Renal Physiology And Excretion Question And Answers

Question 1. Draw and label the parts of a nephron. Explain the formation of urine. (or) Draw an eat labelled diagram of nephron.
Answer:

 

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Formation of urine:

• The urine formation takes place in three steps.
  1. Glomerular filtration:
     • It occurs in the glomerulus.
     • It is the initial step in urine formation, the plasma that transverses the glomerular capillaries is filtered by the highly permeable glomerular membrane and the resultant fluid the glomerular filtrate, is passed into Bowman’s capsule.
     • Glomerular filtrate is a proteinfree filtrate of plasma.
     • All the substances of plasma are filtered except the plasma proteins.
     • During the filtration, the substances pass through a filtering membrane.
     • This filtration depends upon.
       1. Glomerular hydrostatic pressure (HP)
          • It provides driving force for the filtration.
       2. Colloidal osmotic pressure (OP).
          • Oppose the process of filtration.
       3. Intracapsular pressure (ICP).
          • Oppose the process of filtration.
          • The resultant of these factors is termed as the effective filtration pressure (EFP).
            EFP = HP (OP+ICP).
          • Glomerular filtration rate is the rate at which the filtrate is formed.
  2. Tubular reasborsption:
     • When the glomerular filtrate flows through the tubular portion of nehpron, both quantitative and qualitative changes occur.
     • Large quantity of water, electrolytes and other substances are reabsorbed by the tubular epithelial cells.
     • The reabsorbed substances move into the interstitial fluid of renal medulla.
     • From here, the substances move into the blood in peritubular capillaries.

Mechanism:

1. Active reabsorption:

• It is the movement of molecules against the electrochemical gradient.
• It needs liberation of energy.
• Sodium, calcium, potassium, phosphates, sulphates bicarbonates, glucose, amino acids, ascorbic acid uric acid and ketone bodies are actively reabsorbed.

2. Passive reabsorption:

• It is movement of molecules along the electrochemical gradient without energy.
• Chloride, urea and water are passively reabsorbed.

3. Tubular secretion:

• In addition to reabsorption from renal tubules some substances are also secreted into the lumen from the pertibular capillaries through the tubular epithelial cells.
• Substances secreted in different segments of renal tubules are:

Question 2. Describe the changes undergone by the glomerular filtrate as it courses through the proximal and distal convoluted tubule.
Answer:

• When the glomerular filtrate flows through the tubular portion of nephron, both quantitative and qualititative changes occur.

Changes occurring in proximal convoluted tubule:

• The proximal convoluted tubule reabsorbs about 70 – 80% of the filtered and water and almost 100% of the filtered, amino acids and glucose.
• However, there is no change in the osmolarity of the filtrate.

1. Reasorption of sodium (Na+):

• About 80% of Na+ is actively reabsorbed in the proximal convoluted tubule, which is followed by a passive movement of H+.
• Initially Na+ is passively transported through apical membrane followed by active transport into the intercellular space.

2. Reabsorption of bicarbonate (HCO₃^–):

• About 90% of the filtered HCO₃^– is a reabsorbed in the proximal convoluted tubule.
• The secreted H⁺ reacts with filtered HCO₃ to form carbonic acid (H₂CO₃).
  H⁺+ HCO₃^– → H₂CO₃
• Now, carbonic acid dissociates into carbon dioxide and water in the presence of carbonic anhydrase.
• This carbon dioxide and water enters tubular cell where they form carbonic acid.
  CO₂+H₂O→H₂CO₃
• It immediately dissociated into hydrogen and bicarbonate ions.
  H₂CO₃→H⁺+ HCO₃^–
• This newly synthesized HCO₃^– is reabsorbed into the peritubular blood along with Na.
• H+ is secreted into the lumen.

3. Reabsorption of glucose:

• Glucose is completely reabsorbed.
• It is transported by sodium cotransport mechanism.
• Glucose and sodium bind to a common carrier SGLT-2 and is carried into the cell.
• The Na+ is then pumped out of the cell into the intercellular spaces and the glucose is moved into peritubular capillaries via GLUT-2.

4. Reabsorption of water:

• Proximal convoluted tubule is highly permeable to water.
• When sodium is reabsorbed from the tubule, the osmotic pressure decreases.
• It causes osmosis of water from tubule.
• Thus, water reabsorption occurs secondary to the sodium reabsorption, so called obligatory water reabsorption.

Changes occurring in distal convoluted tubule (DCT):

• Distal convoluted tubule is impermeable to water but permeable to solutes.
• The filtrate that enters the DCT is always hypotonic.

1. The early part of the DCT shows reabsorption of solutes like Na+ and CI.

• About 1820% of the filtered Na+ is reabsorbed in DCT.
• Out of this.
  1. 75% reabsorbed by chloride driven sodium transport.
  2. 25% reabsorbed by Na+ H+ exchange and Na+ K+ exchange.

2. The distal part of the DCT shows the actions of aldosterone and ADH.

1. Aldosterone causes Na+ reabsorption.
2. ADH.
   • In the presence of ADH, DCT becomes permeable to water resulting in water reabsorption.
   • About 5% volume reduction occurs and the filtrate becomes hypertonic.

Question 3. What is micturition reflex? Describe the process of urine formation.
Answer:

Micturition:

• It is a process by which the urinary bladder empties itself when it becomes filled.

Micturation reflex:

• Micturition occurs by a reflex process called micturation reflex.
• It constitute of impulses initiated by the stretch receptors in the bladder wall, sensory signals, sacral segments of spinal cord, pelvic nerve then back urinary bladder and parasympathetic nerve fibers.

Mechanism:

Filling of urinary bladder upto 450 ml.
↓
Pressure inside the bladder increases
↓
Stimulation of stretch receptors present on the wall of urinary bladder
↓
Generation of sensory impulses.
↓
Sensory impulses reach the sacral segment of spinal cord via fibers of pelvic nerve.
↓
Efferent impulses are produced in the spinal cord.
↓
These impulses travel to the bladder via efferent fibers of pelvic nerve.
↓
These impulses causes.
↓
Contraction of detrusor muscle.
↓
Relaxation of internal sphincter.
↓
This results in flow of urine from bladder into urethra.
↓
Stimulation of stretch receptors of urethra.
↓
Afferent impulses are send to spinal cord via pelvic nerve.
↓
This causes inhibition of pudendal nerve
↓
Relaxation of external sphincter occurs
↓
Thus, results in micturition.

Question 4. Describe the nerve supply of urinary bladder, and explain how contraction of detrusor muscle is stimulated. (or) Depict the innervation of urinary bladder with a neat labelled
Answer:

Nerve supply of urinary bladder:

• Urinary bladder is innervated by

1. Efferent nerve supply:

1. Sympathetic supply.

• Sympathetic fibers arises from the grey matter of L1 – L2 segments of spinal cord.
• These fibers descend down and form presacral nerve.
• Presacral nerve next divides into two hypogastric nerve which end in hypogastric ganglia.
• Post ganglionic fibers from here supply the bladder.
  Parts innervated and its action:

2. Parasympathetic supply.

• Preganglionic fibers lie in the gray matter of sacral segments of spinal cord.
• These fibers descend down and form pelvic nerve which end in hypogastric ganglia.
• Postganglionic fibers from the ganglia reach the bladder.
• Parts inverted and its action:

• The resultant effect is emptying of bladder.

3. Somatic nerve supply.

• Arises from the sacral segments of spinal cord.
• Passes through the pudendal nerve.
• Supplies posterior urethra and external sphincter.
• It helps the time of micturition reflex as it is voluntarily reflexed.

2. Affrent nerve supply:

Actions:

• Carry stretch sensation from the bladder along parasympathetic fibers.
• Carry pain sensation from bladder along sympathetic fibers.

Stimulation of contraction of detrusor muscle:

• Urinary bladder gets filled upto 450 ml.
• This increases pressure inside the bladder.
• Stretch receptors present on the wall of urinary bladder are stimulated.
• This generates sensory impulses which reach the sacral segments of spinal cord via fibers of pelvic nerve.
• Efferent impulses are produced in the spinal cord.
• These impulses travel to the bladder via efferent fibers of the pelvic nerve and causes contraction of detrusor muscle.

Question 5. Distinguish between cortical nephrons and juxtamedullary nephrons.
Answer:

• Based on the situation of renal corpusles the nephrons are classified into.
  1. Cortical nephron
  2. Juxtamedullary nephron.

Question 6. Proximal convoluted tubule.
Answer:

• It is the coiled portion arising from Bowman’s capsule.

Location:

• It is present in the cortex near the glomerulus.

Size:

• Length 14 mm
• Diameter 55 μ.

Histology:

• It consist of single layer of cuboidal epithelial cells.
• The border of these cells is formed by numerous microvilli, so called brush border.
• They are hair like projections that are directed towards the lumen of tubule.
• Microvilli markedly increases the surface area for absorption.

Function:

• Proximal convoluted tubule is responsible for about 80% of sodium active transport out of the tubular fluid into the peritubular capillaries.

Question 7. Nephron.
Answer:

Definition:

• Nephron is the structural and functional unit of kidney.

Size and number:

• Total length ranges from 4565 mm.
• Each kidney consists of approximately 1 to 1.3 million nephrons.

Parts:

• Each nephron is formed by.
  1. Renal or malpighian corpuscle.
     • It consists of.
       1. Bowman’s capsule.
          • It is initial dilated part of the nephron.
          • It encloses glomerulus.
       2. Glomerulus.
          • It is formed by the invagination of a tuft of capillaries into the Bowman’s capsule.
          • These capillaries are connected to an afferent arteriole on one end and to an efferent arteriole on the other end.
  2. Tubular portion of nephron.
     • It is the continuation of Bowman’s capsule.
     • It consist of
       1. Proximal convoluted tubule.
          • It is the coiled portion arising from Bowman’s capsule.
          • It is situated in the cortex near the glomerulus
       2. Loop of Henle.
          • It consists of descending limb which arises in continuity with the terminal part of the PCT.
          • Descending limb continues into the thin segment, from this segment arises the thick ascending limb.
       3. Distal convoluted tubule.
          • It is the continuation of thick ascending segment and occupies the cortex of kidney.
          • It opens into the collecting tubule.
       4. Collecting ducts.
          • The collecting ducts passes through the renal cortex and medulla to empty into the pelvis of the kidney at the apices of the medulla.

Types:

• Based on the situation of renal corpuscles, the nephrons are classified into.
  1. Cortical nephrons.
     • Present in the outer cortex of the kidney.
  2. Juxtamedullary nephrons.
     • Corpuscles are present in the inner cortex near medullar/corticomedullary junction.

Question 8. Draw and describe the juxtaglomerular apparatus. What are its functions?
Answer:

Juxtaglomerular apparatus:

• It is a specialized organ situated near glomerulus of each nephron.
• It is formed by.

1. Macula Densa:

• The cells of this zone are specialized renal tubular epithelia cells located at the site where thick segment of ascending limb of loop of henle.
• These cells are in direct contact with the mesengial cells, in closes contact with Ig cells and adjoins both afferent and efferent arteriole.

Function:

• Act as chemoreceptors.
• Stimulated by decreased Na+ and causes increased renin release.

2. Extraglomerular mesangial cells:

• They are situated in the triangular region bound by afferent arteriole, efferent arteriole and macula densa.

Functions:

• Phagocytic
• Secrete prostaglandin and cytokines.
• Controls the glomerular filtration.

3. Juxtaglomerular cells:

• They are modified vascular smooth muscle cells present in the wall of afferent arteriole
• They are innervated by sympathetic nerve fibers.

Function:

• Synthesize, store and release rennin.
• Regulates the renin secretion into the blood stream.

Question 9. Reninangiotensin mechanism.
Answer:

Reninsecretion:

• Renin is a glycoprotein with 340 amino acids.

Stimuli for rennin secretion:

• Low blood pressure.
• Low ECF volume.
• Sympathetic stimulation.
• Low plasma sodium.

Reninangiotensin system:

Release rennin acts on angiotensinogen.
↓
Renin converts angiotensinogen into angiotensin I (decapeptide)

Angiotension I is converted into angiotensin II (octapeptide) by angiotensin converting enzyme secreted from lungs.
↓
Angiotensiin II is converted into angiotensin III (heptapeptide) by angiotensinases present in RBCs
↓
Angiotension III converted inti angiotensin IV (hexapeptide)

Actions:

1. Angiotension II.

• Regulates GFR.
• Increases blood pressure
• Increases water intake.
• Increases ADH secretion.
• Increases aldosterone secretion
• Cause vasoconstriction.

2. Angiotensin III and IV.

• Increases aldosterone secretion.
• Causes vasoconstriction.

Question 10. Effective filtration pressure.
Answer:

1. Glomerular hydrostatic pressure (HP)

2. Colloidal osmotic pressure (OP)

3. Intracapsular pressure (ICP)

• HP provides the driving force for the filtration.
• OP and ICP opposes the process of filtration.
• The resultant of these factors is termed as the effective filtration pressure.
• Therefore, for each nephron, effective filtration pressure is.
  EFP = HP-[OP+ ICP]= 60 – (25+15)= 20 mm Hg

Value:

• It is about 20 mm Hg, varies between 15 and 20 mm Hg.

Significance:

• It is essential for maintenance of GFR.
• It is based on starling’s hypothesis.
• It states that the net filtration through capillary membrane is proportional to the hydrostatic pressure difference across the membrane minus the oncotic pressure difference.

Question 11. What is glomerular filtration rate? How it is measured?
Answer:

Glomerular filtration rate:

• Definition:
  • Glomerular filtration rate is the total quantity of filtrate formed in all the nephrons of both the kidneys in the given unit of time.
• Value:
  • 125 ml/min.
  • About 170-180 litres/day.
• Pressure determining filtration:
  1. Glomerular capillary pressure favours GFR
  2. Colloidal osmotic pressureopposes GFR.
  3. Hydrostatic pressure in Bowman’s capsule opposes GFR.
• Measurement of GFR:
  • Effective filtration pressure glomerular hydrostatic pressure [colloidal osmotic pressure + Intracapsular pressure]
    = [Hydrostatic pressure in glomerular capillaries hydrostatic pressure in Bowman’s capsule][colloidal osmotic pressure + Intracapsular pressure]
    = [45-10]-[25+0] = 35-25=10.
  • Now, GFR Kf x EFP.
  • kf Filtration coefficient of the glomerular membrane 12.5 ml/min/mm Hg.
  • Thus, GFR = Kf x EFP
    = 12.5 × 10
    = 125 ml/min.

Question 12. Define renal clearance of tubules. What is its significance?
Answer:

• Renal clearance:
• Definition:
  • It is the amount of plasma that is cleared off a substance in a given unit of time.
  • It is based on Fick’s principle.
• Factors determining renal clearance:
  1. Volume of urine excreted [V]
  2. Concentration of the substance in urine [U]
  3. Concentration of the substance in blood [P]
     Clearance = \(\frac{UV}{P}\)
• Significance:
  1. Renal clearance helps in assessment of.
  2. Glomerular filtration rate.
  3. Renal plasma flow.
  4. Renal blood flow.

Question 13. What are the physiological changes that occur in the body when exposed to high temperatures?
Answer:

• Body responses to hot environment:
  • Heat is lost from the body in several ways.
    1. Convection:
       1. 15% of heat is lost from body to the air by convection.
       2. The air in immediate contact with the skin is warmed up and the heated molecules move away and cooler ones come in to take their place.
       3. These in turn are warmed and so the process goes on.
    2. Radiation:
       • 60% of heat is lost by means of radiation.
       • Heat is lost from the body to cooler objects at a distance.
    3. Conduction:
       • 3% of heat is lost from the surface of the body to other objects by conduction.
       • Heat is lost only when it is in contact with a cooler object.
    4. Evaporation:
       • 22% of heat is lost through evaporation of water.
         1. Insensible water loss.
            • It consists of
              1. Water lost from the skin.
                 • It consists of the passage of water by diffusion through the epidermis.
              2. Water lost from the lungs.
                 • On an average the water loss from the lungs is approx 300 ml/day.
         2. Painting.
            • It occurs only in animals.
         3. Sweating.
            • Exocrine sweat glands take part in thermal regulation.
            • When one litre of sweat is evaporated 580 Kcal heat is lost.

Question 14. Mechanism of urine concentration (or) Describe counter current mechanism operating in the kidney to produce hypertonic and hypotonic urine.
Answer:

Mechanism of urine concentration:

It involves two processes

1. Medullary gradient

• Osmolarity of different parts changes

• This increase in osmolarity is called medullary gradient
• It is maintained through counter current mechanism

Counter current mechanism

• It constitute of loop of Henle and vasa recta
• Flow of fluid is in opposite direction in two limbs of U shaped tubules

1. Loop of Henle:

• Acts as countercurrent multiplier
• It works as follows

Active reabsorption of sodium, chloride and other solutes from ascending limb of Henle’s loop into medullary interstitium
↓
Diffusion of solutes into descending limb + addition of sodium and chloride by filtration into descending limb
↓
Solutes again reaches ascending limb
↓
Increases osmolarity

2. Vasa recta:

Acts as countercurrent exchanger Works as
↓
Reabsorption of NaCl from ascending limb of Henle’s loop
↓
Entry into medullary interstitium
↓
Entry of sodium chloride into descending limb of vasa recta + diffusion of water from descending limb into medullary interstitium
↓
Sodium chloride flows slowly towards ascending limb of vasa recta
Increase of concentration of sodium chloride in ascending limb
↓
Causes diffusion of sodium chloride into medullary interstitium and diffusion of water from medullary interstitium to the ascending limb of vasa recta
↓
Thus, sodium chloride is retained and water is removed in medullary interstitium

2. Role of ADH

• Due to presence of ADH, distal convoluted tubule and collecting duct becomes permeable to water and causes reabsorption of water
• Thus urine becomes hypertonic

Question 15. Describe nerve supply to urinary bladder with a neat diagram. What is micturition reflex?
Answer:

Nerve supply of urinary bladder:

• Urinary bladder is innervated by

1. Efferent nerve supply

1. Sympathetic supply
   • Sympathetic fibres arises from the grey matter of L1L2 segments of spinal cord
   • These fibres descend down and form presacral nerve
   • Presacral nerve next divided into two hypogastric nerve which end in hypogastric ganglia Post ganglionic fibres from here supply the bladder
   • Parts innervated and its action:
   • Resultant effect is retention of urine
2. Parasympathetic supply
   • Preganglionic fibres lie in the grey matter of sacral segments of spinal cord
   • These fibres descend down and form pelvic nerve which end in hypogastric ganglia Post ganglionic fibres from here supply the bladder
   • Parts innervated and its action:
   • Resultant effect is emptying the bladder
3. Somatic nerve supply
   • Arises from the sacral segments of spinal cord
   • Passes through the pudendal nerve
   • Supplies posterior urethra and external sphincter
   • It helps during the micturition reflex as it is voluntary reflexed

2. Afferent nerve supply

Actions:

• Carries stretch sensations from bladder along parasympathetic nerve
• Carries pain sensation from bladder along sympathetic nerve

Micturition reflex:

• It consists of impulses initiated by the stretch receptors on the bladder wall, sensory signals, sacral segments of spinal cord, pelvic nerve then back urinary bladder and parasympathetic nerves

Mechanism:

Filling of urinary bladder upto 450 ml
↓
Pressure inside the bladder increases.
↓
Stimulation of stretch receptors present on the wall of urinary bladder
↓
Generation of sensory impulses
↓
Sensory impulses reach the sacral segment of spinal cord via the fibres of pelvic nerve
↓
Efferent impulses are produced in the spinal cord
↓
These impulses travel to the bladder via efferent fibres of pelvic nerve

These impulses causes,

1. Contraction of detrusor muscle
2. Relaxation of internal spincter
↓
This results in flow of urine from bladder into urethra
↓
Stimulation of stretch receptor of urethra
↓
Afferent impulses are send to spinal cord via pelvic nerve
↓
This causes inhibition of pudendal nerve
↓
Relaxation of external sphincter occurs
↓
This results in micturition

Question 16. Glucose reabsorption in the kidneys in health and diabetes mellitus.
Answer:

Glucose reabsorption in health:

• Glucose is completely reabsorbed in kidneys
• It is actively transported through sodium cotransport mechanism
• According to it, glucose and sodium binds to common carrier called sodium dependent glucose transporter (SGLUT)-2
• By SGLUT-2, glucose and sodium is carried from luminal membrane into cell
• Energy produces by Na+ K+ ATPase helps to pump Na+ out of the cell into lateral intercellular spaces While glucose is transported from tubular cell into medullary interstitium by carrier protein called glucose transporter 2 (GLUT-2)

Glucose reabsorption in diabetes:

• Glucose reabsorption and excretion depends on plasma glucose concentration, PG

• Thus urine excretion rate increases with increase in plasma glucose concentration
• The plasma glucose level at which glucose first appears in urine is called renal threshold of glucose
• Value:
  • Renal threshold of arterial plasma 200 mg/dl
  • Renal threshold of venous plasma 180 mg/dl

Question 17. Functions of kidney.
Answer:

Functions of Kidney:

1. Role in homestasis
   • Kidney regulates carious activities in the body which are concerned with homeostasis
     • Filter the blood and excrete its waste products
     • Conserves water when it decreases and excretes when excess
     • Retains sodium when osmolarity decreases and eliminates sodium when osmolarity increases
     • Maintains pH of the blood and body fluids
2. Hemopoietic function
   • Stimulate erythropoiesis by the release of erythropoietin
3. Endocrine function
   • Hormones secreted by kidney are
     • Erythropoeitin
     • Thrombopoeitin
     • Renin
     • 1,25 dihydroxycholecalciferol
     • Prostaglandins
4. Regulation of arterial blood pressure
   • Through renin angiotensin mechanism and through maintenance of ECF volume
5. Regulation of blood calcium level
   • Kidney regulates blood calcium level by activating 1,25 dihydroxycholecalciferol into vitamin D
   • Vitamin D helps in absorption of calcium from intestine

Question 18. Explain the formation of urine.
Answer:

Formation of urine:

The urine formation takes place in three steps.

1. Glomerular filtration:

• It occurs in the glomerulus
• It is the initial step in urine formation, the plasma that transverses the glomerular capillaries is filtered by the highly permeable glomerular membrane’ and the resultant fluid the glomerular filtrate, is passed into Bowman’s capsule.
• Glomerular filtrate is a proteinfree filtrate of plasma.
• All the substances of plasma are filtered except the plasma proteins.
• During the filtration, the substances pass through a filtering membrane This filtration depends upon
  • Glomerular hydrostatic pressure (HP)
    • It provides driving force for the filtration
  • Colloidal osmotic pressure
    • Oppose the process of filtration
  • Intracapsular pressure
    • Oppose the process of filtration
    • The resultant of these factors is termed as the effective filtration pressure
• Glomerular filtration rate is the rate at which the filtrate is formed

2. Tubular reabsorption:

• When the glomerular filtrate flows through the tubular portion of nephron, both quantitative and qualitative changes occurs
• Large quantity of water, electrolytes and other substances are reabsorbed by the tubular epithelial cells
• The reabsorbed substances move into the interstitial fluid of renal medulla
• From here, the substances move into the blood in peritubular capillaries.

Question 19. Draw a neat diagram of structural and functional unit of the kidney and label its parts. Mention the non excretory functions of kidney.
Answer:

Non excretory functions of kidney:

1. Role in homestasis

• Kidneys regulate various activities in the body, which are concerned with hemostasis
  • Filter the blood and excrete its waste products
  • Conserved water when it decrease and excretes when excess
  • Retains sodium when osmolarity decreases and eliminates sodium when osmolarity increases Maintains pH of the blood and body fluids

2. Hemopoietic function

• Stimulate erythropoiesis by the release of erythropoietin

3. Endocrine function

• Hormones secreted by kidney are:
  • Erythropoietin
  • Thrombopoietin
  • Renin
  • 1,25 dihydroxycholecalciferol
  • Prostaglandin
    1. Regulation of arterial blood pressure
    2. Regulation of blood calcium level

Question 20. Define glomerular filtration rate. Explain the factors influencing the glomerular filtration rate.
Answer:

Definition:

• Glomerular filtration rate is the total quantity of filtrate formed in all the nephrons of both the kidneys in the given unit of time.

Factors affecting glomerular filtration rate:

1. Renal blood flow

• It is directly proportional to GFR.

2. Tubuloglomerular feedback.

3. Glomerular capillary pressure

• It is directly proportional to GFR

4. Colloidal osmotic pressure

• It is inversely proportional to GFR
• In dehydration colloidal osmotic pressure increases which decreases GFR

5. Hydrostatic pressure in Bowman’s capsule

• It is inversely proportional to GFR
• Hydrostatic pressure increases in obstruction of urethra and edema of kidney

6. Blood pressure

• GFR not affected upto when BP is between 60 & 180 mm Hg

7. Sympathetic stimulation

• Mild to moderate stimulation produces no effect
• Strong stimulation causes severe constriction of blood vessels by releasing noradrenaline
• Initially there is increase in GFR later decreases

8. Surface area of capillary membrane

• It is directly proportional to GFR

9. Permeability of capillary membrane It is directly proportional to GFR

• Hormones

Question 21. Functions of kindey.
Answer:

1. Role in homestasis:

• Kidneys regulate various activities in the body, which are concerned with homeostasis.
  1. Filter the blood and excrete its waste products.
  2. Conserves water when it decrease and excretes when excess.
  3. Retains sodium when osmolarity decreases and eliminates sodium when osmolarity increases.
  4. Maintains pH of the blood and body fluids.

2. Hemopoietic function:

• Stimulate erythropoiesis by the release of erythropoietin.

3. Endocrine functions:

• Hormones secreted by kidney are.
  • Brythropoitin
  • Thrombopoietin
  • Renin
  • 1,25 Dihydroxycholecalciferol
  • Prostaglandins.

4. Regulation of arterial blood pressure.

5. Regulation of blood calcium level.

Question 22. Nephrons.
Answer:

Definition:

• Nephron is the structural and functional unit of kidney

Parts:

• Each nephron is formed by
  1. Renal or malpighian corpuscle which consists of.
     1. Bowman’s capsule.
     2. Glomerulus.
  2. Tubular portion consists of.
     1. Proximal convoluted tubule.
     2. Loop of Henle.
     3. Distal convoluted tubule.
     4. Collecting duct.

Question 23. Juxtamedullary nephron.
Answer:

Based on the situation of renal corpuscles, nephrons are of two types.

1. Cortical nephron.

2. Juxtamedullary nephron.

Juxtamdullary nephron:

• It is present at the junction of the cortex and medulla.
• It consists of long Henle’s loop which penetrate deep into the medulla.
• Its vascular supply is formed vasa recta.
• It helps in concentration of urine.

Question 24. Proximal convoluted tubule.
Answer:

It is the coiled portion arising from Bowman’s capsule.

• It is situated in the cortex near the glomerulus.
• It consists of single layer of cuboidal cells bordered by microvilli.
• It is 14 mm long and has diameter of 55 μ.

Function:

• About 80% of active transport of sodium occurs in proximal convoluted tubule.

Question 25. Functions of distal convulated tubule. (or) Draw flowchart of reninangiotensin mechanism.
Answer:

The cells of distal convoluted tubule gets modified and form macula densa.

• Macula densa forms part of juxta – glomerula apparatus.
• These cells function as chemoreceptors.
• They are stimulated by a decreased Na+ ions nd thereby causing increased renin release.

Question 26. Juxtaglomerular apparatus.
Answer:

Definition:

• It is as specialized organ situated near the glomerulus of each nephron of both the kidneys.

Structure:

• It is made up of.
  1. Macula densa.
  2. Extraglomerular mesengial cells.
  3. Juxtaglomerular cells.

Functions:

• Secretes hormonal substances
• Regulates glomerular blood flow
• Regulates GFR.

Question 27. Glomerular filtration rate.
Answer:

Definition:

• Glomerular filtration rate is the total quantity of filtrate formed in all the nephrons of both the kidneys in the given unit of time.

Value:

• 125 ml per min.
• About 170180 litres/day.

Question 28. Micturition reflex.
Answer:

Filling of urinary bladder
↓
Stimulation of stretch receptors
↓
Afferent impulses passes via pelvic nerve
↓
Impulses reaches sacral segments of spinal cord
↓
Efferent impulses travel via pelvic nerve
↓
Causes
↓
Contraction of detrusor and
↓
Relaxation of internal sphincter.
↓
Flow of urine into urethra.
↓
Stimulation of stretch receptors of urethra.
↓
Afferent impulses passes via pelvic nerve
↓
Inhibition of pudendal nerve
↓
Relaxation of external sphincter
↓
Voiding of urine.

Question 29. Composition of urine.
Answer:

• Urine consists of
  1. Water about 10001500 ml/day.
  2. Solids.

Question 30. Ketone bodies.
Answer:

• The metabolism of fats is greatly increased in starvation and severe diabetes mellitus.
• This leads to increased production of ketone bodies.

Conditions:

1. Ketonemia Increased blood level of ketone bodies.
2. Ketonuria Increased urinary excretion of ketone bodies.

Question 31. Pathological constituents of urine.
Answer:

Question 32. Renal tubular function.
Answer:

• Renal tubules bring about.
  1. Secretion:
     • It refers to the transport of solutes from the peritubular capillaries into the tubular lumen.
     • It causes further addition of substances from the circulation into filtrate of renal tubules.
  2. Reabsorption:
     • It means return of substances from the filtrate in the lumen of renal tubules back into circulation.
     • It denotes the active transport of solutes and the passive movement of water from the tubular lumen into the peritubular capillaries.

Question 33. Types of nephron
Answer:

• Based on the situation of renal corpuscles, nephrons are classified into
  1. Cortical nephron
  2. Juxtamedullary nephron

Question 34. Draw labelled diagram of glomerular membrane
Answer:

Question 35. Name two types of sweat glands.
Answer:

Types of sweat glands:

• Eccrine gland
• Apocrine gland

Question 36. Enumerate factors affecting GFR. Give its normal value.
Answer:

Factors affecting GFR:

• Age
• Change in renal blood flow
• Changes in hydrostatic pressure
• Changes in concentration of plasma proteins
• Colloidal osmotic pressure
• Capillary pressure
• Systolic arterial pressure
• Tubuloglomerular feedback
• Size of capillary bed
• Afferent and efferent arteriolar contraction
• Contraction of glomerular mesengial cells Hormones

Value:

• 125 ml per min
• About 170180 litres/day

Question 37. State the normal and abnormal constituents of urine.
Answer:

Normal constituents:

1. Water10001500 ml/day
2. Solids

Abnormal constituents:

• Proteins
• Glucose
• Ketone bodies
• Bilirubin
• Blood
• Porphyrins
• Amino acids

Question 38. Mention two functions of skin.
Answer:

• Protective function.
  • Protects against bacteria, toxins, injury, mechanical blow and ultraviolet rays.
• Sensory function
  • Skin has nerve endings forming cutaneous receptors
• Regulation of body temperature
  • Body temperature is regulated by radiation conduction, convection and evaporation through skin.

Question 39. Cystmetrogram
Answer:

• Cystometrogram allows to assess how bladder and sphincter behave while storing urine and while passing urine.
• This test is done for people with urinary incontinence, people who have difficulty with urination, and in people with neurologic diseases that can affect bladder function.
• This test will measure bladder capacity and pressure.
• By doing this one can identify problems such as a small capacity bladder, overactive bladder or high pressure bladder.

Procedure:

• This test will take about 1520 minutes.
• Patient is positioned on an exam table lying on back
• The urethral opening is cleansed with betadine to eliminate any bacteria on the surface.
• A catheter with a sensor is inserted into urethra and advanced into the bladder.
• The bladder is filled with saline solution and filling pressures are recorded.

Question 40. Name two hormones acting on renal tubules.
Answer:

Question 41. Give the volume of urine excreted per day. Mention the three mechanisms Involved in urine formation.
Answer:

Daily urinary output:

• Normally about 11.5 litres of urine is formed per day.

Mechanism of urine formation:

It includes three processes:

• Glomerular filtration
• Tubular reabsorption
• Tubular secretion

Question 42. Role of renin in regulation of blood pressure.
Answer:

Renin acts on angiotensinogen and converts it into angiotensin I
↓
Angiotensin I is converted into angiotensin II by angiotensin converting enzyme secreted from lungs
↓
Angiotensin II is converted to angiotensin III by angiotensinases present in RBCs
↓
Angiotensin III is converted into angiotensin I