Physiology 2

Question 1

What are the functions of the kindeys in general ?

Answer 1

• Water balance and salt balance
• Maintenance of plasma volume and osmolarity
• Acid-base balance
• Excretion of metabolic waste products and exogenous foreign compounds
• Secretion of renin and erythropoietin
• Conversion of vitamin D into active form (Calcitriol: Ca2+ absorption in GI tract)

Question 2

What is the primary function of the kindeys ?

Answer 2

Primary function is to regulate the volume, composition and osmolarity of the body fluids.

It can excrete or reasborb certain substances such as Na+, K+, Cl+ etc

Question 3

What is the functional unit of the kidney ?

Answer 3

The nephron (as this can do all the functions of the kidney i.e. filter, reabsorb and secrete)

Question 4

What are the 2 types of nephron ?

Answer 4

Juxtamedullary and cortical

Question 5

Describe the structure of the nephron

Answer 5

Question 6

What are the main differences between the juxtamedullar and cortical nephrons ?

Answer 6

• Juxtamedullary nephrons have a much longer loop of henle which will descend into the medulla much more
• Juxta do not have peritubular capillaries instead they have a single capillary called the vasa recta which follows the route taken by the loop of Henle
• Juxta nephrons produce more concentrated urine than cortical nephrons

Question 7

What is the inner layer of the bowmans capsule lined by ?

Answer 7

Podocytes - theres spaces between them for fluid to pass through

Question 8

What is the special feature of the glomerular capillaries which promotes fluid drainage ?

Answer 8

There is large gaps between the endothelial cells which allows for fluid to drain through much more easily

Making the glomerular capillaries qute leaky

Question 9

Describe the juxtaglomerular apparatus and its functions

Answer 9

Consists of 3 types of cells:

1. Macula densa cells - sense salt levels in the tubular fluid and if high then release vasoactive chemical to cause smooth muscle contraction of the afferent arteriole
2. Juxtaglomerular cells - derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls to increase BP
3. Mesangial cells - function unknown

Question 10

Where is the juxtaglomerular apparatus located ?

Answer 10

Located near the vascular pole of the glomerulus

Question 11

What is urine ?

Answer 11

Modified filtrate of the blood

Question 12

What are the main processes which occur in the nephron ?

Answer 12

1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

Question 13

How much of the plasma which enters the glomerulus is filtered ?

Answer 13

Only 20% the other 80% leaves via the efferent arteriole

Question 14

How is the rate of filtration as the glomerulus calculated ?

Answer 14

Filtration of X = [X] in plasma time the GFR

Question 15

How is the rate of excretion of a substance calculated ?

Answer 15

Rate of excretion of X = [X] in urine times Vu (urine flow rate)

Question 16

How is the rate of reasborption calculated ?

Answer 16

Rate of reabsorption of X = Rate of filtration of X - Rate of exretion of X

Question 17

By comparing the rate of excretion to the rate of filtration of a substance how do we know if net reabsorption has occurred ?

Answer 17

If the rate of filtration > rate of excretion

Question 18

How do we calculate the rate of secretion of a substance ?

Answer 18

Rate of secretion of X = Rate of excretion of X - Rate of filtration of X

Question 19

How can we tell if there has been net secretion of a substance ?

Answer 19

If the rate of excretion of X > rate of filtration of X