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Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Primary functions:Introduction
▪ Primary functions:▸ Maintenance of proper internal levels of inorganic solutes (Na+ K+ Cl CO2 etc)solutes (Na+, K+, Cl-, CO2, etc)▸ Maintenance of proper plasma water volume▸ Removal of nonnutritive and harmful substances from metabolism (ammonia, urea, bilirubin, etc)▸ Maintenance of osmotic balance
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Organ systems involved in excretion and retentionIntroduction
g y▪ Respiratory system▸ Regulate O2 and CO2▸ Gills can remove ammonia and HCO3-Gills can remove ammonia and HCO3▸ Participate in acid-base balance
▪ Digestive system▸ R l f di t d f d d t▸ Removal of undigested food and wastes▸ May regulate ion and water
▪ Integumentory system▸ Can excrete organic wastes▸ May regulate salt and water uptake
▪ Renal organsg▸ Filter body fluids▸ Regulate water, ions and organic substances
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Nitrogenous products from nitrogen metabolismIntroduction
Nitrogenous products from nitrogen metabolism▸ Ammonia (NH3)♦ Most bony fishes, larval amphibians and most invertebratesy , p
♦ They are called ammonotelic animals
▸ Urea♦ Most adult amphibians and mammals
♦ They are called ureotelic animals
▸ Uric acid▸ Uric acid♦ Insects, birds, most reptiles, tree frogs and desert toads
♦ They are called uricotelic animals
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Excretion of nitrogenous wastesIntroduction
g
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Renal organs modify body fluids by four basic renal processes:▸ Filtration♦ Movement through a semipermeable membrane
♦ An ultrafiltration is produced
▸ Secretion▸ Secretion♦ Specific solutes are transported into the tubule lumen for excretion
▸ Reabsorptionp♦ Specific solutes are transported back into the body from the lumen
▸ Osmoconcentration♦ Water is removed from the lumen leaving solutes behind
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Schematic of functions of tubular excretory organ
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Schematic of functions of tubular excretory organ
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Functions of the mammalian kidneyThe Mammalian Urinary System
▪ Functions of the mammalian kidney▸ Regulate major inorganic solutes
R l l l▸ Regulate plasma volume▸ Regulate harmful or un-needed organic molecules▸ Osmotic balance▸ Secretion of erythropoietiny p▸ Secretion of renin▸ Conversion of vitamin D to its active formConversion of vitamin D to its active form▸ Excretion of pheromones
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ The KidneysThe Mammalian Urinary System
The Kidneys▸ Located on either side of vertebrae, between T12 and L3▸ Left kidney slightly superior to rightLeft kidney slightly superior to right▸ Adrenal glands sit on superior surface of each kidneys▸ Kidneys lie between dorsal body wall and the parietal y y pperitoneum▸ Each kidney is protected and stabilized by:♦ The renal capsule - layer of collagen fibers
♦ The adipose capsule - thick layer of adipose tissue
♦ The renal fascia dense outer layer of collagen fibers♦ The renal fascia - dense outer layer of collagen fibers
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ The urinary system in a mammalThe Mammalian Urinary Systemy y
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Gross anatomy of the human kidneyThe Mammalian Urinary System
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Internal anatomy of the human kidneyThe Mammalian Urinary System
▪ Internal anatomy of the human kidney
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Gross anatomy of the kidney▸ Renal hilus - prominent medial indentation and point of
f l l d i f i f h entry for renal artery, renal nerves and point of exit for the renal vein▸ Renal sinus - internal cavity within the kidneyy y▸ Renal Cortex - superficial layer in contact with capsule▸ Renal Medulla - inner layer - consists of♦ R l id t i l t t♦ Renal pyramids - triangular structures♦ Renal papilla - projects from the tips of pyramids to sinus♦ Renal columns - separate pyramids
R l l b l id d l i t▸ Renal lobe - renal pyramids and overlying cortex▸ Minor calyx - ducts into which urine drains from papilla▸ Major calyx - collection of two or more minor calycesMajor calyx collection of two or more minor calyces▸ Renal pelvis - funnel-shaped chamber from which urine leaves kidney
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Structure of kidneys and urinary systemThe Mammalian Urinary System
▪ Structure of kidneys and urinary system▸ Paired kidneys, lie retroperitoneal
C d f b 1 200 000 f i l i▸ Composed of about 1,200,000 functional units▸ The functional unit is the nephron▸ Each nephron is composed of a glomerulus and a tubule
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Functional parts of a nephronThe Mammalian Urinary System
▪ Functional parts of a nephron▸ Nephron - the smallest functional unit capable of the kidney’s basic functionsthe kidney s basic functions
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Functional parts of a nephronThe Mammalian Urinary System
▪ Functional parts of a nephron
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Functional parts of a nephronThe Mammalian Urinary System
Functional parts of a nephron▸ Bowman’s (Glomerular) capsule▸ GlomerulusGlomerulus▸ Proximal tubule▸ Loop of Henlep♦ Descending limb (thick & thin)
♦ Loop
♦ Ascending limb (thin & thick)
▸ Juxtaglomerular apparatus (complex)▸ Di t l t b l▸ Distal tubule▸ Collecting duct
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Two types of nephrons in birds & mammalsThe Mammalian Urinary System
▪ Two types of nephrons in birds & mammals▸ Cortical nephrons♦ Originate in cortex♦ Originate in cortex
♦ Glomeruli lie in outer layer of cortex
♦ Hairpin loop only dips slightly into medullary regionp p y p g y y g
♦ Only has peritubular capillaries
▸ Juxtamedullary nephronsy♦ Originate in cortex
♦ Glomeruli lie in inner layer of cortex
♦ Hairpin loop dips plunges deep into medullary region
♦ Peritubular capillaries form vasa recta
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Two types of nephronsThe Mammalian Urinary System
▪ Two types of nephrons▸ Juxtamedullary
C i l▸ Cortical
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Two types of nephronsThe Mammalian Urinary System
Two types of nephrons▸ Juxtamedullary▸ C ti l▸ Cortical
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Cortical nephrons and Juxtamedullary nephronThe Mammalian Urinary System
Cortical nephrons........and Juxtamedullary nephron
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Three capillary bedsThe Mammalian Urinary System
Three capillary beds▸ Glomerular♦ Specifically for filtration
♦ Relatively high blood pressure force solutes out of the blood
▸ Peritubular♦ Adapted for absorption♦ Adapted for absorption
♦ Arise from efferent arterioles that drain glomerulus
♦ Low blood pressure
Ab b l & f h b l♦ Absorb solutes & water from the tubules
▸ Vasa recta♦ Long, thin-walledg,
♦ Looping arterioles that follow loop of Henle
♦ Serve juxtamedullary nephrons
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Vascular elements of the kidneyThe Mammalian Urinary System
▪ Vascular elements of the kidney
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Layers of the glomerular membraneThe Mammalian Urinary System
▪ Layers of the glomerular membrane
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Glomerular filtrationThe Mammalian Urinary System
▪ Glomerular filtration▸ Glomerular membrane 100 times more permeable▸ Filters entire plasma volume 65x a day▸ Filters entire plasma volume 65x a day▸ Filters everything except blood cells and most plasma proteinsplasma proteins▸ Fluid passes through 3 layers:♦ Outer wall is fenestrated - endothelial cells♦ Outer wall is fenestrated - endothelial cells
♦ Basement membrane made of collagen & glycoproteins
♦ Inner layer consists of podocytesy p y
▸ Filtrate passes between the cell layers, not through the cells
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Glomerular filtration - Forces involvedThe Mammalian Urinary System
▪ Glomerular filtration - Forces involved▸ Glomerular capillary blood pressure
Pl ll id i ▸ Plasma-colloid osmotic pressure▸ Bowman’s capsule hydrostatic pressure▸ Bowman’s capsule osmotic pressure
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Pressure drop through kidneysThe Mammalian Urinary System
▪ Pressure drop through kidneys
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Glomerular filtration - Forces involvedThe Mammalian Urinary System
▪ Glomerular filtration - Forces involved▸ Glomerular capillary blood pressure
Pl ll id i ▸ Plasma-colloid osmotic pressure▸ Bowman’s capsule hydrostatic pressure▸ Bowman’s capsule osmotic pressure
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Glomerular filtration - Forces involvedThe Mammalian Urinary System
▪ Glomerular filtration - Forces involved▸ Amt of fluid processed♦ B ’ 180 L/d♦ Bowman’s - 180 L/day
♦ Proximal - 54 L/day
♦ Loop Henle 18 L/day♦ Loop Henle - 18 L/day
♦ Urine - 1.5 L/day
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Glomerular Filtration Rate (GFR)The Mammalian Urinary System
▪ Glomerular Filtration Rate (GFR)▸ Total amount of filtered fluid per minute▸ Directly proportional to net filtration pressure▸ Directly proportional to net filtration pressure▸ Increase in blood pressure leads to increase in GFR
▪ Factors regulating filtration rate at capillary beds▸ Total surface are for filtration▸ Filtration membrane permeability▸ Net filtration pressure (NFP 17 mmHg)
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Control of GFRThe Mammalian Urinary System
▪ Control of GFR▸ Autoregulation - Intrinsic control
R l i f GFR i hi li i▸ Regulation of GFR within limits▸ Myogenic mechanism
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Control of GFRThe Mammalian Urinary System
▪ Control of GFR▸ Autoregulation - intrinsic control♦ M i h i♦ Myogenic mechanism
– Smooth muscle contracts when stretched - blood vessels
♦ Tubuloglomerular feedbacm mechanism♦ Tubuloglomerular feedbacm mechanism– Involves JG apparatus– Involves macula densa– Increased in tubular flow sensed by macula densa release of vasoactive paracrines constriction of afferent arteriole decreased GFR decreased tubular flow– The paracrines are unclear. Maybe endothelin for vasoconstriction and bradykinin for vasodilation
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Control of GFRThe Mammalian Urinary System
▪ Control of GFR▸ Autoregulation - Intrinsic control♦ R l ti f GFR ithi li it♦ Regulation of GFR within limits
♦ Tubuloglomerular feedback mechanism
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Control of GFRThe Mammalian Urinary System
▪ Control of GFR▸ Autoregulation - Intrinsic control♦ R l ti f GFR ithi li it♦ Regulation of GFR within limits
♦ Tubuloglomerular feedback mechanism
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Control of GFRThe Mammalian Urinary System
Control of GFR▸ Intrinsic response♦ Myogenic responsey g p
– GFR constant at MABP between 80 to 180 mmHg
♦ Tubuloglomerular feedback
GFR tubular flow macula densa send chemical signal to JG cells on– GFR tubular flow, macula densa send chemical signal to JG cells on afferent arteriole causing it to constrict and GFR
▸ Extrinsic response♦ Nervous response
– SNS can decrease GFR
♦ Hormonal response♦ Hormonal response
– Angiotensin II - vasoconstrict arterioles– Prostogalndins - vasodilate arterioles
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Tubular Reabsorption may be Active or PassiveThe Mammalian Urinary System
Tubular Reabsorption may be Active or Passive▸ Sodium♦ Active or passivep
♦ Symport - glucose, AA
▸ Water follows sodium♦ Passive
▸ Proteins♦ S ll t♦ Small amounts
♦ Transcytosis
▸ UreaUrea♦ Passive
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Tubular Reabsorption may be Active or The Mammalian Urinary System
Passive▸ Transepithelial transport across 5 barriersTransepithelial transport across 5 barriers
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Tubular Reabsorption may be Active orThe Mammalian Urinary System
▪ Tubular Reabsorption may be Active or Passive
S di b ti▸ Sodium reabsorption
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Active and Passive transport at the PCTThe Mammalian Urinary System
▪ Active and Passive transport at the PCT
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ The renin-angiotensin-aldosterone systemThe Mammalian Urinary System
▪ The renin-angiotensin-aldosterone system▸ Renin secreted into the blood by JG cells♦ D d bl d N Cl♦ Decreased blood NaCl
♦ Decreased ECF volume
♦ Decreased blood pressure♦ Decreased blood pressure
▸ Converts angiotensinogen to angiotensin II l i i I i d i i II▸ In lungs angiotensin I is converted to angiotensin II
▸ Angiotensin II stimulates the release of aldosterone from the adrenal cortex
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ The renin-angiotensin-aldosterone systemThe Mammalian Urinary System
▪ The renin-angiotensin-aldosterone system▸ Renin secreted into the blood by JG cells♦ D d bl d N Cl♦ Decreased blood NaCl
♦ Decreased ECF volume
♦ Decreased blood pressure♦ Decreased blood pressure
▸ Converts angiotensinogen to angiotensin II l i i I i d i i II▸ In lungs angiotensin I is converted to angiotensin II
▸ Angiotensin II stimulates the release of aldosterone from the adrenal cortex
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▪ Osmoconcentration▸ The ability to excrete urine of varying concentrations depends on the medullary concentrations depends on the medullary contercurrent-multiplier system▸ R ll▸ Recall♦ Isotonic (isosmotic)
♦ H t i (h ti )♦ Hypotonic (hypo-osmotic)
♦ Hypertonic (hyperosmotic)
L ti l ti di t i th kid▪ Large vertical osmotic gradient in the kidneys
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▪ Osmoconcentration▸ Large vertical osmotic gradient in the kidneys
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▪ Osmoconcentration▸ Working model of the countercurrent multplier system:system:♦ Assumptions:
– Descending limb highly permeable to H2ODescending limb highly permeable to H2O– Descending limb does not actively transport Na+– Hairpin loop– Ascending limb actively cotransports Na+ and Cl- from lumen– Ascending limb relatively impermeable to H2O– Pump can achieve 200 mOsmol/L maximal difference across the– Pump can achieve 200 mOsmol/L maximal difference across the loop
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▪ Osmoconcentration▸ The Countercurrent Multiplier System
A B C D E F
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200200200200
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200200200200
300300300300
150150150150
350350350350
150150300300
300300350350
125125225225
325325425425
300
300300300
300
300300300
200
200200200
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400400400
400
400400400
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400400400
300
300300300
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500500500
500
300300300500
500
350350350500
400
225425400
600
425425600
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Countercurrent Multiplication SystemThe Mammalian Urinary System
▪ Countercurrent Multiplication System
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Countercurrent Multiplication SystemThe Mammalian Urinary System
▪ Countercurrent Multiplication System
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Countercurrent Multiplication SystemThe Mammalian Urinary System
▪ Countercurrent Multiplication System
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Countercurrent Multiplication SystemThe Mammalian Urinary System
▪ Countercurrent Multiplication System
Principles of Animal PhysiologyExcretory SystemExcretory System
OsmoconcentrationThe Mammalian Urinary System
▸ Recycling of Urea
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▸ Excretion of Urine - concentrated urine
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ OsmoconcentrationThe Mammalian Urinary System
▸ Excretion of Urine - diluted urine
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Bladder storage and micturitionThe Mammalian Urinary System
▪ Bladder storage and micturition
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Bladder storage and micturitionThe Mammalian Urinary System
▪ Bladder storage and micturition
Principles of Animal PhysiologyExcretory SystemExcretory System
▪ Nephrons from the major classes ofThe Mammalian Urinary System
▪ Nephrons from the major classes of vertebrates
Principles of Animal PhysiologyExcretory SystemExcretory SystemThe Avian Urinary
Principles of Animal PhysiologyExcretory SystemExcretory System
The Salt Glands of a Gull
Principles of Animal PhysiologyExcretory SystemExcretory System
Insect Malpighian Tubules
Principles of Animal PhysiologyExcretory SystemExcretory System
Insect Malpighian Tubules
Principles of Animal PhysiologyExcretory SystemExcretory System
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