29. Morphology of blood vessels, Heart sounds, blood pressure Flashcards
When do each of the heart sounds occur
1st: Occurs at the start of ventricular systole
2nd: Occurs at start of ventricular diastole
3rd: Occurs at ventricular diastole
4th: During atrial systole
How is the 1st heart sound generated
3 components
- Valve component- rapid closure of atrio-ventricular valves (mitral closes before tricuspid)
- Muscular component- Vibrations in ventricular walls during isovolumetric contraction
- Vascular component- Vibrations in walls of large arterial vessels ie aorta/pulmonary artery
Generated at very beginning of ejection phase when semilunar valves open
How long is the 1st heart sound
What are its characteristics
90-150ms
Louder and lower pitch than 2nd bc oscillations have larger intensity and lower frequency (50-60 Hz)
How is the 2nd heart sound generated
Vibrations caused by closure of semilunar valves (aorta/pulmonary artery)
Aortic valve closes before pulmonary valve so physiological bifurcation of the heart sound is observed
During deep expiration the delay in pulmonary valve closer is
up to 0.02 sec., while in deep inspiration is up to 0.06 sec.
How long is 2nd heart sound
Characteristics
10-120ms
Lower intensity and higher frequency (80-90Hz) than 1st
How is 3rd heart sound generated
Rarely ausculated
Vibrations of ventricular walls caused by influx of a lot of blood during rapid filling phase
How long is 3rd heart sound
characteristics
100ms
Low intensity and low frequency (20-30Hz) therefore hard to hear
How is the 4th heart generated
Blood flow acceleration due to atrial systole (end filling phases of ventricles)
How long is 4th heart sound
Characteristics
40-80ms
Low intensity low frequency ( <20Hz)
Why cant the 3rd and 4th heart sounds be detected with auscultation
Frequency too low
Under what conditions can you hear the 3rd heart sound
In children and adolescents after physical exercise since blood flow is more rapid in those ages, acceleration of blood flow
What is the benchmark for auscultation
sternal angle
coincides with 2nd rib attachment
What are the main auscultation points
To hear:
Mitral valve: located 5th intercostal space, .5cm lateral (left) of midsternal line . HEAR 1ST HEART SOUND
Pulmonary valve: 2nd intercostal space onleft. HEAR 2ND HEART SOUND
Aortic valve: 2nd intercostal space on right HEAR 2nd HEART SOUND
Tricuspid valve: 5th rib next to sternal edge on right. 1ST HEART SOUND
Erbs point: 3rd left intercostal space, left sternal edge
What is phonocardiogram
objective graphical method for registration of all cardiac sounds
occurring during the work of the heart, regardless of their intensity and
frequency.
What is a phonocardiogram always registered with
an ECG
How does phonocardiogram work
Heart sounds are detected by
microphone placed on the auscultation
points and a transducer afterwards turns
the sound waves into electrical waves.
What is auscultation gap
Temporary disappearance of Korotkoff sounds because greater external pressure was applied when taking the blood pressure or very slow opening of the pressure valve
Auscultation gap can result in detection of lower than actual systolic
pressure or higher than actual diastolic pressure
What are buffering blood vessels
Large arteries and aorta
Elastic and collagen fibers in their walls dampen pressure fluctuations
What are Resistance vessels
Arterioles
Lots of smooth muscle they can chnage their diameter to exert avrapidly changing resistance to blood flow
Important in maintaining diastolic arterial pressure
What are exchange vessels
Capillaries and thin wall venules
Exchange of intracellualr fluid and plasma components takes place across walls
What are capacitance vessels
Veins
Contain most of the blood volume
Changes diameter easily thus alter blood distribution
What are the 2 things circulation depends on
1, pressure gradient
- Vascular resistance that should be overcome to allow blood flow
What is blood flow
Blood flow is the volume of blood passed per
second through a given area of the vascular
system.
It is measured in ml/s.
Blood fow caused by pressure gradient and vascular resistance due to pumping action of heart
What is the equation linking blood flow, pressure gradient, resistance
Q=∆P/R
Blood flow (Q) is directly proportional to the
pressure gradient (∆P) and inversely
proportional to vascular resistance (R):
What equation can you use for laminar flow when blood flow in parallele layers
Q=∆Pπr4/8ηl
Poiseuilles law
What is the property viscosity of blood
What are the factors
When fluid particles exert internal friction during laminar flow
Depends on the number of cells, and content of the plasma proteins
when viscosity low= anaemia and hypoproteinemia
What is linear velocity of blood
Linear velocity of the blood is defined as the
distance that each particle of the blood travels
through a blood vessel per unit time.
It is measured in cm/s.
V=Q/A porportional to blood flow, inversel to cross sectional area
Why is changes in the radius of the vessel important
r^4
When the radius of a vessel (r)
decreases due to
vasoconstriction or partial
occlusion, an increase in
vascular resistance (R) and a
decrease in blood flow (Q) are
observed.
Vascular resistance in SEQUENTIALLY connected blood vessels
The sum of the individual vessel resistances
These are the arrangement of vessels within an organ
major artery~smaller arteries~arterioles~capillaries~venules~veins
Vascular resistance in PARALLELL connected blood vessels
Sum of reciprocal values of
individual vessels resistances
This is the distribution of blood from major arteries coming from aorta
renal circulation, cerebral circulation,
and coronary circulation.
Adv of parallel connected vessels
RESISTANCE IN PARALLEL LESS THAN IN SEQUENTIAL
What is vascular compliance
Differecne between venous and arterial
Stetchability of the vessel
The compliance of arterial system is
significantly smaller than the compliance of
the venous system.
Meaning same change in blood volume leads to smaller pressure increase in venous vessels that arteries
Why does blood flow not stop in diastole when pressure in ventricles is 0
No stopping due to elastic properties of the arteries
In systole they dilate then in diastooe it narrows to normal diameter
How is pulse wave generated
It is generated by deformation (dilation) of the aortic wall during ventricular
systole which is transmitted along the arterial system.
What is the cause of blood pressure
It is caused by pumping out of relatively large volume of blood for the size of
aorta during ventricular systole and the resistance that the blood encounters
as it moves in the vascular system.
What is systolic, diastolic, pulse blood pressure
Systolic is detected at systole, max blood pressure
Diastolic is detected at diastole, minimum blood pressure
Pulse pressure = systolic- distolic
What is mean arterial blood pressure MaP
All pressure values during 1 cardiac cycle
since diastole is longer than systole, it contributes greater to the MaP
Calculated by: diastolic pressure + 1/3 Pulse pressure
What are the major factros determining arterial Blood pressure
Stroke Volume (SV).
Cardiac Output (CA).
Total vascular resistance (TVR).
The compliance (extensibility) of the vessels.
Ratio between speed of ejection and TVR.
Circulating volume of blood.
What are some methods of measuring blood pressure
Invasive by inserting a catheter with a pressuretransducer into the artery.
- Indirect sphygmomanometric method by applying of external pressure on
brachial artery:
Palpatory - based on appearance of pulsation on radial artery (method of
Riva - Rocci).
Auscultatory - based on appearance of sound phenomena (the sounds of
Korotkoff) upon auscultation of brachial artery.
Oscillatory - detection of the oscillations in the wall of brachial artery.
Why brachial systolic pressure measured with the palpation method of
Riva-Rocci is lower than the value assessed with the auscultation method?
Due to delay of the pulse wave. First the pulse wave appear on brachial artery and afterwards on the radial artery.
What causes Korotkoff sounds (auscultation method)
TURBULENT flow in brachaial aretry by reducing external cuff pressure
Lumen of artery only partially open so high blood velocity causes change fromlaminar to turbuelnt
What is optimal values of blood pressure
What is normal blood presrue
systolic= 100-119 mmHg
diastolic= 60-79 mmHg
systolic= 120-129mmHg
diastolic=80-84 mmHg
