CVS Session 2 Flashcards Preview

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Flashcards in CVS Session 2 Deck (108):
0

What is the function of capacitance vessels?

Allow a store of blood so cardiac output is variable

1

Which are the two outflow valves of the heart?

Aortic (left)
Pulmonary (right)

2

Which are the inflow valves of the heart?

Mitral (left)
Tricuspid (right)

3

Describe the specialised form of cardiac muscle.

Discrete cells
Tightly connected
Electrically connected

4

How is force generated in cardiac muscle cells?

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

5

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

1 electrical signal = 1 contraction

6

How long is the contraction of a cardiac muscle cell?

280 Ms

7

What does a cell in systole do to its neighbour?

Trigger it to enter systole

8

What produces a coordinated contraction across the whole heart?

An AP generated in a small group of pacemaker cells

9

Describe the generation of action potentials by pacemaker cells.

Spontaneous at regular intervals

10

Briefly describe the spread of excitation across the heart.

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

11

What prevents tearing of the cardiac muscle during pumping?

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

12

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

It is quick and powerful to fire

13

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

Via the AVN

14

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

Figure of 8 arrangement

15

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

Towards the outflow valves

16

What is the Bundle of His?

Specialised cardiac tissue to accelerate AP conduction

17

What allows the heart to work as a reciprocating pump?

Regular alternating systole and diastole
Inflow and outflow valves

18

What occurs during diastole?

Ventricles fill from the veins

19

What occurs during systole?

Ventricles pump blood into arteries

20

What allows blood into the left ventricle from the atrium?

Mitral inflow valve

21

What closes the mitral valve?

Ventricular pressure > atrial pressure

22

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

Aortic outflow valve

23

What opens the aortic valve?

Intra-ventricular pressure > aortic pressure

24

How are cardiac valves arranged?

Flaps lying over each other or against wall

25

What is needed to close cardiac valves?

Regurgitation to lift valve flaps

26

How do inflow and outflow valves differ?

They are configured in opposite directions

27

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

About once a second

28

Is the length of ventricular systole variable?

Not really, always ~280 ms

29

How long is diastole at rest?

~700 ms

30

What is the variable portion of HR?

Length of diastole

31

Describe the end of ventricular systole.

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

32

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

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

33

What occurs in atrial systole?

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

34

Is limiting loss of regurgitation during atrial systole necessary?

Nope

35

What happens in ventricular systole?

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

36

What opens outflow valves?

p(IV) > p(atrial)

37

What halogens when the outflow valves open?

Rapid ejection phase
Blood moves to arteries
Arterial pressure rises rapidly

38

What happens during systole?

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

39

What is the rapid filling phase?

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

40

When does ventricular filling stop?

When p(IV) = p(atrial)

41

What is diastasis?

Occurs halfway through diastole
Ventricular filling decreases as the ventricles are already full when the atria contract

42

What happens at the end of systole?

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

43

What causes the first heart sound?

Closure of the A/V valves

44

When is the first heart sound heard?

Onset of ventricular systole

45

What causes the second heart sound?

Closure of outflow valves

46

When is the second heart sound heard?

End of ventricular systole

47

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

280 ms (systole)

48

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

700 ms (diastole)

49

What might alter the quality of heart sounds?

Altered valves e.g. calcification

50

What might cause splitting of heart sounds?

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

51

What causes a 3rd heart sound?

Rapid expansion of ventricle in early diastole during rapid filing phase

52

When is a 3rd heart sound more commonly heard?

In thinner people

53

What causes a 4th heart sound?

Atrial systole in children

54

What causes heart murmurs?

Turbulent blood flow

55

What may cause turbulent blood flow?

Valve stenosis
Valve incompetence
Aortic stenosis

56

When do heart murmurs occur?

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

57

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

80 ml

58

How is cardiac output calculated?

Stroke volume x heart rate

59

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

80 ml x 60 bpm = 5 l per minute

60

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

Primary heart fields w/ blood islands

61

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

No

62

What is the progenitor to cardiac tissues?

Cardiogenic field

63

What forms the primitive heart tube?

Lateral folding

64

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

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

65

Around which days does the CVS develop?

25

66

Why does the CVS develop so early?

It is needed by the foetus

67

What brings the primitive heart tube into the thoracic region?

Cephalocaudal folding

68

How is the heart tube arranged after cephalocaudal folding?

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

69

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

Aortic roots
Turn us arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus

70

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

Tail end

71

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

Atrium

72

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

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

73

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

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

74

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

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

What does repositioning of the ventricle primordiums optimise?

Septum formation b/w cavities of the heart

76

Do the primitive chambers of the heart develop symmetrically?

Nope - ventricle enlarges much more than the primitive atrium

77

How does the atrium communicate with the ventricle after looping?

Via atrioventricular canal

78

Briefly describe the development of the sinus venosus.

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

Where does the right atrium develop from?

Most of primitive atrium
Sinus venosus

80

What receives venous drainage from the body and heart?

Right atrium

81

Where does the left atrium develop from?

Small portion of primitive atrium

82

Where does the pulmonary vein arise?

Left atrium

83

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

Absorbed so 4 drain into it

84

What receives oxygenated blood from the lungs?

Left atrium

85

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

Trabeculated component in comparison to the surrounding smooth wall

86

What forms the oblique pericardial sinus?

Expansion and vein absorption of the left atrium

87

What are the lungs bypassed in the foetal circulation?

They are non-functional

88

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

Via placenta and umbilical vein

89

Why is the liver bypassed in foetal circulation?

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

90

What is needed in foetal circulation to transition after birth?

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

91

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

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

92

How does the early arterial system begin?

Bilateral symmetrical system of arched vessels

93

What creates the major arteries leaving the heart?

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

94

What does the 4th aortic arch give rise to?

Right = proximal part of R subclavian artery
Left = arch of aorta

95

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

Right = R pulmonary artery
Left = L pulmonary artery and ductus arteriosus

96

What is the ductus arteriosus?

Foetal vessel needed to bypass lungs

97

What does the ductus arteriosus become in the neonate?

Ligament structure

98

Which nerve corresponds with the 6th aortic arch?

Recurrent laryngeal nerve

99

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

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

100

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

Larynx

101

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

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

102

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

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

Why does the R recurrent laryngeal nerve drop to T1?

More extensive remodelling on the right

104

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

Ductus arteriosus

105

What must happen after looping of the primitive heart tube?

Septation - primitive chambers must be divided

106

Which part of cardiac development is most prone to complications?

Septation

107

What chambers must be divided by septation?

Atrial
Ventricular
Outflow tract