Answer: Kidneys are the functional units of renal system of rom urine and it is essential to maintain homeostasis. Blood is going to enter into the kidney through renal arteries followed by entry of afferent arterioles into the \"glomerulus of nephrons\" & leave the filtrate (according to concentration gradient) finally exists as efferent arteriole Kidneys are the major organs of urinary system. The filtration of blood takes place in the kidneys through the nephrons. Two ureters carry the urine from the kidneys to the urinary bladder. From the bladder, urine is excreted out through the urethra. Relatable analogy is presence of \"similar ureters\" and two bean shaped kidenys with nephrons The different stages in glomerular filtration or urine formation are. Filtration: The movement of water and solutes from the plasma into the renal tubules is known as filtration. The major driving force of the filtration is hydrostatic pressure in the glomerulus capillaries. Blood passes through the capillaries in the glomerulus, due to the hydrostatic pressure in the Bowman’s capsule, plasma is filtered into the Bowman\'s capsule except blood proteins (this is called ultra-filtration). This filtrate is called glomerular filtrate. Hydrostatic pressure is the pressure exerted by the filtrate in Bowman\'s capsule (15 mm Hg). Absorption (or reabsorption): It is the movement of water and solutes from the renal tubule into the plasma. The process of absorption mostly occurs in the proximal tubules (approximately 70% of the filtrate is reabsorbed from the proximal tubules). The process of reabsorption is driven by hydrostatic and oncotic pressure, which is strictly under hormonal regulation. Oncotic pressure is the pressure exerted by the blood proteins, which draws water in to the circulation. Secretion: Tubular reabsorption of water and other substances back to the blood occur while the glomerular filtrate passes through the tubular portion of nephron. About 99% of water and electrolytes are reabsorbed during this process by both active and passive reabsorption process. During tubular secretion, substances pass from the blood into renal tubules. Excretion: Urine from the renal tubules enter into the collecting duct à Papillary duct à Calyx à Renal pelvis à Ureters à Urinary bladder à Urethra (excreted out of the body.). Normal glomerular filtration rate in the Bowman’s capsule is from 90 to 120 ml / min/1.73 m2. Usually older people do have a bit lower normal GFR levels as it is naturally reduce with age. Given GFR is 35mL/min/1.73 m2 (moderate decrease), it tells about the patient’s kidney function that “a sign of chronic kidney disease” because of diabetes, high blood pressure followed by glomerulonephritis. It is better control blood pressure by hormonal release. The three stages of urine formation are 1. Filtration; 2. Tubular reabsorption & secretion; 3. Water conservation Glomerular filtration (GFR): The formation of urine includes 1. Glomerular filtration .

1. Answer:
Kidneys are the functional units of renal system of rom urine and it is essential to maintain
homeostasis. Blood is going to enter into the kidney through renal arteries followed by entry of
afferent arterioles into the "glomerulus of nephrons" & leave the filtrate (according to
concentration gradient) finally exists as efferent arteriole
Kidneys are the major organs of urinary system. The filtration of blood takes place in the kidneys
through the nephrons. Two ureters carry the urine from the kidneys to the urinary bladder. From
the bladder, urine is excreted out through the urethra. Relatable analogy is presence of "similar
ureters" and two bean shaped kidenys with nephrons
The different stages in glomerular filtration or urine formation are.
Filtration: The movement of water and solutes from the plasma into the renal tubules is known as
filtration. The major driving force of the filtration is hydrostatic pressure in the glomerulus
capillaries.
Blood passes through the capillaries in the glomerulus, due to the hydrostatic pressure in the
Bowman’s capsule, plasma is filtered into the Bowman's capsule except blood proteins (this is
called ultra-filtration). This filtrate is called glomerular filtrate. Hydrostatic pressure is the
pressure exerted by the filtrate in Bowman's capsule (15 mm Hg).
Absorption (or reabsorption):
It is the movement of water and solutes from the renal tubule into the plasma. The process of
absorption mostly occurs in the proximal tubules (approximately 70% of the filtrate is
reabsorbed from the proximal tubules). The process of reabsorption is driven by hydrostatic and
oncotic pressure, which is strictly under hormonal regulation.
Oncotic pressure is the pressure exerted by the blood proteins, which draws water in to the
circulation.
Secretion:
Tubular reabsorption of water and other substances back to the blood occur while the glomerular
filtrate passes through the tubular portion of nephron. About 99% of water and electrolytes are
reabsorbed during this process by both active and passive reabsorption process. During tubular
secretion, substances pass from the blood into renal tubules.
Excretion:
Urine from the renal tubules enter into the collecting duct à Papillary duct à Calyx à Renal pelvis
à Ureters à Urinary bladder à Urethra (excreted out of the body.).
Normal glomerular filtration rate in the Bowman’s capsule is from 90 to 120 ml / min/1.73 m2.
Usually older people do have a bit lower normal GFR levels as it is naturally reduce with age.
Given GFR is 35mL/min/1.73 m2 (moderate decrease), it tells about the patient’s kidney

2. function that “a sign of chronic kidney disease” because of diabetes, high blood pressure
followed by glomerulonephritis. It is better control blood pressure by hormonal release.
The three stages of urine formation are 1. Filtration; 2. Tubular reabsorption & secretion; 3.
Water conservation
Glomerular filtration (GFR):
The formation of urine includes
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion: During tubular secretion, substances pass from the blood into renal tubules
mainly including H+, uric acid, nitrogenous waste, urea, creatinine and ammonia to keep blood
PH as 7.4 with homeostasis. Glucose, RBC, WBC along with some water is going to absorb into
peritubular blood capillaries.
Blood passes through the capillaries in the glomerulus, due to the hydrostatic pressure in the
Bowman’s capsule, plasma filtered into the Bowman's capsule except blood proteins (this is
called ultra filteration). This filtrate called glomerular filtrate.
The following pressures are the factors that determine glomerular filtration.
a. Glomerular capillary pressure
b. Colloidal osmotic pressure in the glomeruli
c. Hydrostatic pressure in the Bowman's capsule
Glomerular capillary pressure is the pressure exerted by the blood in glomerular capillaries
(about 60mm Hg), which favors glomerular filtration. Colloidal osmotic pressure is the pressure
exerted by plasma proteins in the glomeruli. Plasma proteins remain in the glomerular capillaries
and develop colloidal osmotic pressure (about 25 mm Hg), which opposes glomerular filtration.
Hydrostatic pressure is the pressure exerted by the filtrate in Bowman's capsule (15 mm Hg),
which opposes glomerular filtration.
Nephron has the following parts & movement of urine takes place in the following order:
1. Bowman’s capsule with glomerulus
2. Proximal convoluted tubule
3. Descending loop of Henle
4. Loop of Henle
5. Ascending loop of Henle
6. Collecting tubules
7. Vas recta
8. Minor calyx
9. Major calyx
10. Ureter

3. 11. Urinary bladder
12. Urethra
Non-steroidal anti-inflammatroy drugs are metabolised by first pass metabolism in liver followed
by formation of inactive metabolic products to eliminate through tubular secretion by blood
filterate through afferent arteriole finally to form glomerular filterate. Efferent arteriole move
away from Bowman's capsule. In the renal filterate, inactive drug metabolite is reabsorbed in
Henle’s loop followed by secretion into distal convoluted tubule and collecting tubule to
eliminate along with nitrogenous waste.
Aquaporins (AQP’s) or water channels are the integral membrane proteins that form pores in the
biological cell membranes. These water channels selectively allow movement of water molecules
in and out of the cell; they do not allow the passage of charged ions at all. These aquaporins
present in nephron play a key role in water reabsorption. Within the kidney, they are present in
the proximal tubule, descending limb of loop of Henle and collecting duct, and increases water
reabsoprtion in response to decreased blood volume.
The second stage of urine formation is called tubular reabsorption & secretion. Brush border
cells lining the proximal convoluted tubules (PCTs) have special projections called microvilli,
which increase their surface area, thus enabling the PCTs to transport about 70% of filtrate back
into blood. These cells possess aquaporins channels to reabsorb water.
Absorption (or reabsorption): It is the movement of water and solutes from the renal tubule into
the plasma. The process of absorption mostly occurs in the proximal tubules (approximately 70%
of the filtrate is reabsorbed from the proximal tubules). The process of reabsorption is driven by
hydrostatic and oncotic pressure, which is strictly under hormonal regulation.
About 65% to 80% of the filtrate is reabsorbed in the proximal convoluted tubule. The
reabsorption of fluid is mainly driven by the sodium transport by the Na+/K+ ATPase in the
basolateral membrane of PCT. The sodium transport needs P-type ATPase, which is the main
transport mechanism in the proximal convoluted tubule.
1). The absorption of salt and water occurs through the transcellular transport (passive), followed
by reabsorption via the basolateral membrane driven by Na+/K+ ATPase (active) pump.
2). Organic molecules such as glucose, amino acids and inorganic molecules such as phosphate
ions and other solutes are absorbed through the secondary active transport. The secondary active
transport has driven by the sodium gradient and needs co-transporters.
3). About 65% of the potassium is reabsorbed by the simple diffusion (passive) and solvent drag
mechanisms.
The quick reabsorption of bicarbonate ions from the basolateral membrane is an essential step in
the maintenance of pH, this needs the activity of carbonic anhydrase enzyme.
The mechanism of a countercurrent multiplier system operates to create a concentration gradient,

4. we can observe this mechanism widely in the nature, and one of the examples is formation of
concentrated urine by the kidneys.
Formation of concentrated urine by countercurrent multiplier system: Upon the influence of
vasopressin (antidiuretic hormone), the permeability of water increases, the water present in the
hypoosmotic fluid of distal tubule and thick ascending limb is lost by osmotic equilibration with
the interstitial fluid along the cortical collecting duct.
As the fluid travels through the distial tubule (DT) and T-connecting tubule (CNT), cortical
collecting duct (CCD), the NaCl is lost, and the osmotic pressure of the fluid becomes equal to
that of the plasma.
This isoosmotic fluid flows into the medullary collecting ducts and further loses more water
because the medullary and papillary interstitial are hyperosmotic, the urine, eventually becomes
hyperosmotic and is excreted as a concentrated urine.
Juxtamedually nephorns possess longer loop of Henle in humans, enable tubular reabsorption
and tubular secretion through the ion channels, and channel pumps existing inside the loops.
Finally, filterate become concentrated and become hypertonic to pass through collecting tubules.
Normally, many of mammals and birds possess loop of Henle and they have higher percentage of
cortical nephrons with shorter loop of Henle. However, in desert animals including Kangaroo
rats, almost higher number of densely packed thick juxtaglomerular nephrons and these are
situated deeply into the renal medulla with longer loop of Henle. These nephrons are useful to
kangaroo rodents for water conservation during the formation of hyperosmotic urine. The level
of urine formation is very lower and this desert adaptation is due to low availability of water.
Secretion of hydrogen ions in the proximal tubule mainly occurs thrugh the Na+/H+ antiport.
Solution
Answer:
Kidneys are the functional units of renal system of rom urine and it is essential to maintain
homeostasis. Blood is going to enter into the kidney through renal arteries followed by entry of
afferent arterioles into the "glomerulus of nephrons" & leave the filtrate (according to
concentration gradient) finally exists as efferent arteriole
Kidneys are the major organs of urinary system. The filtration of blood takes place in the kidneys
through the nephrons. Two ureters carry the urine from the kidneys to the urinary bladder. From
the bladder, urine is excreted out through the urethra. Relatable analogy is presence of "similar
ureters" and two bean shaped kidenys with nephrons
The different stages in glomerular filtration or urine formation are.
Filtration: The movement of water and solutes from the plasma into the renal tubules is known as

5. filtration. The major driving force of the filtration is hydrostatic pressure in the glomerulus
capillaries.
Blood passes through the capillaries in the glomerulus, due to the hydrostatic pressure in the
Bowman’s capsule, plasma is filtered into the Bowman's capsule except blood proteins (this is
called ultra-filtration). This filtrate is called glomerular filtrate. Hydrostatic pressure is the
pressure exerted by the filtrate in Bowman's capsule (15 mm Hg).
Absorption (or reabsorption):
It is the movement of water and solutes from the renal tubule into the plasma. The process of
absorption mostly occurs in the proximal tubules (approximately 70% of the filtrate is
reabsorbed from the proximal tubules). The process of reabsorption is driven by hydrostatic and
oncotic pressure, which is strictly under hormonal regulation.
Oncotic pressure is the pressure exerted by the blood proteins, which draws water in to the
circulation.
Secretion:
Tubular reabsorption of water and other substances back to the blood occur while the glomerular
filtrate passes through the tubular portion of nephron. About 99% of water and electrolytes are
reabsorbed during this process by both active and passive reabsorption process. During tubular
secretion, substances pass from the blood into renal tubules.
Excretion:
Urine from the renal tubules enter into the collecting duct à Papillary duct à Calyx à Renal pelvis
à Ureters à Urinary bladder à Urethra (excreted out of the body.).
Normal glomerular filtration rate in the Bowman’s capsule is from 90 to 120 ml / min/1.73 m2.
Usually older people do have a bit lower normal GFR levels as it is naturally reduce with age.
Given GFR is 35mL/min/1.73 m2 (moderate decrease), it tells about the patient’s kidney
function that “a sign of chronic kidney disease” because of diabetes, high blood pressure
followed by glomerulonephritis. It is better control blood pressure by hormonal release.
The three stages of urine formation are 1. Filtration; 2. Tubular reabsorption & secretion; 3.
Water conservation
Glomerular filtration (GFR):
The formation of urine includes
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion: During tubular secretion, substances pass from the blood into renal tubules
mainly including H+, uric acid, nitrogenous waste, urea, creatinine and ammonia to keep blood
PH as 7.4 with homeostasis. Glucose, RBC, WBC along with some water is going to absorb into
peritubular blood capillaries.

6. Blood passes through the capillaries in the glomerulus, due to the hydrostatic pressure in the
Bowman’s capsule, plasma filtered into the Bowman's capsule except blood proteins (this is
called ultra filteration). This filtrate called glomerular filtrate.
The following pressures are the factors that determine glomerular filtration.
a. Glomerular capillary pressure
b. Colloidal osmotic pressure in the glomeruli
c. Hydrostatic pressure in the Bowman's capsule
Glomerular capillary pressure is the pressure exerted by the blood in glomerular capillaries
(about 60mm Hg), which favors glomerular filtration. Colloidal osmotic pressure is the pressure
exerted by plasma proteins in the glomeruli. Plasma proteins remain in the glomerular capillaries
and develop colloidal osmotic pressure (about 25 mm Hg), which opposes glomerular filtration.
Hydrostatic pressure is the pressure exerted by the filtrate in Bowman's capsule (15 mm Hg),
which opposes glomerular filtration.
Nephron has the following parts & movement of urine takes place in the following order:
1. Bowman’s capsule with glomerulus
2. Proximal convoluted tubule
3. Descending loop of Henle
4. Loop of Henle
5. Ascending loop of Henle
6. Collecting tubules
7. Vas recta
8. Minor calyx
9. Major calyx
10. Ureter
11. Urinary bladder
12. Urethra
Non-steroidal anti-inflammatroy drugs are metabolised by first pass metabolism in liver followed
by formation of inactive metabolic products to eliminate through tubular secretion by blood
filterate through afferent arteriole finally to form glomerular filterate. Efferent arteriole move
away from Bowman's capsule. In the renal filterate, inactive drug metabolite is reabsorbed in
Henle’s loop followed by secretion into distal convoluted tubule and collecting tubule to
eliminate along with nitrogenous waste.
Aquaporins (AQP’s) or water channels are the integral membrane proteins that form pores in the
biological cell membranes. These water channels selectively allow movement of water molecules
in and out of the cell; they do not allow the passage of charged ions at all. These aquaporins
present in nephron play a key role in water reabsorption. Within the kidney, they are present in

7. the proximal tubule, descending limb of loop of Henle and collecting duct, and increases water
reabsoprtion in response to decreased blood volume.
The second stage of urine formation is called tubular reabsorption & secretion. Brush border
cells lining the proximal convoluted tubules (PCTs) have special projections called microvilli,
which increase their surface area, thus enabling the PCTs to transport about 70% of filtrate back
into blood. These cells possess aquaporins channels to reabsorb water.
Absorption (or reabsorption): It is the movement of water and solutes from the renal tubule into
the plasma. The process of absorption mostly occurs in the proximal tubules (approximately 70%
of the filtrate is reabsorbed from the proximal tubules). The process of reabsorption is driven by
hydrostatic and oncotic pressure, which is strictly under hormonal regulation.
About 65% to 80% of the filtrate is reabsorbed in the proximal convoluted tubule. The
reabsorption of fluid is mainly driven by the sodium transport by the Na+/K+ ATPase in the
basolateral membrane of PCT. The sodium transport needs P-type ATPase, which is the main
transport mechanism in the proximal convoluted tubule.
1). The absorption of salt and water occurs through the transcellular transport (passive), followed
by reabsorption via the basolateral membrane driven by Na+/K+ ATPase (active) pump.
2). Organic molecules such as glucose, amino acids and inorganic molecules such as phosphate
ions and other solutes are absorbed through the secondary active transport. The secondary active
transport has driven by the sodium gradient and needs co-transporters.
3). About 65% of the potassium is reabsorbed by the simple diffusion (passive) and solvent drag
mechanisms.
The quick reabsorption of bicarbonate ions from the basolateral membrane is an essential step in
the maintenance of pH, this needs the activity of carbonic anhydrase enzyme.
The mechanism of a countercurrent multiplier system operates to create a concentration gradient,
we can observe this mechanism widely in the nature, and one of the examples is formation of
concentrated urine by the kidneys.
Formation of concentrated urine by countercurrent multiplier system: Upon the influence of
vasopressin (antidiuretic hormone), the permeability of water increases, the water present in the
hypoosmotic fluid of distal tubule and thick ascending limb is lost by osmotic equilibration with
the interstitial fluid along the cortical collecting duct.
As the fluid travels through the distial tubule (DT) and T-connecting tubule (CNT), cortical
collecting duct (CCD), the NaCl is lost, and the osmotic pressure of the fluid becomes equal to
that of the plasma.
This isoosmotic fluid flows into the medullary collecting ducts and further loses more water
because the medullary and papillary interstitial are hyperosmotic, the urine, eventually becomes
hyperosmotic and is excreted as a concentrated urine.

8. Juxtamedually nephorns possess longer loop of Henle in humans, enable tubular reabsorption
and tubular secretion through the ion channels, and channel pumps existing inside the loops.
Finally, filterate become concentrated and become hypertonic to pass through collecting tubules.
Normally, many of mammals and birds possess loop of Henle and they have higher percentage of
cortical nephrons with shorter loop of Henle. However, in desert animals including Kangaroo
rats, almost higher number of densely packed thick juxtaglomerular nephrons and these are
situated deeply into the renal medulla with longer loop of Henle. These nephrons are useful to
kangaroo rodents for water conservation during the formation of hyperosmotic urine. The level
of urine formation is very lower and this desert adaptation is due to low availability of water.
Secretion of hydrogen ions in the proximal tubule mainly occurs thrugh the Na+/H+ antiport.