BIOL 373 midterm #2

Question 1

Roles of the kidney

Answer 1

1) regulation of extracellular fluid volume and blood pressure

2) regulate plasma osmolarity (Na, Cl)

3) regulates ion balance

4) excretion of waste

5) regulates plasma pH

6) endocrine

Question 2

Why not only filter the 1% of filtrate that needs to be excreted?

Answer 2

filtering all the liquid then excreting selected solutes is easier because there isn’t a need for specific transport mechanisms

Question 3

What does the cortex contain

Answer 3

All Bowman’s capsules, proximal and distal tubes

Question 4

What does the medulla contain

Answer 4

loops of Henle and collecting ducts

Question 5

What are the tubular elements of the nephron in order?

Answer 5

1) Bowman’s capsule + glomerus (renal corpuscle)

2) proximal tubule

3) descending limb

4) loop of henle

5) ascending limb

6) distal tubule

7) collecting duct to bladder

Question 6

Conventional circulation

Answer 6

artery -> arteriole -> capillary -> venule -> vein -> heart (nephron: two capillary beds glomerulus capillaries and pertitubular capillaries)

Question 7

Venous portal system

Answer 7

artery -> arteriole -> capillary -> venule -> capillary -> venule -> vein -> heart

Question 8

What is cortical nephron in renal circulation

Answer 8

abdominal aorta -> renal artery -> branches of smaller arteries -> … afferent arteriole -> glomerular capillaries -> efferent arteriole -> peritubular capillaries -> venules - > veins

Question 9

What is the juxtamedullary nephron in renal circulation

Answer 9

afferent arteriole -> glomerular capillaries -> efferent arteriole -> peritubular capillaries / vasa recta -> venules -> veins

Question 10

Overview of kidney function

Answer 10

kidneys process 180L plasma/ day

urine output is only 1.5 l/day

99% of fluid that passes through kidneys is reabsorbed

1) filtration
2) reabsorption
3) secretion

Question 11

What is filtration?

Answer 11

movement of water/ solutes from blood into tubules

-only occurs in renal corpuscles
-once in tubules, filtrate will be excreted unless reabsorbed

Question 12

What is reabsorption?

Answer 12

movement of water/ solutes from filtrate back into blood (peritubular capillaries)

Question 13

What is secretion?

Answer 13

removing molecules from blood, adding them to filtrate

much more selective than filtration

Question 14

Where does filtration occur?

Answer 14

Only in the glomerulus
-blood to lumen

Question 15

Where does reabsorption occur?

Answer 15

Proximal tube, loop of Henle

Question 16

Where does secretion occur?

Answer 16

proximal tubule, distal tube

Question 17

Where does excretion occur?

Answer 17

To bladder and external environment from distal tubule

Question 18

What does urinary excretion depend on?

Answer 18

Filtration, reabsoprtion, and secretion

amount filtered - amount reabsorbed + amount secreted = amount of solute excreted

Question 19

Nephron 1 - Filtration at renal corpuscle

Answer 19

1) afferent arteriole

2) glomerulus

3) efferent arteriole

4) peritubular capillaries

filtrate is almost identical to plasma in composition (minus blood cells and most of the protein)

Question 20

Nephron 2 - Reabsorption and secretion

Answer 20

~70% fluid and solute reabsorbed in proximal tubule (iso-osmotic reabsoprtion)

fluid leaving ascending loop of Henle is hypo-osmotic relative to plasma (at this point, 90% of original filtrate has been reabsorbed)

distal tubule and collecting duct are fine tuning of water/ salt balance it is in endocrine control

Question 21

What is in the liquid after filtration?

Answer 21

100% volume
300 mOsM
180L/day

Question 22

What is liquid at start of loop of Henle?

Answer 22

54L/ day
30% volume
300 mOsM

Question 23

What is liquid at end of loop of Henle?

Answer 23

18L/ day
10% volume
100 mOsM

Question 24

What is in liquid leaving collecting duct?

Answer 24

1.5L/ day
1% volume
50-1200 mOsM
aim for this because this is what we pee a day

Question 25

Filtration at the renal corpuscle

Answer 25

20% of the plasma moves out of glomerular capillaries into tubules (the rest exits in the efferent arteriole

Question 26

What is filtration fraction?

Answer 26

% of total plasma volume that filters into tubule

Question 27

What is the function of the macula densa?

Answer 27

modifies tubular epithelium
-macula densa cells release paracrine factors that act on smooth muscle of afferent arteriole

Monitors tubular salt concentrations and can release paracrine factors that affect afferent arteriole diameter

Question 28

What are barriers to filtration?

Answer 28

glomerular capillary endothelium

basement membrane

specialized epithelium around glomerulus

Question 29

What part of the nephron tubule is part of the juxtaglomerular apparatus?

Answer 29

It is part of ascending limb of the loop of Henle where it connects to the distal tubule