Final Exam - Renal A&P Flashcards
What can we deduce for someone with chronic high blood pressure?
They have a problem with their kidneys because when functioning normally, the kidneys should control our BP.
This could be from a systemic vascular problem affecting the kidneys or the kidneys are blocked from seeing hypertension.
How do the kidneys regulate pH?
- HCO3- : produces bicarb and decides how much of it is reabsorbed
- H+: rids the body of excess protons (long-term control; lungs are short term control)
How do the kidneys regulate RBC?
There are oxygen sensors in the deep medullary portions of the kidney.
When oxygen tension is low, the kidneys release erythropoietin (EPO) to stimulate the bone marrow to produce more RBC.
By increasing the RBC, we can increase the pO2 in the blood.
Describe electrolyte regulation in the body?
The gut essentially abosorbs all electrolytes and the kidneys regulate what electrolytes to reabsorp or excrete
Describe vitamin D regulation by the kidneys?
Vitamin D is activated by the kidney and is necessary for Ca+ absorption
How do the kidneys regulate glucose levels?
Normally, the kidney will reabsorp all glucose that is filtered.
When blood glucose is extremely high, the kidneys will not be able to reabsorp all of it and excretes the excess in the urine
How does the kidney clear drugs?
Some drugs will be secreted by specialized transporters in the kidney out of the body.
What metabolic waste products are removed by the kidneys?
Nitrogenous wastes like urea
How do the kidneys regulate osmolarity?
The kidneys can differentiate Na+ and H2O reabsorption selectively.
ADH manages H2O reabsorption.
Name the vessels that blood travels through from entry to exit in the kidneys?
What structure is denoted by 1 on the figure below?
Renal Artery
What structure is denoted by 2 on the figure below?
Segmental Arteries
What structure is denoted by 3 on the figure below?
Interlobar Arteries
What structure is denoted by 4 on the figure below?
Arcuate Arteries
What structure is denoted by 5 on the figure below?
Interlobular Arteries
Which four components of the cardiovascular system are found in the nephron?
- Afferent Arterioles
- Glomerular Capillaries
- Efferent Arterioles
- Peritubular Capillaries
What percentage of nephrons are cortical nephrons?
90-95%
What percentage of nephrons are medullary nephrons?
5-10%
What is the indicated structure?
Where is this located?
- Paratubular capillaries of cortical nephrons
- Found in the outer medulla
What is the name for deep peritubular capillaries found in medullary nephrons?
Vasa Recta
What is important to note about the difference between the descending and ascending vasa recta?
There are much more ascending than descending vessels of the vasa recta because the vessels branch as they ascend the nephron.
This decreases blood velocity and prevents washout of solutes in the medullary interstitum.
What area of the kidney is most likely to become ischemic during hyoptension?
The deep medullary nephrons.
They are supplied by only 5-10% of the paratubular capillaries (vasa recta) making them very sensitive to changes in blood flow.
What is indicated by 1?
Mesenteric arteries
What is indicated by 2?
Renal vein
What is indicated by 3?
Renal artery
What is indicated by 4?
Adrenal gland
What surface region is indicated by 10 below?
Right Renal Colic Flexure Surface
What surface region is indicated by 12 below?
Right Renal Hepatic Surface
What surface region is indicated by 2 below?
Left Renal Gastric Surface
What surface region is indicated by 3 below?
Left Renal Splenic Surface
What surface region is indicated by 4 below?
Left Renal Pancreatic Surface
What surface region is indicated by 5 below?
Left Renal Descending Colic Surface
Why is renal cancer rare? How does cancer reach kidneys?
- Because the kidneys do not grow new nephrons so low incidence of altered replication.
- Cancer from the many organs that are in contact with the kidney surface.
How do kidney stones affect the kidneys?
Prevent urine excretion and increase pressure upstream of the blockage
Where is kidney pain referred?
The back
What is the indicated structure?
What some issues caused by the structure?
- Prostate gland
- Enlargement squeezes the urethra, preventing full emptying of the bladder
What is the indicated structure?
What is it’s function?
Where does it orginate from in the spine?
- Pudendal gland
- Controls emptying of the bladder and bowels
- Controls erections in males
- S2, S3, and S4
“S2,3,4 keep the stuff off the floor”
Why is prostate removal surgery risky?
Because there is a high risk of severing the pudendal gland which would cause the patient to lose bowel/bladder control and the ability to have an erection
What structure is indicated by 1 on the figure below?
Bowman’s Capsule
What structure is indicated by 2 on the figure below?
Proximal Convoluted Tubule
What structure is indicated by 3 on the figure below?
Proximal Straight Tubule
What structure is indicated by 4 on the figure below?
Descending Thin Limb of the Loop of Henle
What structure is indicated by 5 on the figure below?
Ascending Thin Limb of the Loop of Henle
What structure is indicated by 6 on the figure below?
Thick Ascending Limb of the Loop of Henle
What structure is indicated by 7 on the figure below?
Distal Convoluted Tubule
What structure is indicated by 10 on the figure below?
Cortical Collecting Duct
What structure is indicated by 11 on the figure below?
Medullary Collecting Duct
Where is the Macula Densa located?
End of the TAL of the loop of Henle
What are the structures labeled by number 1?
Right side: cortical nephron
Left side: meduallry nephron
Describe the macula densa’s function?
Macula densa cells sense flow in the TAL of the loop of henle. When flow is low, the macula densa stimulates the juxtaglomerular cells to release renin which becomes angiotensin II that will constrict the efferent arteriole. This increases the P in the golmerular capillaries, increasing GFR, and increasing flow in the tubules.
What is important to know about Linus Pauling?
He was a famous chemist that used high levels of Vitamin C (which reduces oxidation) to treat his prostate cancer for 20+ years
What is the definition of renal clearence?
Amount of plasma cleared of a substance (mL) per unit of time (min)
What does the letter V with a dot over top refer to?
Urine volume per minute
Normal = 1 ml/min
What would be the difference between plamsa in the glomerular capillaries and proximal bowmans capsule for a small positively charged compound (glucose)?
The plasma composition should be the same at both of these points because the glucose is freely filtering with the plasma
How much of all filtrate is reabsorped at the PCT?
2/3
Glucose is normally completely reabsorped. What would it’s clearance be?
Clearance = 0
None of the glucose that was in the plasma was removed in the urine
What is this picture representing?
What would be the clearance of this compound?
None of the compound that was in the plasma was reabsorped by the kidneys.
So, all of the compund has been compacted into the 1 mL of fluid that was not reabsorped.
This makes the clearance of this compound 124 mL/min because 124 mL of plasma were cleared of the compound in 1 minute.
What would the blood concentration of a compoud be entering and leaving the kidney if it is not reabsorped?
The blood concentration entering the kidney would be higher than the blood leaving.
This happens because none of the compound is reabsorped in the PT capillaries, but plasma is being reasborped, diluting the blood that is leaving.
If the concentration of a compound is 1mg/dL and it is freely filtered but not reabsorped, what is the concentration in the urine?
What is the excretion rate?
Assume normal filtration rate.
Filtered load = GFR x Ps
What is the formula for renal clearance?
Also = excretion rate / plasma concentration
How can you calculate excretion rate?
Urine flow rate x concentration in the urine
V x Ux
What ist the best mesurement for GFR?
Using clearance of inulin because it is not reabsorped.
CrCl is usually artifically high because Cr is secreted by the kidneys and released by skeletal muscle
What is the GFR equation?
What is the equation for RPF?
Or RPF = (1-HCT) x RBF
EPAH = PAH extraction ratio
What is the calculation for RBF?
What is the calculation for reabsorption rate?
What is the calculation for secretion rate?
What is the calculation for effective renal plasma flow?
What is the calculation for clearance ratio?
What would the NFP be if renal artery pressure was elevated causing the Pglomerulus to be 90 mmHg?
What should this make the filtration rate?
How do the kidneys manage this?
NFP = 90 mmHg - 32 mmHg - 18 mmHg = 40 mmHg
FR = Kf x NFP = 12.5 x 40 = 500 mL/min
The kidneys have fairly tight regulation over GFR preventing huge losses of fluids during periods of hypertension
Describe the changes in renal autoregulation for a diabetic?
Diabetics have hardened blood vessels which prevents them from relaxing normally. During periods of hypotension, the afferent arteriole cannot dilate out as much, reducing it’s ability to increase renal blood flow. This raises the LLA.
Describe the pathology of renal damage from hypertension.
Our kidneys will autoregulate renal blood flow via constriction of the afferent arteriole. But, hypertension still causes increased glomerular capillary pressure. Increased pressure in the glomerus over time destroys the capillary bed, leading to renal dysfunction.
Where do vasoactive drugs work in the kidneys?
They cause the same effects at both the afferent and efferent arteriole, but every drug has greater effects on the afferent arteriole.
Describe creatinine’s filtration and concentration in the PCT?
Creatinine is freely filtered but not reabsorped; some of it is secreted.
Since most of the water reabsorption is happening at the PCT but none of the creatinine is being reabsorped, the concentration of creatinine increases as it progesses through the PCT.
How does the macula densa sense tubular flow?
It has a sensor that counts the number of Na+ primarily and Cl- passing by per time period.
Explain how the macula densa will respond to a high and low filtration rate but normal reabsorption rate?
High filtration: more Na+ and Cl- ions are making it to the MD which is interpreted as high GFR. The MD will decrease angtiotensin II release to relax the efferent arteriole, decrease glomerular pressure, and decrease GFR.
Low filtration: less Na+ and Cl- ions are making it to the MD which is interpreted as low GFR. The MD will increase angtiotensin II release to constrict the efferent arteriole, increasing glomerular pressure, and increasing GFR
What effect does angiotensin II have on the PCT?
Increases the amount of Na+ reabsorption which increases water reabsorption at the PCT.
Explain how the macula densa would respond to increased Na+ reabsorption at the PCT, but normal GFR?
How could this be treated?
In this situation, a lower number of Na+ ions would make it the macula densa, so the MD would think that GFR is low and increase angtiotensin II release to increase GFR. Because GFR was normal to begin with, this would cause unnecessary hyperfiltration and hypertension. Over time this incresaed pressure would destroy the capillary bed.
An ACEi or ARB would help prevent the effects of angiotensin II here.
What would cause a higher than normal Na+ reabsorption at the PCT?
What effects would this cause?
What disease pathology does this correlate to?
An increase in the amount of glucose or amino acids in the tubules.
AA and glucose are normally both 100 % reabsorped by the body via Na+ dependent co-transporters. Na+ concentrations in the PCT resemble normal levels (140 out/ 14 in)
When glucose or AA levels increase, more is reabsorped causing an increase in Na+ reabsorption along with it, decreasing the Na+ making it to the MD, increasing angiotension II levels, resulting in hyperfiltration by the macula densa, and overtime damage to the nephrons.
This is the pathology of diabetic nephropathy.
Where is all of the glucose reabsorbed in the kidney?
Proximal Convuluted Tubule
What is the name for the tubular side of a tubular cell?
Apical side
What is the name for the interstitial side of a tubular cell?
Basolateral side
How does glucose exit the tubular cells?
What type of transport is this?
GLUT transporters (GLUT 2 in S1 segment and GLUT 1 in S2 segment)
Facilitated diffusion - no energy required
Describe glucose transport in the S1 segment of the PCT?
Accomplished by the SGLT2 transporter (1Na+ / 1 Glucose) - 90 % of glucose reabsorption
SGLT2 is low affinity, high efficency - lots of glucose in early PCT
Moved from the cell to the interstitum by GLUT-2 transporters
Describe glucose transport in the S2 segment of the PCT?
Accomplished by SGLT1 (2 Na+/1 Glucose) - 10% of glucose reabsorption
High affinity pump - needed because glucose in the S2 segment is more dilute and need higher affinity to remove it from solution
What is filtered load?
How can it be calculated?
What would this be for a normal blood glucose?
The quantity of stuff dissolved in an amount of filtrate
If the solute is freely filterable, the amount in the filtrate should equal the amount in the plasma
Filtered load (Qty) = [Solute]plasma x GFR
FLglucose = 100mg/dL x 1.25dL/min = 125mg/min
What does threshold mean for glucose reabsorption?
What happens when threshold is exceeded?
The maximum rate of complete reabsorption.
Not all of the glucose can be reabsorped so it will begin to be excreted in the unrine at a rate equal to the amount over the threshold.
This is caused by the SGLT1 beginning to miss some glucose that is in the S2 segment.
At what level do the kidneys reach transport maximum?
What happens to glucose at this point?
~300 mg/dL
All glucose above the transport maximum will be excreted in the urine
What is the source of renin?
Juxtaglomerular cells
Where is angiotensinogen made?
How is it converted to angtiotensin II?
Liver
Renin converts angtiotensinogen to angiotension I
ACE converts angiotensin I to angiotensin II
What are the 2 ways the macula densa increases GFR?
Increase RBF?
- Release of angiotensin II which constricts the efferent arteriole and increases GFR
- Vasodilates the afferent arteriole which increases renal blood flow via NO and also increases GFR
What are the effects of SGLT inhbition?
Increased glucose excretion in the urine can be a breeding ground for bacteria
Glucose will stick to the tubules and the immune system will see it and cause inflammation
Explain excretion of PAH?
90% of PAH is secreted/filtered and is a good indicator or renal plasma flow
