What are the main components of the urinary system?
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The kidneys and accessory structures.
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What are the main components of the urinary system?
The kidneys and accessory structures.
What follows the glomerulus in the nephron's vascular pathway?
Efferent arteriole.
What structure surrounds the kidney?
The capsule.
What role does secretion play in the urinary system?
To remove waste products and excess ions from the blood into the filtrate.
What is the role of the juxtaglomerular apparatus in the nephron?
To regulate blood flow and pressure through the nephron.
How many nephrons are there per kidney?
Approximately 1 million.
What do the foot processes of podocytes do?
They wrap around the endothelium and form filtration slits.
How does the composition of filtrate entering the proximal tubules compare to plasma?
It is similar in ion composition to plasma.
How do filtered substances enter the tubule lumen?
They pass through endothelial pores and filtration slits.
What is the relationship between sodium (Na+) concentration in the filtrate and in proximal tubule cells?
The [Na+] in filtrate is higher than that in proximal tubule cells.
What is the formula for excretion rate?
Excretion rate = filtration - reabsorption + secretion.
What is one of the key functions of the kidneys?
Excretion of wastes.
What does colloid osmotic pressure in glomerular capillaries result from?
The presence of plasma proteins.
What is the effect of aldosterone on secretion?
It increases the secretion of potassium and the reabsorption of sodium.
What fraction of plasma flow through the kidney filters into the nephrons?
One-fifth (20%).
What changes occur in filtrate volume along the nephron?
Filtrate volume decreases as it moves through the nephron.
What does transport maximum (T m) refer to?
The transport rate at saturation.
What is the juxtaglomerular apparatus?
The site where the initial portion of the distal tubule contacts with the afferent and efferent arterioles of the nephron.
What range of arterial blood pressure can GFR remain constant?
80 - 180 mm Hg.
What is the function of the vasa recta?
It is part of the nephron's vascular system, associated with the loop of Henle.
How does sodium (Na+) enter the proximal tubule cells?
Through membrane proteins, moving down its electrochemical gradient.
What is the role of the afferent arteriole in the urinary system?
It brings blood to the glomerulus for filtration.
What substances are commonly reabsorbed during the reabsorption process?
Water, glucose, amino acids, and ions like sodium and potassium.
What is the significance of the loop of Henle in reabsorption?
It creates a concentration gradient that allows for the reabsorption of water and salts.
How does Na+ move in relation to its electrochemical gradient?
Na+ moves down its electrochemical gradient.
What is the normal capillary blood pressure that favors filtration into Bowman’s capsule?
55 mm Hg.
What is the lumen of Bowman's capsule?
The space where filtered material collects after passing through the filtration barrier.
How does osmolarity change along the nephron?
Osmolarity increases as filtrate moves from the proximal tubule to the collecting duct.
What are the two main regions of the kidney?
The outer cortex and the inner medulla.
Where does urine flow after leaving the nephrons?
Into the renal pelvis.
What is the myogenic response in the context of GFR regulation?
An intrinsic ability of vascular smooth muscle to respond to pressure changes.
What is the primary function of the urinary system regarding plasma pH?
Regulation of plasma hydrogen ion concentration (pH).
What are nephrons?
The functional units of the kidney responsible for urine formation.
What are the basic renal exchange processes in the urinary system?
Glomerular filtration, reabsorption, and secretion.
What are the two main factors that influence GFR?
Net filtration pressure and filtration coefficient.
What types of wastes does the urinary system excrete?
Metabolic wastes (e.g. creatinine, urea, uric acid) and foreign substances (e.g. drugs).
Are there active transporters for urea reabsorption in the proximal tubules?
No, there are no active transporters for urea reabsorption.
What is the primary function of the collecting duct in the urinary system?
To collect urine from the nephron and transport it to the renal vein.
What is the role of SGLT in glucose reabsorption?
It pulls glucose into the cell against its concentration gradient using Na+.
How many times do the kidneys filter the entire plasma volume in a day?
60 times.
What is Bowman’s capsule?
A structure in the kidney that encases the glomerulus and collects filtrate.
What establishes the concentration gradient of urea in the proximal tubule?
Reabsorption of Na+ and other solutes makes the interstitial fluid more concentrated than the filtrate.
What is the role of the peritubular capillaries?
To allow reabsorbed molecules to enter the blood.
What does glucose reabsorption illustrate in the urinary system?
The concept of renal transport saturation.
What happens when the transport maximum for glucose is reached?
The transport becomes saturated, and further increases in plasma glucose do not increase the transport rate.
What happens when all carrier proteins in the system are occupied?
Saturation occurs.
What effect do sympathetic neurons have on vascular smooth muscle?
They cause vasoconstriction via alpha receptors.
What is the purpose of the urinary bladder?
To store urine until it is excreted.
What are the three main processes involved in urinary excretion of solute?
Filtration, reabsorption, and secretion.
What happens to GFR during an increase in blood pressure?
It is maintained.
What is the volume of fluid that filters into the Bowman’s capsule per unit time called?
Glomerular filtration rate (GFR).
What does GLUT facilitate?
Facilitated diffusion of glucose.
What is the result of smooth muscle contraction in the myogenic response?
Vasoconstriction.
What structure collects the filtrate from the glomerulus?
Bowman's capsule.
What process occurs in the proximal tubule?
Reabsorption: lumen to blood.
What is the anatomical position of the kidneys?
They lie in shallow depressions against the posterior abdominal wall and are retroperitoneal.
What happens to the concentrations of other solutes as fluid volume in the lumen decreases?
Concentrations of other solutes increase.
Which surface of each kidney faces the spine?
The concave surface.
What type of muscle is the external sphincter?
Skeletal muscle.
What is the role of the glomerulus in the urinary system?
To filter blood into the lumen of the nephron.
What are the two pathways for tubular reabsorption?
Transcellular transport and paracellular pathway.
What is the lumen of Bowman’s capsule?
The space within Bowman’s capsule where filtered material collects.
What is the role of the tubular epithelium in reabsorption?
It facilitates the transport of substances across membranes.
What happens to the external sphincter during micturition?
It relaxes.
What is the relationship between plasma glucose concentration and glucose filtration in the kidneys?
Filtration of glucose is directly proportional to the plasma glucose concentration.
What is the function of the kidneys in the urinary system?
To filter blood and produce urine.
What is the role of the ureters?
To transport urine from the kidneys to the urinary bladder.
What is the primary driving force for most renal reabsorption?
Active transport of sodium (Na+ - K+ - ATPase).
When does sympathetic activity increase to control GFR?
When mean arterial pressure (MAP) falls below 80 mm Hg.
What is tubuloglomerular feedback?
A paracrine control on the fluid flow through the loop of Henle.
Where does most reabsorption occur in the nephron?
In the proximal convoluted tubule.
What is the role of Angiotensin II in the urinary system?
It acts as a potent vasoconstrictor.
What are the basic renal exchange processes in the urinary system?
Glomerular filtration, reabsorption, secretion, and excretion.
What type of reabsorption occurs for urea in the proximal tubules?
Passive reabsorption.
What is the role of the afferent arteriole in the urinary system?
It supplies blood to the glomerulus.
What is the composition of the filtrate in glomerular filtration?
Filtrate is composed only of water and dissolved solutes.
What occurs during reabsorption in the urinary system?
The selective transport of molecules from the lumen back to the blood.
What type of transporter is Na+ - K+ - ATPase?
An active transporter and membrane protein.
What is reabsorption in the context of renal processes?
The process of moving substances from the lumen back into the blood.
What is a key functional difference between cortical and juxtamedullary nephrons?
Juxtamedullary nephrons help maintain osmotic gradients in the medulla.
What structures emerge from the concave surface of the kidneys?
Renal blood vessels, nerves, and ureters.
What is the function of the macula densa in the nephron?
It senses NaCl delivery and regulates GFR through paracrine signaling.
What is the colloid osmotic pressure gradient (p)?
It is due to proteins in plasma but not in Bowman’s capsule.
What structures are involved in the renal exchange processes?
Collecting duct, distal tubule, afferent arteriole, loop of Henle, efferent arteriole, glomerulus, peritubular capillaries, proximal tubule, and Bowman's capsule.
How does the hydrostatic pressure of fluid in Bowman’s capsule affect filtration?
It favors fluid moving back into the glomerular capillaries.
What is Bowman’s capsule?
The structure that encases the glomerulus and collects filtrate.
What is the difference between the afferent and efferent arterioles?
The afferent arteriole brings blood to the glomerulus, while the efferent arteriole carries blood away from it.
What is the pathway of blood flow in the kidney starting from the renal artery?
Renal artery → smaller arteries → arterioles in the cortex → portal system → renal capillaries → interlobular vein → renal vein.
What is the function of the portal system in the kidney?
It includes afferent arterioles, glomerulus, efferent arteriole, peritubular capillaries, and vasa recta.
How does the urinary system regulate plasma volume and blood pressure?
By controlling the rate at which water is excreted in the urine.
What range of arterial blood pressure can GFR remain constant?
80 - 180 mm Hg.
Where does the active transport of sodium primarily take place?
In the proximal tubule.
What is the function of the urethra?
To carry urine from the bladder to the outside of the body.
What does GFR stand for in the urinary system?
Glomerular Filtration Rate.
How is Na+ reabsorbed in the nephron?
By active transport.
How do kidneys regulate plasma ion balance?
By balancing dietary intake with urinary loss of key ions.
What is the primary function of the glomerulus in the urinary system?
Filtration: blood to lumen.
What is the function of the glomerulus?
It is involved in the filtration of blood to form urine.
Where are cortical nephrons primarily located?
Almost entirely within the cortex.
What is the role of mesangial cells in the glomerulus?
They provide structural support and regulate blood flow within the glomerular capillaries.
What is the osmotic pressure gradient in glomerular capillaries?
About 30 mm Hg, favoring fluid moving back into the capillaries.
What is the function of Na+-K+-ATPase in this process?
It pumps Na+ out of the cell.
What is excretion in the urinary system?
The process of eliminating substances from the lumen to the external environment.
How does urea leave the lumen in the proximal tubule?
Through facilitated diffusion transporters into the interstitial fluid.
What do renal veins carry blood to?
The inferior vena cava.
What is the average Glomerular Filtration Rate (GFR)?
180 L/day.
How is net filtration pressure calculated?
Net filtration pressure = P_H - p - P_fluid.
What are the components of the Loop of Henle?
Thin descending limb, thin ascending limb, and thick ascending limb.
How many sets of capillaries do the kidneys have?
Two sets of capillaries.
How does the transport rate of glucose change with plasma glucose concentration?
Transport rate is directly proportional to plasma glucose concentration until the transport maximum is reached.
What are macula densa cells responsible for?
Sensing the flow in the distal tubule and releasing paracrine factors that affect the diameter of the afferent arteriole.
What is the primary function of reabsorption in the urinary system?
To reclaim water and essential solutes from the filtrate back into the bloodstream.
What surrounds the tubule in the nephron?
Peritubular capillaries.
What type of cells are granular cells?
Specialized smooth muscle cells.
What happens to GFR and renal blood flow when sympathetic activity increases?
GFR and renal blood flow decrease.
What range should plasma pH be maintained in?
In a very narrow range.
What is micturition?
The elimination of urine stored in the bladder.
What is the function of prostaglandins in the urinary system?
They act as vasodilators and adjust the size of glomerular filtration slits.
What is the purpose of the urinary system?
To eliminate waste materials from the body in the form of urine.
What percentage of nephrons are juxtamedullary nephrons?
20%.
What is the function of the glomerulus?
It filters blood to form urine.
How does urea move across the epithelium in the proximal tubule?
By diffusion if there is a concentration gradient.
Where does the majority of reabsorption occur in the nephron?
In the proximal tubule.
How does glucose exit the proximal tubule cell?
Glucose diffuses out the basolateral side using the GLUT protein.
What is the function of the glomerulus?
It filters blood to form urine.
Why are juxtamedullary nephrons important?
They are crucial for producing concentrated urine during water constraints.
Where do renal arteries branch from?
The abdominal aorta.
What blood pressure range allows GFR to stay constant?
Over a wide range of blood pressure, specifically at 90 mmHg.
What is the relationship between filtrate and interstitial fluid?
Filtrate is similar to interstitial fluid.
What is secretion in the context of the urinary system?
Movement of substances from blood to lumen.
What is the role of granular cells in the nephron?
They are involved in the regulation of blood pressure and GFR.
Which ions are primarily secreted by the nephron?
K+ and H+.
What is excretion in the urinary system?
The elimination of waste products from the body.
What is the renal corpuscle composed of?
Bowman's capsule and the glomerulus.
What does reabsorption refer to in the nephron?
Transfer from lumen to blood.
What is the renal threshold?
The plasma concentration at which saturation occurs.
What is the average Glomerular Filtration Rate (GFR) per day?
180 L/day.
What is the significance of the transport maximum?
It indicates the rate of transport at saturation.
What is the basal lamina in the urinary system?
An acellular layer of extracellular matrix with negative-charged glycoprotein.
What type of transporter is SGLT?
Secondary active transporter.
What occurs to GFR during a decrease in blood pressure?
The rate decreases and the system may shut down in case of blood loss.
What drives anion reabsorption in the nephron?
The electrochemical gradient.
Where are the kidneys located in relation to the spine?
On either side of the spine at the level of the eleventh and twelfth ribs.
How does water move in relation to solute reabsorption?
By osmosis, following solute reabsorption.
What are peritubular capillaries involved in?
They are involved in the reabsorption and secretion processes.
What is the role of the collecting duct?
Final reabsorption and secretion before urine is excreted.
What does Bowman’s capsule do?
It collects the filtrate from the glomerulus.
What does secretion refer to in renal exchange processes?
The movement of substances from the blood to the lumen.
What happens to water in the proximal tubule that affects urea concentration?
Water moves from the lumen across the epithelium by osmosis, increasing urea concentration in the filtrate.
What is the role of the afferent arteriole in the nephron?
It supplies blood to the glomerulus for filtration.
What is the function of the glomerulus in the urinary system?
It facilitates glomerular filtration, allowing protein-free plasma to flow into Bowman’s capsule.
What is the fluid pressure (P_fluid) in Bowman’s capsule?
It is the pressure created by the fluid within Bowman’s capsule.
What is the function of the proximal tubule?
It reabsorbs water, ions, and nutrients from the filtrate back into the blood.
What is the function of the afferent arteriole?
To supply blood to the glomerulus.
What is secretion in the context of renal function?
Transport of substances from blood into the lumen of the tubule.
Why is the secretion of K+ and H+ important?
It is important in homeostatic regulation of those ions.
What is the pathway of urine from the kidneys to the external environment?
From the collecting duct to the renal vein, then to the bladder and external environment.
What is the role of the distal tubule in the nephron?
It is involved in the regulation of potassium and sodium balance.
What is required for solutes to be reabsorbed from filtrate to plasma?
Carrier proteins.
What is the average Glomerular Filtration Rate (GFR) per day?
180 L/day.
What effect does plasma volume have on blood pressure?
Plasma volume exerts a direct effect on blood pressure.
What initiates the myogenic response in the urinary system?
Stretch of smooth muscle.
What is the functional unit of the kidney?
Nephrons.
What is the target blood osmolarity maintained by the kidneys?
Approximately 290 mOsM.
What opens after muscle cell depolarization?
Voltage-gated calcium channels.
What percentage of nephrons are cortical nephrons?
80%.
What type of reflex is micturition?
A simple spinal reflex subjected to both conscious and unconscious control from higher brain centers.
What does the filtration coefficient depend on?
Surface area of the glomerular capillaries and permeability of the interface between the capillary and Bowman’s capsule.
What is the role of the collecting duct in the urinary system?
It collects urine from the distal tubule and transports it to the bladder.
What happens to the internal sphincter during bladder filling?
It is passively contracted.
What is the approximate GFR value in ml/min?
125 ml/min.
What is hydrostatic pressure (P_H) in the context of glomerular filtration?
It is the blood pressure that drives filtration.
What happens to the remaining four-fifths of plasma flow?
It flows into peritubular capillaries along with plasma proteins and blood cells.
What is the effect of hydrostatic pressure of blood on glomerular filtration?
It favors filtration into Bowman’s capsule.
What surrounds the glomerulus to form the renal corpuscle?
Bowman's capsule.
What is the difference between filtration and reabsorption in the urinary system?
Filtration is the movement of blood to lumen, while reabsorption is the movement from lumen to blood.
What is the significance of the afferent and efferent arterioles?
They regulate blood flow into and out of the glomerulus.
What is the state of the bladder when it is at rest?
It is in a relaxed (filling) state with tonic discharge.
What is the role of the distal tubule in the nephron?
It is involved in the final adjustments of urine composition.
What are some organic compounds that are secreted by the nephron?
Choline and creatinine.
What is the role of the efferent arteriole?
It carries blood away from the glomerulus after filtration.
What is the first component of the nephron's vascular system?
Afferent arterioles.
What is the glomerulus?
A ball-like network of capillaries.
What type of neurons innervate both afferent and efferent arterioles in the urinary system?
Sympathetic neurons.
What is the glomerulus?
A ball-like network of capillaries in the kidney.
What do granular cells secrete?
Renin, to regulate salt and water balance.
What is the role of the vasa recta?
It is the first set of capillaries in the medulla.
What happens when stretch-sensitive ion channels open?
Muscle cells depolarize.
What happens to sodium (Na+) at the basolateral side of the proximal tubule cell?
It is actively pumped out by the Na+ - K+ - ATPase.
How does the urinary system regulate plasma pH?
By regulating bicarbonate and hydrogen ions in the plasma.
What are the three pressures that influence glomerular filtration?
Hydrostatic pressure of blood, colloid osmotic pressure, and hydrostatic pressure of fluid in Bowman’s capsule.
Which key ions do the kidneys help to balance?
Sodium (Na+), potassium (K+), and calcium (Ca2+).
What type of muscle makes up the bladder?
Smooth muscle.
What is secretion in the context of renal function?
The transport of molecules from the plasma of peritubular capillaries to the lumen of renal tubules.
What percentage of filtrate must be reabsorbed into the blood?
More than 99%.
What is the relationship between filtrate and interstitial fluid?
Filtrate is similar to interstitial fluid.
What is the role of podocytes in the filtration process?
They form filtration slits that help regulate the passage of substances into Bowman’s capsule.
How does the afferent arteriole respond to increased GFR?
It constricts to increase resistance and decrease GFR.
What is the role of higher CNS input in micturition?
It may facilitate or inhibit the reflex.
What percentage of the filtrate is eventually excreted?
Less than 1%.
What type of transport can reabsorption be?
Active or passive.
What is the net filtration pressure in this context?
10 mm Hg.
What factors affect glomerular filtration?
Blood pressure, surface area, pore size, and slit size.
What is the role of the collecting duct in the nephron?
It is involved in the final concentration of urine.
What is the function of the glomerulus?
Filtration of blood to the lumen.
What is the renal threshold?
The plasma concentration at which a solute first appears in the urine.
What is the relationship between hydration and solute concentration in the nephron?
Increased hydration leads to lower solute concentration in the filtrate.
What type of graph represents the relationship between transport rate and plasma glucose concentration?
A linear graph until the transport maximum is reached.
What are the peritubular capillaries?
Capillaries that surround the tubule.
What type of proteins are found on the surface of the endothelium in the urinary system?
Negative-charged proteins.
What is the function of the ureter in the urinary system?
To transport urine from the renal pelvis to the bladder.
How is osmolarity regulated in the body?
By tightly controlling the rate of water reabsorption in relation to solute concentration.
What are podocytes?
Modified epithelial cells in the urinary system.
What is the function of the efferent arteriole?
It carries blood away from the glomerulus after filtration.
What does urine output depend on?
The state of the body.
What is the process of glomerular filtration?
The movement of blood to the lumen of the renal tubules.
How does the body regulate the reabsorption of water?
Through hormones like antidiuretic hormone (ADH).
What is the pathway of solute after filtration?
From the glomerulus to Bowman's capsule, then to the tubule, and finally to the renal vein and bladder.
What is the function of the distal tubule?
Reabsorption and secretion of ions and water.
What is the pathway of excretion in the urinary system?
From the collecting duct to the bladder and then to the external environment.
What is the process of filtration in the urinary system?
Movement of substances from blood to lumen.
What is the pathway of urine from the kidneys to the external environment?
From the collecting duct to the renal vein, then to the bladder and external environment.
What is the function of the loop of Henle?
It plays a crucial role in the concentration of urine.
What is the role of Bowman’s capsule?
It collects the filtrate from the glomerulus.
What does secretion depend on?
Membrane transport systems.
What happens to the filtered blood after passing through the renal tubules?
It is either reabsorbed into the blood or excreted as urine.
What is glomerular filtration?
The process by which substances leave the plasma and enter the tubule lumen through filtration barriers.
What is the significance of the basal lamina in the filtration process?
It acts as a selective barrier that prevents large molecules from passing into the filtrate.
What is the function of the proximal tubule?
It is responsible for the reabsorption of water, ions, and nutrients.
What is the proximal tubule's primary function?
It reabsorbs the majority of filtered water, ions, and nutrients.
What remains in the capillary during glomerular filtration?
Blood cells and plasma proteins.
How are permeable solutes reabsorbed?
By diffusion.
What are the three filtration barriers in the renal corpuscle?
What is the hydrostatic pressure of fluid in Bowman’s capsule?
About 15 mm Hg, favoring fluid moving back into the glomerular capillaries.
What substances are reabsorbed in the proximal tubule?
Glucose, amino acids, ions, and organic molecules.
What is the filtration fraction?
The percentage of total plasma volume that filters into the tubule.
What is secretion in the context of the urinary system?
Transfer of molecules from extracellular fluid into the lumen of the nephron.
What percentage of cardiac output do the kidneys receive at a given time?
20 - 25%.
What percentage of fluid is reabsorbed in the nephron?
19%.
What happens to the filtrate after passing through the distal tubule?
It moves to the collecting duct and then to the renal vein or bladder.
What is the role of peritubular capillaries in the nephron?
To facilitate the exchange of substances between blood and the nephron.
What is the result of secretion in the nephron?
An increase in the quantity of solute excreted in the urine.
What are peritubular capillaries?
They surround the nephron and are involved in reabsorption and secretion.
What is the relationship between the amount of solute filtered, reabsorbed, and secreted?
Amount excreted = Amount filtered - Amount reabsorbed + Amount secreted.
What is the daily GFR in liters?
180 L/day.
What role do both types of nephrons play?
Both are involved in urine formation.
What does reabsorption refer to in the urinary system?
Movement of substances from lumen to blood.
What is the function of the loop of Henle?
Concentration of urine through reabsorption of water and salts.
What is the flow sequence of filtered fluid in the nephron?
Renal corpuscle → Proximal tubule → Loop of Henle → Distal tubule → Collecting duct → Renal pelvis → Ureter.
What is excretion in the urinary system?
Movement of substances from lumen to external environment.
What is the process of secretion in the kidneys?
It involves the transfer of substances from the blood into the tubular lumen.
What is excretion in the context of the urinary system?
The elimination of waste products from the body through urine.
What is the significance of the Loop of Henle in the nephron?
It plays a crucial role in concentrating urine and maintaining osmolarity.
What is the pathway of urine from the nephron to the external environment?
From the nephron to the renal vein, then to the bladder and external environment.
What occurs when stretch receptors in the bladder fire?
Parasympathetic neurons fire, motor neurons stop firing, and smooth muscle contracts.
What is the function of the loop of Henle?
To concentrate urine and facilitate the reabsorption of water and solutes.
What is the pathway of urine from the nephron to the external environment?
From the collecting duct to the renal vein, then to the bladder and external environment.
What occurs during reabsorption in the renal system?
Substances are transported from the lumen back into the blood.
What structures are involved in the juxtaglomerular apparatus?
Macula densa, afferent arteriole, and granular cells.
What happens to NaCl delivery past the macula densa when GFR increases?
NaCl delivery increases.
What are filtration slits?
Narrow gaps between the foot processes of podocytes that allow filtered material to pass into Bowman’s capsule.
What is the Loop of Henle's function?
It plays a crucial role in the concentration of urine.
Why is a high blood flow rate critical for renal function?
It is essential for the kidneys to perform their functions effectively.
What happens to urine output when dehydrated?
Urine output decreases.
What happens to urine output when hydrated?
Urine output increases.
What is the significance of the nephron's configuration?
It can sense fluid flow in the proximal tubule.
What is the total plasma volume entering the afferent arteriole?
100%.
What percentage of plasma entering the kidney returns to systemic circulation?
99%.
What is the function of the afferent arteriole?
It supplies blood to the glomerulus for filtration.
What is the distal tubule's role in the nephron?
It is involved in the reabsorption of sodium and water, and secretion of potassium and hydrogen.
What is the function of the collecting duct?
To collect urine from multiple nephrons and transport it to the renal pelvis.
What is the role of the collecting duct in the nephron?
It is involved in the final concentration of urine.
