Presentation 12 - Osmoregulation And Excretion
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Transcript of Presentation 12 - Osmoregulation And Excretion
OSMOREGULATION AND EXCRETION
Key Concepts
Osmoregulation balances the uptake and loss of water and solutes
An animal’s nitrogenous wastes reflect its phylogeny and habitat
Diverse excretory systems are variations on a tubular theme
Nephrons and associated blood vessels are the functional units of the mammalian kidney
The mammalian kidney’s ability to conserve water is a key terrestrial adaptation
Diverse adaptations of the vertebrate kidney have evolved in different environments
Key Words homeostasis excretion uric acid filtration renal vein urethra nephron proximal tubule collecting duct efferent arteriole antidiuretic
hormone (ADH)
secretion (selective reabsorption)
renal artery urinary bladder renal medulla Bowman's capsule distal tubule afferent arteriole vasa recta
ammonia filtrate ureter renal cortex glomerulus loop of Henle cortical nephrons peritubular
capillaries aldosterone osmoregulation urea
Types of metabolic waste produced by living systems
1. Digestive waste2. Respiratory
waste3. Excess water and
salts (through osmoregulation)
4. Nitrogenous waste (through excretion)
Osmoregulation
Balance of uptake and loss of water and solutes
Controlled movement of solutes between internal fluids and environment Osmoconformer
(marine animals isoosmotic with environment)
Osmoregulator (freshwater, marine, and terrestrial animals that adjust internal osmolarity)
Types of nitrogenous wastes Deamination –
protein and nucleic acid metabolism
Three main types differing in terms of:1. Toxicity2. Amount of water
needed for excretion
3. Energy needed for synthesis 300 – 500
mL/gN1 step rxn
50 mL/gN4 step rxn
10 mL/gN15 step rxn
Type of Organism
Structure Product of excretion
Other features
Plants
Stomata, lenticels Insoluble crystals
Crystals are kept inside plant cells
Cnidarians and echinoderms
No excretory organ -
Osmoconformers, isoosmotic with
environment
Freshwater protists and sponges
Contractile vacuole
Excretory Systems
Dispose of metabolic wastes Regulate solute concentrations in the
body Transport epithelia arranged in tubes 4 major processes
1. Filtration, pressure-filtering of body fluids producing a filtrate (water, salts, sugars, amino acids, N-wastes)
2. Reabsorption, reclaiming valuable solutes (glucose, salts, amino acids) from the filtrate
3. Secretion, addition of larger molecules like toxins and other excess solutes from the body fluids to the filtrate
4. Excretion, the filtrate leaves the system
Flatworms Flame cells
Unsegmented roundworms
Protonephridia, closed network of dead-end
tubes lacking openings
Annelids
Metanephridia, open-ended network of tubes with internal openings that collect body fluids
Type of Organism
Structure Product of
excretion
Other features
MolluscsNephridia or metaphridia
Crustaceans Antennal/green gland
InsectsMalpighian tubules and
digestive tractUric acid
Type of Organism
Structure Product of
excretion
Other features
Marine fishes Gills Ammonia
Elasmobranchs (sharks, skates,
rays)Kidneys Urea
Rectal glands – excrete excess NaCl
Freshwater fishes Gills Ammonia or urea
Amphibians and mammals
Kidneys UreaLiver converts
ammonia to urea
Reptiles and birds Kidneys Uric acid Salt glands
Type of Organism
Structure Product of
excretion
Other features
Proximal tubule – secretion and reabsorption
Filtrate
H2OSalts (NaCl and others)HCO3
–
H+
UreaGlucose; amino acidsSome drugs>> Same concentration of substances in blood plasma
Key
Active transport
Passive transport
CORTEX
OUTERMEDULLA
INNERMEDULLA
Descending limbof loop ofHenle – reabsorption-Permeable to water but not to salt
Thick segmentof ascendinglimb – reabsorption- Impermeable to water but permeable to salt
Thin segmentof ascendinglimb
CollectingDuct – permeable to water but not to salt, bottom portion is permeable to urea
NaCl
NaCl
NaCl
Distal tubule – secretion and reabsorption
NaCl Nutrients
Urea
H2O
NaCl
H2O
H2OHCO3 K+
H+ NH3
HCO3
K+ H+
H2O
1 4
32
3 5
From Blood Filtrate to Urine: A Closer Look
Two solutes: NaCl and urea, contribute to the osmolarity of the interstitial fluid
Cause the reabsorption of water in the kidney and concentrates the urine
H2O
H2O
H2O
H2O
H2O
H2O
H2O
NaCl
NaCl
NaCl
NaCl
NaCl
NaCl
NaCl
300
300 100
400
600
900
1200
700
400
200
100
Activetransport
Passivetransport
OUTERMEDULLA
INNERMEDULLA
CORTEX
H2O
Urea
H2O
Urea
H2O
Urea
H2O
H2O
H2O
H2O
1200
1200
900
600
400
300
600
400
300
Osmolarity of interstitial
fluid(mosm/L)
300
Nervous system and hormones regulate kidney functions
Antidiuretic hormone (ADH) Stimulated by a rise in
the blood’s osmolarity (>300 mosm/L)
Enhances fluid retention by making the kidneys reclaim more water
Increases water reabsorption in the distal tubules and collecting ducts of the kidney
Osmoreceptorsin hypothalamus
Drinking reducesblood osmolarity
to set point
H2O reab-sorption helpsprevent further
osmolarity increase
STIMULUS:The release of ADH istriggered when osmo-receptor cells in the
hypothalamus detect anincrease in the osmolarity
of the blood
Homeostasis:Blood osmolarity
Hypothalamus
ADH
Pituitarygland
Increasedpermeability
Thirst
Collecting duct
Distaltubule
Increased Na+
and H2O reab-sorption in
distal tubules
Homeostasis:Blood pressure,
volume
STIMULUS:The juxtaglomerular
apparatus (JGA) respondsto low blood volume or
blood pressure (such as dueto dehydration or loss of
blood)
Aldosterone
Adrenal gland
Angiotensin II
Angiotensinogen
Reninproduction
Renin
Arterioleconstriction
Distal tubule
JGA
The renin-angiotensin-aldosterone system (RAAS) Responds to a loss of salt
and water in the blood Stimulated by low blood
volume or pressure Increases water and
sodium ion reabsorption in the proximal and distal tubules
Leads to an increase in blood volume and pressure
Opposed by the hormone atrial natriuretic factor (ANF)
Released by atria Inhibits release of
renin
Some medical aspects concerning the excretory system
Urinary tract infection (UTI) bacterial infection cystitis/pyelonephritis treated by antibiotics and prevented through
proper hygiene
Kidney stones solidified crystals in kidneys or ureters
Calcium oxalate Uric acid
nephrolithiasis/urolithiasis prevention:
Drinking adequate water Proper diet low in protein, N, and Na Avoid excess Vitamin C intake
Dialysis Hemodialysis Peritoneal dialysis