Exercise 9:
Renal System
Physiology

Hina Rehmani

Structure and Function of the
Kidney



Wastes produced by metabolism need
to be removed by the body



Kidney is made up of about 1 million
Nephrons



Function of the Kidney



Blood Filtration



Fluid Processing

Structure and Function of the
Kidney



Nephrons are microscopic tubules composed of:



Glomerulus



Renal Tubule



Glomerulus is a tangled capillary bed



Filters fluid from blood into the Renal Tubule



Glomerular Filtration: Fluid moves passively out of
Glomerulus



Renal Tubule is a long tube



Processes the filtrate from the Glomerulus



Tubular Reabsorption: Reabsorbs useful substances



Tubular Secretion: Move wastes towards elimination

Structure and Function of the
Kidney



The Renal Tubule consists of:



Proximal Convoluted Tubule (PCT)



Loop of Henle (Nephron Loop)



Distal Convoluted Tubule (DCT)



Collecting Duct



Last part of the collecting tubule in the nephron



Glomerular capsule surrounds the Glomerulus



Funnels filtrate into the Renal Tubule



Renal corpuscle



Name for the Glomerulus and Glomerular capsule
collectively

Structure and Function of the
Kidney



Blood Supply to the Glomerulus



Afferent Arteriole



Feed the Glomerular Capillary Bed



Efferent Arteriole



Drains the Glomerular Capillary Bed

Stimulating Glomerular
Filtration

Efferent

Afferent

Glomerulu

s

Glomerula

r capsule

PCT

Loop of

Henle

DCT

Collectin

g Duct

Activity 1: Effect of Flow Tube
Radius on Glomerular Filtration



Procedure: Increase the Afferent Arteriole radius
by 0.05 mm increments



What happens to the Glomerular Filtration Rate as
the Afferent radius increases?



It increases!



What would happen to the Glomerular Filtration
Rate if the Efferent radius was increased or
decreased?



If increased then Glomerular Filtration Rate would
decrease



If decreased then Glomerular Filtration Rate would
increase

Activity 2: Effect of Pressure on
Glomerular Filtration



Procedure: Increase the blood pressure
supplying the Glomerulus by 10 mmHg
increments



What happens to the Glomerular Filtration
Rate as the blood pressure increases?



It increases!



Why does this occur?



More pressure allows the Glomerulus to push
out more filtrate

Activity 3: Combined Effects on
Glomerular Filtration



Procedure: Record a baseline run and compare it

to a run with the Outflow Valve Closed



What was the difference between the two runs?



When the Valve was Closed, there was no Glomerular

Filtration Rate and no Urine Production



What would happen if the all the collecting ducts

in the kidney were blocked?



Pressure would build up



Ducts would burst/break



Would kidney function as a whole be affected if

one nephron was blocked?



No, because the kidney has about one million other

nephrons

Activity 3 continued



How could the body increase
Glomerular Filtration Rate in the kidney?



Dilate the Afferent Arteriole



Constrict the Efferent Arteriole



Increase Blood Pressure supplying the
Glomerulus

_________

Review of the Relationships

within the Renal System



Blood Flow, Glomerular Pressure, Glomerular
Filtration Rate, and Urine Production are related



Constricting the Afferent Arteriole causes …



Decrease in Glomerular Pressure



Decrease in Glomerular Filtration Rate



Decrease in Urine Production



Constricting the Efferent Arteriole causes…



Increase in Glomerular Pressure



Increase in Glomerular Filtration Rate



Increase in Urine Production

Stimulating Urine Formation

Effere

nt

Afferent

Glomerulu

s

Glomerular capsule

PCT

Loop of

Henle

DCT

Collectin

g Duct

Activity 4: Role of the Solute
Gradient on Maximum Urine
Concentration



In urine formation, solutes and water move
from the lumen to the interstitial spaces



Total solute gradient will effect the
movement of solute and water to these
interstitial spaces



Antidiuretic Hormone (ADH)



Increases water permeability in DCT and Collecting Duct



Water flows from high solute conc. into the interstitial
spaces



Water is absorbed

Activity 4 continued



Procedure: Increase the Max. Total Solute
Concentration of the Gradient by 300
milliosmole increments, adding ADH as
well



What happens to the Urine Concentration
as Total Solute Concentration Gradient
(Conc. Grad) increases?



It increases because ADH causes water to
move out of urine and the more solute there is
the more concentrated the urine

Activity 5: Effect of Glucose
Carrier Proteins on Glucose
Reabsorption



There is a limit to the amount of
glucose reabsorbed because carrier
proteins are needed to move them to
the interstitial fluid



If glucose carriers are being used,
excess glucose is eliminated in urine



Procedure: Increase the glucose carriers
by increments of 100

Activity 5 continued



What happened to the glucose concentration in urine

as the number of glucose carriers increased?



Glucose concentration in the urine decreased because

the carriers were able to get the glucose across



If there was more glucose than could be transported

by the available number of glucose carrier proteins,

what would happen to the urine?



An increased glucose concentration in the urine



Why do we expect to find glucose in the urine of a

diabetic person?



The lack of insulin causes a high glucose concentration



The glucose can’t all be absorbed because there are

only so many glucose carriers

Activity 6: Effect of Hormones on
Urine Formation



Excess water = dilute urine



Dehydration = concentrated urine



Hormones control urine concentration



ADH – Produced by Hypothalamus and

Stored in Posterior Pituitary Gland



Increases water permeability



Works at DCT and Collecting Duct



Aldosterone – Produced by Adrenal Gland



Reabsorbs sodium ions and water but loses

potassium ions



Works at the DCT

Activity 6 Continued



Procedure: Compare a baseline run with one when

Aldosterone is added and one when ADH is added



How are the results different when Aldosterone is

added?



Urine Volume decreases



Sodium and Water are retained



Potassium Conc. increases because it is kicked out



How are the results different when ADH is added?



Urine Concentration increases



Urine Volume decreases



Are the effects of Aldosterone and ADH similar or

antagonistic?



Similar (Agonists) - both conserve Sodium and Water

_________

_________

________

_________

_________