Chap 26 Urinary Student 3

8/11/2019 Chap 26 Urinary Student 3

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Chapter 26

The

Urinary System

Diaphragm

Esophagus

Left adrenal

(suprarenal) gland

Left renal vein

LEFT KIDNEY

Abdominal aorta

Inferior vena cava

LEFT URETER

Rectum

Left ovary

Uterus

RIGHT KIDNEY

RIGHT URETER

URINARY

BLADDER

URETHRA

Right renal artery

I. QUICK ANATOMY

Transverse

plane

POSTERIOR

ANTERIOR

Pancreas

Body of

L2

Liver

View

RIGHT KIDNEY

Large intestine

LEFT KIDNEY

Spleen

Rib

Stomach


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(b) Parasagittal section through right kidney

POSTERIOR ANTERIOR

Lung

SUPERIOR

Liver

Adrenal (suprarenal)

gland

Peritoneum

RENAL CAPSULE

Large intestine

Diaphragm

Right kidney

Hip bone

Parasagittal

plane

23-5

II. FUNCTIONS

A. Filter blood plasma

B. regulate blood pressure andvolume

C. regulate osmolarity of body fluids

D. renin, EPO, and calcitriol

E. regulate PCO2and acid-base

balance of blood

F. detoxify drugs/toxins


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III. KIDNEY

A. Cortex - filtration to form urine;

B. Medulla - collect and excrete urine

Renal capsule

Collecting duct

Minor

calyx

NephronRenal

cortex

Renal

medulla

Renal

papilla

(a) Anterior view of dissection of right kidney

Renal cortex

Renal medulla

Renal column

Renal pyramid

in renal medulla

Renal papilla

Renal capsule

Renal artery

Renal vein

Nephron

Collecting duct

PATH OF URIN E DRAINAGE:

Minor calyx

Major calyx

Renal pelvis

Ureter

Urinary bladder

Renal

hilum


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The real story:

PCT

DCT

Renal corpuscle

(external view)

Afferentarteriole

Efferentarteriole

Endothelium of

glomerulus

(a) Renal corpuscle (internal view)

Capsular space

Glomerular capsule

Proximalconvoluted

tubule

Glomerulus

Renal Corpuscle:

A. renal corpuscle - filters blood plasma;

consists of:

1. glomerulus

-_______________capillaries

-blood enters glomerulus via _______

-blood leaves glomerulus via _______

-no venule


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Filtration slit

1

Pedicel

Fenestration (pore) of glomerularendothelial cell: prevents filtration of

blood cells but allows all

components of blood plasma topass through

Basal lamina of glomerulus:prevents filtration of larger

proteins

Slit membrane between pedicels:prevents filtration of medium-sized

proteins

2

3

Renal corpuscle

(external view)

Afferentarteriole

Efferentarteriole

Endothelium of

glomerulus


Capsular space

Glomerular capsule

Proximalconvoluted

tubule

Glomerulus

Renal Corpuscle:

2. Bowmans (glomerular) capsule -

encloses glomerulus

3. capsular space-separates the two layers of the capsule

-

filtrate- everything that gets pushed through the capillary

walls into the capsule


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DCT

Interstitial fluidin renal cortex

Interstitial fluid inrenal medulla

Papillary

duct

Dilute

urine

Loop of

Henle

PCT

i. PCT - simple cuboidal epithelium

ii. Loop of Henle

- thin segments:

*simple squamous epithelium

*

- thick segments:

*simple cuboidal epithelium

*

iii. DCT

-cuboidal epithelium without

microvilli;

-

ii. Loop of Henle


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B. renal tubule

1. anatomy

2. function -

a. Secretion: body into tubule

b. Reabsorption: tubule back into body

How substances move:

-- across tubular epithelium

-- into peritubular fluid

-- into peritubular vessels that surround renal tubule

tubular epithelium

peritubular

capillaries

peritubular fluid

Afferentarteriole

Renal corpuscle Renal tubule and collecting duct

Efferentarteriole

Reabsorption:

tubular fluid into

blood

Secretion: blood

into tubular fluid

1

2 3


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1

I. Quick Anatomy

II. Functions

III. Kidney

IV. Nephron

A. Renal corpuscle and glomerulus

B. Renal tubule

V. URINE FORMATION3 steps

A. Glomerular filtration

B. Tubular reabsorption and secretion

C. Water conservation

1

2 3

Glomerular Filtration(Interactions Animation)

Renal Filtration

You must be connected to the internet to run this animation
http://www.wiley.com/college/tortora/0470084715/animations/anim_renal_filt/screen0.swfhttp://www.wiley.com/college/tortora/0470084715/animations/anim_renal_filt/screen0.swf


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The daily composition of plasma, filtrate, and urine are compared.

Glomerular Filtration

Total

Amount in

Plasma

Amount in 180 L

of filtrate /day)

Amount

returned to

blood/d

Reabsorbed)

Amount in

Urine /day)

Water passive) 3 L 180 L 178-179 L 1-2 L

Protein active)

200 g 2 g 1.9 g 0.1 g

Glucose active)

3 g 162 g 162 g 0 g

Urea passive)

1 g 54 g24 g

about 1/2)

30 gabout 1/2)

Creatinine

0.03 g 1.6 g0 g

all filtered)

1.6 g

none reabsorbed)

1. filtrationonly in renal corpuscle

--

--

A. Glomerular Filtration

2. filtration pressure

a. hydrostatic pressure -

i.glomerular blood hydrostatic pressure

GBHP


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1

GLOMERULAR BLOOD

HYDROSTATICPRESSURE

(GBHP) = 55 mmHg

Proximal convoluted tubule

Capsular

space

Glomerular

(Bowman's)

capsule

Efferent arteriole

Afferent arteriole

1

2. filtration pressure

a. hydrostatic pressure -

` i.glomerular blood hydrostatic pressure

GBHP

fluid pushing through wall of glomerulus55 mm Hg

ii. capsular hydrostatic pressure

CHP

GLOMERULARBLOOD

HYDROSTATIC

PRESSURE(GBHP) = 55 mmHg

CAPSULARHYDROSTATIC

PRESSURE(CHP) = 15 mmHg

Proximal convoluted tubule

Capsular

space

Glomerular

(Bowman's)

capsule

Efferent arteriole

Afferent arteriole

1 2


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1

b. blood colloid osmotic pressure

BCOP-

GLOMERULARBLOOD

HYDROSTATIC

PRESSURE(GBHP) = 55 mmHg

CAPSULARHYDROSTATIC

PRESSURE

(CHP) = 15 mmHg

BLOOD COLLOIDOSMOTIC

PRESSURE(BCOP) = 30 mmHg

NET FILTRATION PRESSURE (NFP)

= GBHPCHPBCOP

= 55 mmHg15 mmHg30 mmHg= 10 mmHg

Glomerular

(Bowman's)

capsule

Efferent arteriole

Afferent arteriole

12

3

3. glomerular filtration rate (GFR) -

amount of filtrate produced every minute

GFR is regulated 3 ways:

a. renal autoregulation

b. neural regulation

c. hormonal regulation


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1

a. renal autoregulation - nephrons adjust their

own blood flow and GFR without hormonal or nervous

control

two ways:

i. muscular

I . HOW IT WORKS:

increased arterial blood pressure stretches the

afferent arteriole

arteriole constricts (reflex) and

decreased arterial blood pressure,

the afferent arteriole relaxes and

RESULT: filtration rate remains stable

ii. tubuloglomerular feedback

mechanism:

--glomerulus receives feedback from the

___________________on the status of the downstreamtubular fluid

--glomerulus adjusts filtration to regulate the

composition of the fluid and systemic blood pressure

-- juxtaglomerular apparatus


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1

Renal corpuscle

(external view)

Afferent arteriole

Juxtaglomerular cell

Macula densa

DCT

Mesangial cell

Efferent arteriole

Endothelium of

glomerulus


Podocyte of visceral layer of

glomerular (Bowmans) capsule

Pedicel

Mesangial cell

Capsular space

Parietal layer of glomerular

(Bowmans) capsule

Proximal

convoluted

tubule

ii. tubuloglomerular feedback mechanism:

I. The Juxtaglomerular Apparatus

two cell types involved:

1. macula densa

--epithelial cells at end of the nephron loop and

beginning of DCT

--senses variations in flow or fluid composition and

2. juxtaglomerular (JG) cells

--smooth muscle cells in the

--respond to paracrine by

HOW IT WORKS:

If GFR rises :

1. the flow of tubular fluid increases and

less NaCl is reabsorbedso macula densa senses

2. macula densa signals JG cells to contract

which constricts afferent arteriolewhich


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1

PCT

DCT

Some stimulusdisrupts

homeostasis by

Glomerularfiltration rate

(GFR)

ReceptorsMacula densacells of JGAdetect increaseddelivery of Na+,Cl , and water

Control centerJuxtaglomerular

apparatus

Effectors

Decrease inGFR

Return tohomeostasis when

response bringsGFR back to normal

Increasing

Decreasedsecretion

of nitric oxide

Afferent arterioleconstricts, whichdecreases bloodflow throughglomerulus

Output

Input

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

High GFR Reduced GFR

Rapid flow of

filtrate in renal tubules

Sensed by

macula densa

Constriction of

afferent arteriole

Paracrine

secretion


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1

If GFR falls :

1. the flow of tubular fluid decreases and

more NaCl is reabsorbedso macula densa senses

2. macula triggers afferent arterioles to

relax (dilate)which increases blood flowwhich

b. nervous system control of GFR -

ANS - sympathetic division

i. sympathetic nervous system

cause constriction of

reduce GFR

redirect blood to

c. hormonal regulation

i. atrial natriuretic peptide (ANP) -

hormone

--high BP in heart triggers release

--inhibits

--dilates

bottom line: ________in blood pressure


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1

ii. juxtaglomerular apparatus

low blood pressuretriggers JG cells to release

renin catalyzes a series of chemical reactions:

result is

Renal corpuscle

(external view)

Afferent arteriole

Juxtaglomerular cell

Macula densa

Ascending limb

of loop of Henle

Mesangial cell

Efferent arteriole

Endothelium of

glomerulus


Podocyte of visceral layer of

glomerular (Bowmans) capsule

Pedicel

Mesangial cell

Capsular space

Parietal layer of glomerular

(Bowmans) capsule

Proximal

convoluted

tubule

ii. juxtaglomerular apparatus

Angiotensin II functions:

(bottom line: restores systemic fluid volume and BP)

--system-wide vasoconstriction

--constriction of

--in PCT, increase

-- trigger production of

--increase sense of thirst


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1

1

2 3

Peritubular capillaries

Afferent

arteriole

Renal corpuscle Renal tubule and collecting duct

Glomerular filtration (filtration

of blood plasma by glomerulus)

Efferent

arteriole

Tubular reabsorption

from glomerular

filtrate into blood

Tubular secretion

from blood into

glomerular filtrate

Urine

(contains

excreted

substances)

GlomerulusGlomerular

capsule

Blood

(contains

reabsorbed

substances)

1

2 3

Glomerular filtrate

in renal tubule

Fluid in

tubule

lumen

Na+

Paracellular

reabsorption

Na+

Transcellular

reabsorption

Apical

membrane

Na+ Na+

Na+

Na+ Na+ATP

ADP

Tubule

cell

Tight junction

Basolateral

membrane

Interstitial

fluid

Diffusion

Active transport

Sodiumpotassium

pump (Na+/K+ATPase)

Peritubular

capillary

Key:


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2

DCT



Papillary

duct

Dilute

urine

Loop of

Henle

PCT

CollectingDuct

B. Tubular Reabsorption and Secretion

1. PCT - 65% of glomerular filtrate and

100% of glucose reabsorbed here

a. microvilli

b. lots of mitochondria for transporters

c. reabsorption starts with

d. water follows solutes

e. solvent drag -

f. water and nutrients taken up by

g. 100% of _______ reabsorbed here

i. ___________________


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2

Fluid in

tubule

lumen

Cl

K+

Ca2+

Mg2+Urea

Peritubular

capillary

Proximal

convoluted

tubule cell

Diffusion

Osmosis H2OH2O

Cl

K+

Ca2+

Mg2+

Urea

Fluid in

tubule

lumen

Na+

Na+ Na+

Proximal

convoluted

tubule cell

Tight junction Interstitial

fluid

Peritubular

capillary

2 Na+

GlucoseGlucoseGlucose

ATP

ADP

Na+glucose symporter

Glucose facilitated diffusion transporter

Diffusion

Sodiumpotassium

pump

Key:

Brush border (microvilli)

Total

Amount in

Plasma

Amount in 180 L

of filtrate /day)

Amount

returned to

blood/d

Reabsorbed)

Amount in

Urine /day)

Water passive)

3 L 180 L 178-179 L 1-2 L

Protein active)

200 g 2 g 1.9 g 0.1 g

Glucose active)

3 g 162 g 162 g 0 g

Urea passive)

1 g 54 g24 g

about 1/2)

30 gabout 1/2)

Creatinine

0.03 g 1.6 g0 g

all filtered)

1.6 g

none reabsorbed)


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2

DCT



Papillary

duct

Dilute

urine

Loop of

Henle

PCT

CollectingDuct

2. Loop of Henle -

-- another 25% of original filtrate volume

reabsorbed

--loop generates ____________ for water

conservation

a. thick = cuboidal actively transports

sodium and chloride out of tubule

Fluid in

tubule

lumen

Na+

Na+K+2Clsymporter

Diffusion

Leakage channels

Sodiumpotassium pump

Key:

Thick

ascending limb

cell

Vasa recta

Na+

Na+ Na+Na+

ATP

ADP

Cations:

Na+

K+

Ca2+

Mg2+Apical

membrane

(impermeable to

water)

Interstitial fluid is

more negative than

fluid in tubule lumen

Cations

2Cl2Cl2Cl2Cl

K+ K+


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2

b. thinsquamousvery permeable to

water

c. tubular fluid becomes very dilute


300

400200

100

1,200

700

900

400600

Na+

K+

Cl

H2O

1

2

3

5

4

The more salt thatis pumped out of the

ascending limb, thesaltier the ECF is inthe renal medulla.

Na+

K+

Cl

Na+

K+

Cl

Na+

K+

Cl

Na+

K+

Cl

Na+

K+

Cl

H2O

The saltier the fluid in theascending limb, the more

salt the tubule pumps intothe ECF.

The more water that leavesthe descending limb, the

saltier the fluid is thatremains in the tubule.

H2O

H2O

H2O

The higher the osmolarityof the ECF, the more water

leaves the descending limbby osmosis.

More salt is continuallyadded by the PCT.

Countercurrent Multiplier

(b) Recycling of salts and urea in the vasa recta(a) Reabsorption of Na+CIand water in a long-loop juxtamedullary nephron

Glomerular (Bowmans) capsule

Afferent

arteriole

Efferentarteriole

Glomerulus

Distal convoluted tubule

Proximalconvoluted

tubule

Symporters in thickascending limb cause

buildup of Na+and Cl

Interstitial fluidin renal medulla

300

1200

1000

800

Osmotic

gradient

600

400

H2OH2O

H2O

200

1200

980

600780

400580

200380

300

100

Loop of Henle1200 Concentrated urine

300

300

320

400

600

800

1000

1200

800

H2O

Urea

Papillaryduct

Collectingduct

300

500

700

900

1100

1200

400

800

1000

600

Na+CI

Blood flow

Flow of tubular fluid

Presense of Na+-K+-2CIsymporters

Interstitialfluid in

renal cortex

320

Juxtamedullary nephron

and its blood supply

together

Vasarecta

Loop of

Henle

H2O

H2O

H2O

H2O

H2O

H2O

H2O

1

H2O

H2O

Na+CI

Na+CI

H2O

Na+CI

H2O

Na+CI



Afferent

arteriole

Efferentarteriole

Glomerulus


Proximalconvoluted

tubule




300

1200

1000

800

Osmotic

gradient

600

400

H2OH2O

H2O

200

1200

980

600780

400580

200380

300

100


300

300

320

400

600

800

1000

1200

800

H2O

Urea

Papillaryduct

Collectingduct

Countercurrent flowthrough loop of Henle

establishes an osmoticgradient

300

500

700

900

1100

1200

400

800

1000

600

Na+CI

Blood flow




renal cortex

320



together

Vasarecta

Loop of

Henle

H2O

H2O

H2O

H2O

H2O

H2O

H2O

1

2

H2O

H2O

Na+CI

Na+CI

H2O

Na+CI

H2O

Na+CI



Afferent

arteriole

Efferentarteriole

Glomerulus


Proximalconvoluted

tubule




300

1200

1000

800

Osmotic

gradient

600

400

H2OH2O

H2O

200

1200

980

600780

400580

200380

300

100


300

300

320

400

600

800

1000

1200

800

H2O

Urea

Papillaryduct

Collectingduct

Countercurrent flowthrough loop of Henle

establishes an osmoticgradient

Principal cells incollecting duct

reabsorb morewater when ADH

is present

300

500

700

900

1100

1200

400

800

1000

600

Na+CI

Blood flow




renal cortex

320



together

Vasarecta

Loop of

Henle

H2O

H2O

H2O

H2O

H2O

H2O

H2O

1

2

3

H2O

H2O

Na+CI

Na+CI

H2O

Na+CI

H2O

Na+CI



300

1200

1000

800

Osmotic

gradient

600

400

H2OH2O

H2O

200

1200

980

600780

400580

200380

300

100

1200 Concentrated urine

300

300

320

400

600

800

1000

1200

800

H2O

Urea

Papillaryduct

Urea recyclingcauses buildup

of urea in therenal medulla

Collectingduct

Principal cells incollecting duct

reabsorb morewater when ADH

is present

300

500

700

900

1100

1200

400

800

1000

600

Na+CI

Blood flow




renal cortex

320

H2O

H2O

H2O

H2O

H2O

H2O

H2O

3

4

H2O

H2O

Na+CI

Na+CI

H2O

Na+CI

H2O

Na+CI


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d. countercurrent multiplier

i. fluid flowing in opposite directions in

ii. positive feedback loop

iii. increases salinity of medulla

iv. increases water reabsorption

Glomerular (Bowman's) capsule

Glomerulus

Distal convoluted

tubule

Interstitial

fluid in

renal

cortex

Collecting

duct

Interstitial

fluid in

renal

medulla

Papillary

duct

Dilute

urine

Loop of

Henle

Proximal

convoluted

tubule

Afferent

arteriole

300

300

350

550

750

900

750 750550

550 350 550

300

350 150 350

100

90

80

70

65

65

Efferent

arteriole

Bottom line: beginning of DCT is very dilute urine

DCT

Papillary

duct

Dilute

urine

Loop of

Henle

PCT Collecting

Duct


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2

3. DCT and collecting duct - fluid arriving contains

about 20% of original filtrate fluid

a. more water reabsorption needed

b. hormone regulation

i. aldosterone

released when systemic blood pressure is low

--

--

ii. ADH -

released when systemic blood pressure is _____

-- DCT and collecting duct become

iii. atrial natriuretic peptide -

released when systemic blood pressure is _____

--

--inhibits production of aldosterone and

ADH

--result =

PROXIMAL CONVOLUTED TUBULE

Reabsorption (into blood) of filtered:

Water 65% (osmosis)

Na+ 65% (sodiumpotassium pumps, symporters,

antiporters)

K+ 65% (diffusion)

Glucose 100% (symporters and facilitated diffusion)

Amino acids 100% (symporters and facilitated diffusion)

Cl 50% (diffusion)

HCO3

8090% (facilitated diffusion)Urea 50% (diffusion)

Ca2+, Mg2+ variable (diffusion)

Secretion (into urine) of:

H+ variable (antiporters)

NH4+ variable, increases in acidosis (antiporters)

Urea variable (diffusion)

Creatinine small amount

At end of PCT, tubular fluid is still isotonic to blood (300

mOsm/liter).

LOOP OF HENLE

Reabsorption (into blood) of:

Water 15% (osmosis in descending limb)

Na+ 2030% (symporters in ascending limb)

K+ 2030% (symporters in ascending limb)

CI 35% (symporters in ascending limb)

HCO3 1020% (facilitated diffusion)



Urea variable (recycling from collecting duct)

At end of loop of Henle, tubular fluid is hypotonic (100150

mOsm/liter).

RENAL CORPUSCLE

Glomerular filtration rate:105125

mL/min of fluid that is isotonic to

blood

Filtered substances:water and all

solutes present in blood (except

proteins) including ions, glucose,

amino acids, creatinine, uric acid

EARLY DISTAL CONVOLUTED TUBULE


Water 1015% (osmosis)

Na+ 5% (symporters)

CI 5% (symporters)

Ca2+ variable (stimulated by parathyroid

hormone)

LATE DISTAL CONVOLUTED TUBULE AND

COLLECTING DUCT


Water 59% (insertion of water channels

stimulated by ADH)

Na+ 14% (sodiumpotassium pumps

and sodium channels stimulated by

aldosterone)

HCO3 variable amount, depends on H+

secretion (antiporters)

Urea variable (recycling to loop of Henle)


K+ variable amount to adjust for dietary

intake (leakage channels)

H+ variable amounts to maintain acid

base homeostasis (H+ pumps)

Tubular fluid leaving the collecting duct is

dilute when ADH level is low and

concentrated when ADH level is

high.

Urine


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c. primary site for Ca++reabsorption

i. parathyroid hormone -

increases calcium reabsorption in DCT

d. secretion -

e. acid-base balance secrete H+or CO2

H2O + CO2 H2CO3 HCO3-+ H+

Fluid in

tubule

lumen

Na+ Na+

Proximal

convoluted

tubule cell

Interstitial

fluid

Peritubular

capillary

Na+/H+antiporter

HCO3facilitated diffusion transporter

Diffusion

Sodiumpotassium pump

Key:

Na+CA

ATP

ADP

HCO3HCO3

HCO3

H2CO3

CO2

Na+

H+

H+

Na+

Metabolic reactions

CO2 CO2

(a) Na+reabsorption and H+secretion

H2O

DCT



Dilute

urine

Collecting

Duct


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2

C. Water Conservation -

1. collecting ductstarts in cortex and leads

into medulla

a. many nephrons are dumping into

collecting duct

b. cd reabsorbs water andconcentrates urine

2. medulla of kidney

a. very high solute concentration;

b. water leaves collecting duct to

follow those solutes (osmosis)

Vasa

recta

300

Loop of

Henle

Juxtamedullary

nephron and its

blood supply

together

380

580

780

980

1200

800

600

400

200

100

H2O

H2OH2O

200

300

300

320

400

600

800

1000

1200

1200


Glomerulus

Distal convoluted

tubule

Efferent

arteriole

Afferent

arteriole

Proximal

convoluted

tubule

Interstitial fluid

in renal medulla

Osmotic

gradient

Symporters in

thick ascending

limb cause

buildup of

Na+and Clin

renal medulla

Countercurrent

flow through loop

of Henle

establishes

osmotic gradient

300

400

600

800

1000

1200

300 320

400

600

800

1000

1200

1100

900

700

500

Principal cells in

collecting ductreabsorb more

water whenADHis present

Urea recycling

causes buildupof urea inrenalmedulla

Papillary duct

Concentrated urine

Collecting duct

Loop of Henle

Urea

Na+Cl

H2O

Na+Cl

H2O

Na+ClH2O

Na+

Cl

H2O

Na+Cl

Interstitial

fluid in

renal cortex

H2O

Na+Cl

Blood flowPresence of Na+K+2Clsymporters


1

2

3

4

H2O

H2O

H2O

H2O

H2O

H2O

H2O

(a) Reabsorption of Na+, Cl, and water in

long-loop juxtamedullary nephron

(b) Recycling of salts and urea in vasa

recta

PROXIMAL CONVOLUTED TUBULE

Reabsorption (into blood) of filtered:

Water 65% (osmosis)

Na+ 65% (sodiumpotassium pumps, symporters,

antiporters)

K+ 65% (diffusion)

Glucose 100% (symporters and facilitated diffusion)

Amino acids 100% (symporters and facilitated diffusion)

Cl 50% (diffusion)

HCO3

8090% (facilitated diffusion)Urea 50% (diffusion)



H+ variable (antiporters)

NH4+ variable, increases in acidosis (antiporters)

Urea variable (diffusion)

Creatinine small amount

At end of PCT, tubular fluid is still isotonic to blood (300

mOsm/liter).

LOOP OF HENLE


Water 15% (osmosis in descending limb)

Na+ 2030% (symporters in ascending limb)

K+ 2030% (symporters in ascending limb)

CI 35% (symporters in ascending limb)

HCO3 1020% (facilitated diffusion)



Urea variable (recycling from collecting duct)

At end of loop of Henle, tubular fluid is hypotonic (100150

mOsm/liter).

RENAL CORPUSCLE

Glomerular filtration rate:105125

mL/min of fluid that is isotonic to

blood

Filtered substances:water and all

solutes present in blood (except

proteins) including ions, glucose,

amino acids, creatinine, uric acid

EARLY DISTAL CONVOLUTED TUBULE


Water 1015% (osmosis)

Na+ 5% (symporters)

CI 5% (symporters)

Ca2+ variable (stimulated by parathyroid

hormone)

LATE DISTAL CONVOLUTED TUBULE AND

COLLECTING DUCT


Water 59% (insertion of water channels

stimulated by ADH)

Na+ 14% (sodiumpotassium pumps

and sodium channels stimulated by

aldosterone)

HCO3 variable amount, depends on H+

secretion (antiporters)

Urea variable (recycling to loop of Henle)


K+ variable amount to adjust for dietary

intake (leakage channels)

H+ variable amounts to maintain acid

base homeostasis (H+ pumps)

Tubular fluid leaving the collecting duct is

dilute when ADH level is low and

concentrated when ADH level is

high.

Urine


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VI. URINE EXCRETION -

--urine is produced continually

-- storage possible thanks to

A. route:

collecting ductrenal pelvisureterbladder

urethra

1. ureter -

Frontal

plane

Anterior view of frontal section

Rugae of mucosa

Peritoneum

Trigone

Internal urethral sphincter

(involuntary)

External urethral sphincter

in deep muscles of

perineum (voluntary)

External urethral orifice

Detrusor

muscle

Internal urethral orifice

Urethra

Hip bone

(pubis)

Ureters

Ureteral openings

Sagittal

plane

Uterus

Urinary bladder

Pubic symphysis

Urethra

External urethral

orifice

Rectum

Vagina

(a) Sagittal section, female


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Sagittal

plane

Urinary bladder

(b) Sagittal section, male

Pubic symphysis

Prostate

Deep muscles of

perineum

Penis

Spongy urethra

External urethral

orifice

Testis

Scrotum

Rectum

Prostatic urethra

Membranous

urethra

2. urinary bladder - holds about 500 mL

a. detrusor muscle - contracts to

expel urine into urethra

b. internal urethral sphincter

c. external urethral sphincter

3. urethra - shorter in female;

Fig. 23.24


Stretch receptors

From pons

Pelvic nerve

Urethra

S2

S3

S4

5 6 7

2

3

4

8

1

1

2

3

4

5

6

7

8

Involuntary micturition reflex

Stretch receptors detect filling

of bladder, transmit afferent

signals to spinal cord.

Signals return to bladder from

spinal cord segments S2 and S3

via parasympathetic f ibers in

pelvic nerve.

Efferent signals excitedetrusor muscle.

Efferent signals relax internal

urethral sphincter. Urine is

involuntarily voided if not

inhibited by brain.

Voluntary control

For voluntary control, micturition

center in pons receives signals

from stretch receptors.

If it is timely to urinate,

pons returns signals to

spinal interneurons that

excite detrusor and relax

internal urethral sphincter.

Urine is voided.

If it is untimely to urinate,

signals from pons excite

spinal interneurons that

keep external urethral

sphincter contracted. Urine

is retained in bladder.

If it is timely to urinate, signals

from pons cease and external

urethral sphincter relaxes. Urine

is voided.

Sacral segments

of spinal cord

To pons

Motor

fiber

Sensory

fiber

Full

urinary bladder

Para-

sympathetic

ganglion in

bladder wall

Somatic motor fiber

of pudendal nerveExternal urethral

sphincter (voluntary)

Internal urethral

sphincter (involuntary)

Motor fibers to

detrusor muscle

B. micturition - urination


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1. involuntary micturition reflex

a. stretch receptors in bladder sense

when bladder is full communicate with spinal cord

b. spinal cord issues a command from S2 and S3

c. detrusor muscle

d. internal urethral sphincter

2. voluntary micturition reflex

a. stretch receptors in bladder signal pons

b. if brain OKs urination detrusor muscle is

and

internal urethral sphincter is

c. if brain NOT in favor of urination

pons excites external urethral sphincter

which constricts and holds urine in bladder

until it is time to urinate

Documents

Chap 26 Urinary Student 3