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 GlomerulusGlomerular

capsule

PCT

Loop of Henle

DCT

Collecting 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

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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

Efferent

Afferent Glomerulus Glomerular capsule

PCT

Loop of Henle

DCTCollecting

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

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