The Kidneys Reabsorption Principles governing the tubular reabsorption of solutes and water Figure 1911 Na is reabsorbed by active transport Electrochemical gradient drives anion reabsorption ID: 380425
Download Presentation The PPT/PDF document "Chapter 19b" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Chapter 19b
The KidneysSlide2
Reabsorption
Principles governing the tubular reabsorption of solutes and water
Figure 19-11
Na
+
is reabsorbed by active transport.
Electrochemical gradient drives anion
reabsorption.
Water moves by osmosis, followingsolute reabsorption.
Concentrations of other solutesincrease as fluid volume in lumendecreases. Permeable solutes arereabsorbed by diffusion.
Na+
Anions
H2O
K+, Ca2+,urea
Tubularepithelium
Extracellular fluid
Tubule lumen
Filtrate is similar tointerstitial fluid.
1
2
3
4
1
2
3
4Slide3
Reabsorption
Transepithelial
transport
Substances cross both apical (lumen side) and basolateral membraneParacellular pathwaySubstances pass through the junction between two adjacent cellsSlide4
Reabsorption
Figure 19-12
[Na
+
] high
[Na
+
] high
[Na+] low
K+Na+
ATP
Proximal tubule cell
Interstitialfluid
TubulelumenNa+ reabsorbed
Na+ enters cell through membrane proteins,moving down its electrochemical gradient.
Na+ is pumped out the basolateral side
of cell by the Na+-K+-ATPase.
ATP
= Active transporter
= Membrane proteinKEY
Na
+Filtrate is similar to
interstitial fluid.
1
2
1
2
Sodium reabsorption in the proximal tubule Slide5
Reabsorption
Sodium-linked glucose reabsorption in the proximal tubule
Figure 19-13
= SGLT secondary active transporter
= GLUT facilitated diffusion carrier
[Na
+
] high
[glu] low
Na+Na+
[Na+] high
[glu] low
glu
glu[Na+] low[glu] high
K+
ATPGlucose and Na+
reabsorbed
+Na+
moving down its electrochemical gradientusing the SGLT protein pulls glucose into thecell against its concentration gradient.
Glucose diffuses out the basolateral side ofthe cell using the GLUT protein.
Na+
is pumped out by Na+-K+-ATPase.
Proximal tubule cell
Interstitial fluid
Tubule lumen
ATP
= Active transporter
KEY
Filtrate is similar to
interstitial fluid.
1
2
3
1
2
3Slide6
Reabsorption
Urea
Passive reabsorption
Plasma proteins
TranscytosisSlide7
Reabsorption
Saturation of mediated transport
Figure 19-14
Renal threshold is
plasma concentration
at which saturation
occurs.
Transport maximum (T
m) is transportrate at saturation.
Saturation occurs.Plasma [substrate] (mg/mL)
Transport rate of substrate (mg/min)Slide8
Reabsorption
Glucose handling by the nephron
Figure 19-15aSlide9
Reabsorption
Figure 19-15bSlide10
Reabsorption
Figure 19-15cSlide11
Reabsorption
Figure 19-15dSlide12
Secretion
Transfer of molecules from extracellular fluid into lumen of the nephron
Active process
Important in homeostatic regulation
K+ and H+Increasing secretion enhances nephron excretionA competitive process
Penicillin and probenecidSlide13
Excretion
Excretion = filtration – reabsorption + secretion
Clearance
Rate at which a solute disappears from the body by excretion or by metabolism
Non-invasive way to measure GFRInulin and creatinine used to measure GFRSlide14
Inulin Clearance
Inulin clearance is equal to GFR
Figure 19-16
Glomerulus
Peritubular
capillaries
Afferent
arteriole
Efferent
arteriole
Nephron
Filtration
(100 mL/min)
= 100 mL of
plasma or filtrate
Inulin concentration
is 4/100 mL.
GFR = 100 mL /min
100 mL plasma is
reabsorbed. No inulin
is reabsorbed.
100% of inulin is
excreted so inulin
clearance = 100 mL/min.
Inulin
molecules
100 mL,
0% inulin
reabsorbed
Inulin clearance
= 100 mL/min
100% inulin
excreted
KEY
1
2
3
4
1
2
3
4Slide15
Inulin Clearance
Figure 19-16, steps 1–4
Glomerulus
Peritubular
capillaries
Afferent
arteriole
Efferent
arteriole
Nephron
Filtration
(100 mL/min)
= 100 mL of
plasma or filtrate
Inulin concentration
is 4/100 mL.
GFR = 100 mL /min
100 mL plasma is
reabsorbed. No inulin
is reabsorbed.
100% of inulin is
excreted so inulin
clearance = 100 mL/min.
Inulinmolecules
100 mL,
0% inulin
reabsorbed
Inulin clearance
= 100 mL/min
100% inulin
excreted
KEY
1
2
3
4
1
2
3
4Slide16
GFR
Filtered load of X = [X]
plasma
GFRFiltered load of inulin = excretion rate of inulinGFR = excretion rate of inulin/[inulin]plasma = inulin clearanceGFR = inulin clearanceSlide17
Excretion
Table 19-2Slide18
Filtration
(100 mL/min)
Glucose
molecules
100 mL,
100% glucose
reabsorbed
Glucose
clearance
= 0 mL/min
(a) Glucose clearance
No glucoseexcreted
Plasma concentrationis 4/100 mL.
GFR = 100 mL /min100 mL plasma is
reabsorbed.Clearance depends onrenal handling of solute.
KEY
= 100 mL ofplasma or filtrate
1
2
34
1
2
3
4Excretion
The relationship between clearance and excretion Figure 19-17aSlide19
Excretion
Figure 19-17b
(b) Urea clearance
Plasma concentration
is 4/100 mL.
GFR = 100 mL /min
100 mL plasma is
reabsorbed.
Clearance depends on
renal handling of solute.
KEY
Filtration
(100 mL/min)
Ureamolecules
100 mL,50% of ureareabsorbed
50% of ureaexcreted
Ureaclearance = 50 mL/min
= 100 mL ofplasma or filtrate
1
2
3
4
1
2
3
4Slide20
Excretion
Figure 19-17c
(c) Penicillin clearance
Plasma concentration
is 4/100 mL.
GFR = 100 mL /min
100 mL plasma is
reabsorbed.
Clearance depends on
renal handling of solute.
KEY
Filtration
(100 mL/min)
100 mL,0 penicillinreabsorbed
Someadditionalpenicillinsecreted.
Penicillinclearance =150 mL/min
More penicillinis excreted than
was filtered.Penicillin
molecules
= 100 mL ofplasma or filtrate
1
2
3
4
1
2
3
4Slide21
Gout
Limit animal protein.
Avoid or severely limit high-
purine
foods, including organ meats, such as liver, and herring, anchovies and mackerel. Red meat (beef, pork and lamb), fatty fish and seafood (tuna, shrimp, lobster and scallops) are associated with increased risk of gout. Because all animal protein contains purines, limit your intake.
Eat more plant-based proteins. You can increase your protein by including more plant-based sources, such as beans and legumes. This switch will also help you cut down on saturated fats, which may indirectly contribute to obesity and gout.
Limit or avoid alcohol. Alcohol interferes with the elimination of uric acid from your body. Drinking beer, in particular, has been linked to gout attacksSlide22
Micturition
The storage of urine and the
micturition
reflex
Figure 19-18a
Bladder
(smooth muscle)
Internal sphincter (smooth
muscle)
passively contracted
External sphincter (skeletal muscle) stays contracted
(a) Bladder at rest
Tonicdischarge
Relaxed(filling)state
HigherCNSinputIncontinenceSlide23
Micturition
Figure 19-18b
Stretch receptors fire.
Parasympathetic neurons fire.
Motor neurons stop firing.
Smooth muscle contracts.
Internal sphincter passively
pulled open. External sphincter
relaxes.
(b) Micturition
Internal sphincter
External sphincter
Tonic
discharge
inhibited
Higher CNSinput mayfacilitate orinhibit reflex
Sensory neuron
Parasympatheticneuron
Motor neuron
Stretchreceptors
1
2
3
1
2
3
2
3Slide24
Summary
Functions of the kidneys
Anatomy
Kidney, nephron, cortex, and medulla
Renal blood flow and fluid flow from glomerulus to renal pelvisOverview of kidney functionFiltrationPodocytes, filtration slits, and mesangial cellsFiltration fraction, GFR, and regulation of GFRSlide25
Summary
Reabsorption
How solutes are transported
Transport maximum and renal threshold
SecretionExcretionClearance, inulin, and creatinineMicturition