CVS Session 2 Flashcards
0
Q
Which are the two outflow valves of the heart?
A
Aortic (left)
Pulmonary (right)
1
Q
What is the function of capacitance vessels?
A
Allow a store of blood so cardiac output is variable
2
Q
Which are the inflow valves of the heart?
A
Mitral (left)
Tricuspid (right)
3
Q
Describe the specialised form of cardiac muscle.
A
Discrete cells
Tightly connected
Electrically connected
4
Q
How is force generated in cardiac muscle cells?
A
Electrical event in cell membrane –> increase calcium –> actin and myosin sliding filaments interact
5
Q
What is the unique feature of electrical signals in cardiac muscle cells?
A
1 electrical signal = 1 contraction
6
Q
How long is the contraction of a cardiac muscle cell?
A
280 Ms
7
Q
What does a cell in systole do to its neighbour?
A
Trigger it to enter systole
8
Q
What produces a coordinated contraction across the whole heart?
A
An AP generated in a small group of pacemaker cells
9
Q
Describe the generation of action potentials by pacemaker cells.
A
Spontaneous at regular intervals
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
11
Q
What prevents tearing of the cardiac muscle during pumping?
A
Relaxation takes place outside to inside (opp. direction to excitation)
12
Q
Why is the SAN not overridden as the ‘master node’ of the heart?
A
It is quick and powerful to fire
13
Q
In a normal heart what is the only route for atrial to ventricular excitation spread?
A
Via the AVN
14
Q
How is the arrangement of muscle in the ventricle used to maximise expulsion?
A
Figure of 8 arrangement
15
Q
In which direction does the spread of excitation from the apex upwards force the blood to flow?
A
Towards the outflow valves
16
Q
What is the Bundle of His?
A
Specialised cardiac tissue to accelerate AP conduction
17
Q
What allows the heart to work as a reciprocating pump?
A
Regular alternating systole and diastole
Inflow and outflow valves
18
Q
What occurs during diastole?
A
Ventricles fill from the veins
19
Q
What occurs during systole?
A
Ventricles pump blood into arteries
20
Q
What allows blood into the left ventricle from the atrium?
A
Mitral inflow valve
21
Q
What closes the mitral valve?
A
Ventricular pressure > atrial pressure
22
Q
What allows blood to flow from the left ventricle to the aorta?
A
Aortic outflow valve
23
Q
What opens the aortic valve?
A
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
