Cardiovascular (Peter) Flashcards
distribution of blood by volume
9% pulmonary circuit
7% inside the heart
84% systemic circuit
pressure and resistance in the pulmonary circuit vs systemic circuit
medium resistance and pressure in the pulmonary circuit vs. high resistance and pressure in the systemic circuit
inlet valves prevent
high-pressure blood in the pumping chamber from returning to the veins
function of the appendage/auricle
increase the capacity of the atria
how does having the inlet and outlet on the same end of the heart improve its function?
chamber can shorten in length as well as in width
pulmonary vein orientation vs vena cava
pulmonary vein(s) are very horizontal while the vena cava is very vertical
the _____ of the heart is the pointed tip of the left ventricle. At the opposite end from the _____ is the _____.
the apex of the heart is the pointed tip of the left ventricle. At the opposite end from the apex is the base.
peak pressure of…
- left atrium
- left ventricle
- right atrium
- right ventricle
- left atrium = 8mmHg
- left ventricle = 120mmHg
- right atrium = 5mmHg
- right ventricle = 27mmHg
inlet valves constructed of
fibrous connective tissue
fate of the blood from the gut
the deoxygenated, nutrient rich blood travels to the liver via the hepatic portal vein
function of chordae tendineae
prevent the bicuspid and tricuspid valve from bursting upwards into the atrium during systole
name of the ligament between the aorta and pulmonary trunk
ligamentum arteriosum
names and location of the atrioventricular valves
bicuspid/mitral on the left
tricuspid on the right
chordae tendineae are loose during
distole
ratio of size of ventricles in a foetus
the same boiiiiiiiiiiiiiiii
outlet valves names and location
SEMILUNAR VALVES
pulmonary on the right
aortic on the left
ratio of peak pressure in the LV:RV
5:1
ratio of wall thickness in the LV:RV
3:1
openings to the coronary arteries
in the aorta, just after the semilunar aortic valve
how many cusps in the outlet valves? cords or nah?
3 cusps, no cords
The ____ of the heart points inferiorly and anteriorly to the left. About 1/3 of the mass of the heart lies to the _____ of the midline of the body and about 2/3 to the _____. The right border of the heart is formed mainly by the ____ ______. The inferior border is formed mainly by the _____ ______. The left border is formed mainly by the _____ ______.
The apex of the heart points inferiorly and anteriorly to the left. About 1/3 of the mass of the heart lies to the right of the midline of the body and about 2/3 to the left. The right border of the heart is formed mainly by the right atrium. The inferior border is formed mainly by the right ventricle. The left border is formed mainly by the left ventricle.
Pericardium made of (inner and outer wall)
single layer of squamous mesothelial cells
what constitutes the heart wall
endocardium - myocardium - epicardium (visceral pericardium)
what constitutes the pericardium
epicardium (visceral pericardium) - pericardial space (serous fluid) - parietal pericardium - fibrous pericardium (tough fibrous sac)
cardiac tamponade
blood in the pericardial space
fibrous skeleton of the heart structure
2 complete fibrous rings around the mitral and aortic valves and 1 incomplete ring around the tricuspid valve
pericardium function
no friction when the heart beats
what is present where the fibrous skeleton is incomplete?
fatty connective tissue
relative speed of conduction and reason:
- SA node - Atrial myocardium
- AV node
- AV bundle (bundle of his) - Purkinje fibre
- SA node - Atrial myocardium = SLOW 0.5m/s
- atrial contraction - AV node = VERY SLOW 0.05m/s
- 100ms delay - AV bundle (bundle of his) - Purkinje fibre = FAST 5m/s
- even ventricular constriction (systole)
ventricular filling
- DIASTOLE.
- starts when pressure in the ventricle drops below the pressure in the atrium (less than 5mmHg).
- Mitral valve opens quietly and blood enters the ventricle to ~80% of its capacity.
- Accounts for half the total cycle time
the cardiac cycle duration
1 second
Atrial contraction
left atrium contracts and completes the filling of the left ventricle. Tops up 20% volume.
during atrial contraction, the increase in pressure in the left atrium is relatively small due to…
- atrial muscle layer is thin
2. there are no valves preventing blood flowing back into the pulmonary veins
Isovolumetric ventricular contraction
- SYSTOLE
- mitral valve closes = first heart sound (“lub”)
- ventricular pressure is increasing but still less than that in the aorta
- aortic valve remains closed
- 0.05 seconds
ventricular ejection
- SYSTOLE continues
- ventricular pressure is greater than pressure in the aorta
- aortic valve opens quietly
- blood leaves the ventricle
- pressure in the aorta and ventricle continues to rise
why does pressure in the aorta and ventricle continues to rise during ventricular ejection?
Because blood is being ejected into the aorta faster than it can run-off into the distributing arteries. Thus eventually levels-off then decreases
Isovolumetric ventricular relaxation
- ventricle relaxes
- sudden drop in ventricle pressure
- flow reverses in the aorta
- aortic valve fills with blood and closes = second heart sound (“dub”
- mitral valve closed because, even though it is falling, pressure in the ventricle is still higher than the atrium
- ventricle isolated from the rest of the circulation
- 0.05 seconds
- preceds ventricular filling
2 functions of the fibrous skeleton
- support and anchor the valve leaflets to the heart wall
2. insulate ventricles from SA node
which valve has no fibrous skeleton?
pulmonary
maximuma and minimum blood volume of the left ventricle
120 max
40mL min
when is the pressure in the aorta at its lowest? what is this value?
just before ventricular ejection = 80mmHg
blood leaving the ventricle referred to as…
bolus
Function of elastic artery
- near the heart.
- during systole they store the bolus of blood leaving the ventricle.
- during diastole they push blood out by elastic recoil
- smooth the pulsatile flow of blood leaving the heart
structure of elastic artery
many thin sheets of ELASTIN in the middle tunic.
Diameter the size of a finger
Muscular artery function
- distribute blood around the body at high pressure and to the lungs at medium pressure
- rate of flow adjusted by using smooth muscle to vary the radius
Flow and radius
flow is proportional to the fourth power of radius
structure of muscular artery
many layers of circular smooth muscle wrapped around the vessel in the middle tunic (media).
Diameter the size of a pencil-pin
3 layers of arteries
outer tunic (externa) middle tunic (media) inner tunic (interna - intima)
arteriole function
- control blood flow into the capillaries
- largest drop in pressure
- greatest resistance to flow
- degree of constriction determines TOTAL PERIPHERAL RESISTANCE which itself affects MEAN ARTERIAL BLOOD PRESSURE
Structure of arteriole
1-3 layers of circular smooth muscle in the middle tunic.
Thickest muscular wall relative to size than any other blood vessel.
Lined with endothelial cells.
Diameter the size of a hair.
cardiohypertrophy
enlargement of the heart causes boot shape. In an x-ray a larger cardio-thoracic ratio is visible (~50%)
aortic stenasis (narrowing)
often due to rheumatic fever - causes body to create antibodies which attack your own body tissue. In the case of the aortic valve it can recover but will be scarred and its integrity damaged. the valve is narrowed as a result and the left ventricle has to work harder.
Capillary function
- thin walled to allow exchange of gases, nutrients and wastes between blood and tissue fluid.
- slow blood flow to allow time
- leaky - plasma escapes to form interstitial/tissue fluid
capillary structure
- 9μm diameter, the same as a RBC
- single layer of endothelium
- external basement membrane
- NO SMOOTH MUSCLE
- NO CONNECTIVE TISSUE
Venule function
- low-pressure drain for capillary beds
- where WBCs leave blood circulation
venule structure
small venules have usual endothelium + some connective tissue. Large venules have a single layer of smooth muscle.
Vein function
- low-pressure
- drain blood back to atria (besides portal veins)
- small pressure change causes large change in venous volume, therefore they act as a RESERVOIR WHICH STORES BLOOD
- 64% of blood volume occurs in systemic veins and venules
vein structure
- thin and soft walls
- larger veins have valves to prevent backflow
angina
chest pain
ischemia
low oxygen
anastomoses
artery-to-artery junctions
clinical importance of cardiac veins
NONE
if a coronary artery narrows to about 20% of its diameter by atheroma…
significant obstruction of blood flow to the myocardium which then runs low on oxygen (ischemia) causing angina. Severe ischemia can result in death (infarction).
idiopathic
cause unable to be identified
Dilated cardiomyopathy
- cause often idiopathic - probably a viral infection
- infected muscle fibres attacked by lymphocytes - many die or are weakened and slow to contract
- left ventricle most affected because of high pressure
- Left ventricle dilates (chamber enlarged but wall thickness remains the same)
- fibrous ring supporting mitral valve stretches
- mitral valve flaps no longer meet during systole, causing MITRAL REGURGITATION
why does the left ventricle dilate?
due to the lengthening of the cardiac muscle fibres
when the left ventricle dilates how is the thickness of the wall changed?
it doesn’t change. ratio of RV:LV remains at 1:3
mitral regurgitation
blood regurgitates from the left ventricle into the left atrium during systole
how does the regurgitated blood affect the pressure of the LA
increases
Heart sound due to mitral regurgitation
Lub-shhhhh-dub (“shhhh” due to regurgitation)
regurgitation =
backflow of blood
in mitral regurgitation, the mitral valve is said to be…
incompetent
BREATHLESSNESS
why does a problem on the left (systemic) side of the heart cause problems in the right (pulmonary circuit)?
- To maintain cardiac output the LV must pump a greater volume of blood
- Assuming the heart remains the same, LV volume at the end of filling (diastole) must increase
- in order to fill the ventricle the LA works harder
- LA pressure increases
- Pulmonary venous pressure increases
- Pulmonary capillary pressure increases
- pulmonary capillary leakage increases
- Lungs heavier and wetter
- Lungs more rigid
- Breathing requires more muscular work
in mitral regurgitation, how much of the blood ejected by the LV is actually regurgitated into the LA?
as much as half. It returns to the LV during the next diastole along with fresh blood.
Dyspnoea
discomfort during breathing, consciousness of laboured breathing.
