Kidney Structure & Function

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Kidney Structure& Function

Collecting ductLoop of Henle

Aminoacids

Glucose

H2O

H2O

H2O

H2O

H2O

H2O

Na+ Cl-

Mg++ Ca++Na+ Cl-

Removing IntracellularWaste

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intracellular waste

Animal systems evolved to support multicellular life

O2

CHO

CHO

aa

aaCH

CO2

NH3aa

O2

CH

O2

aa

CO2CO2

CO2

CO2

CO2

CO2 CO2

CO2

CO2

CO2

NH3

NH3 NH3

NH3

NH3

NH3

NH3NH3

O2

aa

CH

aa

CHO

O2

Diffusion too slow!

single cell

but whatif the

cells areclustered?

for nutrients in & waste out

extracellular waste

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Overcoming limitations of diffusion Evolution of exchange systems for

distributing nutrients circulatory system

removing wastes excretory system

systems to support multicellular organisms aa

CO2CO2

CO2

CO2

CO2

CO2 CO2

CO2

CO2

CO2

NH3

NH3 NH3

NH3

NH3

NH3

NH3NH3

O2

aa

CH

aa

CHO

O2

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Osmoregulation

Why do all land animals have to conserve water? always lose water (breathing & waste) may lose life while searching for water

Water balance vs. Habitat freshwater

hypotonic to body fluids water flow into cells & salt loss

saltwater hypertonic to body fluids water loss from cells

land dry environment need to conserve water may also need to conserve salt

hypotonic

hypertonic

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Intracellular Waste What waste products

are made inside of cells? what do we digest our food into…

carbohydrates = CHO lipids = CHO proteins = CHON nucleic acids = CHOPN

CO2 + H2ONH2

=ammonia

CO2 + H2O CO2 + H2O

CO2 + H2O + N CO2 + H2O + P + N

|

| ||H

HN C–OH

O

R

H–C–

Animalspoison themselves

from the insideby digesting

proteins!

lots!verylittle

cellular digestion…cellular waste

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Nitrogenous waste disposal Ammonia (NH3)

very toxic very soluble

easily crosses membranes must dilute it & get rid of it… fast!

How you get rid of nitrogenous wastes depends on who you are (evolutionary relationship) where you live (habitat)

aquatic terrestrial terrestrial egg layer

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Nitrogen waste Aquatic organisms

can afford to lose water ammonia

most toxic Terrestrial

need to conserve water

urea less toxic

Terrestrial egglayers

need to conserve water need to protect

embryo in egg uric acid

least toxic

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Freshwater animals Hypotonic environment

water diffuses into cells Manage water & waste together

remove surplus water & waste use surplus water to dilute ammonia & excrete it also diffuse ammonia continuously through gills

overcome loss of salts reabsorb in kidneys or active transport across gills

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Land animals Nitrogen waste disposal on land

need to conserve water must process ammonia so less toxic

urea = larger molecule = less soluble = less toxic 2NH2 + CO2 = urea produced in liver

kidney filter solutes out of blood reabsorb H2O (+ any useful solutes) excrete waste

urine = urea, salts, excess sugar & H2O urine is very concentrated concentrated NH3 would be too toxic

OC

HNH

HNH

Ureacosts energyto synthesize,

but it’s worth it!

mammals

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Egg-laying land animals

itty bittyliving space!

Nitrogen waste disposal in egg no place to get rid of waste in egg need even less soluble molecule

uric acid = BIGGER = less soluble = less toxic birds, reptiles, insects

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N

N N

N

O

HO

O

H

HH

Uric acid And that folks,is why most

male birds don’t have a penis! Polymerized urea

large molecule precipitates out of solution

doesn’t harm embryo in eggwhite dust in egg

adults still excrete N waste as white pasteno liquid wasteuric acid = white bird “poop”!

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Mammalian System Filter solutes out of blood &

reabsorb H2O + desirable solutes Key functions

filtration fluids (water & solutes) filtered out

of blood reabsorption

selectively reabsorb (diffusion) needed water + solutes back to blood

secretion pump out any other unwanted

solutes to urine excretion

expel concentrated urine (N waste + solutes + toxins) from body

blood filtrate

concentratedurine

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Mammalian Kidney

kidney

bladder

ureter

urethra

renal vein& artery

nephron

microvilli onepithelial

cells

adrenal glandinferior

vena cavaaorta

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Nephron Functional units of kidney

1 million nephrons per kidney

Function filter out urea & other

solutes (salt, sugar…) blood plasma filtered

into nephron high pressure flow

selective reabsorption ofvaluable solutes & H2O back into bloodstream greater flexibility & control “counter current

exchange system”

whyselective reabsorption

& not selectivefiltration?

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Mammalian kidney

Proximaltubule

Distal tubule

Glomerulus

Collecting ductLoop of Henle

Aminoacids

Glucose

H2O

H2O

H2O

H2O

H2O

H2O

Na+ Cl-

Mg++ Ca++

Interaction of circulatory & excretory systems

Circulatory system glomerulus =

ball of capillaries Excretory system

nephron Bowman’s capsule loop of Henle

proximal tubule descending limb ascending limb distal tubule

collecting duct

How candifferent sectionsallow the diffusion

of different molecules?

Bowman’s capsule

Na+ Cl-

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Nephron: Filtration At glomerulus

filtered out of blood H2O glucose salts / ions (Na+ / Cl–) urea

not filtered out cells proteins

high blood pressure in kidneys force to push (filter) H2O & solutes out of blood vesselBIG problems when you start out with high blood pressure in systemhypertension = kidney damage

H2O&

solutes

cells &large

molecules

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Nephron: Re-absorption Proximal tubule

reabsorbed back into blood NaCl

active transport of Na+

Cl– follows by diffusion

H2O glucose HCO3

-

bicarbonate buffer for

blood pH

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Nephron: Re-absorptionstructure fits

function! Loop of Henle descending limb reabsorbed

H2O structure

many aquaporins in cell membranes

high permeability to H2O

no Na+ or Cl– channels impermeable

to salt

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Nephron: Re-absorptionstructure fits

function! Loop of Henle ascending limb reabsorbed

Na+ & Cl–

structure many Na+ / Cl– channels

in cell membranes high permeability

to Na+ & Cl–

no aquaporins impermeable to H2O

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Nephron: Re-absorption Distal tubule

reabsorbed salts H2O bicarbonate

HCO3-

regulate blood pH

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Nephron: Reabsorption & Excretion Collecting duct

reabsorbed H2O = through

aquaporins excretion

concentrated urine

to bladder impermeable

lining = no channels in cell membranes

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Osmotic control in nephron How is all this re-absorption achieved?

tight osmotic control to reduce the energy cost of excretion

use diffusion instead of active transportwherever possible

the value of acounter current exchange system

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Summary Not filtered out of blood

cells u proteins remain in blood (too big)

Reabsorbed back to blood: active transport Na+ u amino acidsu glucose

Reabsorbed back to blood: diffusion H2O u Cl–

Excreted out of body urea excess H2O u excess solutes (glucose,

salts) toxins, drugs, “unknowns”

whyselective reabsorption

& not selectivefiltration?

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Any Questions?