osmoregulation chapter 44 osmoregulation balance of water & solute concentration intracellular...
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Osmoregulation
Chapter 44
Osmoregulation
Balance of water & solute concentrationIntracellular & extracellularIons (solutes)Na+1, Cl-1
Osmolarity
HyperosmoticHypoosmoticIsoosmoticNormal saline (0.9%)5% dextrose
Solutes Water
Selectively permeablemembrane
Net water flow
Hypoosmotic side:• Lower solute
concentration• Higher free H2O
concentration
Hyperosmotic side:• Higher solute
concentration• Lower free H2O
concentration
Osmoregulation
OsmocomfomersBody fluids have same concentration as environmentOcean invertebratesOsmoregulatorsConstant blood osmolarityVertebrates
Osmoregulation
(a) Hydrated tardigrade (b) Dehydrated tardigrade
50 µm
Nitrogenous wastes
Proteins, DNA & RNA contain nitrogenBreak downs-waste (NH2)
Aquatic animalsNH3
Mammals, amphibiansUreaBirds, reptiles, insects Uric acid
Nitrogenous wastes
Urea
Uric acid
Nitrogen wastes
Many reptiles(including birds),insects, land snails
Ammonia Uric acidUrea
Most aquaticanimals, includingmost bony fishes
Mammals, mostamphibians, sharks,some bony fishes
Excretory process
Excretory systemsRegulate solute concentrationsProduce urineRefine filtrate from body fluids
Excretory process
FiltrationBlood (body fluids) is filtered Forms filtrate (urine)ReabsorptionIons & nutrients are recoveredReturned to body from filtrate
Excretory process
SecretionWastes/water from capillaries to filtrate (urine)ExcretionRelease filtrate (urine) from bodyRelease nitrogenous metabolites
Excretion
Capillary
Excretion
Secretion
Reabsorption
Excretorytubule
Filtration
Filtrate
Urin
e
Figure 44.12a
Posteriorvena cava
Renalcortex
Excretory Organs Kidney Structure Nephron Types
Renalmedulla
Renalartery
Renalvein
Ureter
Renal pelvis
Renalmedulla
Renalcortex
Corticalnephron
Juxtamedullarynephron
Renal arteryand vein
Aorta
Ureter
Urethra
Urinarybladder
Kidney
Anatomy
KidneyUreterBladderUrethraRenal artery/vein Blood supply of kidney
Anatomy
Renal cortexOutside of kidneyRenal medullaInside of kidney (hypertonic)Renal pelvisFunnel shapedUreter meets kidney
Kidney
Anatomy
Nephron:Functioning unit of kidney1 million in each kidneyGlomerulusBowman’s capsuleProximal (convoluted) tubuleLoop of henleDistal (convoluted) tubule
Nephron
Kidney
Kidney
Pathway
Pathway through kidney
Blood forced into glomerulusBed of capillariesBlood cells & proteins are too largePlasma goes through with minerals & waterFiltrateEnters Bowman’s capsuleProximal tubuleLocated in renal cortex
Pathway through kidney
Enters loop of HenleIn the loop goes deep in the renal medulla Fluid returnsDistal tubule Drains into collecting ductGoes into renal pelvis (urine)Ureter
Pathway through kidney
Nephron
Corticalnephron
Juxtamedullarynephron
Collectingduct
(c) Nephron types
Torenalpelvis
Renalmedulla
Renalcortex
Nephron
Pathway through kidney
Capillaries surround the loopReabsorb water & ions
NephronAfferent arteriolefrom renal artery
Efferentarteriole fromglomerulus
SEM
Branch ofrenal vein
Descendinglimb
Ascendinglimb
Loop ofHenle
(d) Filtrate and blood flow
Vasarecta
Collectingduct
Distaltubule
Peritubular capillaries
Proximal tubule
Bowman’s capsuleGlomerulus
10 µm
Pathway through kidney
1000-2000L of blood flow through a day180 L of water a dayUrinate only 1.5 L per dayReabsorb glucose, aa, vitamins & water Excrete wastes, harmful substances, H+ & waterMaintain homeostasis (blood volume, pH electrolytes & BP)
Regulation diagram
Closer look
Proximal tubuleMost nutrients reabsorbed to blood NaCl, H2O, HCO3
-1 reabsorbed to bloodNH3, H+1 secreted into the tubule from blood
Bowman’s Capsule and Proximal Tubule
Closer look
Loop of HenleDescending loop water is reabsorbedAscending loop NaCl is reabsorbedLonger loop-more NaCl is absorbed
Closer look
Distal tubuleRegulation of K+1 & NaCl here Depends on body’s needsK+ is secreted into tubuleNaCl reabsorbed into tubule
Loop of Henle and Distal Tubule
Closer look
Collecting ductNaCl can be reabsorbed hereSome urea diffuses out of tubeRemaining filtrate passes as urine
Collecting Duct
Regulation diagram
Transport
Key
ActivetransportPassivetransport
INNERMEDULLA
OUTERMEDULLA
H2O
CORTEX
Filtrate
Loop ofHenle
H2O K+HCO3–
H+ NH3
Proximal tubule
NaCl Nutrients
Distal tubule
K+ H+
HCO3–
H2O
H2O
NaCl
NaCl
NaCl
NaCl
Urea
Collectingduct
NaCl
Regulation of kidney
ADH (antidiurectic hormone)VasopressinReleased by posterior pituitary glandReleased in response to increased solute concentration in plasmaDehydrated or eating salty foodsDistal tubule/collecting duct become more permeable to waterDecreases the amount of water in urine Reabsorbs more water
ADH
Thirst
Drinking reducesblood osmolarity
to set point.
Increasedpermeability
Pituitarygland
ADH
Hypothalamus
Distaltubule
H2O reab-sorption helpsprevent further
osmolarityincrease.
STIMULUS:Increase in blood
osmolarity
Collecting duct
Homeostasis:Blood osmolarity
(300 mOsm/L)
(a)
Osmoreceptors inhypothalamus trigger
release of ADH.
ADH
ADHreceptor
ADH
cAMP Secondmessenger
COLLECTINGDUCT CELL
LUMENCollectingduct
Proteinkinase A
Storagevesicle
Aquaporinwaterchannel
Exocytosis
H2O
H2O
Effect of ADH
Regulation of kidney
Low blood volumeJuxtaglomerular apparatus Tissue located near artery supplies blood to glomerulusSecretes renin (enzyme)Angiotensinogen to angiotensin IAngiotensin I to angiotension IICauses blood vessels to constrictCauses release of aldosterone
Regulation of kidney
AldosteroneReleased by the adrenal cortexDue to low sodium levelsDue to low blood volumeStimulates distal tubules/collecting ducts to reabsorb sodium Chlorine & water followStimulates potassium to be excreted
Regulation of kidney
AldosteroneIncreases serum sodium levelsIncreases water (blood volume)Decreases serum potassium levelsACE inhibitor Blood pressure medicationBlocks the affects of aldosterone
Aldosterone
Renin
Distaltubule
Juxtaglomerularapparatus (JGA)
STIMULUS:Low blood volumeor blood pressure
Homeostasis:Blood pressure,
volume
Liver
Angiotensinogen
Angiotensin I
ACE
Angiotensin II
Adrenal gland
Aldosterone
Arterioleconstriction
Increased Na+
and H2O reab-sorption in
distal tubules
Regulation of kidney
ANH (atrial natriuretic homone)Secreted by right atriumDue to increased blood volumeCauses sodium/water to be released Lowers blood volumeOpposes aldosterone
Problems
Diabetes insipidusLacks ADHPituitary problemIncreased urinationLeads to dehydration & low BPAlcohol consumptionBlocks ADH