Test 5 🤠 Flashcards
What are 2 major functions of the cardiovascular system?
-Transporting nutrients to tissues
-Transporting waste product away from tissue
How does the CV get messages to other parts of the body?
Transports hormones for signaling
Which system is responsible for putting hormones into the vascular system?
Endocrine System–CV system then delivers the hormones to where they needs to go
What is a typical measurement for volume?
L, mL, ,Gal
What is velocity measuring?
Units of distance/ Time
m/s or km/hr
What does pressure measure?
How much force do you need to drive a column of Hg up 1mm
How is pressure measured in CV system?
mmHg
How is pressure measured in the lungs?
cmH2O
What does cross-sectional area measure?
Area within the center of a tube
internal diameter of a cylinder
What is surface area?
Walls of a cylander
Would a large cylinder have a lot or a little surface area?
Large cylinder has lots of surface area
What are the units for blood flow?
Volume/ Time
-mL/min
-L/min
-mL/sec
What are 3 of the important determinants of blood flow discussed in class?
-Vascular resistance
-Vasular conductance
-Poiseulle’s Law
What happens to blood flow with increased vascular resistance at a tissue bed?
More difficult for blood to flow
Do we want high vascular resistance or low vascular resistance?
Lower vascular resistance to allow for greater blood flow
What does vascular resistance determine in the body?
Blood pressure–how much pressure we have
What would you expect the pressure to be between the heart and an area of high resistance distal?
High pressure–measuring upstream of constricted spot is higher pressure
What would the pressure be below a high pressure constricted spot in a vessel?
Lower pressure–downstream of constriction is lower pressure
What is pressure used for in the body?
Used to drive flow
What is an example of the body using pressure to drive flow?
Brain uses CPP to drive brain blood flow–changes based on vascular resistance in the body
What is vascular conductance?
How easy it is to drive some type of flow through a conduit
Inverse of vascular resistance
If a vessel is easy to drive blood flow through, what would the conductance be?
High vascular conductance
If a vessel is difficult to drive blood flow through, what is the conductance?
Low vascular conductance
What is Poiseulle’s Law?
Includes other variables to make sense of vascular resistance and pressures
Where is most of the blood in our body stored?
The veins
What is adequate cardiac output dependent on?
A system where blood in the veins can make it back to the heart
Which organ controls how much fluid is in our body?
The kidney
Why is fluid in the body important?
Fluid in the body is directly related to how much blood we have
What happens to blood volume if the kidney holds on to more fluid?
Blood volume increases
What are 2 important functions of the kidney?
-Important controller of overall volume in CV system
-Filter
What are 2 different ways the CV system blood vessels can be constructed?
-System in Series
-System in Parallel
How are system in series set up?
Connect vessels from end to end to make one long tube
What happens to resistance with system in series?
Resistance in the 2 individual tubes doubles when they are stacked together length wise
Why does resistance increase when vessels are stacked length wise?
Harder to pump blood through a longer tube
How are systems in parallel set up?
increased number tubes of the same size, length, and resistance
creates more pathways for blood to flow
What happens to resistance in systems in parallel?
Blood has options on where to flow–increased pathways lowers resistance
What type of system of blood vessels is in the kidney?
Has both system in series and system in parallel
What is the formula for series system?
Rtotal= R1 + R2 + R3
What is the formula for parallel system?
1/R total= (1/R1) + (1/R2) + (1/R3)
What is the internal diameter of the aorta?
2.5 cm
How does the cross sectional area of the aorta compare to small arteries in the body?
Other arteries have small internal diameter–but there are more of them in the body
total cross sectional diameter of all the arteries is larger than aorta because there are more
What is the cross sectional area of small arteries?
20cm^2
How does total cross sectional area of capillaries compare to arteries?
More capillaries than arteries, so cross sectional area of capillaries is bigger than arteries
What is the total cross sectional area of capillaries?
2500 cm^2
What is blood flow speed dependent on?
Cross sectional area of specific spot in the circulation
What is the velocity of blood flow in a small cross sectional area?
Decreased path for blood to flow through
Blood will flow quickly if only one small tube for the blood to move through
What happens to total cross sectional area as blood travels further from the heart?
cross sectional area increases
What happens to blood velocity in areas with increase cross sectional area?
Velocity is lower because there are so many options for where the blood can flow
Why is blood flow through the capillaries slow if the cross sectional area of a single capillary is small?
Blood flow is slower because there are so many capillaries the blood has many different routes to take
What is the pressure like in the left atrium?
Low pressure
What is the pressure in the left ventricle and aorta?
High pressure
What happens to pressure with increased distance from the heart?
Further from the heart pressure will decrease
At what part in the circulatory system do we see a decrease in pressure?
Large arteries pressure is the same as aorta
Small arteries–pressure starts to decrease a little
further decrease pressure in arterioles
Blood has ___________ pressure as it flows through a conduit that has _____________ resistance.
reduced , high
What are the high resistance blood vessels in systemic circulation?
Small arteries and arterioles
What part of the vasculature does phenylephrine work on?
squeezes small arteries and arterioles
What happens to pressure proximal to the high resistance vessel when phenylephrine is given?
Pressure increases
What happens to pressure distal to the high resistance vessel when phenylephrine is given?
pressure is lower
What vessels determine blood pressure?
Small arteries and arterioles–resistance vessels
What is resistance like in the veins?
Not very much resistance
Thin walled and compliant
What is the pressure gradient between the end of capillaries and the right atrium?
10mmHG (very small amount)
What is needed to control blood flow?
Pressure
How does the kidney manage blood/fluid flow?
The kidney adjusts vascular resistance
What dictates blood flow?
Metabolic rate of the tissue
What needs to happen in the body if a tissue has a high metabolic rate?
Increase blood flow/volume to the tissue
What is laminar flow?
blood in the middle of the vessel flows faster than blood closer to the walls
Is laminar flow a good thing?
Yes, it is orderly flow–efficient and doesnt cause problems
Why does blood flow slow down the closer it is to the walls in laminar flow?
The walls of the vessel are resistance to the flow
What is it called when blood flow is disorderly?
Turbulent flow
What is happening with turbulent flow?
-Not efficient blood flow
-Movement of blood in all different direction
-blood runs into the walls of the vessel and causes remodeling over time
Why is turbulent flow so bad?
Blood runs into the walls of the vessel and causes remodeling over time–things will get stuck in the wall (CHO, Ca2+)
What initially causes turbulent flow?
Clot or blockage in the vessel
-Narrow opening for blood to go through–blood will shoot through opening (high velocity) and spray the other side of the obstruction
What is the Reynolds equation used for?
Predicts the odds that turbulent flow is going to occur
What are the “2 parts” of the heart circulatory system?
Right heart and left heart
How is each part of the heart circulatory system set up?
In parallel–lots of choices where to go (brain, coronaries, GI, kidney)
How much cardiac output goes to the kidneys?
22% (1100mL/min)
Why does the kidney require so much perfusion?
Kidneys have much more perfusion than they actually need–use extra blood flow to work as efficient filter
Does kidney blood flow correlate with metabolism?
only partially, only place in the body where flow doesnt correspond to metabolism
What can ultrasound of an artery measure?
blood flow
What is the resistance portion of ohms law in regards to electrical stuff?
Cell wall
How is Ohms law used in the CV system?
Swap some of the variable
delta BP= blood flow x vascular resistance
What does Delta Pressure measure?
The distance between one side of the tube and the other
What is flow represented by small delta P?
Less flow
What is the flow represented by a large delta P?
more flow
What small change can result in a large change in blood flow?
Blood vessel diameter
What happens to blood flow when a vessel relaxes a little bit?
Can account for a big increase in blood flow through the vessel
What happens to blood flow when a vessel constricts a little bit?
Can reduce flow by a lot
What is the formula for vascular resistance?
R= Delta P / Force
What is vascular resistance dependent on?
Delta P and blood flow of the organ
What is the BP in the renal artery?
100mmHg at abdominal aorta
What is BP in the renal vein?
0 (probably more like 10mmHg)
How to calculate blood flow in the kidney:
20% cardiac output–1100mL/min
What are capillary Starling Forces used for?
4 forces that determine whether fluid will move out of the blood into the interstitial space OR into the blood
Why is blood pressure low in the veins?
Veins are on the other side of the high vascular resistance
What happens to blood pressure as it move through an area of high resistance?
Blood pressure is reduced as the blood flows further through the area of resistance
What is systemic blood pressure usually measuring?
Blood pressure in the large arteries proximal to resistance
What does CVP measure?
Distal pressure
Where do we measure pressure in the kidneys?
Proximal and distal pressures
What causes the drop in pressure from large arteries to capillaries?
High vascular resistance as we move away from the heart
Where does a pressor work in the vasculature?
Constricts arterioles and drives up blood pressure
Which arteries are able to contract and why?
Smaller arteries can contract and relax–large arteries usually dont contract
What is filtration?
Movement of fluid out of the capillary
What part of the capillary has forces that factor filtration?
Arteriole end
What is reabsorption?
Fluid absorbed by the capillary–fluid moved back into the capillary
Where are the forces that favor reabsorption in the capillary?
At the venous end
How many capillaries do we have in our body?
10+ billion capillaries
How much surface area is made up of capillaries within the body?
500-700 square meters of surface area
What is the primary function of capillaries in the periphery?
Primary place for nutrient exchange and waste product collection in the circulation
What controls the blood flow through the capillaries?
Controlled by the arterioles
What allows for arterioles to regulate blood flow?
Smooth muscle cells packed into arterioles allows regulation of blood flow to tissues downstream of arterioles
How many layers of smooth muscle is there is small arteries and arterioles?
4 layers of thick smooth muscle
How do the capillaries function in gas exchange?
Offload O2 and pick up CO2 to carry to the lungs for removal
What is the total cross sectional area of the aorta?
4.5cm^2
What is the velocity like through the aorta?
High velocity–especially during systole (ejection)
How many vena cava?
2–inferior and superior
How do the vena cava internal openings compare to the aorta?
Each vena cavae has a slightly larger opening than the aorta
What is the internal diameter for each vena cava?
3cm
What is the cross sectional area for the vena cava?
multiply x2 since there are 2 vena cava it increases total cross sectional area that blood moves through
18cm^2
What is the velocity in the vena cava compared to aorta?
Lower velocity in both vena cavae since there is more cross sectional area for the blood to move through when returning to right atrium
What is the internal diameter of arterioles?
30mcg–very small
What composes arteriole walls?
Thick walls from lot of smooth muscle
high wall thickness to internal diameter ratio
What are capillary walls composed of?
very thin–one cell layer thick of endothelial cells
Where in the body are endothelial cells?
Inner layer of all heart chambers
One layer of endothelial cells in veins and arteries
Why cant capillaries contract?
No smooth muscle
Why is lack of smooth muscle and thin walls good in the capillaries?
Less to get in the way for nutrient exchange (inward or outward)
What is the cross sectional area of the capillaries?
4500cm^2
Order these vessels from lowest velocity to highest velocity: veins, aorta, capillaries
Capillaries, veins, aorta
What does delta P measure?
Tendency of fluid to move through a capillary
What is normal BP at arteriole end of systemic capillary?
30mmHg
What is normal BP at the venous end of the systemic capillary?
10mmHg
What is average aortic BP?
100mmHg
Why is it important to have a balanced system of filtration and reabsorption?
Prevents too much or too little fluid in the tissue
What are the forces that determine whether fluid will move out of the blood into the interstitial space or into the blood?
Capillary Starling Forces
What does “P” stand for?
Pressure
What is Pcap?
blood pressure in the capillary
Physical fluid pressure (hydraulic pressure) that exists in the blood in the capillary
What is Pcap at arteriole and venous end?
Arteriole: 30mmHg
venous: 10mmHg
What does Pcap determine?
How much fluid is forced outward through the capillary membrane
What are capillaries fairly permeable to?
Only one cell layer thick, permeable to water and small ions
What happens to resistance is there are forces in the capillary that are pushing fluid out of the capillary?
There will not be much resistance in the capillary beds
What is P(isf)?
Pressure in the ISF–outside the capillary and outside the cells
What is a normal ISF pressure?
-3mmHg
What is ISF pressure negative?
lymphatics operate to pull excess fluid out of the interstitium like a vacuum which pulls fluid from the capillary
What happens to reabsorption when lymphatics are pulling excess fluid out of interstitium?
more fluid movement out of the capillaries–Reduces amount of reabsorption at the venular end of the capillary
What does it mean if P(isf) is a positive number?
force fluid inward through capillary membrane
impairs filtration filtration at the arteriole end and promotes reabsorption at the venous end
What happens with a high positive pressure in the ISF?
could either oppose filtration or promote reabsorption if high enough
What would happen with fluid movement if P(isf) is +10mmHg?
Oppose fluid going into the capillary–reduce filtration and promote more reabsorption
How does fluid move when P(isf) is negative?
Forces fluid outward
What does p(cap) stand for?
Plasma oncotic pressure or Capillary colloid plasma oncotic pressure
How does fluid move with a normal p(cap)?
Causes osmosis of fluid inward through capillary membrane
How does p(cap) keep fluid inside the capillary?
All colloids dissolved in blood will hold fluid inside the capillary
What is the ideal plasma oncotic pressure in peripheral capillary for a healthy person?
28mmHg
What are the 3 main plasma proteins that make up plasma oncotic pressure?
Albumin
Globulins
Fibrinogen
What are globulins?
Antibodies, things generated by the immune system
What is fibrinogen?
Coagulation factor
What could happen that would lower plasma oncotic pressure?
Hemorrhage
What happens when plasma oncotic pressure is low?
difficult to keep the fluid within the CV system
lacking the colloids needed to keep the fluid there
What are examples of conditions that would cause plasma oncotic pressure to be low?
Hemorrhage
Capillaries become porous
What happens if the walls of the capillaries become more porous than normal?
colloid proteins can escape through the openings
once wall is permeable to proteins, the proteins not longer have as much osmotic pressure associated with them
What is osmotic pressure dependent on?
Semipermeable membrane where fluid can move but some dissolved substances cant
Is osmotic pressure affected if the capillary is porous but the proteins are still inside the capillary?
Yes. it creates a problem even before the colloids start leaking out
Even if protein are still in there capillary, they do not have osmotic pressure when the walls of the capillary are porous
What condition would cause porous capillaries?
Sepsis
If a patient is septic, why doesnt albumin solve the problem by replacing plasma proteins that are leaking out?
Primary issue is that the protein doesnt matter if the cell wall is already permeable to the proteins
secondary issue is the proteins leaking out
What does p(isf) stand for?
Interstitial fluid colloid osmotic pressure
What is p(isf) measuring?
Amount of proteins in the ISF
where are most proteins in the ISF?
Proteins in ISF are usually a matrix protein between cells
What are 2 common protein found in the ISF?
Proteoglycan Filaments
Hyaluronic Acid
What are Proteoglycan filaments?
large string of proteins in interstitial space
Why does hyaluronic acid stay in the interstitial space?
Large protein that cant move into capillary easily
How does osmotic pressure in ISF compare to capillary plasma pressure?
not as many proteins in ISF as in the CV system
What is a normal ISF osmotic pressure?
8mmHg
How does fluid move in response to ISF osmotic pressure?
causes a little movement of fluid outward through capillary membrane to ISF–usually outweighed by plasma oncotic pressure
What could cause elevated ISF colloid pressure?
Could be due to damage causing cells to burst (crush injury, bacterial infections)
or increased permeability in the capillaries
What is happening at the tissue with elevated ISF colloid pressure?
Causes swelling from all the proteins that were in the cell that are now in the environment
proteins in environment pull more fluid out from the capillary into the tissues
If there was increased permeability to the capillaries and proteins leak into ISF, what happens once the issue is fixed and the capillaries are intact again?
Swelling in the tissue stays even after the capillary is fixed–proteins still sitting in ISF with no way back into CV system
How can proteins get back into the plasma?
Lymphatics can slowly pick up the proteins–not specialized to do this so it takes a long time
What are lymphatics dependent on to function normally?
Lymphatics increase rate of action when skeletal muscle is active
What is the normal function of the lymphatic system?
specialized to get rid of excess fluid in ISF
lymphatics can increase work they are doing 20-40X normal is the body is working properly
Where are lymphatic capillaries located?
Near all tissues and capillaries
lymphatic system is a big circulatory system in the body–important to know topography of lymphatic circulatory system before surgery
What is K(f)?
Capillary filtration coefficient
What does K(f) measure?
capacity of the capillary membrane to filter water
measurement of capillary permeability and takes into account surface area
How does movement within a capillary change if the capillary expands (increases surface area)?
More surface area for movement which increases movement
What is the rate of fluid filtration in a tissue determined by?
The size of pores in each capillary and the
number of capillaries
What system is responsible for collecting excess filtration?
Lymphatic circulation system
What are the areas of collection in lymphatic system?
Lymph nodes
Why drives venous blood flow?
Skeletal muscle activation from moving around
What drives lymphatic circulation?
Skeletal muscle activation from moving around
Why are venous and lymphatic systems so reliant on skeletal muscle to function?
Venous and lymphatic system is a one way valve
need skeletal muscle compressing and relaxing against them to get fluid moving in one direction
Where does lymphatic system return fluid to?
Back to CV system at the top of the chest (lymphatic ducts)
Where are the lymphatic ducts located and what is their purpose?
Located at the top of the thorax connect with large veins
entry point for lymphatic fluid to be returned to CV system
What speed does lymphatic flow normally flow at?
Flow is normally low–with increased activity lymphatic flow can increase up to 20X if needed
What happens to lymphatic system if someone if bed bound?
Not using skeletal muscles that are required for lymphatic to work at optimum level
excess fluid isnt being recollected as quickly as it should be
What happens to someone in regards to lymphatic system if they are in a hospital bed not walking around?
Fluid gets stuck in lower extremities
What can be used to simulate movement in the legs when someone is in the hospital bed bound?
SCDs–help with venous return, prevent clots, and important for lymphatic movement
What is net filtration pressure (NFP)?
Sum of the Starling Forces
What does it mean if net filtration pressure is positive?
There will be a net fluid filtration across the capillary (favors movement out of the capillary)
How is NFP calculated?
Add up components that favor movement out of the capillary starting at either arteriole or venous
Minus forces that is opposing filtration
What would NFP be at the arteriolar end of the capillary?
(30+3+8)-(28)= +13mmHg
Favor filtration
What does it mean if net filtration pressure is negative?
Net fluid absorption from the interstitial space into the capillaries
What would NFP be at the venous end of the capillary?
(10+3+8)-(28)= -7mmHg
Favors reabsorption (fluid moving into the capillary)
Why are the number of filtration and reabsorption in a capillary not equal/opposite to balance out?
Ends up being excess filtration compared to reabsorption
What happens to the excess filtration?
Extra fluid is scavenged by the lymphatic system
What forces in the capillary favor filtration?
arteriole/venous BP
ISF hydrostatic pressure
ISF oncotic pressure
What forces in the capillary favor reabsorption?
Plasma oncotic pressure
What would happen to tissues if lymphatic system wasnt working?
Excess fluid build up in the tissues from the excess filtration happening
What is net capillary pressure definition and value?
Average Capillary blood pressure in systemic circulation
17.3mmHg
Why is net capillary pressure not 20mmHg (directly in between 10 and 30)?
A lot of capillaries get larger in width when moving from front to end of the capillary
What is the typical net filtration pressure in the individual capillary?
0.3-there are so many capillaries it is highly dependent on getting excess fluid scavenged from ISF
What are some things that capillaries are permeable to?
Water
Sodium Chloride
What is the permeability of NaCl?
0.96
What is the specialized capillary bed that doesnt allow NaCl through?
Blood brain barrier
What type of molecules have a difficult time getting through the capillary wall?
Larger molecules (albumin, glucose)
What is the capillary permeability of albumin?
albumin is very large so low permeability: 0.001
What is the molecular weight of albumin?
69,000 (very large)
What is the capillary permeability of glucose?
0.6
Lower permeability than NaCl since glucose is larger
How does glucose get into the brain?
GLUT transporters
What is the blood pressure in the renal artery?
100mmHg
What is the blood pressure when the blood is exiting the kidney?
Blood encounters resistance in all the blood vessels in the kidney so but the time its exiting BP is really low
What does BP reduction in the kidney depend on?
amount of vascular resistance encountered
Why does blood pressure decrease in areas of vascular resistance?
Requires energy to be removed from the blood to move through a high resistance vessel
What is delta P in the kidney?
around 100mmHg
What lies in front of the arteriole in the kidney?
Larger arteries that split a bunch of times before getting to arteriole
The name for the blood vessel sitting in front of glomerular capillaries in the kidney:
Afferent arteriole
Why is the afferent arteriole important?
Determines the pressure in the glomerular capillaries
How do we find the blood pressure in the glomerular capillaries?
Amount of resistance between renal artery and glomerular capillaries
What is the average BP in glomerular capillaries?
60mmHg
What causes the decrease from 100mmH in the renal artery to 60mmHg in the glomerular capillaries?
resistance in afferent arteriole getting from renal artery to glomerulus
What is the function of the glomerular capillaries?
Area for filtration
first capillary set in a series of 2 capillary beds in the kidney
How many capillary beds are there in the kidney?
2
What is the first capillary bed encountered in the kidney?
Glomerular capillaries
What defines how much filtration occurs in the glomerular capillaries?
Pressure in the glomerular capillaries
What is GFR?
Rate of fluid moving from glomerular filtration bed into a compartment for processing everything that has been filtered
What happens if glucose makes it into filtration?
Body doesnt want to lose glucose so if working normally it should reabsorb it
What is reabsorbed from the filtrate and what happens to the rest that is not reabsorbed?
Body reabsorbs things it needs to keep
other things can pass through and leave body in the urine
What does a high GFR mean?
The higher the processing the better the organ
What allows for alot of filtration at the glomerulus?
High pressure of 60mmHg (x2 the pressure in vascular capillary)
What is the total filtration rate of all glomerular capillaries in the body?
125mL/min
What are things that arent filtered by the kidney (unless something is wrong)?
RBCs
Large proteins
What could cause large compounds to be filtered by the kidneys?
If the glomerular capillaries are not intact d/t life time of poorly controlled diabetes or hypertension
What is manipulated in the kidney by the body to maintain normal levels of blood flow and filtration?
Afferent arteriole
How does the kidney respond if it senses blood flow is too low?
Afferent arteriole relaxes to increase perfusion
How does the kidney respond if renal blood flow is too high?
Afferent arteriole constricts to limit over perfusion
How is autoregulation in the kidney different different than other areas in the body?
The kidney does not have a flat line within the normal limits of autoregulation
slanted line
Why is the slanted line in kidney autoregulation significant?
Helps maintain long term blood pressure control–slant allows for kidney to get rid of fluid when BP is high and retain fluid when BP is low
What is plasma oncotic pressure in afferent arteriole?
28mmHg
What is plasma oncotic pressure trend in the glomerular capillaries?
30mmHg at arteriole end
32mmHg in the middle
36mmHg at the end
What does glomerular plasma oncotic pressure trend up the further along you go?
More fluid is being filtered so the proteins are becoming more concentrated
Where is fluid filtered into from the glomerulus?
Tubule (bowmans capsule)
What does P(tubule) stand for?
hydrostatic pressure in the tubule
What is the value of P(tubule)?
18mmHg
What is the plasma oncotic pressure in the tubule?
0mmHg
proteins should not be filtered if healthy
Where are the proteins that are necessary for the cells in the tubule located?
Tethered to the tubule–dont have any osmotic pressure associated with them
How is NFP calculated in the tubule?
-start with glomerular capillaries
-oncotic pressure in the capillaries
-presssure in the tubule
60-32-18= 10mmHg
What is the NFP in the tubule?
10mmHg
What is the NFP in the tubule so high?
It drives filtration at 125mL/min
What is normal glomerular filtration rate?
125mL/min
What is the purpose of the filtration coefficient? (Kf)
Helps to figure out what the filtration rate is
What is the equation for filtration rate?
Filtration rate= NFP x Kf
What is the second arteriole in the kidney behind glomerulus?
efferent arteriole
What does the kidney use efferent tone/regulation for?
Finetune GFR
What makes the efferent arteriole the highest vascular resistance vessel in the kidney?
Large decrease in BP from 60mmHg in the glomerulus to 18mmHg at the end of efferent arteriole
compared to afferent (40 point difference)
What happens as a result if the efferent arteriole is constricting?
upstream pressure is increased which means higher pressure in glomerulus and more filtration
What happens as a result if the efferent arteriole is dilating?
Easier for blood to flow downstream so glomerular capillary blood flow is reduced and filtration is reduced
What does the body do in response to low GFR?
constricts efferent arteriole to drive GFR up
What does the body do in response to high GFR?
Efferent arteriole relaxes to decrease GFR
What vessel has the greatest vascular resistance of any segement of blood vessel in the kidney?
efferent arteriole
Where does most of the blood that moves through the kidneys end up?
Stays in the Cv system and passes into efferent arteriole
What is the second set of capillaries in the kidney?
Peritubular Capillaries
What is the primary action happening at the peritubular capillaries?
Reabsorption
What processes are used for reabsorption from the tubule to the peritubular capillaries?
Pumping systems aor channels where fluid is sent in the tubule and then can be selectively decided what to reabsorb
What percent of filtrate is reabsorbed?
99%
What percent of filtrate is excreted in the urine?
1-2%
What is the route for absorption from the tubule to the peritubular capillaries?
Through or between the cells that line the walls of the tubule
What type of particles fir between the cells?
Wide gaps in the cells in the tubule
water and small things can take that route to be reabsorbed
What is the net filtration pressure in the peritubular capillaries compared to the glomerular capillaries?
NFP is lower in peritubular capillaries
net reabsorption pressure is high in the peritubular capillaries
What is the plasma oncotic pressure in the middle of the peritubular capillaries?
32mmHg (same as glomerular capillaries)
What is the trend for plasma oncotic pressure in the peritubular capillaries?
Reabsorbing more fluid so protein concentration is more dilute as you travel down the peritubular capillary
What is the BP in the peritubular capillaries?
13mmHg
What is BP at the beginning of the peritubular capillaries?
18mmHg (end of efferent arteriole)
How does the kidney use the 2 capillaries to manage equilibirum?
Equal forces of reabsorption in the peritubular capillaries as there are filtration forces in the glomerular capillaries
Where is the reabsorbed fluid emptied back into CV system?
reabsorption ends at the end of the peritubular capillary and empties content into renal vein
What goes through the renal vein?
The blood flowing through the kidney plus everything the kidney reabsorbed
Where is the renal interstitium located?
outside the tubule
What is the renal interstitium made of?
Protein matrix tha contains ions, electrolytes, and larger energy compounds
What does the renal interstitium separate?
Intermediate space between tubule and blood vessels
Everything reabsorbed must pass through the _________ at some point.
Renal interstitium
What is the ISF protein osmotic pressure in the kidney?
15mmHg
What is the pressure in the renal interstitium? (Pisf)
6mmHg
What is the role of pressure in the renal interstitum?
Plays a role in how much fluid is reabsorbed from the filtrate
What is the net filtration pressure in the renal interstitium?
-10mmHG
same as +10mmHg Net reabsorption pressure
What is the process of excretion?
removing waste products from the body via urine
How much is filtered in the kidney?
filtration rate: 125mL/min
RBF: 1100mL/min
a little over 10% of the blood that moves through the kidney is filtered
Are RBCs filtered through the kidney?
No
What portion of the plasma that moves through the kidney is filtered?
1/5
What happens to excretion with increased filtration?
Increases excretion
Where does the end of the tubule empty into?
Ureters then into bladder
What is the equation to calculate excretion?
filtration- reabsorption + secretion
How can excretion be represented and with what units?
Volume or quantities of specific substances being dissolved in the fluid that is being filtered
mL of fluid, mol or mg or a compound
What is secretion?
ability of the bodyd to pump things into the tubule
What is used to pump items back into the tubule?
special transporters
What is the path for items that are being secreted?
Movement from peritubular capillaries into renal interstitium and back into the tubule through the cells
Are special transporters for secretion only for large molecules?
No. Secretion can be used of large or small molecules
How does the kidney get rid of excess potassium?
physically pumps potassium from blood into the tubule to remove it from the body
What part of the kidney decides whether to secrete or excrete?
Processing is dependent on what the tubule cells want to do
What does secretion of specific items depend on?
Location of tubule, hormones in the body that influence the secretion
What usually causes the kidney to filter more fluid at the glomerular capillaries?
Constriction of the efferent arteriole
makes it harder for blood to flow from glomerulus to efferent arteriole and forces more blood to be filtered
What happens to glomerular colloid osmotic pressure when the kidney is filtering more fluid?
colloids would be more concentration when more fluid is filtered
What causes the kidney to filter less fluid?
relaxation of efferent arteriole
What happens to glomerular colloid osmotic pressure if the kidney is filtering less fluid?
proteins arent as concentrated as normal
What happens to filtration fraction with increased glomerular filtration?
increased filtration fraction
What happens to filtration fraction with decreased glomerular filtration?
decreased filtration fraction
What is filtration fraction?
how much fluid is filtered and how much plasma has made it through the kidney
What is a normal filtration fraction?
20%
How is filtration fraction calculated?
FF= GFR/ Renal plasma flow
What is renal plasma flow?
660 mL/min
What is normal renal blood flow?
1100mL/min
If hct is .4 what portion of the blood is plasma vs RBC?
40% of 1100 = RBC volume
60% of 1100= plasma volume
How is renal plasma flow calculated?
0.6 x 1100= 660mL/min
What is a normal filtration fraction?
0.19
Where do changes in renal vascular resistance occur?
Either occur at afferent arteriole or efferent arteriole or both
What is the site for renal autoregulation?
Afferent arteriole
(by default also autoregulates GFR)
Where is the site for GFR fine tuning?
Efferent arteriole
What is expected if resistance is increased at afferent arteriole (constriction)?
downstream of high resistance, pressure will be lower
glomerular capillary BP in lower
decreased GFR and decreased renal blood flow
What happens if efferent arteriole is constricted?
occluding outflow from glomerular capillaries
pressure upstream increases
increased pressure in glomerular capillaries–increases GFR but reduces renal blood flow
What happens to renal blood flow with constriction of efferent or afferent arteriole?
Decreased renal blood flow
What happens when afferent arteriole relaxes?
increases glomerular capillary pressure
increases GFR
increases renal blood flow
What happens when efferent arteriole is relaxed?
decreased glomerular capillary pressure
decreased GFR
increase renal blood flow
What happens to renal blood flow when either the afferent or efferent arterioles are dilated?
Renal blood flow increases
What pressure does the kidney autoregulation function at?
50-150mmHg
GFR starts to drop off at pressure above 50mmHg
Why is autoregulation in the kidney compromised with a sick/unhealthy person?
when sick, blood vessels have a hard time dilating
What is renal autoregulation dependent on?
Ability of afferent arteriole to dilate
Why does someone with chronic HTN or uncontrolled DM likely have poor renal autoregulation?
Blood vessels (including afferent arteriole) do not relax normally
What is the lower limit for renal autoregulation in a sick person?
50mmHg is ok for healthy person but a sick person probably needs a higher BP for kidneys to be happy
Is renal blood flow is autoregulated, what is also regulated by default?
GFR: constant amount of blood going through the kidneys should provide relatively constant GFR
What does it mean that autoregulation on a graph remains pretty flat even at pressures higher than 150mmHg?
The kidney is good at autoregulating GFR at high pressures
Why is it important to have good GFR autoregulation at high pressures?
Prevents massive amounts of fluid output via urine
How would it be problematic if GFR wasnt well regulated at high pressures?
If someone had area of ischemia the body is trying to perfuse by increasing BP–the kidney wouldnt allow it because it would just dump that extra fluid out into the urine
What happens to GFR autoregulation at low pressures?
GFR is not as well autregulated compared to renal blood flow at low pressures
GFR starts to drop off well above 50mmHg
What is urine output correlated with?
renal blood flow and GFR autoregulation
What is normal urine output for healthy person?
1mL/min
What happens to UOP with increased BP?
increased UOP
What happens to UOP with decreased BP?
decreased UOP
Why does GFR drop with low BP (ex: 60mmHg)?
reducing GFR reduces urine output to conserve volume and increase BP
renal blood flow is still regulated
Does renal autoregulation rely on RAAS?
no, it is independent
What can the tubule do to help if renal filtration isnt doing enough?
tubular secretion can help–cells in tubule grab things to pump into tubule
What type of filtration patter does sodium follow?
Filtration and partial reabsorption
What filtration pattern does glucose follow?
Filtration and complete reabsorption
Where is filtered glucose reabsorbed?
proximal tubule
What is indicated if there is glucose in the urine?
There should not be glucose in the urine
Pt either has high blood sugar where its not getting reabsorbed or there is something wrong with transport system used to reabsorb
How does filtration with heavy secretion work?
only a small amount was filtered, the rest travels past efferent arteriole then is actively secreted via a transport system that moves all of the compound into the renal tubule for excretion
What is an example of a compound that goes through filtration with heavy secretion?
Para amino kippuric acid (PAH)
What is Para amino kippuric acid?
Diagnostic compound used to estimate renal blood flow
removal is dependent on blood moving through the kidney
How can you tell renal blood flow from PAH levels removed from circulation?
Lower amounts of PAH being removed from circulation = lower renal blood flow
higher amounts being removed from circulation= higher renal blood flow
How much filtrate is reabsorbed based on GFR?
124mL/min
Why is there no protein osmotic pressure in the tubule?
There should not be any proteins in the tubule
What is the inner layer of the glomerular capillaries composed of?
inner layer made of endothelial cells
What makes the glomerular capillaries more permeable that systemic capillaries?
Fenestrations
What are fenestrations in the glomerular capillaries?
specialized opening in renal glomerular endothelium
What are the 3 layers of glomerular capillaries?
Inner layer: endothelial cells
Basement membrane (middle): big piece of connective tissue
Outer layer: Epithelium
What is the epithelial layer of glomerular capillaries designed for?
back end of the capillary–a layer of epithelial cells specialized to provide support and structure to capillary bed
Why is support needed by the epithelial layer for the glomerular capillaries?
Support is needed because pressure is really high in these capillary beds
What makes up the epithelial layer?
Podocytes
What are podocytes?
similar function as astrocytes in the brain
they help support glomerular capillaries in the kidney
How does fluid still get through podocytes?
Podocytes have foot processes and slit pores–allows fluid to still pass through
What is found in the area around the epithelium and basement membrane to control what gets into the glomerulus?
A bunch of different negative charges–used to help repel things also have a negative charge from getting into fenestrations
What type of molecules are repelled by the negative charge of epithelium and basement membrane?
anything with a negative charge
proteins in the blood are negatively charged so they are repelled and prevented from being filtered
What do podocytes help with when glomerular pressure is really high?
Help with swelling in glomerular capillaries
help to keep surface area of glomerular capillaries in check
What happens to glomerular capillaries if BP is high for a REALLY long time?
Eventually podocytes cant protect them and the capillaries are blown out and swollen by the high BP and eventually fall apart
What is Dextran?
Big synthetic sugar compound that chemists can modify to make larger or smaller
How does a neutral particle compare to a positively charged particle when looking at filterability?
positively charged will be more filterable because it doesnt have negative charge to repel it from getting through fenestrations
What does polyanionic mean?
Multiple negative charges on it
How does neutral dextran filterability compared to polyanionic dextran?
Polyanionic has much lower filterability–its repelled from getting through fenestrations
What happens to filterability as the size of a compound increases?
filterability is reduced
larger compounds arent as likely to sneak through fenestrations
What is inulin used for?
synthetic compound injected into patient to figure out clearnace of inulin
more accurate number for GFR
Why is inulin better predictor of GFR than creatinine?
Creatinine has variability from person to person–doesnt follow same kinetics through kidney as inulin
What are some things discussed in class than can be easily filtered?
-small things (water, sodium)
-glucose
-inulin
Can myoglobin be filtered through the glomerulus?
MW is 17,000
its filterable but less than water and Na (0.75)
we shouldnt have myoglobin floating int he blood so not an issue
What is the filterability of albumin?
Low (0.005)
big molecular weight
What things is the kidney a longer term manager of?
BP
Acid/base balance
Hematocrit
Electrolyte balance
Calcium levels
Long term blood glucose
Drug clearance
Metabolic waste products
Water reabsorption
What is the primary issue if someone has high blood pressure?
Something messed up with the kidneys
How does the kidney function to for longer term acid/base balance?
The kidney manages bicarb levels and can get rid of excess protons
What system decides how much bicarb to reabsorb?
The kidney
How is bicarb filtered?
Small, easily filtered
What happens if we need more bicarb than the kidney is filtering?
The kidney can make its own bicarb
Besides bicarb filtration, how else can the kidney manage pH?
Kidney gets rid of excess protons
What is the short term pH regulator in the body?
Respiratory system
How does the respiratory system manage pH?
Blows off CO2 to reduce proton in the blood temporarily
only short term because lungs expire CO2 but they cant directly expire protons
How does the kidney manage hematocrit?
O2 sensors deep in the kidney–look at O2 levels in the deep medullary portions of the kidney
What happens if the deep medullary portions of the kidney sense a low O2?
The kidney releases erythropoietin
What is the function of erythropoietin?
Increases RBC in circulation by stimulating bone marrow to produce more RBCs–increases ability to transport O2 around and increases oxygenation levels
How does the kidney maintain electrolyte balances?
Everything we eat get absorbed into blood stream–kidney gets rid of excess electrolytes that come in from our food (EX: Na+)
How does the kidney manage calcium levels?
Kidney can pick and choose how much Ca2+ to reabsorb from food
What is the formula for renal clearance?
(Urinary flow x Urinary concentration of compound) / plasma concentration
