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by kidney

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11.3 Osmoregulation in mammals

a.explain the process of ultrafiltration, reabsorption and

secretion in the formation of urine

b.explain the role of ADH and aldosterone, and the related

hormones in regulating water, sodium and potassium ions of

urine

c.explain the regulation of pH of tissue fluid.

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Copyright 2009, John Wiley & Sons, Inc.

Overview of kidneyfunctions

Regulation of blood ionic composition

Regulation of blood pH

Regulation of blood volume

Regulation of blood pressure Maintenance of blood osmolarity

Production of hormones (calcitrol anderythropoitin)

Regulation of blood glucose level

Ecretion of wastes from metabolic reactionsand foreign substances (drugs or toins)

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Structure of the kidney

5

$ach "idne#

contains around a

million units called

nephrons

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Kidneys produced urine and

excreted it out from the body.

situated in the dorsal of the

abdomen.

STRUCTURE OF THE KIDNEYS

$ach "idne#

% has a cortex &outer' la#er,% medulla &inner'% pel(is &opens into ureter'% consists of numerous tubular

unit called nephrons% $ach "idne# consist of about

one million nephrons.

6

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SECTI!"# $I"%"' o( )I$!E*+!CTI!"# !IT -

!E/!

Proximal

convoluted tubule

Distal convoluted

tubule

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FUNCTIONAL UNIT : A NEPHRON

Distal con(oluted

tubule

)roximal con(oluted tubule

Distal con(oluted

tubule

)eritubularcapillaries

*ollecting

ductDescending

limb

Ascending

limb

Loop of

Henle

+asa

ecta

Afferent

arteriole fromrenal arter#

$fferent arteriole

from glomerulus

-ranch of (ein

lomerulus

-owmann capsule

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$ach nephron consists of /

i % a -owman0s capsule which begins in the

cortex.ii% continues to form the proi!"#

con$o#uted tu%u#ewhich leads to the

medulla.

iii % form a %shaped loop called #oop of

Hen#eand leads on to form theiii % dist"# con$o#uted tu%u#ebefore opens

into

i(% a co##ectin& duct'

( % 2n the -owman0s capsule is a little mass

of capillaries, arise from a branch of the

renal arter# glomerulus.

(i% capillaries lea(e the glomerulus to

surround the tubule before enter a branch

of the renal (ein.

A Nephron

9

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The ro#e of kidney

(' As "n ecretory or&"n/ &excretion'

produces urinein which certain products ofmetabolism and excessi(e inta"e of certain chemicals

toxic substances are ecreted out of the %ody.

)' As "n os!ore&u#"tory or&"n: *os!ore&u#"tion+

it controls the regulation of the

i %% $o#u!eof water in the bod#

ii 4 os!otic pressure iii 4 ions concentr"tion

i( 4 blood pH

Excretion- the removal of the metabolites that have exceeded a

critical concentration

Osmoregulation- control the regulation of the volume &com osition o bod luid. s3lt 3n 3ter

10

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1. !R"#E $ORM%&"O#

a) Ultrafiltration

b) Reabsorption / selective reabroption

c) Secretion

11

Hi t l f l

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Histology of a renalcorpuscle

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!'&R%$"'&R%&"O# is

A process in which smaller molecules are filtred from the

blood in the glomerulus into the -owman capsule

(a) Details of filtration membrane

Filtration slit

Pedicel

Fenestration (pore) of glomerular

endothelial cell: prevents filtration of

blood cells but allos all components

of blood plasma to pass through

!asal lamina of glomerulus:

prevents filtration of larger proteins

Podoc"te of visceral

la"er of glomerular

(!oman#s) capsule

$

%

8 52L!A!2O6 7$7-A6$ 8

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Filtration slitPedicel of podoc"te

Fenestration (pore) of

glomerular endothelial cell

!asal lamina

&umen of glomerulus

(b) Filtration membrane

' *+,---x

(a) Details of filtration membrane

Filtration slit

Pedicel

Fenestration (pore) of glomerular

endothelial cell: prevents filtration of

blood cells but allos all components

of blood plasma .ater small solute0 to pass through

Podoc"te of visceral

la"er of glomerular

(!oman#s) capsule

$

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$ORM%&"O# O$ !R"#E ultra*ltrationreabsorptionsecretion

involves

1. !'&R%$"'&R%&"O#

Process occurs at the glomerulus+iameter of the eferent arteriole which carries

blood out of the glomerulus issmaller than thea,erent arteriole which carries blood into theglomerulus&he high hydrostatic pressure develops in theglomerulus

&he high hydrostatic pressure causes manyconstituents of blood plasma to be *ltered out fromthe glomerulus into -owman.s capsule (ultra*ltration)&he *ltrate is called glomeruler *ltrate

15

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16

%,erent

arteriole

E,erentarteriole

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!he concentration of each of these solutes is

thes"!eas it is in the blood plasma.Howe(er, as the plasma contains plasma

proteins in solution, so the total concentration

of all solute is greater in the blood plasma.!herefore, plasma has a lower solute

potential than the glomerular filtrate.

lomerular filtrates is hypotonicto the blood

plasma.

5iltrate then mo(es along the nephron for

reabsorption to occur

1

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20

Ren"# corpusc#eof a

human

6ote/

1. 2nterlobular arter# and its

endothelial and smooth

muscle cells8

9. the (ascular &top left' and

urinar# &bottom' poles8

3. the capillar# plexus of the

glomerulus and

-owman:s capsule8

;. the distal con(oluted

tubule &abo(e the

corpuscle'.

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Proi!"# "nd dist"#con$o#uted tu%u#es.

7allor#%ax

6ote/

1. )roximal ones ha(e

brush borders, an

acidophilic c#toplasm andbasal striations can be

seen in some places8

9. Distal ones ha(e a less

acidophilic c#toplasm.

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)'' SELECTI,E REA-SORPTION

( by proximal convoluted tubule)

=>? occurs in the proximal con(oluted tubule

@electi(e reabsorption occurs b# diffusion "nd

"cti$e tr"nsport .

A## ucose. "!ino "cids. $it"!ins so!es"#ts are reabsorb b# acti(e transport. Ure" is

not re"%sor%ed.

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Selective reabsorption

"s (iltere (li :o;es 3long t

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Reabsorption and secretion in theproimal convoluted tubule

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!he substances &such as glucose and amino acids'

diffuse from filtrate to the cells of the tubule wall.!he cubical epithelial cells which line the tubule

wall ha(e numerous microvilli on their free

surfaces which increase the surface area of wall

exposed to the glomerular filtrate. @ubs. then are actively transported into the

basal channel where the# diffuseinto the blood

capillaries.

!he solutes than carried awa# in the blood, so

maintaining the conc. gradient.

2

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@ome mineral ions such as sodium ions are

acti(el# transported across the infoldedmembrane. !he# are followed b# chloride

ions.B & C this increased osmotic pressure of

the cell cause water to be ta"en up

osmoticall#' !he remo(al of amino acids, glucose and

mineral ions ma"e the filtrate more dilute and

water potential increases

/"ter &E?' then mo(es out b# osmosis and

is caried awa#.

2

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At the end of the proximal tubule, a balanced

has been reached and the filtrate is isotonicwith

the plasma. @o, as the filtrate enters the loop of Henle, it is

isotonic to the blood and contains water, some

salt and urea

%bout 123 of water / some salts arereabsorbed

into the blood capillaries by osmosis /active transport

If a person is suering from diabetes melitus, theconcentration of glucose in the ltrate may be higher thanusual. It may therefore not all glucose be reabsorbed. This iswhy glucose may appear in the urine of a suerer

( glycosuria). 29

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e3

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RE%-4ORP&"O# at 'OOP O$ HE#'E!he fitrate now onl# contain water, some salts urea

passes along the loop of Henle.

About 9>? of water some salts are reabsorbedinto the blood capillaries b# osmosis acti(e transport.

!hen it continue to pass through distal con(oluted tubule

and collecting duct, where some water salts are

reabsorbedinto the blood capillaries depends on blood

osmotic pressure.

the reabsorption of water regulated b# ADH &antidiuretic

hormone'the reabsorption of salts regulated b# Aldosterone

hormone. 75

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ROLE THE LOOP OF HENLE

to ma"e tissue fluid and the tissues

!edu##"of the between the nephron

& interstitial tissues' $ery concentr"ted0ith so#utes'

& lowest water potential in the bod#'

7

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Ro#e of #oop of Hen#e

C !he wor"ing of the loop of Henle

!he ascending limb acti(el# transported 6aFout

of the filtrate into surrounding tissues. *l%follows

pasi(el#.

@urrounding tissue becomes more concentrated

with salt than the filtrate. Gater molecules cannot

follow b# osmosis as the wall of ascending limb

is impermeable to water.

40

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!he #on&erthe loop, the more sodium chloride

can be transported and the !ore

concentr"ted the medulla tissues canbecome.

!he deeper part of the medulla near the pel(is

becomes most concentrated and so has the

#o0est 0"ter potenti"#'

!here is a water potential gradient between

the deep part of the medulla and the part near

the cortex.

41

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6aF4F pump in the thic" ascending limb of the

loop of Henle

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The 1ist"# Con$o#uted Tu%u#e

!he cells of the wall of the distal con(olutedtubule &D*!' are si!i#"r to those of proximal

con(oluted tubule.

!he role is to reabsorbs (ar#ing Iuantities of

inor&"nic ionsaccording to the bod#Js needs

2t also can secrete substances into the filtrate.

5or example, it contro#s the pH of the blood b#

secreting the h#drogen ions into the filtratewhen the blood is too acidic and if it is too

al"aline it secretes h#drogen carbonate ion into

the filtrate.

45

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tubular Secretion

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4

"lthogh rine (or:3tion occrs pri:3rily

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4

$i((erent concentr3tionD

7

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9O#4ER:%&"O# "4 % ;E< &O

&ERRE4&R"%' %+%P&%&"O# %s the *ltrate =ows inthe collecting ductpast interstitial =uid ofincreasing osmolarity0

more water moves outof the duct by osmois0thereby concentratingthe solutes0 including

urea0 that are leftbehind in the *ltrate

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1. 4E9RE&"O#

As filtered fluid mo(es along tubule and through collecting duct,other material secreted into fluid such as wastes, drugs, and

excess ions 4 remo(es substances from blood

!he process in(ol(es the pumping out of the waste

products from the peritubular capillaries into the tubule

&)*! and D*!'

!he waste products such as urea, uric acid ammonia

and h#drogen ions arepumped out of the blood

capillaries into the distal con(oluted tubule b# acti(e

transport.

@ome drug, h#drogen ions, ammonium and other toxin

b# simple diffusion, along the )*!.

!he final glomerular filtrate which remains in the

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.. 4E9RE&"O#

4ome drug and other toin by simple di,usion0

along the tubule&he *nal glomerular *ltrate which remains inthe collecting duct is called urine

&he ma>or constituents of urine are ?@3 ofwater0 163 nitrogenous products (urea0 uric

acid0 ammonia0 creatinine)0 A63 salts / bilepigments$rom the collecting ducts0 urine is channelledinto the pelvis / carried out of the kidney by theureter to the urinary bladder / ecreted out of thebody by urethra

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4 f *lt ti b ti d

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4ummary of *ltration0 reabsorption0 andsecretion in the nephron and collecting duct

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& egulation of blood water potential4 by kidney of mammals'

1efinition :

C 2s the process of controlling of the

0"ter content and the concentr"tion of

s"#t2 inor&"nic ionsin the bod#

& animal or proto

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The os!otic concentr"tion of the %#ood !ust %e!"int"ined "t " ste"dy st"te 3'

I!port"nce :

!o bathed bod# cells in isotonic tissue f#uid withtheir c#toplasm

!his pre$ents ecessi$e "!ounts of 0"ter

entering or lea(ing cells osmoticall# which woulddamage the cells.

*ells can carr# out metabolic reactions efficient#y

( Regulation of blood water potential by kidney of mammals )

56

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5

Osmoregulation K. achie(ed with the help of

A1H or $"sopressin that controls thepermeabilit# of the wall of D*! and *D

&collecting duct'

Antidiuretic hor!one * A1H +

)roduced in hypoth"#"!us stored in posterior pituit"ry "nd.

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5

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Antidiuretic hor!one * A1H +

Function A1H :

1.!he presence of ADH, increases the permeabilit# of thewall of dist"# con$o#uted tu%u#eand co##ectin& ducts

to water.

H2O in filtrate cortex & medulla blood capillary

(in DCT) reabsorb

9. Also increases the permeabilit# of the collecting duct

with ure". rea from filtrate diffuses into the interstitial

fluid of medulla. Increases the osmotic conc ( decreasewp)of the medulla tissue resulting in the reabsorption of

water from the decending limb of Henle.

59

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!he presence of ADH causes the production

of hypertonic or concentr"ted urine

( More DH ! more concentrated urine

absence"less DH ! dilute(#ypotonic urine)

Ho0 this condition h"ppens4

60

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1. !he receptor 8 os!oreceptor situated in

h#pothalamus will detect the ch"n&es in theblood osmotic concentration & 0"ter potenti"#+

9. 2f the blood osmotic concentration flowing near the

osmoreceptors below than the normal level .

impulses are transmitted to the posterior pituit"ry"nd and is stimulates to release AH into the

blood

61

When blood osmotic concentration is

high !Dexcessive s$eatin% in%est excess salt not take inade'uate $ater it diet

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3. ADH circulates in the blood and affects on its

t"r&et ce##s, the cells of the walls of the distal

convoluted tubule and collecting duct

;. !he membrane of the cells become !ore

per!e"%#e to 0"ter, and water molecule is

reabsorb from filtrate into cortex and medulla

and .

E. !his will produced a less (olume and

hypertonic urine and excreted out of the bod#

b# the "idne#

62

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. !his process also increases the blood osmotic

concentration (wp) bac" to normal as waterdrawn in from nephron tubule into the (asa

recta.

.. !he osmoreceptors also stimulate a sens"tion

of thirst.

=. Although the wp has been controlled, s0e"tin&

will ha(e #ed to " reduction in the (olume of

bod# fluids which is restored b# drin"ing.

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M. Ghen the blood osmotic concentration

(wp) rises bac" to normal, theosmoreceptors are not longer stimulated.

1>. !he release of ADH is reducedstopped, the

cells of the walls of D*! and *D becomemuch morei!per!e"%#e to 0"ter.

11.!he water remains in the urine, hypotonic

urine is produced and the wp becomes

lowered as more water is lost relati(e to thesolutes.

64

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!he reabsorption of water in the "idne# is

regulated b# antiduresis hormone &ADH'

released b# pituitar# gland

)2!2!AN LA6D

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6

The "$/ or 3nti iretic hor:one is respons

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&HE RO'E O$ %'+O4&ERO#E&o control the concentration of sodium

and potassium ions in the blood

Sodium"lthogh 9= o( the soi: h3s 3lre3y

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!he5ut"o!eru#"r "pp"r"tus *67A+, is a

specialised tissue in the (accinit# of the arterioles

leading to glomeruli of the "idne#

respondto a decrease in blood pressure

or blood (olume b# releasing

en

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2

#o > rennin

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Renin initiates the con(ersion of

"n&iotensino&en&plasma protein' to itsacti(e form, "n&iotensin I& in the

bloodstream' which then is con(erted to

"n&iotensin II8

An&iotensin II :

a' act directl# to incre"se %#ood pressureb#

causing arterioles to constrict.

7

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b' act to incre"ses %#ood

$o#u!e b#

i' signaling )*! to reabsorp more

6a*l and water

ii' signaling the adrenal gland toreleased "#dosterone, and this

hormone will stimulates the

acti(e reabsorption of 6aF

&and *l%' across the cells walls

of the 1CT. esults in the

mo(ement of water out of 1CT

b# osmosis into the blood.

"$E!"# %#"!$

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O@7OLA2!N of the blood

High concentration high osmotic pressure low G)

Drin"ing reduces the osmolarit# of the blood and inhibit the secretion of ADH

!he blood pressure rises

until it returns to the setpoint.

!hus, the releasing of renin

, lead to an incre"se in

%#ood $o#u!eand %#oodpressure. results that

complete the feedbac"

circuit b# suppressing the

further release of renin..

6

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HO7O6AL *O6!OL O5 2D6$N b# negati(e feedbac" mechanism

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#ormal bloodsodium concentration

,lood volume

and blood

pressure rises

Less renin

producedLess angiostensin 22

formed

Adrenal cortex

produces less

aldosterone

#ormal bloodsodium

concentration

Adrenal cortex

produces more

aldosteron

7ore angiostensin 22

formed

7ore renin

produced

-lood (ol.and

pressure f"##s

-a. rises

-a. falls

-a. falls

-a. rises

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9

&HE REB!'%&"O# O$ -'OO+ pHby Kidney

#ormal blood pH is D5

-lood and interstitial fluid ha(e a pH of about 9'

!he pH must be "ept constant or within narrow limit

because en

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0

9an blood pH change from the set pointD5

high 9O1 concentration due to cellular respiration

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egulation of blood pH

ole of "idne#

eabsorption of bicarbonate and h#drogen ions

$xcretion of bicarbonate and h#drogen ions

-lood and interstitial fluid ha(e a pH of about 9''!he presenceof carbon dioxide reduces the blood pH

Abrupt change in blood pH is pre(ented b# the presence of

plasma proteins in the blood, while h#drogen carbonate and

phosphate ions act together as %uffers.

-# peritubule of

"idne#

1

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2f the blood pH is f"## %e#o0 9', due to high *O9 concK.

the cells of the )*! and D*!, combine water and carbon

dioxide to form carbonic acid which the dissociates into HF

and H*O3% .

H*O3% ions are acti(el# absorb into the blood combine with

excess HF ions in the blood, pH of %#ood rise to thenor!"# st"te

h#drogen ions from dissociation of carbonic acid are acti(el#

pumped into the filtrate& lumen of D*!' , and combine with

H)O;9% to form H9)O;% and are excreted in the urine

2

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5

eninne o( the (nctions o( the Biney is to :onitor

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correcti;e 3ction i( it shol rop. The Biney oes this

11. 3 kidney.ppt

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