urinary system 2/3

Question 1

3 basic processes of a nephron?

Answer 1

glomerular filtration
tubular reabsorption
tubular secretion

Question 2

what is glomerular filtration?

Answer 2

the formation of a protein-free filtrate (ultrafiltrate) of plasma across the glomerular filtration membrane

Question 3

how many times a day is the body’s entire extracellular fluid volume filtered in an adult?

Answer 3

about 12 times

Question 4

what is the filtration membrane formed by and what does it do?

Answer 4

glomerular capillaries and podocytes

Permits filtration of water and small solutes​.
Prevents filtration of most plasma proteins, blood cells and platelets.

Question 5

what is net filtration pressure?

Answer 5

the total pressures that drives glomerular filtration

both hydrostatic and osmotic pressures

Question 6

define the 3 pressures in net filtration pressure

Answer 6

-Blood hydrostatic pressure (55mmHg)
the main force that “pushes” water and solutes through the filtration membrane (promotes filtration).​

• Capsular hydrostatic pressure (15 mmHg) exerted against the filtration membrane by fluid in the capsular space (opposes filtration). ​
• Blood osmotic (oncotic) pressure (30 mmHg) the pressure of plasma proteins “pulling” on water (opposes filtration).

Question 7

what is the glomerular filtration rate?

Answer 7

the amount of filtrate formed in all the renal corpuscles of both kidneys each minute.

Question 8

describe the 3 mechanisms that regulate GFR (glomerular filtration rate)

Answer 8

Renal autoregulation occurs when the kidneys themselves regulate GFR.​

Neural regulation occurs when the ANS regulates renal blood flow and GFR.​

Hormonal regulation involves angiotensin II and atrial natriuretic peptide (ANP).

Question 9

what is tubular reabsorption?

Answer 9

the process of returning important substances (filtered water, organic solutes such as glucose and ions such as Na+ and Cl-) from the filtrate back into the renal interstitium, then into the renal blood vessels, and ultimately back into the body.

Question 10

3 steps in the reabsorption process?

Answer 10

1. Solutes reabsorbed by active and passive processes​
2. Water follows by osmosis​
3. Small proteins by pinocytosis

Question 11

what is tubular secretion?

Answer 11

the transfer of materials (ions such as H+, NH4+; creatinine and drugs for example, penicillin) from the blood and tubule cells into glomerular filtrate.

Question 12

name 2 routes of reabsorption

Answer 12

1. paracellular (passive, between cells)

2. transcellular (active transport through cells, uses sodium/potassium pump)

Question 13

review primary and secondary active transport

Answer 13

Primary active transport
-Na+/K+ pump uses energy from ATP to pump ions across membrane

Secondary active transport

• energy stored in an ions electromagnetic gradient drives a substance across membrane
• symporters/antiporters

Question 14

2 types of osmosis and where they occur?

Answer 14

Obligatory water reabsorption: occurs when water is “obliged” to follow the solutes (Na+, Cl-, and glucose) being reabsorbed (‘water follows sodium’)​. It occurs in the proximal convoluted tubule and the descending limb of the loop of Henle.

Facultative water reabsorption: adapted to specific needs.​ It occurs in the collecting duct under the control of antidiuretic hormone.

Question 15

what is reabsorbed by the proximal convoluted tube (PCT)?

Answer 15

100% of most filtered organic solutes such as glucose and amino acids; ​
80–90% of the filtered HCO3-​
65% of the filtered water, Na+ and K+​
50% of the filtered Cl- and filtered urea; ​
A variable amount of the filtered Ca+, Mg2+ and HPO42-

Question 16

how does reabsorption of bicarbonates occur?

Answer 16

through facilitated diffusion through the basolateral membrane​. For every H+ secreted into the tubular fluid, one filtered bicarbonate eventually returns to the blood.

Question 17

what is reabsorbed by the Loop of Henle?

Answer 17

15% of the filtered water​
20–30% of the filtered Na+, and K+ ​
35% of the filtered Cl-,​
10–20% of the filtered HCO3-​
a variable amount of the filtered Ca+2, and Mg+2

Question 18

2 pathways of reabsorption in the Loop of Henle?

Answer 18

1. at the apical membrane
   - Na+-K+-2Cl- symporters
   - leakage channels
   - paracellular route
2. at the basal membrane
   - active transport of Na+
   - leakage channels

Question 19

does water reabsorption occur in the ascending or descending limb of the loop of henle?

Answer 19

descending (~15%)

Question 20

what reabsorption occurs in the distal convoluted tubule (DCT)?

Answer 20

10–15% of the filtered water
5% of the filtered Na+ ​
5% of the filtered Cl- ​​

Question 21

Reabsorption of Na+ and Cl- is done by Na+ and Cl- (symporters or antiporters)?

Answer 21

symporters

Question 22

How is Ca2+ reabsorbed in the DCT?

Answer 22

Parathyroid hormone (PTH) stimulates reabsorption depending on the body’s needs​

Question 23

how is water reabsorbed in the DCT?

Answer 23

DCT is not very permeable to water ​

No/little water reabsorption

Question 24

Five hormones which affect the tubular reabsorption and secretion in the renal tubules?

Answer 24

Angiotensin II​
Aldosterone​
Antidiuretic hormone​
Atrial natriuretic peptide​
Parathyroid hormone

Question 25

Which of those hormones increase reabsorption of sodium?

Answer 25

Angiotensin II

Aldosterone