Week 4 - Renal (Kidney) Physiology

Question 1

Roles of the Renal System

Answer 1

• Regulate extracellular fluid volume and blood pressure
• Regulate osmolarity
• Maintain ion balance
• Regulate pH
• Excrete waste (urea)
• Produce hormones

Kidneys AND lungs act to regulate pH*

Question 2

Anatomy of Renal System

Answer 2

Question 3

Histology of Kidney

Capsule prevents swelling or shrinking…

Answer 3

Question 4

Nephrons.. Critical units of Renal System

Answer 4

Question 5

Nephron: up close

Answer 5

• Blood flows through Bowman’s capsule, afarent and efernt arteriols bring blood.. If this constrics the flow to Bowmans capsule goes down. If efferent arteriol is constricted, pressure increases in Bowmans capsule and more water is filtered out of blood and into kidney..
• FIlters about 180 L of fluid per day

Question 6

Where does absorption and secretion happen in nephrons?

Answer 6

Question 7

What is GFR?

Answer 7

Urine Production Rate =

Glomerular Filtration Rate - Tubular Reabsorption Rate

Normal GFR = ~180 L/day

Normal Urine Rate = ~1-2 L/day
(highly variable depending on fluid intake)

Question 8

Filtration, Reabsorption, and Secretion in tubules…

What is the amount filtered?

Answer 8

• The urinary excretion of substance depends on its filtration, reabsorption, and secretion
• Filtration of plasma out of the blood occurs in Bowmans capsule
• Mostly water, some are salts, drugs, organic molecules
• As it passes through tubule certain things are reabsorbed and peritubules can secreted selected molecules
• Clearance - measurment of how much blood is totally cleared of a given substance (not an amount of stuff, it how much blood is cleared from that substance)
• Inulin or creatinen are two substances that can be used go determine GFR.. the plasma and urine concentrations are equal for these substances.

Question 9

What is glucose handling by nephron?

Answer 9

It depends on plasma concentration of glucose

There are special mechanisms that will extract glucose back out of the urine and into plama…

Question 10

Reabsorption of glucose

Answer 10

375 is max amount kidneys can handle

Question 11

Renal Threshold…

Answer 11

Diabetes mell.. sweet urine..

Question 12

Renal control of blood volume and blood pressure

Answer 12

Sodium and water Excretion*

Negative feed back system*

Question 13

The negative feedback mechanisms of renal control of blood volume and blood pressure…

Answer 13

Sodium and water excretion.

Kidney is involved with the LONG TERM blood pressure regulation..