Cardiovascular System Flashcards
1
Q
Atrioventricular valves
A
- separates the atria and ventricles
- bicuspid valve (mitral)=left
- tricuspid valve=right
2
Q
Semilunar valves
A
- separates the ventricles and the arteries
- aortic valve
- pulmonary valve
3
Q
What can the heart be described as?
A
A dynamic pump
4
Q
When looking at the human body, the left is the?
A
right hand side of the individual
5
Q
When looking at the human body, the right is the?
A
left hand side of the individual
6
Q
Superior (cranial, rostral)
A
Above
7
Q
Inferior (caudal)
A
Below
8
Q
Posterior (dorsal)
A
- Towards the back of the body
- Behind
9
Q
Anterior (ventral)
A
- Towards the front of the body
- Front
10
Q
Lateral
A
- Away from the midline of the body
- Further from the midline
11
Q
Medial
A
- Towards the median line/midline of the body
- Nearer to the midline
12
Q
Coronal plane (frontal)
A
- vertical plane for division into anterior and posterior
- putting a crown on example
13
Q
Median plane (sagittal)
A
Division into left and right along the midline to give equal halves (slice from head to foot)
14
Q
Midline
A
An imaginary vertical line which divides the body equally
15
Q
Tranverse plane
A
Horizontal plane through the body, dividing it into superior and inferior (hand to hand)
16
Q
Parasagittal plane
A
Vertical plane (head to foot) parallel to the median plane but off the midline -cut from ear if head down to the toes
17
Q
Location of the heart
A
Left of thorax sitting in the mediastinum
18
Q
Structure of the pericardium
A
- Fibroserous sac surrounding the heart and its great vessels
- The serous layer is a single membrane folded in on itself
- protective sac surrounding the muscular organ
- 2 layers=fibrous and serous
- the fibrous membrane provides protection and structural support
- the serous membranes have a secretory function providing lubrication between the heart and the fibrous membrane
19
Q
5 layers of the heart
A
1) endocardium
2) myocardium
3) visceral pericardium (serous)
4) parietal pericardium (serous)
5) fibrous pericardium
20
Q
Endocardium
A
- One cell thick layer which is the interface between the heart and the blood
- very inside layer
- attached to this is a basement membrane and elastic tissue
21
Q
Myocardium
A
- Thick layer of cardiac muscle cells
- Thicker on the left hand side of the heart compared to the right hand side because the left hand side of the heart is part of the systemic circulation so has to pump the blood a longer distance around the body
22
Q
Visceral pericardium
A
- Layer of serous tissue between the myocardium and the pericardial space
- Otherwise known as the epicardium
- Inner layer of the pericardium
- Adheres to the heart
23
Q
Parietal pericardium
A
- Layer of serous tissue lining the fibrous pericardium and facing the pericardial space
- Outer layer giving support and structure
24
Q
What is the space between the visceral pericardium and the parietal pericardium filled with?
A
- Pericardial fluid
- Lubricates the movement between the visceral and parietal pericardium
25
Fibrous pericardium
Connective tissue to protect the heart and hold it in position
-External to the parietal pericardium
26
What is the tricuspid valve otherwise known as?
Right atrioventricular valve
27
What is the bicuspid valve otherwise known as?
Mitral valve or left atrioventricular valve
28
How many cusps do the tricuspid valve, aortic valve, and pulmonary valve have?
3 cusps
29
Atrium
Receiving chamber for the circulated blood
30
Characteristics of right ventricle?
-Thinner muscular wall than the left ventricle as only pumping the blood a short distance to the lungs
31
Passage of the blood on the right hand side of the heart (pulmonary circulation)
- vena cava (superior if head or arms and inferior if from rest of the body)
- Right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary valve
- Pulmonary trunk (exit vessel) which bifurcates into pulmonary arteries going to the left and right lung
32
Passage of the blood on the left hand side of the heart (systemic circulation)
- pulmonary veins from both sides
- left atrium
- mitral valve (bicuspid)
- left ventricle
- aortic valve
- ascending aorta into the aortic arch and then arteries branch off here
33
Define trunk vessel
- tends to be short
| - quickly splits into other blood vessels
34
Structure of the mitral valve
- bicuspid meaning it is composed of 2 cusps
- only valve with 2 cusps
- not equal cusps
35
How do we prevent the inversion of the heart valves?
- chordae tendineae (heart strings) attached to papillary muscles
- Papillary muscles are similar to the internal structure to the heart
- give support and structure
36
Intraventricular and septum
-muscular wall between the atrium and ventricles of the left and right hand side of the heart
37
Apex
Tip/muscular end of the heart
38
Walls of the blood vessels
- tunica externa
- elastic lamina
- tunica media
- elastic lamina
- tunica intima
39
Tunica externa
- outer layer of the blood vessel
- predominantly made of collagen
- provides structure to the vessel
40
Tunica media
-Mostly smooth muscle with collagen and elastic tissue
41
Tunica intima
-mainly vascular endothelium (layer of endothelial cells) with a basement supporting matrix
42
Lamina
- elastic layers bordering the three layers
| - internal and external elastic lamina
43
Why are arteries and arterioles circular?
- muscular and carry high pressure blood
| - need to expand equally
44
Why are veins and venules not circular?
-distortable with valves to maintain unidirectional flow
45
Arteries
- conduit vessels
| - take blood from one place to another
46
Arterioles
- resistance vessels
| - gatekeeper to the capillary beds, controlling the blood flow into the copious numbers of capillary beds
47
Capillaries
- exchange vessels
- exchange gases in the lungs and absorb nutrients in the gut
- release nutrients to other tissues in the body
- thin walls and small vessels
48
Veins
- capacitance vessels
- large capacity because at any one time 70% of blood is in the veins
- blood here is under low pressure and returning to the vena cava of the heart
49
Name the blood supply of the heart
- Coronary circulation
- perfuses the myocardium with oxygen rich blood
- coronary arteries branch for blood flow to every cell
- coronary arteries are split into proximal, mid and distal
50
Where do the coronary vessels arise?
- Superior to the aortic valve (requires oxygen rich blood because of heart importance)
- blood vessels from left and right cusp of the valve
51
Right coronary artery
-origin from the right cusp of the aortic valve to the right hand side of the heart
-branches into the right posterior descending artery
and a large marginal branch-perfuses the right ventricle myocardium
52
Left anterior descending artery
- origin from the left cusp of the aortic valve
- going down on the front of the heart
- branches off left coronary artery and supplies blood to the front of the heart muscle
- perfuses the left ventricle and septum myocardium
53
Circumflex artery
- origin from the left cusp of the valve
- encircles/goes around the heart and supplies the back of the heart
- branches off the left coronary artery
- perfuses the left ventricle myocardium
54
Right conus artery
- Additional coronary artery although not counted in the 3 main groups (right coronary, left anterior descending and circumflex)
- arises from right coronary artery
55
Proximal
-closer to the point of origin or trunk of the body
56
Distal
-further from the point of origin or trunk of the body
57
Where do the veins returning the blood back to the heart muscle come together in most cases?
- Coronary sinus
- acts as a collecting duct
- large vessel at the back of the heart
- empties into the bottom of the right atrium where mixed venous blood returns for passage to become oxygenated and rid of carbon dioxide/waste products
58
Anterior interventricular vein
-front of the heart muscle between the left ventricle and the right ventricle
59
Where do the arteries branch divergently from?
- The aorta
| - main artery
60
Primary branches
-often trunk vessels which branch/bifurcate into smaller arteries
61
What are arteries named after?
- the organ perfused
- the anatomical location
- side of the body
-some major conduit arteries go by different names in different parts of the body
62
How many branches does the aortic arch have?
3
- brachiocephalic trunk
- left common carotid artery (middle/second branch)
- left subclavian artery
- perfuses the arms and head
63
Brachiocephalic trunk
- brachiocephalic artery
- right side
- variation means that some people have a left brachiocephalic trunk
- 'arm head' trunk
- bifurcates (splits equally from one blood vessel into two) into the right common carotid artery and the right subclavian artery (continues to give axillary artery then brachial artery=lateral)
- supply right hand side of the head and neck
- bifurcates into smaller arteries
- carotid artery bifurcates again to give the internal carotid artery and the external carotid artery
- carotid pulse is on the right hand side of the neck at the carotid sinus, superior to the carotid artery bifurcation
64
What does the brachial artery bifurcate into?
- radial artery
| - ulnar artery
65
Subclavian artery
below the clavicle
66
Abdomen arterial network
- Abdominal aorta which bifurcates in the perineum to the iliac arteries
- the iliac arteries continue to the femoral arteries, popliteal arteries and then bifurcate to give the anterior tibial artery and posterior tibial artery
- branches of abdominal aorta start below the diaphragm
67
How are the venous network and arterial network similar?
- similar pattern/match location(need to bring blood back from wherever it is taken in the arteries)
- collect blood
68
What are veins named after?
- organ drained
- anatomical location
- side of the body
69
Where do most veins converge and come together?
vena cavae (superior and inferior)
70
MRI imaging interpretation
- nipple=not median plane (sagittal)
| - look at chambers to determine valves
71
What is not present in circulation?
- Air
| - Air is a type of embolus which obstructs blood flow
72
Features of a pre-transplant heart connected to the Organ Care system
- aim to keep heart alive
- cannula securely collects blood from the pulmonary artery
- blood is pumped into the aorta
- the vena cavae are clamped to prevent drainage of the blood out of the system (locked into right atrium)
- the pulmonary veins are not clamped
- right hand side of the heart is airtight
- whole heart is contracting but only the right hand side of the heart is pumping the blood
- blood is pumped into the aorta (retrograde perfusion) because the blood flow is blocked by the closed aortic valve and will bounce back to be pushed down the coronary arteries to keep the myocardium alive with the oxygenated blood
- Blood from the coronary arteries will then drain into the left side to the drainage vent of the left ventricle apex
- drainage vent is not placed through aorta because we use the closed functional aortic valve as a barrier for the coronary circulation
- drainage vent line is placed into the apex of the left ventricle via the pulmonary veins, left atrium and mitral valve
- wire is a pacing cable and because heart is disconnected and we want to ensure it works properly by beating at a minimum rate (rate < 60bpm, the pacing wire will ensure the heart keeps beating)-blood into vena cava to begin with, right atrium, right ventricle and out through pulmonary artery cannula to a reservoir meeting the vent and going into a pump (generation of a driving force to perfuse coronary circulation because blood in the reservoir is stationary)
- sweep gas (mixture of 100% and air) at gas exchanger=thin membranes enable gases to move into the blood from a supply
- blood will then enter the aorta, hitting the aortic valve for most blood to go down the coronary arteries. Some blood goes through the aortic valve and enters the left ventricle. If blood stays here (stasis), it will clot so the drainage vent present prevents the blood clotting.
- The vent joins the pulmonary artery cannula in the reservoir
- filter present to prevent blood clots formed returning to the heart
- keeps the heart alive but also flushes the system to clear harmful materials accumulated in tissues
73
Valve acronym
```
Andy, pandy, teddy and me
Andy=aortic
Pandy=pulmonary
Teddy=tricuspid
Me=mitral
```
74
Systemic circulation
- large network of dividing blood vessels
| - network to the rest of the body, except for the lungs
75
Ventricle
Pumps blood out of the heart
76
How do we view the contraction of a healthy adult heart?
nuclear magnetic resonance imaging (MRI)
77
Define stroke work
- Work done by the heart to eject blood under pressure into the aorta and pulmonary artery
- Determined by the volume of blood ejected during each stroke multiplied by the pressure at which the blood is ejected
- Shown by the equation: stroke work= stroke volume x pressure
78
What factors can influence stroke volume?
-preload and afterload
79
What factor can greatly influence pressure?
-cardiac structure
80
Define Law of LaPlace
when the pressure within a cylinder is held at a constant level, the tension on the walls will increase with increasing radius
- Laplace's equation is where the wall tension= the pressure in the vessel x radius of the vessel
- If wall thickness is incorporated, there is a change in the equation to: wall tension=(pressure in the vessel x radius of the vessel)/wall thickness
81
Law of LaPlace in terms of the heart
- same wall tension across the heart despite the different pressures in the right and left ventricles (right is lower)
- requires pressure in the right ventricle to decrease
- law allows you to keep the wall tension value the same by increasing the radius of curvature of the right ventricle
- radius of curvature of walls of left ventricle is less than that of the right ventricle allowing the left ventricle to generate higher pressures with similar wall tension
82
Superficial
-Close to the body surface
83
Deep
-Furthest from the body surface
84
Great vessels of the heart
- Aorta
- Superior vena cava and inferior vena cava
- Pulmonary veins
- Pulmonary trunk
85
Law of LaPlace applications
- In giraffes, the wall tension is kept by by the long, narrow and thick-walled ventricle which has a small radius of curvature to generate high pressures
- In frogs, pressures are kept lower so the ventricles are almost spherical giving a large radius and low pressure
- Heart structure becomes important for failing hearts (dilated cardiomyopathy)=we see an increase in wall tension because of an enlarged radius
86
Single ventricular cell(cardiac muscle cell)
-rod shaped
-length of 100 micrometers
-width of 15 micrometers
-striated structure
cell surface is invaginated at various points by T -tubules (transverse tubules)
-cells can be filled with fluorescent dye sensitive to internal calcium, giving more fluorescence when it binds calcium=used to measure internal calcium concentrations
-electrical event begins the pathway as a stimulation (action potential) giving rise to calcium transient (influx and release of calcium ions). As calcium rises, it will bring about a contractile event=couple excitatory event to the contractile event
87
What does the heart need to beat?
- external calcium
- must have calcium entering the cell from the extracellular environment
- restores good contractility of the heart muscle
- Calcium release is evoked by calcium influx in cardiac tissue so we need external calcium to begin with
88
How is skeletal muscle different to cardiac muscle?
- Does not require calcium ions for its cells for contraction
- skeletal muscle has mechanical linkage between the L-type calcium ion channel and the SR calcium release channel which does not exist in cardiac muscle cells so calcium is required as the mechanical link
- L type activation is linked directly to SR calcium release channel to open
89
T-tubule characteristics and function
- T tubules are finger-like invaginations from the cell surface, are small (200 nanometers in diameter) and are spaced approx. alongside each Z line of every myofibril
- Carry the surface depolarisation deep into/inside a cell
- Sarcoplasmic reticulum overlies the myofilaments and is next to the T-tubules, which is the main calcium store in the cell
- Sarcoplasmic reticulum only occupies 4% of the cell volume, with most of the muscle cell volume being myofibrils
- There is a number of cell proteins on the surface of the T-tubules as well as on the surface of the sarcoplasmic reticulum membrane
90
Why do mitochondria occupy a large proportion of the cell volume in cardiac muscle cells?
- Require large quantities of ATP for activity
| - mitochondria are closely located to functioning myofibrils
91
Excitation-contraction coupling
| -Pathway for muscle cells to contract
- During excitation, the depolarisation carried into the cell is sensed by the L-type calcium ion channel which opens up
- This allows exterior calcium to enter the cell into the sarcoplasm down it's concentration gradient
- Some calcium will activate the myofibrils (directly causes contraction) but most of this will bind to the SR calcium release channel (ryanodine receptors=RyR) causing a conformational change opening up the channel and allowing calcium store from sarcoplasmic reticulum to efflux into the sarcoplasm (calcium induced calcium release)
- Calcium can then bind to troponin to activate actin-myosin interactions to give contraction
92
Excitation-contraction coupling
| Pathway for the muscle cells to relax
- pump calcium ions back into the sarcoplasmic reticulum from the sarcoplasm by calcium ion ATPase
- uses hydrolysis of ATP to pump calcium against its concentration gradient for storage
93
How do we prevent high calcium build up from calcium entry?
- calcium ions effluxed by sodium/calcium exchanger on cell surface membrane
- Does not use ATP, instead uses downhill energy gradient of sodium from high concentration outside of the cell to the low concentration inside the cell (calcium ions co-transport with sodium ions)
- same amount of calcium entering the cardiac muscle cells to trigger calcium release is removed during the relaxation period=gives balance
94
Complex relationship between force production and intracellular (cytoplasmic) calcium ion concentration
- force production depends on the amount of calcium ions in the cytoplasm supplied to the myofilaments
- sigmoidal relationship
95
Length-tension in relation to cardiac muscle
- Experiment to stimulate cardiac tissue attached to force transducer. Measures amount of force produced by the preparation from baseline to peak=do for further stretched versions of same tissue
- Showed increase in length means an increase in force produced and increase in baseline level
- Hence, as the sample preparation is stretched, the active force production increases(up to a point)
- Passive force production is the line of the baselines at the diastolic/resting level
96
Stimulation of muscle gives?
Contraction and relaxation event
97
What does stretch of the cardiac and skeletal muscle result in with isometric contraction (no shortening)?
- Increase in active force production
- Increase in passive force production
- In both skeletal and cardiac muscle, as the muscle is stretched (up to an optimum point), more force is generated=show length-tension relationship
- After this point is reached, more stretching does not generate more force because there is not enough overlap between the filaments to produce more force in the contraction
98
Total force
Passive force + Active force
99
What is passive force (exists whether or not the muscle is active) based on?
- The resistance to stretch of the muscle
| - Passive force is the isometric contraction
100
Why does cardiac muscle produce more passive force compared to skeletal muscle?
- more resistant to stretch and less compliant compared to skeletal muscle
- Due to the properties of the extracellular matrix and the cytoskeleton
101
Pulling a muscle
-overstretched skeletal muscle, meaning the actin filaments and myosin filaments cannot come together and interlock again so the muscle fibres are broken up
102
Why can't cardiac muscle be overstretched?
- contained in the pericardium which restricts the stretching
- in physiological condition, the descending limb does not happen and hence only the ascending limb of the relationship works (important in cardiac muscle)
103
Which two forms of contraction exist in the cardiac cycle?
- isometric
| - isotonic
104
Isometric contraction
- no change in length of the muscle fibres but change in tone
- initial contractile event when pressure increases in the ventricles (valves are all closed at this point) uses this type of contraction
105
Isotonic contraction
- shortening of muscle fibres
| - blood is ejected from the ventricles by this type of contraction
106
Define preload
- The weight that stretches the muscle before it is stimulated to contract
- slight stretching by preload allows for greater force production when contracted
- MORE PRELOAD=MORE FORCE
- preload governs the amount of force the muscle is capable of producing
- force-preload graph for isometric contraction is the same shape as the force-length graph
107
Define afterload
- The weight not apparent to muscle in the resting state
- Only encountered once the muscle has started to contract (stimulation)
- weight/mass/pressure that the muscle tries to overcome
108
Shortening-afterload graph for isotonic contraction
- amount of shortening in comparison to weight pulled (afterload)
- increased afterload (larger weight) means less shortening
- velocity of shortening-afterload graph behaves in a similar way with increased afterload leading to lower velocity of shortening
- However, if a larger preload with the same amount of afterload used, we can shorten the muscle more and generate more force
109
In vivo correlates of preload
- VENTRICULAR FILLING
- as blood fills the ventricles during diastole (blood returning to the heart), it stretches the resting ventricular walls
- The stretch will determine the preload of the ventricular cells before ejection
- Hence preload is dependent upon venous return to the heart (more blood returning=more stretch=more preload)
- Measures of preload include the end-diastolic volume (sets stretch which when excited can produce force), the end-diastolic pressure and the right atrial pressure
110
In vivo correlates of afterload
- PRESSURE IN THER AORTA
- The force (aortic pressure) which the heart must overcome to eject blood from the left ventricle after opening the aortic valve(Diastolic blood pressure)
- Ventricular cells have to work against this pressure to eject blood=back pressure
- Hypertension is a risk factor for cardiac disease because the afterload is increased (higher pressure in the heart) so the ventricle has to work harder for ejection of same amount of blood
- An increase in afterload, decreases isotonic shortening and the velocity of the shortening so blood effluxes the heart slower
- measures of afterload include diastolic blood pressure
111
Afterload and preload in the heart
- Afterload=diastolic blood pressure
| - Preload=stretch
112
Frank-Starling Relationship (Starling's law)
- main intrinsic mechanism governing cardiac function
- Increased diastolic fibre length increases ventricular contraction (force of contraction increases)
- An increase in stretching (preload) leads to an increase in shortening, velocity of shortening and more force produced
113
Consequence of Starling's law
- with a larger preload, the ventricles have to pump a greater stroke volume so that at equilibrium, cardiac output exactly balances the larger venous return
- more blood return means the ventricles will stretch, leading to increased ventricular contraction accommodating for increased venous return (balance between cardiac output and venous return)
- volume of blood returning determines the strength of the ventricular contraction and therefore the volume of the blood leaving the ventricles=adaptation
114
Which two factors caused the Frank-Starling relationship?
- change in the number of myofilament cross bridges that interact
- Changes in the calcium sensitivity of the myofilaments
115
Change in the number of myofilament cross bridges that interact
- At short muscle lengths lower than the optimum, the actin filaments overlap on themselves, thus decreasing the number of myosin cross bridges that can be made
- As the sample is stretched, the length increases so actin filaments do not overlap
116
Changes in the calcium sensitivity (unclear mechanism)
-myofilaments change response to calcium ions as the preparations are stretched=increased sarcomere lengths for same calcium concentration leads to more force produced because of the sensitivity increase
117
Mechanism 1 for calcium sensitivity change
- Calcium ions are required for myofilament activation
- Troponin C (TnC) is a thin filament that binds to calcium ions and regulates cross-bridge formation between actin and myosin
- at longer sarcomere lengths, the affinity of TnC for calcium increases because of a conformational change (increases sensitivity)=less calcium therefore required for myofilament activation and the same force generated
118
Mechanism 2 for calcium sensitivity change
- change in lattice spacing
- with stretch, the lattice spacing (spacing between the actin and myosin filaments decreases)=thinner sample
- With decreasing myofilament lattice spacing, the probability of forming strong cross-bridges increases
- This produces more force for the same amount of activating calcium ions
