Week 11 - Overview of Kidney Function

Question 1

Is there a link between high bp and salt intake

Answer 1

Only a minority of people with high salt diets will have high bp because of this

Question 2

4 examples of water and electrolyte homeostasis problems

Answer 2

Haemorrhage
Unusual eating/drinking behaviour
Severe dehydration, rapid fluid loss from the gut or after burns.
Unintended consequences of drug actions

Question 3

What is the bodies typical water intake and output

Answer 3

2.5L/day

Intake - water, food and metabolic

Output - urine, sweat, faeces, insensible loss

Question 4

What is insensible loss

Answer 4

Water that comes out the body through means other than the ureter e.g respiratory water loss, water out the skin not as sweat

Question 5

In hot conditions/humid or during heavy exercise what can sweat loss increase to

Answer 5

between 2-10L per day

Question 6

UK recommendation for salt intake

Answer 6

6g/day

Question 7

What percentage of blood goes to the kidney

Answer 7

25% of the entire CO

Question 8

What is blood pressure in the glomerular capillaries

Answer 8

50-60mmHg e.g high

Question 9

Renal artery structure

Answer 9

Short and relatively large radius

Question 10

Describe the sequence of blood vessels

Answer 10

Afferent arteriole -> Glomerular capillaries -> efferent arteriole -> tubular capillaries -> venule

Question 11

What drains the fluid from the collecting duct

Answer 11

Ureter

Question 12

Cortex

Answer 12

Region between medulla and capsule

Question 13

What is the functional unit of kidney

Answer 13

Nephron

Question 14

How many nephrons in each kidney

Answer 14

1000000

Question 15

What are the 2 types of nephron

Answer 15

Superficial and juxta-medullary

Question 16

Which type of of nephron is water reabsorption more effective in

Answer 16

Longer juxta-medullary nephrons

Question 17

What are the 4 sections of nephron in order

Answer 17

Proximal convoluted tubule loop
Loop of Henle
Distal convoluted tubule
Collecting duct

Question 18

What is the filtration rate of the glomerular capillaries

Answer 18

90-140ml/min

Question 19

3 functional stages of renal glomerular filtration system

Answer 19

Ultrafiltration - filtration through glomerular capillaries and driven by high blood pressure
Reabsorption - active pumping from filtrate into efferent arteriole.
Secretion - active pumping from efferent arteriole to tubules.

Question 20

Which substances are retained during reabsorption

Answer 20

Water, glucose, amino acids, electrolytes

Question 21

Examples of substances which are secreted

Answer 21

Hydrogen
Ammonia
Uric acid
Some drugs

Question 22

What structure do water and small molecules pass through during ultrafiltration

Answer 22

Slits in the podocytes

Question 23

Which molecules can fit through the slits of the podocytes

Answer 23

Small proteins, urea, ions, glucose, amino acids,

Question 24

Which molecules are fully reabsorbed into the efferent arterioles from the the proximal convoluted tubules

Answer 24

Glucose
Amino acids

Question 25

Which molecules are partially

Answer 25

Na+
Water

Question 26

By what fraction does the volume of the filtrate reduce

Answer 26

1/3

Question 27

Compare the thickness of loop of henle in the medulla

Answer 27

Ascending is thicker than descending

Question 28

What happens to the osmotic pressure of the loop of henle

Answer 28

Ion pumping develops high osmotic pressure at the tip of the loop

Question 29

How does electrolyte and water re-absorption differ between DCT and PCT

Answer 29

Less intense electrolyte and water re-absorption

Question 30

What drug/hormone sets collecting duct permeability

Answer 30

Anti-diuretic hormone
(ADH/AVP)

Question 31

What happens when ADH is present

Answer 31

Aquaporins are inserted into the luminal membrane to allow water movement

Question 32

What happens to plasma osmolarity when someone is dehydrated

Answer 32

It increases

Question 33

What happens to plasma osmolarity when someone drinks too much

Answer 33

Plasma osmolarity decreases

Question 34

What is the role of renin

Answer 34

When blood pressure is too low, glomerular hypofiltration occurs. Renin is secreted by the juxtaglomerular apparatus. Renin splits angiotensinogen to produce angiotensin I which is converted into angiotensin II - a powerful vasodilator.

Question 35

What is the role of aldosterone

Answer 35

Is secreted by glomerulosa cells of the adrenal cortex when electrolyte concentration falls.

Aldosterone increases reabsorption of Na,Cl ions from loop, distal tubules and duct cells. It also increases K+ secretion.

Electrolyte reabsorption also causes increased water reabsorption.