topic.9. powerpoint.9.3 Flashcards
(35 cards)
Describe blood flow using these terms arteries, arterioles, veins, venules and capillaries
They are all blood vessels that make up the circulatory system.
Arteries-arterioles-capillaries-venules-veins
capillaries: exchange material with interstitial fluid
Describe the 3 layers of the walls of arteries
inner: endothelial cells
middle: smooth muscle
outer: elastic fibers; made up of elastin, which is a protein found in connective tissue.
What controls the amount of flow and pressure of blood that enters capillaries?
arterioles
T/F
1) Arteries have low resistance to flow
2)Arteries have thick walls
True because they have large diameters
True: to withstand high pressure
Explain why the pressure never drops to zero in arteries?
A process called elasticity:
Blood flows out from the heart, stretches the arteries, and stores PE. PE is released when ventricles relax, causing the artery wall to recoil. This rebounding action helps maintain blood flow even while the ventricle is relaxing, preventing the pressure from dropping to zero between heartbeats.
What is the difference in structure between arteries and capillaries?
Capillaries unlike arteries have…
-thin wall, single endothelial layer
-no smooth muscle
-large SA
How is contraction controlled in capillaries and arterioles?
arterioles: smooth muscle
-low O2 and high CO2 in tissue, smooth muscle dilates, increasing diameter of
arterioles and allowing more blood flow
Capillaries: precapillary sphincters
is a band of smooth muscle that can contract and close the branches off to blood flow
Capillaries involve an exchange of material with interstitial fluid. Having said so, do we expect a faster or slower rate of blood flow than arteries and veins?
Slower, maximizes time for exchange of material
Two major mechanisms drive exchange of substances
We are talking about capillaries:
-bulk flow: movement of material in/out of capillaries according to pressure differences.
-diffusion along concentration gradient
O2, CO2 can passively move across the walls of capillaries based on their concentration differences.
Capillaries have ___ and ___ that allow water-soluble substances to diffuse from capillaries to interstitial fluid
-fused vesicle channels (membrane-bound sacs)
-intercellular clefts (b/n endothelial cells 1& 2)
How does hydrostatic pressure relate to capillaries?
Hydrostatic pressure is the pressure of the blood, when it’s higher than interstitial fluid pressure at the point where arterioles meet capillaries(ateriole end of capillaries), forces water and small solutes into the venous end of capillaries
The fluids leave the capillaries at the arterial end because…
the net filtration pressure of the blood is higher at the arterial end than it is at the venous end.
The fluids reenter the capillaries at the venous end because…
the net filtration pressure of the interstitial fluid is higher than hydrostaic pressure at the venous end than it is at the arterial end.
***fluid constantly leaking out and being pulled back in, thus helping to
distribute fluid
Starling forces
net filtration pressure affect the distribution of fluid across the capillary, because fluid constantly leaking out and being pulled back in, thus helping to
distribute fluid
is interstitial fluid considered tissue?
yes
Whether fluid will move out of or into a capillary depends on
- net filtration pressure, hydrostatic pressure of blood in capillaries minus hydrostatic pressure of interstitial fluid outside capillaries
2)oncotic pressure aka osmotic pressure
solutes are generally the same in __ and __
tissue(interstitual fluid) and plasma(in capillaries)
___is greater than protein
concentration of interstitial fluid
protein concentration of plasma;
because plasma proteins are too large to pass through the pores in the capillary walls, restricting their filtration into the interstitial fluid. As a result, the protein concentration in the plasma remains higher than in the interstitial fluid.
What is colloid osmotic pressure?
colloid osmotic pressure is the pressure that wants to draw interstitial fluid out of the capillaries.
mechanism: A higher concentration of plasma proteins in blood plasma creates a higher osmotic pressure.
What is oncotic pressure?
is the pressure that wants to draw interstitial fluid into the capillary through osmosis.
Colloid osmotic pressure is greater in the ___than in the___
plasma, interstitial fluid
What is the equation to calculate distribution of fluid across capillary wall?
(Pc+πi)- (Pi+πp)
fluid out -fluid in
Pc-hydrostatic pressure in capillary
πi: colloid osmotic pressure of interstitial fluid
Pi: hydrostaic pressure of interstiual fluid
πp: colloid osmotic pressure of blood plasma
In this equation, what can we expect to always be zero?
(Pc+πi)- (Pi+πp)
πi: colloid osmotic pressure of interstitial fluid
Because there are no plasma proteins in interstitial fluid and thus it creates no pressure
Lymphatic system
Key component of the immune system
-Extensive network of vessels that collects excess interstitial fluid (becomes lymph), filters and returns it to the venous blood
