Cardiovascular Systems 2 Flashcards
What is the role of the circulatory system?
Provide Oxygen and other nutrients to every cell in the body AND;
Remove Carbon dioxide and other waste products from every cell in the body
What is the driving force of the circulatory system?
The heart
What is the conduit system of the circulatory system?
Vascular Beds - including arteries, capillaries and veins
What do arteries do?
Take blood away from the heart (generally oxygenated)
What do capillaries do?
Deliver blood to tissues
What do veins do?
Take blood to the heart (generally deoxygenated)
What is the relationship between systemic circulation and pulmonary circulation?
The two systems work in parallel - Systemic circulation transports oxygenated blood from the heart throughout the body. Pulmonary circulation brings deoxygenated blood back to the heart.
What is the order of blood flow for systemic circulation?
Left atrium
Left Ventricle
Aorta
Arteries
Arterioles
Capillaries
Venules
Veins
Vena Cava
Right Atrium
Right Ventricle
What is the percentage of cardiac output during pulmonary circulation?
100%
What is systemic circulation?
Systemic circulation transports oxygenated blood from the heart (from the left side) throughout the body.
What is pulmonary circulation?
Pulmonary circulation brings deoxygenated blood back to the heart (into the right side).
What is the order of blood flow for Pulmonary circulation?
Right atrium
Right ventricle
Pulmonary artery
Arterioles
Capillaries
Venules
Pulmonary vein
Left atrium
Left ventricle
What is larger: an artery or vein?
Artery
What is larger: Capillaries or veins?
Veins
Do arteries or veins have more elastic layers in their wall?
Artery
Does an artery or a vein have a wider lumen?
Vein
What order does blood flow through: capillaries, arteries, venules, veins, arterioles.
Arteries
Arterioles
Capillaries
Venules
Veins
What is the largest artery in the body?
Aorta
What does the vena cava enter into?
The right atrium
Which blood vessels are classified as microvasculature?
Terminal arteriole
Capillary
Venule
Size of a blood vessel correlates to what?
The thickness of the wall
Does the aorta or an artery have more smooth muscle?
Artery
Why is there small diffusion distance in capillaries?
Because there is no elastic tissue, smooth muscle or fibrous tissue in their wall.
What is Q?
Blood flow
What is resistance (R) primarily determined by?
Blood vessels
What is the relationship between Q (blood flow) and R (resistance)?
Inversely proportional - meaning if R increases Q decreases.
What is the equation for blood flow?
Flow = Pressure gradient / resistance (Q=P/R)
What does proportional and inversely proportional mean?
Proportional = as one increases so does the other
Inversely proportional = as one increases the other decreases.
If diameter is increased what happens to resistances and flow?
Lower R and higher Q
What is Poiseuille’s Law?
Equation used to calculate resistance in a blood vessel
R = 8In / (pie)r^4
R = resistance
I = blood vessel length
n = fluid viscosity
r = blood vessel radius
What is fluid viscosity?
Referring to the thickness of the fluid
Symbol = n
Radius is to the power of 4, what does this mean?
That even a very small change in radius will cause a large change in resistance
What is the relationship between Resistance and radius?
Inversely proportional
What is Q proportional to?
Pressure gradient (P)
Blood vessel radius (r)
What is Q inversely proportional to?
Resistance (R)
Blood vessel length (l)
fluid viscosity (n)
What is the radius?
Half the circumference (half the length of the inside of a circle)
What do all walls of blood vessels contain: elastic tissue, endothelium or smooth muscle?
Endothelium
What is CSA?
Total vascular cross sectional area
Does resistance increase or decrease as blood vessel size increases?
Decreases (meaning the aorta has smaller resistance than arterioles)
In what blood vessels does pulsatile flow occur?
But doesn’t the aorta prevent any pulsatile flow
Aorta, arteries and arterioles
(pulsatile flow is due the contraction and relaxation of the ventricles - therefore only occurs in early arteries because as you get further away from the heart the effect is not felt).
As CSA increases what happens to velocity?
It decreases - area and velocity are inversely proportional
(Velocity = flow / CSA)
What blood vessel has the largest CSA?
Capillaries
What blood vessel has the fastest velocity?
Aorta (because smaller CSA)
Where is the lowest pressure in the systemic system?
Right atrium
What effect does vascular branching have on CSA, velocity and blood pressure?
High vascular branching increases CSA, decreases velocity and has no relationship to pressure.
How does the high elastic tissue in arteries relate to their function?
High elastic tissue results in elastic recoil (the tendency of stretched elements to return to their original shape).
What structure of arterioles makes them efficient in contraction and relaxation?
High smooth muscle contents
What are the two functions of the aorta and large elastic arteries?
Distribute blood
Pressure reservoir
What does a pressure reservoir do?
Reduce fluctuations in pressure and flow resulting in maintaining flow throughout the cardiac cycle
What enables there to be a pressure reservoir?
Elastic tissue
Does stretch occur during systole or diastole?
Systole
Is stored energy released during systole or diastole?
Diastole
When does recoil occur?
During diastole
What is compliance?
Compliance is the ability of something to stretch (stretchiness).
What is the equation for compliance?
compliance = change in volume / change in pressure
As we get older how does the structure and function of arteries change?
Increased vascular stiffness
Increased vessel diameter
Endothelial dysfunction
VSMC hypertrophy and proliferation
What is hypertrophy?
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells.
What wraps around the vessel of arterioles?
Smooth muscle cells
What is vasoconstriction?
Contraction of the lumen reducing the diameter of blood vessel
What is vasodilation?
The widening of blood vessels as a result of the relaxation of the blood vessel’s muscular walls.
Vasoconstriction of arteries is important in controlling what?
Regulation of blood flow
Why does vasoconstriction change blood flow?
Because it reduces the radium of the blood vessel which effects resistance and in turn decreases blood flow.
What is the units for pressure?
mmHg
What causes the dicrotic notch?
Aortic valves shutting (causing a short increase in pressure).
What is diastolic pressure (DP)?
The minimum pressure just before ventricle contraction
What is systolic pressure (SP)?
The maximum arterial pressure during peak ventricular ejection
What is normal measured BP as SP/DP?
120/80 mmHg
What is hypotension and its likely measured values as SP/DP?
When the pressure of blood circulating around the body is lower than normal or lower than expected.
< 90/60 mmHg
What is hypertension and its likely measured values as SP/DP?
When the pressure of blood circulating around the body is higher than normal or higher than expected.
> 140/90 mmHg
What is pulse pressure?
PP = SP-DP
What is Mean Arterial Pressure (MAP)?
The average blood pressure across the whole body.
MAP = DP + 1/3 x PP
(1/3 because more time in diastole than systole)
What does arterial pressure depend on?
Q and TPR
What is TPR?
Total peripheral resistance = the sum of global resistance from all systemically vascular beds
What sort of variable is MAP?
Homeostatic
Does vasoconstriction increase or decrease MAP in arteries?
Increase
What is meant by altered metabolic demands?
That different parts of the body need different supplies = regional dependant change
If there is regional dependant change in blood flow how is total blood flow affected?
It is not effected - Q can be increased in one area but the same total volume of blood is distributed therefore no overall change in pressure and MAP stays the same.
What is extrinsic control?
Exist outside the organs they control
What is intrinsic control?
Exist inside the organ it controls
What sympathetic nervous system hormone is released for vasoconstriction?
Noradrenaline
What does noradrenaline bind to in order to cause vasoconstriction?
a1-adrenergic receptors
Why does the brain have low numbers of a1-adrenergic receptors?
To ensure that there is limited vasoconstriction - important because the brain needs constant flow of blood.
Why does the skin and GI have a high number of a1-adrenergic receptors?
To allow for high levels of vasoconstriction - which is important because flow needs to be flexible to adapt to day to day activities that require variable levels of blood supply
What do postganglionic autonomic nerves release in order to cause vasodilation?
Nitric oxide
What does the release of nitric oxide cause?
It relaxes smooth muscle cells surrounding arterioles thus causing vasodilation (increased blood flow).
Where in the body is there a specialised innervation system to allowed for increased blood flow?
GI tract and reproductive system (the penis)
What hormones trigger vasoconstriction?
Adrenaline, Angiotensin 2 and vasopressin
+ Noreadrenaline
What hormones trigger vasodilation?
Adrenaline and atrial natriuretic peptide
Why can adrenaline trigger both constriction and dilation?
Because there are different types of adrenaline receptors expressed:
a1-adrenergic receptors causing constriction
and
b2-adrenergic receptors causing dilation
What is the predominant receptor expressed on skeletal muscle?
B2-adrenergic receptor
What does it mean to be vasoactive?
Actively affecting the diameter of blood vessels
How does ADH/vasopressin increase blood volume?
It increases H2O reabsorption
How does angiotensin 2 increase blood volume?
stimulates Na+ reabsorption
How does Atrial Natriuretic peptide (ANP) decrease blood volume?
Decreased H20 reabsorption
What hormone decreases H2O reabsorption?
Atrial Natriuretic Peptide (ANP)
What are not involved in intrinsic control of vascular diameter?
No nerves or hormones involved
What is active hyperemia?
Hyperaemia is the auto regulation process by which the body adjusts blood flow to match change in local metabolism.
It is a tissue specific response
Where in the body is there a highly developed active hyperaemia system?
Skeletal muscles and cardiac tissue because they have high metabolic demands
What is reactive hyperaemia?
Control of blood flow to maintain flow with change in perfusion pressure - meaning that it is in response to a drop in blood pressure in muscle (not local metabolism)
(also called flow auto regulation)
What are the two types of intrinsic controls of arterial diameter?
Active and reactive hyperaemia
*reactive hyperaemia also called auto flow regulation
What is perfusion pressure?
Perfusion pressure is how much pressure it takes to push blood through all the blood vessels in a specific area.
What does myogenic mean?
From the muscle
What is the primary function of capillaries?
Exchange of nutrients and metabolic end products
What is the approx diffusion distance between capillaries and cells?
< 100 um
What makes the diffusion distance between capillaries and cells small?
capillaries have thin walls due to endothelial cells and no smooth muscle
Approx how many km of capillaries are in an adult?
Around 80,000 km (meaning it is a very highly branches network).
What is the benefit of low velocity of blood flow in capillaries?
More time for diffusion
What are pre capillary sphincters?
Segments of smooth muscle that help direct blood flow into capillaries from arterioles.
What is capillary circulation between arterioles and venules controlled by?
Local metabolic factors, precapillary sphincters and metarterioles
What are metarterioles?
Small vessel that links arterioles to capillaries.
What is the link between arteries and veins?
Capillaries
What is Starlings forces?
The balance of fluid movement in and out of capillaries across the membrane - which determines the overall direction that fluid will move.
What is capillary hydrostatic pressure?
The pressure exerted by the fluid within the capillaries.
*same as perfusion pressure
What is capillary osmotic pressure?
Pressure due to the amount of solute in capillaries or interstitial
What direction does interstitial osmotic pressure push water?
out of capillary
What direction does capillary osmotic pressure push water?
into the capillary
What direction does capillary hydrostatic pressure push water?
out of capillary
What direction does interstitial hydrostatic pressure push water?
In to capillary
What does the balance of fluid exchange in capillaries depend on?
Location along the arteriole or venule - the driving forces at arteriolar and venous ends are not equal
What is a major determinant of Pc (capillary hydrostatic pressure)?
The resistance in the small arterioles upstream
If there is a high Pc is water moving in or out?
fluid out
Is there net filtration or net reabsorption at the arteriolar end?
Net filtration (collection of fluid in the interstitial spaces)
Is there net filtration or net reabsorption at the venular end?
Net reabsorption (movement of fluid into the blood)
What is the lymphatic system?
Drainage system - drains excess interstitial fluid (ISF) back into the systemic circulation
What disease is developed as a result of poor draining of excess fluid from ISF?
Lymphedema
What do venules and veins do?
Collect blood from capillaries and take it back to the heart
What percentage of blood resides within the venous system?
60%
Are veins or arteries more compliant and why?
Veins - because they have thinner walls
Why does the pressure in veins plateau more significantly than in arteries?
Veins are more compliant (more easily distensible) than arteries. This means that they can accommodate a larger volume of blood with only a small increase in pressure. This property helps to buffer changes in blood volume and pressure.
What is the difference between venoconstriction and vasoconstriction?
The most obvious difference is that Venoconstriction occurs in veins and Vasoconstriction occurs in arteries.
Venoconstriction increases flow in veins whereas vasoconstriction reduces flow in arteries.
What is the effect of noradrenaline binding to a1-adrenergic receptors in veins?
Venoconstriction causing increase in flow
What is venous return and what is it determined by?
VR is the flow of blood back into the heart and it is determined by venous pressure.
In what position does blood pool in lower limbs?
When standing / in a vertical position
Is venous pressure higher in the head or in the feet?
In the feet - venous pressure increases with distance below the heart
Where does blood pool when lying in horizontal position?
No where - venous pressure is similar throughout the body / same gravitation forces.
What prevents venous pooling?
Valves in veins and skeletal muscle pump
What happens to valves in veins that are inferior to contracting muscle?
The are forced closed - preventing the back flow of blood to the capillaries.
(Valves superior to the contracting muscle open allowing blood to move towards the heart).
What happens to the diaphragm during inhalation?
It contracts
How does the diaphragm contracting facilitate venous return?
It decreases intrathoracic pressure and increases intra-abdominal pressure - as a result it pulls blood in thoracic vena cava which compresses.
What is arterial pressure (MAP) precisely regulated at?
90mmHg
What are baroreceptors?
Blood Pressure receptors that are receptive to changes in stretch of the arterial wall
Where is the Nucleus Tractus Solitarius (NTS) located?
Medulla of the brainstem
Where are baroreceptors located?
Aortic arch and carotid sinus
If there is an increase in MAP does the stretch of the arterial wall increase or decrease?
Increased MAP = Increase Stretch
What nerves are involved in the regulation of MABP afferent pathway?
Carotid sinus nerve and aortic (vagus) nerve
Where are carotid baroreceptors located?
carotid sinus nerve
What causes a change in action potential frequency in afferent nerves?
A change in baroreceptor stretch
What nucleus detects a variation in MABP and sends instructions for change via efferent activity?
NTS = Nucleus Tractus Solitarius
What is the automatic nerve low pressure response to a change in MABP?
Activation of the Sympathetic NS
What is the autonomic nerve high pressure response to a change in MABP?
Activation of the Parasympathetic NS
Where are post-ganglionic neuron’s of the SNS located?
Located in the sympathetic ganglia, which then act on the heart and blood vessels to increase blood pressure.
Where do pre-ganglionic nerves of the PSNS originate from?
Vagus nerve
What do post-ganglionic nerves of the PSNS act on?
The heart directly (PSNS has no major role in the vasculature/vessels).
If there is an increase in MABP how does the body restore it?
Arterial barorecpors detect stretch in arterial wall and response by an increased firing of AP.
Decrease in sympathetic outflow to heart arterioles and veins and an increase in parasympathetic outflow to the heart.
= Decreased contractility (SV)
= Vasodilation = decreases TPR but also decreases BP
*With less resistance to blood flow, the heart doesn’t need to pump as hard to move blood through the circulatory system, resulting in lower blood pressure.
What is the reflex in response to MABP via?
Reflex via medullary cardiovascular centres.
What is a haemorrhage?
“An escape of blood from a ruptured vessel”
What percentage of blood volume is taken when donating blood?
10%
What are the three stages of restoration (after hemorrage)?
Immediate = baroreflex
Intermediate = cardiovascular volume restoration
Long-term = total body volume restoration
In the event of a haemorrhage does arterial pressure increase or decrease?
Decrease
What are the three pathways to restore MAP in the immediate haemorrhage response?
Heart: by decreasing PSNS and increasing SNS which increases CO and thus pressure.
Veins: increase in venoconstriction to increase venous return which increase CO and thus pressure.
Arterioles: increase vasoconstriction to increase TPR and thus pressure.
Does the immediate baroreflex response restore blood volume?
No - only MAP is restored in the immediate response
How long after blood lose does the immediate response occur?
Within seconds
How long after blood lose does the intermediate response occur?
Within seconds to minutes
How long after the blood lose does the long term response occur to restore total body volume?
Within minutes to hours
Blood volume needs to be restored quickly in order to maintain what?
Perfusion pressure
Is increasing blood volume or maintaining the correct blood composition more important?
Blood volume (we can tolerant lower concentrations of RBC)
How is blood volume restored in the intermediate response after haemorrhage?
Increased absorption of interstitial fluid by the capillaries –> balance of starlings forces shifted towards net reabsorption of H2O from interstitial fluid = increasing capillary hydrostatic pressure
How long does it take for RBC to be fully replaced?
4-8 weeks
Post-haemorrhage where are large amounts of H2O absorbed from?
Non-vital areas such as the skin and gut
What is RAAS?
Renin - Angiotensin - Aldosterone System
When haemorrhage occurs what is the pathway to restore total body volume?
Decrease in renal perfusion pressure and increase in renal sympathetic stimulation > Renin release > Ang 2 release > aldosterone release > Na+ and water reabsorption = increase total body volume
Increase in Ang2 also leads to Vasoconstriction which increase MABP.
What is Renin regulated by?
NaCl
Renal Perfusion Pressure
Renal Sympathetic Innervation
What is blood flow regulated by?
Myogenic control (arterioles)
Neural control
Metabolic requirements
Is the regulation of blood flow the same for all organs?
No - some vascular beds are specialised
Where does the heart muscle gets its blood supply from?
Coronary circulation
What is the coronary system?
The circulation of blood in arteries and veins that supply blood to the heart tissue (myocardium).
What is a anastomosis?
A junction of vessels
Where are large vessels of the coronary system located?
Epicardial surface
What do the smaller vessels of the coronary system penetrate?
Penetrate into the myocardium
What is the first tissue to be perfused in systemic circulation?
The heart
What percentage of cardiac output goes to the heart?
5%
Where do coronary arteries arise from?
The aortic root
What structure enables the recoiling of the aorta during diastole and what effect does it have on coronary arteries?
Elastic tissue
Helps perfuse coronary arteries
Where does the right main coronary artery supply blood to?
predominantly the right side of the heart = RA, RV, and the inferior-posterior region of the LV
Where does the left anterior descending artery supply blood to?
Supplies blood to the anterior side of the LV
Where does the circumflex artery supply blood to?
The LA and posterior LV
Does skeletal muscle or cardiac muscle have a closer association with capillaries?
Cardiac muscle - every cardiomyocyte has several capillaries near.
Does every skeletal muscle cell have a capillary close?
No
Why does cardiac muscle require closer association to capillaries than skeletal muscle?
Because cardiac muscle has aerobic metabolism only (requiring oxygen always) whereas skeletal muscle have aerobic and anaerobic metabolism (doesn’t always require oxygen to function).
Therefore cardiac muscle has a greater demand for capillaries which enable gas exchange.
What is the difference between aerobic and anaerobic metabolism?
Aerobic metabolism occurs with oxygen.
Anaerobic metabolism occurs without oxygen.
Where do coronary veins drain deoxygenated blood into?
Directly into the right atrium
What does the coronary sinus do?
Collects blood from cardiac veins and empties into the right atrium
What is the first and shortest circulation around the body?
Coronary circulation
What percentage of myocardial perfusion occurs during diastole?
75%
Does the left or right side of the heart have a more powerful contraction and why?
Left - thicker wall - more cardiac muscle - greater force of contraction because more cross bridges
Does cardiac muscle have a large oxygen extraction reserve?
No - cardiac muscle has minimal O₂ extraction reserve:
The heart extracts a significant portion of oxygen from the blood, around 65-75%. This is much higher than other tissues, which typically extract about 25% of oxygen.
Because the heart already extracts most of the oxygen available, it has a minimal O₂ extraction reserve. This means that during increased demand (e.g., during exercise or stress), the heart has limited ability to extract more oxygen.
Can cardiac tissue operate under anaerobic conditions?
No
If blood flow increases does oxygen consumption increase?
Yes - supply meets demand
What is meant by transient regulation?
Temporary changes in order to maintain homeostasis during changing conditions
Why is the release of noradrenaline from SNS a transient response?
Not sustainable - the effect of SNS is overcome by metabolic auto-regulation
When noradrenaline is released by SNS as an extrinsic regulation of coronary blood flow what two receptors can it bind to and what does each receptor do?
A1-adrenergic receptors causes vasoconstriction and B2-adrenergic receptors causes increased HR and SV (vasodilate?)
What is the primary regulator of coronary flow?
Active hyperaemia (metabolic auto regulation)
What are the metabolic messengers that cause coronary vasodilation?
Nitric oxide
Adenosine
Hypoxia (state of low oxygen)
What causes vasodilation in endothelial cells?
Nitrix oxide
What percentage of cardiac output goes through pulmonary circulation?
100%
How does the pressure, resistance and compliance of pulmonary circulation compare to systemic circulation?
Pulmonary circulation has lower resistance and pressure but higher compliance.
Does CO effect pulmonary pressure?
Not much - it is able to accomodate increases in CO without increasing pressure.
This is important because we do not want to disrupt pulmonary circulation.
What does low pulmonary perfusion pressure prevent?
Prevents pulmonary capillary H2O loss
Thin capillary walls creates leakage of what?
Albumin
In pulmonary capillaries a net direction of reabsorption is important to prevent what?
Alveolar flooding (fluid building up in the lungs).
Compare the upper and lower regions of the lungs in relation to pulmonary blood flow:
Upper regions have lower hydrostatic pressure which results in vessels partially collapsing - have high resistance - this low blood flow.
Lower regions have high hydrostatic pressure meaning the vessels distend/swell - low resistance - thus high blood flow.
What is meant by redundancy in the lungs?
The fact that the upper regions of the lungs are at rest partially collapsed = meaning that when demand increases (e.g., exercise) the upper lobes are recruited
What is HPV?
Hypoxic pulmonary vasoconstriction = is a physiological mechanism in the lungs that optimizes gas exchange by directing blood flow away from poorly oxygenated (hypoxic) regions of the lungs to areas that are better oxygenated. This helps to match ventilation (airflow) with perfusion (blood flow) more efficiently.
What is required for optimal gas exchange?
Ventilation-perfusion matching
(blood being in the most ventilated areas of the lungs)
Does nitric oxide or endothelin-1 caused vasoconstriction?
endothelin-1
it contracts smooth muscle cells causing vasoconstriction therefore causing increased resistance and decreased blood flow.
What does an imbalance between constriction and dilation lead to?
Pulmonary hypertension
What size vessels are A1-adernoreceptors expressed on?
Large arteries at the start of pulmonary system (left and right pulmonary artery)
What size vessels are B2-adrenoreceptors expressed on?
Smaller resistance vessels
What is done to overcome hypoxic vasoconstriction that occurs when your in a hypoxic environment (altitude - less oxygen)?
Activation of the SNS which activates b2-adrenorecptors and caused vasodilation to counteract the natural vasoconstriction induced by reduced oxygen.
How does circulation between adults and a fetus differ?
Adults have series circulation whereas fetus has parallel circulation.
Where does a fetus get its oxygen from?
O2 from placenta (whereas an adult gets its oxygen from lungs).
Does a fetus use its lungs for gas exchange?
No - the lungs are not used for O2 and CO2 exchange in fetus and instead it relies on the placenta.
What is the placenta?
The placenta is an organ that forms in the endometrium during pregnancy.
It is connected to a developing fetus by the umbilical cord. Through the umbilical cord, the placenta provides oxygen and nutrients to a developing baby.
Does material and fetal blood mix?
No
How many umbilical arteries are there?
2
What brings maternal and fetal blood into close proximity?
Chorionic villi (placenta capillary system)
What organs do not have the same function in a fetus compared to born alive human?
Lungs (uptake of O2)
Kidney (waste removal)
Intestine (nutrient uptake)
= all functions are performed by the placenta
Is resistance high or low in the placenta?
Low resistance
What are the three bypasses in the fetus that redirect blood?
Foramen Ovale
Ductus Arteriosus
Ductus Venosus
What are the lungs of a fetus filled with?
fluid
What allows the fetus blood to bypass the lungs?
Foramen ovale - blood goes from RA directly into the LA bypassing the RV and the lungs
Is pulmonary arterial pressure higher in adult or fetus?
Fetus (extreme pulmonary vasoconstriction)
Is pulmonary vascular resistance higher in adult or fetus?
Fetus
Is pulmonary blood flow higher in fetus or adult?
Adult (100%) whereas only 10% CO in fetus.
What is the name of the artery that takes blood to the placenta?
Umbilical artery
What is the name of the vein that takes blood from the placenta to the liver?
Umbilical vein
What does the ductus arteriosus do?
Takes blood from pulmonary artery directly into the aorta (bypassing the lungs and the whole left side of the heart).
Where is the ductus arteriosus located?
After the carotid artery branches
What percentage of fetus CO goes though the pulmonary vascular shunts?
90%
Pulmonary vascular shunts includes foramen ovale and ductus arteriosus.
What does the ductus venosus do?
Takes oxygen rich blood from the umbilical vein directly into the inferior vena cava bypassing the liver
What percentage of blood uses the ducts venous bypass?
50-60%
Where does the maternal and fetal streams of blood merge?
Inferior Vena Cava (but they stay in separate laminar streams because of their slightly different properties = they do not mix).
What are the respective percentages of O2 in the IVC and SVC during fetal circulation?
IVC = inferior vena cava
SVC = superior vena cava
SVC = 40%
IVC = 67%
What percentage of O2 is in Umbilical venous blood compared to adult arterial blood?
70%-80% (98% in adult arterial blood)
Where is there a separation of oxygenated and deoxygenated blood within the fetal circulation?
IVC entering the RA
Why is there more O2 (67%) in the upper body of fetus compared to the lower body
(60%)?
because there are higher metabolic demands in the upper body of the fetus
Is oxygen supply in fetus or adult higher?
Adult
What organs of the fetus receive the most oxygenated blood?
Brain and heart because greatest metabolic demand during fetal development
What is the Eustachian Valve (EV)?
A tissue flap at the IVC/RA junction that directs blood from he IVC though the FO (foreman ovale - allowing blood to flow RA directly to LA)
What shunt means you bypass pulmonary circulation?
Foramen Ovale
The ductus arteriosus shunts blood from?
The pulmonary artery to the aorta
When a baby is born what organs take over the roles of the placenta?
Intestine now used for nutrient uptake
Kidney now used for waste removal
Lungs now used for uptake of O2
Is the Intestine, Kidney and Lung function instant when a baby is born?
yes
Why is the baby’s first cry significant?
It signifies that the lungs have been inflated and triggers the switch to adult circulation (intestine, kidney and lung take over from placenta).
When a newborns lungs are filled with air for the first time how does pulmonary pressure, resistance and flow change and why?
Pressure and reistance decrease and flow increases
Change because no more hypoxic vasoconstriction of the pulmonary vessels.
What causes the foramen ovale to close?
Reduction in pulmonary pressure decreases RA pressure
Loss of the placenta increases systemic vascular resistance and LA pressure
Leads to a switch of pressure gradient = systemic greater than pulmonary gradient into pulmonary circulation.
What drives newborn inhalation?
Build up of CO2 (due to metabolism continuing once placenta cut off)
What causes the ductus arteriosus to close?
Loss of placenta decrease prostaglandins causing the contraction of ductus arteriosus (within 72h)
What is the name of hormones released from the placenta?
prostaglandins
What causes closure of the ductus venous?
Loss of the placenta meaning that there is a decrease in umbilical sinus pressure narrowing the ductus and there is functional closure.
