Renal processes involved in Urine excretion

Question 1

Urine

Answer 1

-product of renal function

Question 2

Processes important for renal function and formation of urine

Answer 2

1.Filtration (glomeruli)- filter water, solutes, into Bowman’s capsule
2. Reabsorption (tubules)- avoid excretion of plasma and solutes
3.Secretion (tubules)- removal of substances from peritubular capillaries and dumping them into the tubules. Ex. Drugs/toxins
**each nephron does all 3 processes

Question 3

Excretion equation

Answer 3

Excretion= Filtration – Reabsorption + secretion

Question 4

Rates of excretion

Answer 4

-filtration and reabsorption rates are significantly higher than excretion (for most solutes)

Question 5

Plasma filtered by kidneys daily

Answer 5

1.5L/day= 180 L/day-178.5L/day + 0

Question 6

Increase in plasma filtration

Answer 6

-10% increase in filtration (198L/day) will result in an excretion of 19.5 L/day if reabsorption stays the same
**shows how slight changes can have huge impact on excretion

Question 7

Why is the amount of filtration and reabsorption so high?

Answer 7

-because of very high permeability of the glomerular capillaries
-everything is freely filtered except cells and proteins
-concentration of most solutes in the plasma and within Bowman’s capsule is almost the same

Question 8

What is the benefit of high filtration and reabsorption?

Answer 8

-the entire plasma is filtered many times each day
-waste products are removed faster

Question 9

Different substance excretion

Answer 9

1.Filtration only (most of waste products, eg. Creatinine, uric acid)
2.Filtration and partial reabsorption (most of electrolytes, eg. Na, Cl)
3.Filtration and complete reabsorption (nutritional substances, eg. Glucose, amino acids)
4. Filtration and secretion (when rapid clearance is needed, eg. Organic acids)

Question 10

Our body plasma volume is 3L, renal filtration rate is 180 L/day, how many times a day is our entire plasma filtered?

Answer 10

60x