?

A

Cephalocaudal folding

68
Q

How is the heart tube arranged after cephalocaudal folding?

A

It is suspended in the pericardial cavity by a membrane that subsequently degrades

69
Q

What are the regions of the primitive heart tube from head to tail end?

A 
Aortic roots
Turn us arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus
70
Q

Which end of the heart tube does blood from the embryonic body enter?

A

Tail end

71
Q

Which part of the primitive heart tube is the pulsatile structure?

A

Atrium

72
Q

Describe the movements of the cephalic and caudal portions of the heart tube during looping.

A

Cephalic: forward, down and right
Caudal: backwards, up and left

73
Q

How does the pericardial cavity grow in relation to the heart tube?

A

It does not grow as much so it becomes filled by the heart tube

74
Q

What are the results of looping of the primitive heart tube?

A

Arteries in front of veins
Transverse pericardial sinus forms
Primordium of right ventricle closest to outflow tract
Primordium of left ventricle closest to inflow tract
Atrium dorsal to bulbus cordis

75
Q

What does repositioning of the ventricle primordiums optimise?

A

Septum formation b/w cavities of the heart

76
Q

Do the primitive chambers of the heart develop symmetrically?

A

Nope - ventricle enlarges much more than the primitive atrium

77
Q

How does the atrium communicate with the ventricle after looping?

A

Via atrioventricular canal

78
Q

Briefly describe the development of the sinus venosus.

A

R+L sinus horns equal in size –> venous return shifts to RHS –> L sinus horn recedes so RHS dominant –> R sinus horn absorbed by enlarging R atrium

79
Q

Where does the right atrium develop from?

A

Most of primitive atrium

Sinus venosus

80
Q

What receives venous drainage from the body and heart?

A

Right atrium

81
Q

Where does the left atrium develop from?

A

Small portion of primitive atrium

82
Q

Where does the pulmonary vein arise?

A

Left atrium

83
Q

What happens to the proximal parts of the pulmonary vein in the left atrium?

A

Absorbed so 4 drain into it

84
Q

What receives oxygenated blood from the lungs?

A

Left atrium

85
Q

How does the wall of the left atrium near the pulmonary vein compare to t he surrounding wall?

A

Trabeculated component in comparison to the surrounding smooth wall

86
Q

What forms the oblique pericardial sinus?

A

Expansion and vein absorption of the left atrium

87
Q

What are the lungs bypassed in the foetal circulation?

A

They are non-functional

88
Q

How does the utero-placental circulation receive oxygenated blood from the mother?

A

Via placenta and umbilical vein

89
Q

Why is the liver bypassed in foetal circulation?

A

So all of the oxygen being carried is not used up by the especially high activity of the liver in the foetus

90
Q

What is needed in foetal circulation to transition after birth?

A

A series of shunts and diversions that can be shut off immediately

91
Q

What is needed to flow through the right ventricle in the foetal circulation?

A

Small amount of blood so there is resistance for muscle to work against

92
Q

How does the early arterial system begin?

A

Bilateral symmetrical system of arched vessels

93
Q

What creates the major arteries leaving the heart?

A

Extensive remodelling of aortic arches resulting in loss and movement of different parts

94
Q

What does the 4th aortic arch give rise to?

A 
Right = proximal part of R subclavian artery
Left = arch of aorta
95
Q

What does the 6th aortic arch (pulmonary arch) give rise to?

A 
Right = R pulmonary artery
Left = L pulmonary artery and ductus arteriosus
96
Q

What is the ductus arteriosus?

A

Foetal vessel needed to bypass lungs

97
Q

What does the ductus arteriosus become in the neonate?

A

Ligament structure

98
Q

Which nerve corresponds with the 6th aortic arch?

A

Recurrent laryngeal nerve

99
Q

Where do the left and right recurrent laryngeal nerves descend to?

A

Left: T4-T5 through mediastinum
Right: T1-T2

100
Q

What does the nerve corresponding to the 6th aortic arch innervate?

A

Larynx

101
Q

What influences the course of the L and R recurrent laryngeal nerves?

A

Caudal shift of developing heart
Expansion of developing neck
Need for foetal shunt b/w pulmonary trunk and aorta

102
Q

Briefly describe the determination of the course of the L and R recurrent laryngeal nerves.

A

Aortic arches remodelled –> heart descends and nerve hooks on 6th aortic arch, turning back on itself –> L nerve hooked on ductus arteriosus, R nerve drops to T1 around R subclavian artery

103
Q

Why does the R recurrent laryngeal nerve drop to T1?

A

More extensive remodelling on the right

104
Q

What is the name of the pulmonary trunk-aorta shunt in the foetus?

A

Ductus arteriosus

105
Q

What must happen after looping of the primitive heart tube?

A

Septation - primitive chambers must be divided

106
Q

Which part of cardiac development is most prone to complications?

A

Septation

107
Q

What chambers must be divided by septation?

A

Atrial
Ventricular
Outflow tract

Semester 2 (45 decks)

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