Tissue Fluid Flashcards
What is the blood flow equation
What is poiselles law
Change in pressure / resistance
Flow = pie r cubed x change in pressure / (8 x viscosity x length)
What will longer vessels have and what does this mean
What do medications affect
What is the biggest effector of flow
A large surface area and a greater resistance.
Blood viscosity. Taking erythropoietin increases rbc count and gives thicker blood.
Pie x radius because a very small radius decrease will cause a massive flow decrease.
What part of the capillary has the highest resistance and why
What is another name for this place
Where is the best place to treat high bp
The arterioles have the highest resistance because the radius has decreased when it splits off from the artery. They are called resistance vessels.
The arterioles are a key place where blood pressure can be treated due to their high resistance.
Why can vessels collapse
What is the law of Laplace
They are elastic and not rigid.
This pressure from the surrounding tissue can collapse vessels is the blood pressure becomes too low.
For open vessels:
Transmural pressure = tension/ radius
Tension = p x r / wall width.
Aneurysm
Ballooning of the vessel due to a weak point in the vessel wall.
The smaller it is the greater pressure on the vessel wall.
The bigger it gets the thinner the wall gets and the more likely it is to burst.
What is compliance
Are veins or arteries more compliant
Vessel walls have a certain degree of give.
Compliance = change in volume times pressure
Veins are more compliant than arteries and store more blood and they are called capacitance vessels.
Which vessels are elastic
How does this help blood flow
Arteries and veins
When the left ventricle is in systole the vessels will stretch due to blood and during diastole the vessels will recoil.
This results in pulsatile continuous flow due to the continuous stretch and recoil. Windkessel effect.
In a rigid tube this would not happen.
Laminar and turbulent blood flow
Which flow is in alveolar vessels
In laminar flow the blood will travel in a straight line down the tube.
Turbulent is irregular with tiny whirlpool regions and hitting walls.
Turbulent because the rbcs are tumbling around and hitting the walls and this is needed for gas exchange.
What is bad about laminar flow
Why don’t cell live long
It can produce blood clots because of how orderly the blood will flow and won’t be mixed.
The blood cells don’t have a long lifespan due to all the turbulence.
What is the mean arteriolar pressure
Why does blood velocity decrease in arterioles
Where is the greatest amount of blood volume stored.
35mmHg
High resistance
Venous system
How much of the body’s blood is in capillaries
What is velocity like in capillaries
What are inactive capillaries
5%
Low it takes 2/3 seconds to pass through a whole capillary.
Inactive capillaries have their sphincters closed so no blood can enter
Pre capillary sphincters direct blood flow to or away from capillaries
Tissue fluid formation
Plasma in blood can leave capillaries and go into surrounding tissues and become interstitial fluid.
Filtration through cells is transcellular and between cells is paracellular.
The net fluid transfer forms tissue fluid.
Tissue fluid formation depends on
The hydrostatic pressure difference between the capillary and interstitial fluid.
The difference in colloid osmotic pressure. The more proteins in the blood the greater the pressure and the less fluid that will leak out of capillaries.
The balance between the two pressures determines the net tissue fluid.
High blood pressure causes more tissue fluid production
What is the capillary filtration coefficient
The ease of flow across the vessel wall. Depends on the size and frequency of holes in capillaries.
How is tissue fluid removed
By lymph
The general structure of blood vessels are….
What can the endothelium of arteries do
How many cells thick are capillaries and what is one of their properties
The same excluding capillaries.
The differences in them are the proportions of the various layers such as smooth muscle.
Produce nitric oxide.
One cell thick and they are leaky.
What is a vessels resting tension determined by.
Myogenic regulation
Metabolite regulation
The smooth muscle and elastic fibres working together.
The vessels can control their own diameter and if the vessel is stretched it evokes a contraction.
Substances such as o2 and co2 can cause blood vessel diameter changes too.
Extrinsic control of vessel diameter by sympathetic input
And how it varies in different parts of the body
Arteries have a tonic sympathetic adrenergic constrictor input.
Pre capillary vessels will vasodilate in response to ach
Cerebral areas have low sympathetic input because you never want to decrease blood flow to the brain so not many constrictors are needed.
Cutaneous areas have many constrictors to constrict when cold to preserve heat.
What are four ways of humoral extrinsic control
Adrenaline hormone causes vasoconstriction to the skin and viscera. Not needed for fight or flight.
Adrenaline causes vasodilation to skeletal muscle and the liver so muscles have plenty of oxygen and the liver can convert glycogen to glucose for energy.
Blood goes to the heart and skeletal muscle and there is greater venous return to the heart for a greater cardiac output.
Bradykinin is a vasodilator which reduced bp by accumulating in the blood. Can also cause a tickle cough.
Angiotensin 2 is a vasoconstrictor which increases bp. Renin in the kidney will act on precursors when blood pressure falls.
Local extrinsic control of vessel diameter
Prostaglandins are vasodilators used in hypoxic tissues.
Platelets release seratonin which will vasoconstrict vessels to stop the bleeding and help blood clots form.
An arm being pulled off hardly bleeds but cut would bleed loads. Vasoconstriction can occur when it is pulled off.
Histamine is released from mast cells and causes vasodilation. This happens during allergy infection.
Endothelium derived relaxing factor and how it works
How else is it produced
Nitric oxide is released by endothelium cells in vessels.
This vasodilates blood vessels by stimulating cGMP in muscle and causing relaxation
Nitroglycerin produces nitric oxide too and increases vasodilation and blood flow.
This can be taken to help angina.
Central control of vessels diameter
CNS centres receive diverse inputs from the rest of the body.
Emotional responses and visual cues are sent to the brain to alert it of exercise so it will vasodilate.
What are the three medullary centres
Which one slows the heart beat and why
Cardioexcitatory.Cardioinhibitory and vasomotor.
The carotid sinus is stretched and the Glossopharyngeal nerve will fire an impulse to the cardioinhibitory centre
It will travel though C1 and to the heart and slow down the heart beat causing vasodilation. PARA
How to medullary neurons affect the diameter of vessels.
And what happens if they are crushed.
They respond to changes in pH and oxygen and co2.
And can cause changes in diameter.
Raised inter cranial pressure due to swelling will cause a fall in blood return to the brain.
This will lead to brachycardia and vasoconstriction because the medullary neurons will be crushed and they can’t respond properly.
The risk of death is high and they have to be checked for low blood pressure.
Peripheral proprioceptors.
What they do
What are long and short term regulators of bp
Found in carotid arch and sinus and are baroreceptors that detect high pressure.
They will cause an increase in vagal activity and a decrease in cardiac output and stroke volume and blood pressure.
This is short term bp regulation.
Long term is done by the kidneys.
What does the hypothalamus do
Thermoregulation
Vasodilation and sweating when warm.
Vasoconstriction and shivering when cold.
Medial preoptic area for sexual responses.
