LECTURE 32 11/28/22 (LECTURE 17 SLIDES: RENAL PHYSIOLOGY) Flashcards
Secretion from the blood vessels into the renal tubule is driven by ________________.
Secondary Active Transporters that rely on the sodium gradient (11:33)
Fluid that is left over at the end of the nephron tubule will be ___________.
Excreted (11:52)
What is formula for Excretion?
Excretion = Filtration - Reabsorption + Secretion (12:46)
Label 1-4
- Filtration
- Reabsorption
- Secretion
- Excretion
(14:40)
Describe what is happening in A, B, C, D
Which substance will most closely represent PAH?
What will be the clearance rate of PAH?
Substance D.
600 cc/min (equivalent to renal plasma flow)
(19:00)
In a healthy individual, how many ways can creatinine enter the nephron?
In a healthy individual, how many ways can creatinine get reabsorbed?
2 (creatinine is mainly filtered and slowly secreted into the nephrons)
0 (creatinine does not get reabsorbed)
(20:20)
Rank the filterability of a neutral dextran, polycationic dextran, and polyanionic dextran from most filterable to least filterable.
Most filterable: Polycationic Dextran
Neutral Dextran
Least filterable: Polyanionic Dextran
*dextrans with the highest relative filterability will have a small radius and positive charge. (23:33)
Which substance can be filtered?
Which substance can not be filtered?
What are two reasons albumin can not be filtered?
- Albumin is too big.
- Albumin has a negative charge
(24:00)
Glomerular Anatomy: Label A through D
How many layers are there in the glomerulus?
What kind of charge are in each layer?
3 Layers:
Endothelium
Basement Membrane
Epithelium
All three layers have negative charges and repel things that shouldn’t be filtered (ie: albumin) (27:28)
Endothelium contains _______________ to allow filtration of huge amounts of fluid.
Fenestrations (25:28)
What is the basement layer of the glomerulus composed of?
Connective Tissue, Collagen, Proteoglycan, Filaments. (26:00)
What is outer layer of the glomerulus?
What is the outer layer of the glomerulus composed of, what is the purpose of these structures?
Epithelial Layer (26:20)
Podocytes. They provide support, allow large amounts of fluids to pass through the slit pores, and prevent proteins from leaving the glomerulus. The blood pressure of the glomerulus is 60 mmHg, the podocytes helps maintain the integrity of the glomerulus. (30:30)
What can cause proteins to be filtered through the glomerulus?
Can proteins be reabsorbed from the tubule?
- Infection
- High Blood Pressure
No, there are no specific transporters for protein reabsorption.
(28:00)
How much pressure is lost when blood goes from the glomerular capillaries to the peritubular capillaries?
What causes the drop in blood pressure in the peritubular capillaires?
47 mmHg lost.
Glomerular capillary blood pressure (60 mmHg)
Peritubular capillary blood pressure (13 mmHg)
High resistance in the efferent arterioles.
(35:00)
What is the difference in oncotic pressure between the glomerular capillaries and the peritubular capillaries?
0 mmHg
Glomerular capillary oncotic pressure (32 mmHg)
Peritubular capillary oncotic pressure (32 mmHg)
(36:00)
What is the peritubular capillary hydrostatic pressure?
What is the peritubular capillary oncotic pressure?
What is the interstitial fluid hydrostatic pressure?
What is the interstitial fluid oncotic pressure?
13 mmHg (Peritubular hydrostatic pressure)
32 mmHg (Peritubular oncotic pressure)
6 mmHg (Interstitial fluid hydrostatic pressure)
15 mmHg (Interstitial fluid oncotic pressure)
What are the pressures that favor reabsorption to the peritubular capillaries?
What are the pressures that opposes reabsorption to the peritubular capillaries?
What is the Net Reabsorption Pressure?
Forces that favor reabsorption:
Peritubular oncotic pressure (32 mmHg)
Interstitial fluid hydrostatic pressure (6 mmHg)
Forces that oppose reabsorption:
Peritubular hydrostatic pressure (13 mmHg)
Interstitial oncotic pressure (15 mmHg)
10 mmHg
(38mmHg - 28mmHg)
(39:00)
Explain how 99% of all filtrates that leave the glomerular capillaries gets reabsorbed in the peritubular capillaries.
There is an equal but opposite net reabsorption pressure at the peritubular capillaries (10 mmHg) compared to the net filtration pressure at the glomerular capillaries (10 mmHg).
(40:15)
When blood pressure is higher than normal how do the vessels in the kidney compensate?
When blood pressure is lower than normal, how do the vessels in the kidney compensate?
Autoregulation of renal blood flow is between _______ mmHg to _______ mmHg
What blood vessel will autoregulate renal blood flow and maintain GFR?
Vessels will tighten to prevent over-perfusion.
Vessels will relax to prevent under-perfusion.
50 mmHg to 150 mmHg
Afferent Arteriole
(46:00)
What is a specialized structure located in the nephron tubule that keeps an eye on GFR?
Macula Densa
Where is the Macula Densa located?
What two vessels does the Macula Densa come in contact with?
How does the Macula Densa measure GFR?
Distal Convoluted Tubule.
The macula densa comes into contact with the afferent and efferent arterioles.
Macula Densa measure GFR by counted the number of sodium and chloride that pass by the structure. (53:00)
What will the macula densa “see” if there is an increase in GFR? How will the system respond?
What will the macula densa “see” if there is a reduction in GFR? How will the system respond?
The macula densa will sense more sodium and chloride.
Afferent Arteriole will constrict.
Efferent Arteriole will relax.
The macula densa will sense less sodium and chloride.
Afferent Arteriole will relax.
Efferent Arteriole will constrict.
(54:00)
The decrease in afferent arteriolar resistance is mediated by __________ release.
What mechanism is used to control the tone of the efferent arterioles?
Nitric Oxide
Angiotensin II and Renin will control arteriolar resistance.
(74:00)
The cells located in our afferent and efferent arterioles are known as ____________.
What do these cells produce?
Granular Cells (Juxtaglomerular Cells)
Renin
(75:00)
Renin is the rate-limiting step in the production of _____________ .
Angiotensin II
(75:40)
What is between the peritubular capillaries and the tubular cells?
The renal interstitium/ interstitial space/ interstitium.
What are other names for luminal side of the renal tubule?
Apical Side
Tubular Side
Luminal Side
…The Pee Side
What are other names for the side of the renal tubule that borders the interstitium?
Interstitial Side
Basal Side
Blood Side
What are the two reabsorption pathways from the lumen?
Transcellular Reabsorption
Reabsorbing substances through the cell wall
Paracellular Reabsorption
Reabsorbing substances through spaces between neighboring cells.
(84:00)
What part of the nephron allows lots of reabsorption through the paracellular route due to not so tight junctions?
The Proximal Convoluted Tubule
(85:20)
What are the 3 main transporters in the proximal convoluted tubule?
Na+/glucose symporter (SGLT2 and SGLT1)
(reabsorption of glucose/Na+)
Na+/amino acid symporter (reabsorption of amino acids/Na+)
Na+/H+ antiporter (NHE)
(secretion of H+/ reabsorption of Na+)
(87:00)
How is chloride reabsorbed in the proximal convoluted tubule?
Through the paracellular pathway.
(91:00)
What is the name for a specialized water channel?
What is another route for water reabsorption?
Is water reabsorption passive or active?
Aquaporins
Paracellular pathway
Passive. Water is reabsorbed by moving down its concentration gradient.
(92:30)
What added a high surface area to the tubular cells?
Brush borders
(94:00)
What is the resting membrane potential of the tubular epithelial cells.
-70 mV
(95:55)
The negative charge gradient plays a role in reabsorbing what two ions?
Ca⁺⁺ & Mg⁺⁺
Additionally, K⁺ making the lumen more + and thus “repulsing” the Mg⁺⁺ & Ca⁺⁺ along their paracellular paths I think. someone delete if wrong.
(96:30)
What compound is important to the brush border?
Carbonic Anhydrase
(97:00)
How would the composition of the fluid at the proximal tubule be described?
Isosmotic. The filtrate osmolarity is similar to plasma osmolarity due to proportionally reabsorption of water and electrolytes. (98:00)
What are the concentration trends of the following substance as it moves through the proximal tubule?
Creatine
Na+
Cl-
Osmolarity
HCO3-
Glucose
Amino Acids
What is the concentration of creatine at the end of the proximal tubule?
3mg/dL
(101:00)
What substances will be reabsorbed at the PCT?
What substances will be secreted at the PCT?
Reabsorption: Na+, Cl-, H2O, HCO3-, K+, Ca2+, glucose, and amino acids
Secretion: H+, organic acids/bases
(potential select all that apply question)
Besides reabsorption, what are other actions of the proximal tubule?
-pH regulation
-Urea management
-Organic Anion Transporter and Cation Transporter to secrete drugs into the tubular fluid.
What concentrates the renal interstitium?
Urea concentrates the renal interstitium and increase the body’s ability to hold on to water.
(104:11)
What is the NHE?
Sodium Hydrogen Exchanger located at the proximal tubule. Antiporter that secretes one H+ for reabsorption of one Na+.
Describe glucose reabsorption in S1/S2/S3 segments of the proximal tubule.
S1: 90% of glucose reabsorption.
SGLT-2 (sodium glucose transporter isoform 2) will remove one Na+ and one glucose out of the tubular lumen.
GLUT-2 will move glucose into the interstitium through facilitated diffusion.
S2/S3: 10% of glucose reabsorption
SGLT-1 will remove TWO Na+ and one glucose out of the tubular lumen.
GLUT-1
(111:00)
In a healthy individual, all the glucose will be reabsorbed before reaching the S2 and S3 segments of the proximal tubule.
What will happen if excess glucose is reabsorbed to the very end of the proximal tubule.
What happens if we have chronic hyperglycemia?
In the S2 and S3 segments, there will be twice the amount of reabsorption of Na+ for one glucose.
The increased reabsorption of Na+ will leave less Na+ in the tubules which will trigger the Macula Densa to misinterpret that there is a decrease in GFR. Kidney will try to compensate by relaxing the afferent arteriole and constrict the efferent arteriole.
Chronically high, renal damage, and Diabetic Nephropathy. (119:00)
Chronically ingesting large amounts of amino acids will result in similar issues
What are ways to combat diabetic nephropathy?
Use an ACE-inhibitor or an Angiotensin II Receptor Blocker to relax efferent arterioles and bring down GFR.
