Lecture 60 - Control of Excretion

Question 1

What compounds does the body excrete as waste?

Answer 1

H+
Creatinine
Urea

Question 2

Where is sodium and water found?

Answer 2

Extracellular fluid:

• plasma
• interstitial fluid

Question 3

Where do H+ come from?

What do we have to do to them?

Answer 3

Metabolism

They must be excreted, otherwise we become acidotic.

Must be maintained and pH 7.4

Question 4

What is creatinine?

Answer 4

By product of muscle metabolism

Question 5

What is blood made from?

Answer 5

Plasma

Question 6

How much blood must be filtered to make 2 litres of blood?

Answer 6

200 L

Question 7

What is the blood flow to the kidney, in terms of cardiac output?

Answer 7

25%

Question 8

Which compounds are concentrated in the urine?

Answer 8

K+
PO4 (phosphate)
Urea
Creatinine

Question 9

Which things aren’t present in the urine?

Answer 9

HCO3
Albumin
Glucose

Question 10

What is HCO3 used in the body?

Answer 10

Buffer in the blood

Question 11

What is the role of Albumin in the blood?

Answer 11

• Osmotic active substance: maintains colloid osmotic pressure
• Binds other compounds in the blood

Question 12

What other proteins in the blood must not be lost?

Answer 12

Immunoglobulins

Fibrinogen

Question 13

Draw the nephron

Answer 13

Slide 5

Question 14

Name the structures of the nephron

Answer 14

Bowman's Capsule, Glomerulus
Proximal convoluted tubule (PCT)
Loop of Henle:
- descending limb
- ascending limb
Distal convoluted tubule (DCT)
Collecting duct

Question 15

Where is the DCT?

Why is this important?

Answer 15

Near the glomerulus

The cells near the glomerulus release hormones that affect the DCTs secretion and reabsorption

Question 16

Describe what happens in the glomerulus

Answer 16

Blood comes in via afferent arteriole
Filtration in the capillary
Remaining blood leaves by efferent arteriole

Question 17

What is stuff reabsorbed back into?

Answer 17

Peritubular capillaries

Question 18

What is reabsorbed in the PCT?

Answer 18

Water

salt

Question 19

Where is reabsorption occuring?

Answer 19

PCT
Loops of Henle
DCT
Collecting duct

Question 20

Where is secretion occuring?

Answer 20

PCT
DCT
Collecting duct

Question 21

Describe what happens to water in the kidneys

Answer 21

Vast majority is reabsorbed

Question 22

What happens to Na+ in the kidneys

Answer 22

Vast majority is reabsorbed

Question 23

What happens to K+ in the kidneys

Answer 23

Secreted

Question 24

Describe what happens to creatinine in the kidneys

Answer 24

100% filtered

None reabsorbed

Question 25

Describe what happens to urea in the kidneys?

Answer 25

50% of what is filtered is reabsorbed

Question 26

What do arterioles have that capillaries don't?

Answer 26

Arterioles have smooth muscle in their wall Thus, they can constrict and relax

Question 27

Describe the structure of the Bowman's capsule

Answer 27

- Capsular epithelium - Glomerular capillaries - Podocytes - Lumen of Bowman's Capsule

Question 28

What is the role of podocytes?

Answer 28

Control what is and isn't filtered from the blood Forms filtration slits

Question 29

What is GFR?

Answer 29

Glomerular filtration rate Volume of plasma filtered by the glomerulus per unit time?

Question 30

What is the filtration fraction?

Answer 30

Portion of blood going through glomerulus that is filtered 20%

Question 31

In a clinical setting, how do we measure kidney function

Answer 31

Measure GFR | Measure creatinine function

Question 32

What is the most important force that affects GFR?

Answer 32

Hydrostatic pressure in the glomerular capillary

Question 33

What does oncotic in the glomerulus do?

Answer 33

Opposes filtration However, hydrostatic pressure is very strong, so it overcomes this.

Question 34

What is oncotic pressure in the Bowman's capsule?

Answer 34

Should be zero, because no albumin can get out into the Bowman's capsule

Question 35

What is net filtration pressure? | What affects this pressure?

Answer 35

10 mmHg Glomerular hydrostatic pressure Glomerular colloid osmotic pressure Bowman's capsule fluid pressure

Question 36

Does colloid osmotic pressure in the glomerular capillary change?

Answer 36

Yes It increases along the glomerular capillary Because water is being removed