lecture 7: chapter 16 Flashcards
what does the term microcirculation refer to
functions of the capillaries and the neighbouring lymphatic vessels
what percentage of blood is present in the capillaries at any given time
5%
TRUE or false; since there is only 5% of blood in circulation in capillaries it is not important
false, it is important for all gaseous exchanges
what is good about having 3-10 billion capillaries
there is a larger surface area which allows them to perform the function of solute and fluid exchange
=a lot of places to move places around
what are the 4 functions of the microcirculation
Ensures constant plasma and interstitial fluid communication
Accelerates distribution of nutrients, and hormones, and dissolves gases through tissues
Transports insoluble lipids and tissue proteins that cannot cross capillary walls
Flushes bacterial toxins and chemicals to immune system tissues
what is the capillary bed/plexus
it connects 1 arteriole to 1 venule
are vascular anastomoses more common in veins or arteries?
veins
what do arterial anastomoses provide
alternate pathways (collateral channels) for blood to reach a body region
explain how arterial anastomoses provide alternate channels
If one branch is blocked, the collateral channel can supply the area with adequate blood supply
what is an example of arteriovenous anastomoses
thorough fare channels
where are vascular anastomose common
joints, in skin, abdominal organs, brain, heart
what is the trajectory of blood in microcirculation
arteriole
meta arteriole
capillaries
venules
what is the composition of arterioles
one mono layer or endothelial cells and 1 layer of smooth muscle
what is the composition of meta arteriole
one mono layer of endothelial cells with occasional smooth muscle
what is the composition of capillaries
1 layer of endothelial with no smooth muscle cells at all
what is the composition of venules
1 mono layer of endothelial and some smooth muscle
where is the pre capillary sphincter
present at the junction where the capillaries arises from the meta arteriole
what to sphincters respond to
local metabolytes
nerological signals
what is the function of the sphincters
regulate flow direction into true capillaries or through channels
guard the entrance to each capillary
what allows blood flow to be changed by sphincters
vasomotion-contraction and relation cycle of capillary sphincters
what causes the blood flow in capillary beds to constantly change routes
sphincters
what is blood flow regulated by and what does that mean
regulated by vasomotor nerves and local chemical condition, so it can either bypass or blood the capillaries
true or false: blood always floods and flows through the enter capillary bed
no, it can be redirected dependant on tissue needs
what are the 3 types of capillaries
continuous
fenestrated
sinusoidal
where are continuous capillaries usually found
in skin and muscles
true or false: continuous capillaries are not efficient at moving substances in and out because the endothelial cells are so close together
true
what is characteristic of endothelial cells in continuous capillaries
the endothelial cells are so close so they provide an uninterrupted lining
what are adjacent cells held together with
tight junctions
what allows the passage of fluids in continuous capillaries
intercellular clefts
where is an example of continuous capillaries of the brain and why its used there
in the brain
there are tight junctions completely around the endothelium
constitute the blood-brain barrier to make a protective against toxins
where are fenestrated capillaries found
where there is active capillary absorptions or filtrate formation occurs
(ex: small intestine, endocrine glands, kidneys
explain the endothelium in fenestrate capillaries
riddled with pores (fenestrations)
which type of capillaries have the greatest permeability to solutes and fluids
fenestrate capillaires
true or false: since fenestrated capillaries have pores they don’t have intercellular clefts
false, they do have
what are sinusoid (discontinuous) capillaries
highly modified, leaky, fenestrated capillaries with large lumens
where are sinusoid (discontinuous) capillaries
found in the liver, bone marrow, lymphoid tissue and some endocrine organs
which capillaries have the biggest pores
discontinuous
what is the function of discontinuous capillaries
allow large molecules (proteins and blood cells) to pass between the blood and surrounding tissues
true or false: has blood passes from continuous to discontinuous is becomes more sluggish/less laminar
true
what are capillaries composed of
unicellular layer of endothelial cells surrounded by basement membrane
how does solute and water move across capillary wall
intercellular cleft (space between cells) or by plasmalemma vesicles.
what is the diameter of capillaries
4-9 microns
what is the main passage of substances through capillary to tissue
through clefts
what are the smallest blood vessels
capillaries (allow only 1 single RBC to pass at a time)
what is the width of capillary intercellular slit pores?
6-7 nanometers
what does the The permeability of the capillary pores for different substances varies according to
their molecular diameters.
true or false and why: The capillaries in different tissues have no differences in their permeabilities
The capillaries in different tissues have extreme differences in their permeabilities
because of fenestrations
give an example of how different tissues have different permeability
liver takes large molecules so their capillaries will have a higher fenestration
how do water, ions, and small molecules (glucose) get diffuse
diffuse between adjacent endothelial cells
or through fenestrated capillaries
how do some ions like NA+, K+ ca2+ and Cl- diffuse through
though channels in cell membranes
how do large, water soluble compounds pass through/diffuse
pass through fenestrated capillaries (and occasionally through endothelial cells)
how do lipids and lipid soluble materials (o2 and co2) diffuse through
through endothelial cell membranes
how to plasma proteins diffuse through
cross endothelial lining in sinusoids (really large pores)
the larger the side the harder/easier to permeate
harder to permeate
true or false: since hemoglobin and albumin have the same molecular weight, they have the same permeability
false, albumin has a harder time permeating
why is albumin harder to permeate than hemoglobin?
Gibbs Donnan effect
albumin have a greater osmotic force
explain why albumin has a greater osmotic force
albumin has a negative charge (attracts sodium ions)
albumin binds a small number of chloride ions (attracts more sodium ions)
explain why albumin has a hard time permeating
because of its greater osmotic force is pulls liquid towards it
Most important means by which substances are transferred between plasma and interstitial fluid is by what
diffusion
since salt has a high osmotic force what does that do for diffusion
it attracts fluid in the capillary (pulls water out)
what is the space between cells called
interstitium
what is the fluid in the interstitium called
interstitial fluid
what is the consistency of interstitial fluid
gel
what are the two major types of solid structures in the interstitium called
collagen fibers and proteoglycan filaments (coiled molecules composed of hyaluronic acid)
true or false: there is very little free fluid under normal conditions in interstitium
true
the collagen bundle fibers in the interstitium provide what
structure
explain the capillary exchange at the arterial end of the capillary
fluid moves OUT of the capillary
into the itnersticial fluid
explain capillary exchange at the venous end of capillary
fluid moves INTO capilary
OUT OF THE INTERSTICUAL FLUID
what are the 2 hydrostatic forces
capillary hydrostatic pressure
interstitial fluid hydrostatic pressure
where is capillary hydrostatic pressure higher and why
higher at the arteriolar end than venule
*because of ressitance)
where does capillary hydrostatic pressure force fluid
forces fluid outward through the capillary membrane
pushes fluid from cap to interstitium
Normally interstitial fluid hydrostatic pressure is negative or positive
negative
what is the negative pressure in the interstitual fluid hydrostrate pressure caused by
pumping action of lymphatics
the fluid is constantly drained and leaking out of interstitium which helps push more fluid in
where does interstitial fluid hydrostatic pressure force fluid
usually pushes fluid from cap to interstitium (except for when pressure is positive)
when interstitial fluid pressure is positive what happens
it opposes filtration
capillary hydrostatic pressure is good for absorption or filtration
filtration
interstitial fluid hydrostatic pressure is good for filtration or absorption
reabsorption (when pos)
what are the osmotic forces
plasma colloid osmotic pressure
interstitial fluid osmotic pressure
what is another name for plasma colloid osmotic pressure
plasma oncotic pressure
what is the major determinants of oncotic pressure
plasma proteins
what is the most abundant plasma protein and what does it generate
albumin, generates 70% of oncotic pressure
plasma colloid osmotic pressure/plasma oncotic pressure tends to cause what
IN AWARD (INTO CAPILLARY) MOVEMENT OF FLUID
WHAT IS another name for interstitial fluid osmotic pressure
interstitial fluid oncotic pressure
what is interstitial fluid osmotic pressure caused by
small amount of plasma proteins that leak into the interstitial space
interstitial fluid osmotic pressure tends to cause inward or outward movement of fluid
outward movement
plasma colloid osmotic pressure opposes what and what does that cause
opposes filtration, causing osmosis of water inward through the membrane
interstitial fluid colloid pressure promotes what and why
promotes filtration by causing osmosis of fluid outward through membrane
what is filtration
The sum of the hydrostatic and osmotic forces favours the net movement of water from the capillary to the interstitial space
what is reabsorption
The sum of the hydrostatic and osmotic forces favors the net movement of water from the interstitial space to the capillary
what is the filtration rate
the net filtration pressure (NFP) multiplied by the coefficent filtration
what is the NNFP format
NFP= PC - Pic - Pip + Piif
what is the filtration coefficent
Kf
product of surfeace area times the hydraulic conductiveity of memberan
know the determinants of net fluid movement across capillaries
diagram of capillary and 4 pressures
what is the starling equilibrium
The Starling equation describes the net flow of fluid across a semipermeable membrane. It describes the balance between capillary pressure, interstitial pressure, and osmotic pressure.
what is the normal capillary hydrostatic pressure
approx 17 mmHg
what is the normal interstitial fluid pressure in most tissues
-3
what type of organs have positive interstitial pressures
encapsulated organs
what is the negative interstitial fluid pressure caused by
pumping of lymphatic system
what is colloid osmotic pressure caused by
large proteins
what increases the colloid osmotic effect of proteins
presence of negative ions on proteins (Gibbs Donnan)
what is the reflection coefficient of capillaries
it quantitates the amount of protein that is reflected away from capillary membrane
what does a reflection coefficient of 1 mean
all proteins are reflected and none pass through pores
what does a reflection coefficient of 0 mean
it is permeable to all proteins
true or false: physiologically you can never have a coefficient of 1 or 0
true
go over the 3 slides about forces causing filtration, reabsorption etc
what is the net filtration pressure and what does that cause
0.3 mmHG which causes a net filtration rate of 2 ml/min for the entire body
(this means we are constantly moving more fluid from capillary to interstitium than opposite)
even though there is a net outward force (moving fluid from cap to interstitium) do the vessels swell
no because of the draining from lymphatic systems
where is the transition point
it is a point between filtration and reabsorption where there is equilibrium
is the transition point closer to venous end or arterial end
closer to venous
true or false: capillaries filter more than they reabsorb
true
is the transition point always the same? give example
no it changes depending on the needs of the tissue (whether they need more filtration or reabsorption)
ex: in skeletal we need a lot of filtration so it will, be closed to venous side
during filtration, are we only moving fluid?
no also moving oxygen, glucose etc
during reabsorption are we only moving fluid?
no also waste products
