Session 1 Flashcards
Why does the heart need a blood supply if the LV is already filled with oxygen?
The cells are too far from the source of oxygen and diffusion only works over very small distance
What is infarction?
Death of cells due to insufficient blood supply
What is the wall structure of capillaries?
Composed of a single layer of endothelial cells (simple squamous epithelium) surrounded by a basal lamina
How do small water soluble molecules pass through capillaries?
Pass through spaces between endothelial cells
How do lipid soluble molecules/oxygen pass through capillaries?
Diffuse through the capillary cell wall
What are 3 factors affecting diffusion?
Area available for exchange
Diffusion resistance
Concentration gradient
What is capillary density?
How many capillaries there are in a certain tissue
What is the relationship between a more metabolically active tissue and its capillary density?
More metabolically active tissue will have a higher capillary density so there is more area for diffusion to take place
What 3 organs require a high constant flow of blood?
Brain
Heart
Kidneys
What happens to the blood flow to the heart during exercise? What happens to blood flow to skeletal muscle during exercise?
It increases
Can be very high
When is blood flow to the gut at its highest?
After a meal
What is the typical cardiac output for a 70kg man at rest? What can it increase to depending on exercise?
5 litres/minute
25 litres/minute
What is the position of the heart in the body? (2)
Sits behind the sternum
Largely in the middle of the chest
What is the position of the apex of the heart in the body? (2)
Sits on the left hand side of the body
In the 5th intercostal space
What does the heart sit between and within?
Between the lungs
Within the pericardial sac
What is the physical relationship between the heart and the diaphragm?
It is attached to the diaphragm at the bottom
What are the different layers of the pericardium from the outside inwards?
Fibrous layer Parietal layer Pericardial cavity Visceral layer Myocardium Endocardium
What are the properties of the fibrous layer of the pericardium?
Very thick and not elastic (won’t stretch)
What is found within the pericardial cavity?
A small amount of lubricating fluid
What is cardiac tamponade?
Where excess fluid builds up in the pericardial cavity and compresses the heart as the fibrous layer is not able to stretch
What is pericardiocentesis? Why would it be carried out? (2)
Removal of fluid from the pericardial cavity
For testing/relieve compression
What is the transverse pericardial sinus? What is the clinical significance of it?
The passage between the aorta and pulmonary artery anteriorly and the superior vena cava posteriorly
The passage allows clamps to be placed around certain vessels when a heat lung bypass is required during surgery
What is the position of the right side of the heart in-situ?
Right side forms the inferior part of the heart and sits on the diaphragm
Anterior part is largely right side of the heart
Where do the left and right coronary arteries stem from? Where do they rise?
They are the first vessels to stem from the aorta
Arise just above the cusps of the valves
Where does the left coronary artery specifically arise?
Where does the right coronary artery specifically arise?
In the left aortic sinus
In the right aortic sinus
Where does the anterior interventricular artery stem from?
What is the clinical significance of the anterior interventricular artery?
What does the anterior interventricular artery pass and supply?
Left coronary artery
Often blocked in someone with an MI
Passes down the septum and supplies the septum, apex and right and left ventricles
What vessel carries out the main venous drainage of the heart?
The coronary sinus
Where does the coronary sinus drain into?
The right atrium
What type of arteries are coronary arteries?
End arteries with few anastomoses
What can a blocked major coronary artery result in? Why?
MI
There is no collateral blood supply to certain parts of the heart resulting in cell death and myocardial infarction
Coronary arteries are prone to accumulation of…
Fatty deposits (atheroma)
What is the difference between plasma and serum?
Plasma is the fluid found in unclotted blood
Serum is the fluid found in clotted blood - plasma minus the clotting factors (fibrinogen)
What is peripheral resistance? What happens to peripheral resistance during arterial constriction and dilation?
Resistance of the arteries to blood flow
During constriction —> PR increases
During dilation —> PR decreases
What is the cancer of plasma cells called?
Multiple myeloma
Multiple myeloma can result in an increase in plasma viscosity and can lead to…
Increased whole blood viscosity and sludging of blood in the peripheries
As well as multiple myeloma what else can cause sludging of blood in the peripheries?
Polycythaemia
Thrombocythaemia
Leukaemia
Why is sludging of blood more likely to happen at the peripheries?
There is a lower temperature in these areas, so blood is more likely to set
What are 3 examples of acute phase plasma proteins? Changes in these can be used to measure what?
Fibrinogen
Complement factors
CRP
Plasma viscosity
Plasma viscosity can be used to measure what? How?
The inflammatory response
The acute phase plasma proteins are seen at increased levels during inflammation and changes in these are what allows plasma viscosity to be measured
What is the most common way to measure inflammation?
C-reactive protein
Fluids move from regions of _____ pressure to regions of _____ pressure
High to low
Name two different types of blood flow
Laminar flow
Turbulent flow
Describe the laminar flow of blood
Usual flow of blood in streamlines
The velocity of the blood in the centre of the vessel is greater than the blood towards the outer edge
Why does blood in the centre of the vessel flow faster in laminar flow?
There is less friction compared to blood that flows towards the outer edge
Describe turbulent flow of blood
Blood flowing in all directions and continually mixing within the vessel
When does turbulent blood flow occur? (5)
When the rate of blood flow becomes too great (anaemia)
When it passes by an obstruction in a vessel (stenosis)
When it makes a sharp turn
When it passes over a rough surface (atheroma)
When there is increased resistance to blood flow
Flow is measured in…
Volume per unit time e.g. Litres/min
Pressure is measured in…
Psi (pounds per square inch)
What does compliant mean in regards to blood vessels?
Volume of blood vessel will change in response to a change in pressure
Changes in blood flow give a pulse, the more quickly the flow changes…
The greater the pulse
What is a stenosis?
A narrowing
In the arterial system anything beyond the stenosis is _____ and anything before the stenosis is _____
Distal
Proximal
What effect will stenosis have on the flow distally…
It will result in the flow distally decreasing but the velocity increasing (increased kinetic energy of the liquid)
The increased velocity of the blood following a stenosis will…
Likely stretch the artery after the stenosis result in an aneurysm
Where is it common for one stenosis to be followed by another stenosis?
In the legs
What happens if there is one stenosis followed by another?
The flow will stop - pressure is reduced as the blood passes through each stenosis and eventually the flow will stop resulting in ‘critical ischaemia’ in the legs
Why are you less likely to be able to feel/take a pulse in an elderly person?
In elderly people arteries can calcify resulting in vessels that are less compliant
What is a thrill?
The vibrations you FEEL when there is a stenosis as a result of the turbulent blood flow
What is a bruit?
The turbulent sound you HEAR when you listen with a stethoscope at the point of a stenosis
If you hear a turbulent sound across a heart valve it is called a…
Murmur
What does a pressure tracing usually measure?
The pressure changes in the descending aorta
What is the upwards segment of a pressure tracing called? What is the downwards segment of a pressure tracing called?
Anacrotic limb
Dicrotic limb
What are the different stages of a pressure tracing?
Systolic uptake Peak systolic pressure Systolic decline Dicrotic notch Diastolic runoff End diastolic pressure
What parts of the pressure tracing indicate systole and which parts indicate diastole?
Systole = from end-diastolic pressure to dicrotic notch
Diastole = from dicrotic notch to end-diastolic pressure
What does the area under the curve in a pressure tracing equate to?
The mean arterial pressure
What does the anacrotic limb show?
The pressure rising as blood is ejected into the descending aorta (systolic uptake) until it reaches a max (peak systolic pressure)
What happens after the peak systolic pressure is reached?
The aorta begins to stretch and the left ventricle begins to relax. Pressure in the descending aorta falls (systolic decline)
What does the dicrotic notch represent? What happens to the pressure at the dicrotic notch?
The point where the aortic valve snaps shut and systole ends
There is a small increase in pressure
Where is the lowest pressure seen in a pressure tracing?
At the end of diastole - end-diastolic pressure
What is the pulse pressure? What value does it commonly take?
Difference between the peak systolic pressure and end-diastolic pressure
40 mmHg
What can the mean arterial pressure be estimated as? What value does it commonly take?
Diastolic pressure + 1/3 of pulse pressure
93 mmHg
What value does mean arterial pressure have to fall below for organ perfusion to be impaired?
70 mmHg
The pulse pressure is the main determinant of …
How strong a pulse you feel
What can happened to the flow of blood in arteries during diastole?
Retrograde flow can occur especially when the peripheral resistance is high
What is meant by the volume of the pulse?
The strength of the pulse
What 2 factors affect the volume of the pulse?
The force with which the left ventricle is able to eject blood into the arterial system
The pulse pressure
What is a bounding pulse?
A strong pulse
What effect does bradycardia have on pulse pressure and the pulse?
Widens pulse pressure and leads to a bounding pulse
Why does bradycardia result in an increased pulse pressure?
Slow heart rate means diastole has longer to occur so increased pulse pressure and bounding pulse
What is another term for a weak pulse?
A thready pulse
What can result in a reduced pulse volume (thready pulse)?
LV failure
Aortic Valve Stenosis
Hypovolaemia
What are two causes of hypovolaemia?
Severe dehydration
Bleeding
Vasodilation will have what effect on peripheral resistance?
Means a low peripheral resistance
What can cause vasodilation? (3)
Hot bath
Exercise
Pregnancy
What effect does low peripheral resistance have on the diastolic pressure, the pulse pressure and the pulse?
Lower diastolic pressure
Increased pulse pressure
Bounding pulse
What are the normal systolic and diastolic blood pressures?
120 mmHg
80 mmHg
When taking a blood pressure measurement what 2 factors are important in producing an accurate reading?
Taking more than 1 reading and then calculating an average
Using the right size blood pressure cuff
How big must the blood pressure cuff be in relation to the patient?
Must go around at least 80% of the arm circumference
What effect will a blood pressure cuff that is too small have on the blood pressure reading?
You will get a falsely high reading
