Holes Cha 20 Urinary Pt 2

8/2/2019 Holes Cha 20 Urinary Pt 2

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1

Kidney Structure

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Renal pelvis

Minor calyx

Major calyx

Renal papilla

Renal pyramid

Nephrons

Renal sinus

Renal medulla

Renal capsule

Renal cortex

Ureter

(a)

(b) (c)

Renal corpuscle

Papilla

Minor calyx

Renal column

Fatin renal sinus

Collecting

duct

Renalmedulla

Renal

cortex

Renaltubule

2


Inferior vena cava

Renal cortex

Renal pyramid

Renal medulla

Minor calyx

Renal column

Renal papilla

Renal pelvis

Suprarenal artery

Abdominal aorta

Adrenal gland

Renal capsule

Hilum

Renal vein

Suprarenal vein

Ureter

Renal artery

3

Renal Blood VesselsCopyrightTheMcGraw-Hill Companies,Inc.Permissionrequired for reproductionor display.

b:L.V. Bergman/TheBergmanCollection

(a)

(b)

Cortex

Medulla

Renal pelvis

Ureter

Afferent arteriole

Cortical radiateartery and vein

Arcuateveinand artery

Interlobarvein and artery

Renalartery

Renalvein

Peritubularcapillary

Efferentarteriole

Proximalconvolutedtubule

Cortical radiateartery and vein

Distal convolutedtubule

CopyrightTheMcGraw-Hill Companies,Inc.Permissionrequired for reproductionor display.

(a) :Tissues and Organs:A Text-Atlas ofScanning ElectronMicroscopy,byR.G.Kessel and R.H.Kardon.1979W.H.Freemanand Company(b) :CourtesyofR.B. WilsonMD,EppeleyInstitutefor ResearchinCancer,UniversityofNebraskaMedical Center

Glomerulus

(a)

Renaltubules

Glomerulus(b)


Efferentarteriole

Afferentarteriole

Glomerularcapsule

4

Nephrons

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Glomerulus

Visceral layer ofglomerularcapsule


Parietal layerof glomerular

capsule

Glomerularcapsule

Bloodflow

Afferent

arteriole

Efferent

arteriole

Bloodflow

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David M. Phillips/VisualsUnlimited

Sl it pore Ped ic el

Slit pore

Pedicel

Primary process

of podocyte

Primary process

of podocyte

Glomerulus

Collecting duct

Nephronloop Ascending

limb

Descendinglimb


Efferentarteriole


Renalmedulla

Renalcortex

Corticalra diateartery

Corticalra diatevein

Glomerularcapsule

Afferentarteriole

Distalconvolutedtubule

Fromrenal

artery

To renalvein

6

Animation:

Renal Process

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Juxtaglomerular Apparatus

Glomerulus

Nephronloop

Glomerulus

Afferent arteriole

Glomerularcapsule

Efferent arteriole

Podocyte

Maculadensa

(a)

(b)

Glomerularcapsule

Afferentarteriole

Juxtaglomerularapparatus

Distal

convolutedtubule

Efferentarteriole


Juxtaglomerularapparatus

JuxtaglomerularCells (granular)

Ascending limbof nephron loop

8

Cortical and Juxtamedullary Nephrons

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Cortical nephron

Juxtamedullarynephron

Collectingduct

Renal

medulla

Renal

cortex

9

Blood Supply of a Nephron

Copyright TheMcGraw-HillCompanies, Inc.Permissionrequired forreproductionor display.

Glomerulus

Nephronloop

Collecting duct

Afferent arteriole

Vasarecta

Peritubularcapillaries

Efferentarteriole


Glomerularcapsule

Corticalradiateartery and vein

Distalconvolutedtubule

CopyrightThe McGraw-HillCompanies, Inc.Permissionrequired forreproductionor display.

Renalartery

Corticalradiateartery

Afferent arteriole

Efferent arteriole

Corticalradiate vein

Renalvein

Arcuateartery

Interlobarartery

Glomerularcapillaries

Peritubularcapillaries

Arcuatevein

Interlobarvein

10

Animation: Fluid Exchange Acrossthe Walls of Capillaries

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11

Urine Formation

The main function of the nephrons and collectingducts is to control the composition of body fluidsand remove wastes from the blood, the productbeing urine

Urine contains wastes, excess water, andelectrolytes

Urine is the final product of the processes of:

Glomerular filtration

Tubular reabsorption

Tubular secretion12

Urine Formation

Arteriole Venule

Venule

Renal tubule

Tubular fluid Urine

Net reabsorption

Net filtration

Interstitial fluid

Bloodflow

(a) In most systemic capillaries, filtration predominates at thearteriolar endand osmotic reabsorptionpredominates at the venularend.

Peritubular

capillaries

Afferentarteriole

Glomerularcapillaries

Efferentarteriole

Bloodflow

Tubularreabsorption

Tubularsecretion

Glomerular

filtration

(b) In the kidneys, the glomerular capillaries are specialized for filtration. The renal tubule isspecialized to control movements of substances back into the blood of the peritubular

capillaries (tubular reabsorption) or from the blood into the renal tubule (tubular secretion).

Filtered

fluid


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Glomerular Filtration

Glomerular filtration Substances move from the blood to the

glomerular capsule

Fenestrae

(a) (b)

Podocyte

Podocyte

Glomerulus

Glomerularcapsule

Proximalconvolutedtubule Capillary

endothelium

Glomerularfiltrate

Efferentarteriole

Bloodflow

Afferentarteriole

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Plasma, Glomerular Filtrate, and Urine Components

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Filtrate Rate

Net filtration pressure = force favoring filtration forces opposing filtration

(glomerular capillary (capsular hydrostatic pressure

hydrostatic pressure) and glomerular capillary osmotic pressure)

Glomerular filtration rate (GFR) is directlyproportional to the net filtration pressure

Normally the glomerular net filtration pressure ispositive causing filtration The forces responsible include hydrostaticpressure and osmotic pressure of plasma and thehydrostatic pressure of the fluid in the glomerularcapsule

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Filtrate Pressure The main force that moves substances by filtrationthrough the glomerular capillary wall is hydrostaticpressure of the blood inside

Hydrostatic

pressure ofblood

Glomerularhydrostatic

pressure

Capsularhydrostaticpressure

Plasma colloidosmotic pressure

Net Outward Pressure

Outward force, glomerularhydrostatic pressure = +60 mm

Inward force of plasma colloid osmotic pressur e = 32 mmInward force of capsular hydrostatic pressure = 18 mm

Net filtration pressure = +10 mm

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Control of Filtrate Rate

GFR remains relatively constant = renalautoregulation.- Certain conditions can override autoregulation

3 main mechanisms keep GFR constant:

1) Myogenic mechanism:- If systemic BP increases = vasoconstriction of

afferent arterioles = drop in GFR- If BP declines = vasodialation of afferent arterioles

= increase in GFRA Sympathetic response

The hormone-like renin-angiotensin system There also is the hormone atrial natriuretic peptide

(ANP) affects sodium causing an increase in GFR18

Control of Filtrate Rate

2. Tubuloglomerular mechanism: directed by maculadensa cells of juxtaglomerular mechanism- macula densa cells respond to NaCl levels

- when GFR increases, little time for reabsorption

and tubular NaCL is high- macula densa release vasoconstrictor chemicalthat constricts afferent artieroles

3. Renin-angiotensin mechanism: hormone (enzyme?)renin produced by granular cells- produced in response to sympathetic system &baroreceptor granular cells


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Bloodstream

AngiotensinI

LiverKidney

Lung capillaries

AngiotensinIIAngiotensinogen

Renin

Stimulation

Angiotensin-convertingenzyme

Release intobloodstream

Vasoconstriction of arterioles increasing systemic BP Increased aldosterone secretion reduces amount Na+ in urine Stimulates hypothalamus to release ADH & stimulate thirstcenter (both result in increased BP) Increases fluid reabsorption by decreasing peritubular cap.hydrostatic pressure by constricting efferent arterioles

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Tubular Reabsorption

Tubular reabsorption Substances move from the renal tubules into the

interstitial fluid where they then diffuse into theperitubular capillaries The proximal convoluted tubule reabsorbs (70%):

Glucose, water, urea, proteins, and creatine Amino, lactic, citric, and uric acids Phosphate, sulfate, calcium, potassium, andsodium ions

Some is by osmossis, some by diffusion, some by active transport

21

Copyright The McGraw-Hill Companies,Inc . Permission required for reproduction or display.

Glomerulus

(a) (b)

Blood flowBlood flow

Glomerulus

Bloodflow

Afferentarteriole

Glomerularcapsule

Glomerularfiltrate

Efferentarteriole


Tubularreabsorption

Renaltubule

Renaltubule

Tubularsecretion


Efferentarteriole

Afferentarteriole

Bloodflow

Glomerularcapsule

Glomerularfiltrate

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Glomerulus

+

+

+++

+

++

+

++++++

1

2

3

4

Bloodflow

Glomerularcapsule

BloodflowGlomerular

filtrate

Proximalconvolutedtubule Sodium ions

are reabsorbed byactive transport

Negatively charged ionsare attracted to positively

charged ions electrochemical attraction

As concentration of ions (solutes) increases in plasma(blood becomes hypertonic) osmotic pressure increases

Water moves from proximal

tubule to capillary byosmosis

Bloodflow

Isotonic

tubular fluid

Na+Na+

PO43

N+

Cl

HCO3

Cl

Na+

H2O

H2O

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Glomerular

FiltrateUrine

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Tubular Secretion

Tubular secretion Substances move from the plasma of theperitubular capillaries into the fluid of the renaltubules

Active transport Secretion of substances such as drugs, K+ & H+- i.e., gets some things out of blood that

werent filtered- Since all K+ is reabsorbed in the PCT it helps

keep blood K+ from being to high- helps control blood Ph


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Blood flowPeritubularcapillary

Distal convoluted tubule

Na+Na+

Na+

Na+

Na+K+ K

+

K+

K+

H+

H+

Collecting duct

K+ or H+

Na+

Tubular reabsorption Tubular secretion

Tubular fluid

Ascending limbof nephron loop

Na+Na+

Na+

Na+

Na+

Na+

Na+Active Tr.

Passive - K+ or H+ go

to negatively chargestubule

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Regulation of Urine Concentration and Volume

Hormones such as aldosterone (reabsorb NA+) and atrial

natriuretic peptide (excrete Na+)

The ability of the kidneys to maintain the internalenvironment rests in a large part on their ability to concentrate

urine by reabsorbing large volumes of water The distal convoluted tubule and the collecting duct are

impermeable to water, so water may be excreted as diluteurine

If Antidiuretic Hormone is present, DCT and Collecting ductbecome permeable, and water is reabsorbed by osmosis

A countercurrent mechanism in the nephron loops (thedescending and the ascending limbs) ensures that the

medullary interstitial fluid becomes hypertonic This mechanism is known as the countercurrent multiplier

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Collecting duct

Dilute urine Concentrated urine

Collecting duct

H2O

H2O

(a) (b)

Medullaryinterstitial fluid

Distal convolutedtubule

Hypertonicinterstitialfluid

Hypertonicinterstitialfluid

high ADH levelslow ADH levels

H2O

H2OH2O

H2OH2O

H2O

Medullaryinterstitial fluid

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29

Isotonic fluid

Hypotonic fluidNa+Cl

(a) (b)

Na+

Cl

Salty

H2O1

2

3

Descendinglimb(permeableto water)

IncreasingNaClconcentration

Thick ascendinglimb (impermeableto water)

Hypertonicfluid

Medullaryinterstitialfluid

Moresalty

Evenmoresalty

Na+

Cl

H2O

Na+

ClH2O

H2O

H2O

H2O

Na+Cl

Na+Cl

Counter current multipier:- ensures that medullary interstitial

fluid becomes hypertonic

Loop of Henle: Countercurrent Mechanism

Figure 25.14

Isotonic


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NaCl

NaCl

NaClNaClNaCl

NaCl

NaCl

NaCl

Blood

flow

IncreasingNaCl

concentration

Bloodflow

Medullary

interstitialfluid

Vasa

recta

diffusion

Summary of Nephron Function

Figure 25.16

33

Urea and Uric Acid Excretion

Urea: By-product of amino acid catabolism Enters the renal tubules through glomerular filtration Reabsorbed (and tubular secretion) It contributes to reabsorption of water from the

collecting duct About 80% is recycled

Uric acid: Product of nucleic acid metabolism Enters renal tubules through glomerular filtration Most reabsorption occurs by active transport About 10% is secreted and excreted

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Urine Composition

Urine composition reflects the volumes of waterand solutes that the kidneys eliminate or retain tomaintain homeostasis Varies from time to time due to dietary intake andphysical activity, but is:

About 95% water Usually contains urea, uric acid, and creatinine May contain trace amounts of amino acids and

varying amounts of electrolytes Volume varies with fluid intake and

environmental factors

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Elimination of Urine

After forming along the nephrons, urine: Passes the collecting ducts to:

Openings of the renal papillae: Enters the minor and major calyces: Passes through the renal pelvis: Enters into the ureters: Enters into the urinary bladder:The urethra carries the urine out of thebody

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Micturition Reflex

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Holes Cha 20 Urinary Pt 2