Podcast
Questions and Answers
The accumulation of plasma proteins and macromolecules in glomerular capillaries contributes to the formation of ______ pressure, which pulls water into the capillaries.
The accumulation of plasma proteins and macromolecules in glomerular capillaries contributes to the formation of ______ pressure, which pulls water into the capillaries.
colloid osmotic
In the glomerulus, the ______ pressure represents the blood pressure within the glomerular capillaries, driving the initial filtration process.
In the glomerulus, the ______ pressure represents the blood pressure within the glomerular capillaries, driving the initial filtration process.
glomerular hydrostatic
The ______ filtration pressure is the net pressure acting across the glomerular capillaries, which determines the rate at which filtrate is formed.
The ______ filtration pressure is the net pressure acting across the glomerular capillaries, which determines the rate at which filtrate is formed.
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During ultrafiltration, the filtration of fluid from blood plasma along the capillaries causes the ______ osmotic pressure in the glomerular capillaries to increase.
During ultrafiltration, the filtration of fluid from blood plasma along the capillaries causes the ______ osmotic pressure in the glomerular capillaries to increase.
The ______ consists of sections colored in purple while the collecting system consists of section colored in tan.
The ______ consists of sections colored in purple while the collecting system consists of section colored in tan.
The regulation of blood plasma composition and volume is achieved through controlled excretion of solutes and water by the ______.
The regulation of blood plasma composition and volume is achieved through controlled excretion of solutes and water by the ______.
Organs such as gills, salt glands, and malpighian tubules, while structurally different from the kidneys, perform a similar ______.
Organs such as gills, salt glands, and malpighian tubules, while structurally different from the kidneys, perform a similar ______.
The vertebrate kidney, unlike the Malpighian tubules of insects, primarily relies on ______ and reabsorption for urine production.
The vertebrate kidney, unlike the Malpighian tubules of insects, primarily relies on ______ and reabsorption for urine production.
In the nephron, blood plasma is filtered in the Bowman's Capsule lumen, creating an ______.
In the nephron, blood plasma is filtered in the Bowman's Capsule lumen, creating an ______.
During urine formation, approximately 99% of the water and most electrolytes are reabsorbed in the tubules, while ______ remains in the filtrate.
During urine formation, approximately 99% of the water and most electrolytes are reabsorbed in the tubules, while ______ remains in the filtrate.
Besides reabsorption, the nephron also performs ______ of various substances via active transport to fine-tune the composition of urine.
Besides reabsorption, the nephron also performs ______ of various substances via active transport to fine-tune the composition of urine.
The Malpighian tubules in insects employs a kidney that relies on ______ and reabsorption.
The Malpighian tubules in insects employs a kidney that relies on ______ and reabsorption.
The ______ carries out the essential processes of excretion and osmoregulation to the kidneys in mammals.
The ______ carries out the essential processes of excretion and osmoregulation to the kidneys in mammals.
During active reabsorption in the kidneys, substances such as glucose, amino acids, and various ______ are transported back into the bloodstream.
During active reabsorption in the kidneys, substances such as glucose, amino acids, and various ______ are transported back into the bloodstream.
In contrast to active reabsorption, passive reabsorption involves substances like urea and water moving across the renal tubules based on ______ gradients.
In contrast to active reabsorption, passive reabsorption involves substances like urea and water moving across the renal tubules based on ______ gradients.
The distal convoluted tubule (DCT) plays a crucial role in maintaining electrolyte balance by variably reabsorbing sodium, chloride and ______ ions based on the body’s needs.
The distal convoluted tubule (DCT) plays a crucial role in maintaining electrolyte balance by variably reabsorbing sodium, chloride and ______ ions based on the body’s needs.
Unlike mammals, fish amphibians, and reptiles can produce urine with an osmolality that is less than ______ percent of the plasma osmolality, demonstrating their adaptive kidney function.
Unlike mammals, fish amphibians, and reptiles can produce urine with an osmolality that is less than ______ percent of the plasma osmolality, demonstrating their adaptive kidney function.
The collecting duct’s permeability to water, and thus its role in concentrating urine, is hormonally regulated by aldosterone and ______ hormone
The collecting duct’s permeability to water, and thus its role in concentrating urine, is hormonally regulated by aldosterone and ______ hormone
The walls of the ascending limb of the Loop of Henle are essentially impermeable to ______, which is vital for creating a concentration gradient in the kidney's medulla.
The walls of the ascending limb of the Loop of Henle are essentially impermeable to ______, which is vital for creating a concentration gradient in the kidney's medulla.
The active transport of NaCl out of the ascending limb of the Loop of Henle not only dilutes the fluid within limb but also concentrates the ______ fluid, contributing to the osmotic gradient.
The active transport of NaCl out of the ascending limb of the Loop of Henle not only dilutes the fluid within limb but also concentrates the ______ fluid, contributing to the osmotic gradient.
The process in the Loop of Henle that establishes a concentration gradient, allowing for the production of urine with varying osmolality, is known as ______ multiplication.
The process in the Loop of Henle that establishes a concentration gradient, allowing for the production of urine with varying osmolality, is known as ______ multiplication.
The glomerular filtration rate refers to the amount of ______ the kidneys produce each minute.
The glomerular filtration rate refers to the amount of ______ the kidneys produce each minute.
Non-mammalian vertebrates can adjust kidney function by altering the ______ of functional nephrons in response to environmental changes.
Non-mammalian vertebrates can adjust kidney function by altering the ______ of functional nephrons in response to environmental changes.
In mammals and birds, the auto-regulation of GFR relies primarily on the rapid renal ______ response, which involves vasoconstriction.
In mammals and birds, the auto-regulation of GFR relies primarily on the rapid renal ______ response, which involves vasoconstriction.
Changes in ______ concentrations in the tubular fluid are detected by the macula densa cells.
Changes in ______ concentrations in the tubular fluid are detected by the macula densa cells.
The macula densa controls ______ excretion from the granules of the walls of afferent arterioles.
The macula densa controls ______ excretion from the granules of the walls of afferent arterioles.
______ is released when $Ca^{2+}$ decreases, stimulating an increase in calcium levels.
______ is released when $Ca^{2+}$ decreases, stimulating an increase in calcium levels.
Unlike parathyroid hormone, ______ is excreted when $Ca^{2+}$ increases to prevent hypercalcemia and excessive bone dissolution.
Unlike parathyroid hormone, ______ is excreted when $Ca^{2+}$ increases to prevent hypercalcemia and excessive bone dissolution.
______ primarily regulates water turnover in mammal kidneys by promoting water absorption.
______ primarily regulates water turnover in mammal kidneys by promoting water absorption.
The kidneys reabsorb all the useful ______ nutrients from the filtrate in the proximal and distal convoluted tubules.
The kidneys reabsorb all the useful ______ nutrients from the filtrate in the proximal and distal convoluted tubules.
The ______ segment of the nephron loop is a unique feature found only in the kidneys of mammals and birds.
The ______ segment of the nephron loop is a unique feature found only in the kidneys of mammals and birds.
The diagram of the bird kidney and the mammalian-type nephron highlights differences in their ______ and urine concentrating abilities.
The diagram of the bird kidney and the mammalian-type nephron highlights differences in their ______ and urine concentrating abilities.
Compared to saltwater fish, freshwater fish tend to have ______ glomeruli to facilitate more water excretion.
Compared to saltwater fish, freshwater fish tend to have ______ glomeruli to facilitate more water excretion.
Unlike mammals, amphibians and reptiles do not possess ______, limiting their ability to produce concentrated urine.
Unlike mammals, amphibians and reptiles do not possess ______, limiting their ability to produce concentrated urine.
In saltwater environments, bony fish are ______ to the surrounding water, leading to water loss through their gills.
In saltwater environments, bony fish are ______ to the surrounding water, leading to water loss through their gills.
While bony fish in saltwater drink water to compensate for water loss, they also gain salt, which they excrete via the ______.
While bony fish in saltwater drink water to compensate for water loss, they also gain salt, which they excrete via the ______.
Cartilaginous fish, such as sharks, retain ______ in their blood to maintain a plasma that is iso-osmotic or slightly hyperosmotic compared to seawater.
Cartilaginous fish, such as sharks, retain ______ in their blood to maintain a plasma that is iso-osmotic or slightly hyperosmotic compared to seawater.
Hagfish kidneys differ significantly from other vertebrates as they lack ______, leading to the secretion of ions rather than significant osmoregulation.
Hagfish kidneys differ significantly from other vertebrates as they lack ______, leading to the secretion of ions rather than significant osmoregulation.
Teleost fishes actively secrete ______ into their urine to manage salt and water balance in a marine environment.
Teleost fishes actively secrete ______ into their urine to manage salt and water balance in a marine environment.
Flashcards
Kidney Function
Kidney Function
Regulates blood composition/volume via controlled excretion of solutes/water. Excretes nitrogenous wastes.
Urine
Urine
Complex solution from blood plasma, containing inorganic and organic solutes.
Malpighian Tubules
Malpighian Tubules
In insects, they use secretion and reabsorption for kidney function.
Blood Plasma Filtration
Blood Plasma Filtration
Occurs within the Bowman's capsule.
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Nephron
Nephron
Functional unit of the mammalian kidney
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Tubular Reabsorption
Tubular Reabsorption
99% of water and most electrolytes are reabsorbed.
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Tubular Secretion
Tubular Secretion
Various substances are secreted via active transport.
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"Kidney" Like Organs
"Kidney" Like Organs
Kidney-like organs perform similar functions in different species groups.
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Renal Corpuscle
Renal Corpuscle
The structure formed by the glomerulus and Bowman's capsule.
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Colloid Osmotic Pressure (PCOP)
Colloid Osmotic Pressure (PCOP)
The pressure created by proteins in the blood that pulls water into the capillaries.
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Glomerular Hydrostatic Pressure (GHP)
Glomerular Hydrostatic Pressure (GHP)
Blood pressure within the glomerular capillaries.
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Net Filtration Pressure (NFP)
Net Filtration Pressure (NFP)
The sum of forces that determines the rate of fluid filtration.
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Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR)
The amount of filtrate kidneys produce each minute.
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GFR in Non-Mammals
GFR in Non-Mammals
Non-mammals can adjust nephron count based on blood pressure and environmental factors.
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Auto-regulation of GFR
Auto-regulation of GFR
GFR remains stable despite blood pressure changes due to kidney adaptations, primarily in afferent arterioles.
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Macula densa
Macula densa
Located in the distal tubule, detects NaCl concentration, releasing vasoactive substances to control vascular tone and renin excretion.
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Anti-diuretic hormone (ADH)
Anti-diuretic hormone (ADH)
Regulates water reabsorption in kidneys.
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Aldosterone
Aldosterone
Increases sodium reabsorption (and water follows).
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Atrial Natriuretic Peptide (ANP)
Atrial Natriuretic Peptide (ANP)
Decreases sodium reabsorption.
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Parathyroid hormone
Parathyroid hormone
Excreted when calcium levels decrease.
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Calcitonin
Calcitonin
Excreted when calcium levels increase; prevents excess calcium in blood and protects skeleton.
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Proximal and Distal Convoluted Tubules
Proximal and Distal Convoluted Tubules
Reabsorb nutrients and water; secrete wastes. Thin segment only in Mammals and Birds
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Active Reabsorption
Active Reabsorption
Reabsorption of glucose, simple sugars, amino acids, vitamins, and ions in the kidney.
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Passive Reabsorption
Passive Reabsorption
Reabsorption of urea, lipid-soluble materials, chloride ions, and water in the kidney.
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Secretion (Kidney)
Secretion (Kidney)
Secretion involves moving substances like hydrogen, ammonium, creatinine, drugs, and toxins into the kidney tubules.
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Urine Osmolality (Non-Mammals)
Urine Osmolality (Non-Mammals)
Fish, amphibians, and reptiles create urine with an osmolality lower than 10% of their plasma.
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DCT Functions
DCT Functions
Variable reabsorption of sodium, chloride, calcium, and water; secretion of hydrogen, ammonium, creatinine, drugs, and toxins.
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Collecting Duct Regulation
Collecting Duct Regulation
Hormonally regulated by aldosterone (sodium, potassium, and water balance) and antidiuretic hormone (ADH; water reabsorption) to regulate water permeability and solute loss.
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Ascending Limb Function
Ascending Limb Function
Active transport of NaCl out of the ascending limb dilutes the fluid within the tubule and concentrates the surrounding interstitial fluid.
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Countercurrent Multiplication
Countercurrent Multiplication
Process where the kidney maintains a concentration gradient, enabling production of hyperosmotic urine; creates high osmotic pressure.
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Medullary Thickness & Urine Concentration
Medullary Thickness & Urine Concentration
Mammals' ability to concentrate urine correlates with the thickness of their kidney's medulla.
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Nitrogen Excretion
Nitrogen Excretion
The process where animals eliminate nitrogenous waste products.
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Hagfish Kidney
Hagfish Kidney
Kidneys of hagfish lack tubules, Bowman's capsule connects directly to the collecting tube; they primarily secrete ions.
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Saltwater Bony Fish
Saltwater Bony Fish
They drink seawater, excreting excess salt through their gills.
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Freshwater Fish Kidneys
Freshwater Fish Kidneys
Freshwater fish produce a large amount of diluted urine and their gills absorb sodium and chlorine from the water.
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Cartilaginous Fish & Urea
Cartilaginous Fish & Urea
Cartilaginous fish retain urea in their blood to maintain osmotic balance with seawater.
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Amphibian/Reptile Kidneys
Amphibian/Reptile Kidneys
Unlike mammals, they lack Loops of Henle in their kidneys.
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Teleost Fish Kidney Secretion
Teleost Fish Kidney Secretion
They actively secrete magnesium sulfate into their urine
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Urinary System and Osmotic Balance
- This lecture covers the urinary system and osmotic balance in animals
- The lecture explains the relationships between physiology and anatomy in the context of larger animal orders
- The lecture includes a discussion of acid/base regulation
- The lecture explains kidney function
- The lecture explains water and salt balance in larger animal orders
- The lecture includes an explanation of the anatomical and physiological adaptations animals develop to live in aquatic environments
- The lecture covers the functions of excretory systems in larger animal orders
Water and Salt Balance
Kidney
- The kidney refers to tubular structures that discharge directly or indirectly to the outside world
- Kidneys produce and eliminate aqueous solutions derived from blood plasma or other extracellular body fluids
- Kidneys excrete nitrogenous waste products
- They regulate the composition and volume of blood plasma and other extracellular body fluids via controlled excretion of solutes and water
- Organs like kidneys include gills, salt glands, and malpighian tubules
Urine
- Urine refers to a complex solution containing multiple inorganic and organic solutes
- All the constituents of urine, including water, are drawn from blood plasma via osmosis
Production of Primary Urine
- Insects use Malpighian tubules for secretion and reabsorption
- A secretion-reabsorption kidney uses active and passive transport
- Vertebrate kidneys use filtration and reabsorption
Kidney - Mammals
- The internal anatomy includes the renal cortex, renal medulla, renal pyramids, renal veins, renal arteries
- Also included are segmental arteries, interlobar veins, interlobar arteries
- Arcuate veins, arcuate arteries, cortical radiate veins, cortical radiate arteries are involved
- Renal pelvis, major and minor calyxes are anatomical structures
- The nephron, kidney lobe, renal papilla, ureter, renal columns, and fibrous capsule are structures in the kidney
Kidney - Mammals - Nephron
- The functional unit of the mammalian kidney is the nephron
- Blood plasma filtration results in ultrafiltrate in the Bowman’s Capsule lumen
- Tubular reabsorption reabsorbs about 99% of water and most electrolytes, urea remains
- Tubular secretion involves the secretion of various substances via active transport
Nephron Anatomy
- Afferent arterioles bring blood to the glomerulus while efferent arterioles take blood away
- The nephron is composed of the proximal convoluted tubule, loop of Henle, and distal convoluted tubule which then connects to the collecting system
Glomerular Filtration
- Renal corpuscle = Bowman's Capsule + Glomerulus
- Capsular fluid is primary urine formed by ultrafiltration from blood plasma
Features in a Renal Corpuscle
- Complexly porous barrier between blood and capsular fluid
- Capillary endothelium is perforated with fenestrations
- The Bowman's capsule consists of podocytes with interdigitated processes forming slits
Colloid Osmotic Pressure (or Oncotic Pressure) = PCOP
- Formed due to ultrafiltration, accumulation of plasma proteins, and other macromolecules in glomerular capillaries
- Draws water into the capillaries
- Filtration of fluid from blood plasma along the capillaries increases the colloidal osmotic pressure in the glomerular capillaries
- Pcop increases non-linearly along glomerular capillary
Glomerular Filtration - Starling Forces
- Glomerular hydrostatic pressure (GHP) in the glomerular capillaries pushes water and solute molecules into the filtrate and averages 50 mm Hg
- Blood colloid osmotic pressure (BCOP) draws water out of the filtrate and into the plasma and averages about 25 mm Hg
- Net filtration pressure (NFP) represents the sum of hydrostatic and colloid osmotic pressures for an average of 10 mm Hg
- Capsular hydrostatic pressure (CsHP) opposes GHP, pushing water and solutes out of the filtrate and into the plasma
Kidney Facts
- Human kidneys form 180 L of filtrate per day
- Humans excrete about 1 L of Urine per day
- All plasma water in a human body is filtered every 30 minutes
Glomerular Filtration Rate (GFR)
- GFR (glomerular filtration rate) is the amount of filtrate the kidneys produce each minute
GFR factors varying with species
- Permeability of glomerular capillaries for water
- Net filtration pressure
- Mammals generally have higher arterial blood pressure compared to non-mammalian vertebrates (fish, amphibians, reptiles, birds)
- Size of the glomerulus
GFR in Non-Mammals
- Non-mammalian vertebrates can increase or decrease the amounts of their nephrons to regulate filtration
- Affected by internal changes in flood pressure and environmental factors that affect fluid and salt balance
- In aquatic non mammals, GFR is usually higher for animals acclimatized to different salinities, relative to those in freshwater
Auto-Regulation of GFR in Mammals and Birds
- Relatively independent of blood pressure changes due to adaptation in the kidneys
- Afferent arterioles primarily responsible
- Includes a rapid renal myogenic response of vasoconstriction and slower tubulo-glomerular feedback mechanism
- Protects against high blood pressure, such as during disease or training
Macula Densa
- Located in the distal tubular epithelium
- It releases vasoactive substances that control vascular tone
- It controls renin excretion from granules in the walls of afferent arterioles
Renin-Angiotensin-Aldosterone System (RAAS)
- The RAAS detects decreasing blood flow to the kidneys and acts, in part, by directing aldosterone to increase Na+ and water retention
Water and Salt Balance - Regulation
Anti-Diuretic Hormone (ADH)
- Vasopressin, regulates water turnover in kidneys, stimulates water absorption
Aldosterone
- Increases reabsorption of sodium
Atrial Natriuretic Peptide (ANP)
- Counteracts aldosterone, decreases reabsorption of sodium
Parathyroid Hormone
- Excreted when Ca2+ decreases
Calcitonin
- Excreted when Ca2+ increases, prevents hypercalcemia and dissolution of the skeleton
Proximal and Distal Convoluted Tubules
- Reabsorb all the useful organic nutrients in the filtrate
- Reabsorb more than 90% of the water from the filtrate
- Secrete waste products that did not pass into the filtrate at the glomerulus
Collecting Duct
- Allows for variable reabsorption of water, reabsorption or secretion of sodium, potassium, hydrogen, and bicarbonate ions
Overview of Urine Formation
- Filtration occurs in the renal corpuscle
- Water reabsorption occurs in the proximal convoluted tubule and the descending thin limb of the nephron loop
- Variable water reabsorption occurs in the distal convoluted tubule and collecting system
- Solute reabsorption occurs along the proximal convoluted tubule, thick ascending limb, distal convoluted tubule, and collecting system
- Variable solute reabsorption or secretion occurs at the proximal convoluted tubule, the distal convoluted tubule, and the collecting system
Transport Activities at the Proximal Convoluted Tubule
- Sodium enters a tubular cell from the filtrate via diffusion, cotransport, or countertransport
- Sodium is then pumped into the peritubular fluid by the sodium-potassium exchange pump
- Reabsorbed solutes are ejected into the peritubular fluid by separate active transport mechanisms
- Bicarbonate absorption is associated with sodium reabsorption and hydrogen ion secretion
Proximal Convoluted Tubules
- Actively reabsorb glucose, other simple sugars, amino acids, vitamins, and ions like sodium, potassium, calcium, magnesium, phosphate, and bicarbonate
- Passively reabsorb urea, chloride ions, and lipid-soluble materials, water
- Secrete hydrogen ions, ammonium ions, creatinine, drugs, and toxins
Proximal and Distal Convoluted Tubules
- Na+ and Cl- are reabsorbed in the proximal convoluted tubule, the tubule absorbs water leaving the tubular liquid approximately isosmotic to the blood plasma
- Walls of the distal convoluted tubule are poorly permeable to water in animals in diuresis and the tubular fluid becomes dilute as salt and chloride ions are reabsorbed
Distal Convoluted Tubules
- Reabsorption: Sodium ions (variable), chloride ions, calcium ions (variable), Water (variable)
- Secretion: Hydrogen ions, ammonium ions, Creatinine, drugs, toxins
Collecting Duct
- This is where kidneys receive tubular fluid from many nephrons
- Here, permeability is hormonally regulated via Aldosterone and Antidiuretic hormone
- Important secretions occur to control levels of pH
Loop of Henle
Processes that generate the single effect.
- the ascending-limb active transport of NaCl out dilutes the fluid and concentrates interstitial fluid
- the descending limb walls are permeable to water, so water loss through the limb concentrates fluids
The Single effect to a End Gradient-Henle
- The single gradients are created side to side
- This difference in end concentration becomes multiplies
Low Volume and Hyperosmotic Urine Production
Cortex
- High transfer, equal osmotic balance
Inner Medulla
- Some areas have a urea gradient making it very concentrated
Urine concentration and Medulla thickness
- Increased urine volume is the more renal papilla
Nitrogen Excretion
- Some classes of animal have different ways of excreting Nitrogen wastes
- Mammals use Urea
- Reptiles use Uric acid
- Teleosts use Ammonia
Avian Kidney
- The kidney is a central organ to maintain ion balance
- Uses Nephrons to actively engage in water retention
Non-Mammalian Vertebrates
- The tubules filter and reabsorb in the distal convoluted tubule
- Some animals will retain Urea
Fish Gill Processes
- The kidneys absorb NA+ and CL- from the water
- Absorb salt via the Gills tissue
Migrating Fish - Gills
- When a fish moves from freshwater to saltwater, Na+ in plasma increases, which stimulates cortisol and growth hormone excretion
Adaptations by Fish Kidneys as the migrate
- Changes in water volume are mediated by physical processes to influence osmotic balance
Amphibian Skin
- Water channels, aquaphorins, allows some permeability
- Moisture for diffusion and active transport of salts
Extracorporeal Organs in Verbrates
- Organs help with osmoregulation as a cellular mechanism in kidneys
- Cartilaginous fish have a separate rectum
- Birds and Reptiles have different skulls and internal processes to help them function
Salt Gland Secretion
- passive flux of Na+ occurs along paracellular pathways, with some water
Final thoughts - Key Points
- There are many forms of excretion and osmoregulation
- A few processes vary and are specific to animals and their adaptation
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