Intro to Renal

Question 1

What is a nephron?

Answer 1

Filtering unit –> 1 million in each kidney

Question 2

What are the 2 broad functions of the kidney?

Answer 2

1. Homeostasis

2. Hormone secretion

Question 3

How do the kidneys regulate fluid balance? How does it do this?

Answer 3

Urine volume

Osmolarity –> concentration of particles exerting an osmotic pressure (glucose)

Question 4

What electrolytes do the kidneys regulate?

Answer 4

Na, K, urea, creatinine

Question 5

How do the kidneys regulate acid-base balance?

Answer 5

Maintains an optimum pH for cellular function

• Bicarb is filtered through the glomerulus and reabsorbed back from proximal tubule through process of regeneration
• Removal of fixed acid

Question 6

What is risk of hyperkalaemia?

Answer 6

Medical emergency –> can stop heart

Question 7

What are normal potassium levels?

Answer 7

3.5 - 5.0 mmol/L

Question 8

How can kidney disease cause acidaemia/acidosis?

Answer 8

Kidneys don’t reabsorb enough bicarb

Don’t remove enough fixed acid

Question 9

What small molecules are the kidneys involved in the recovering of?

Answer 9

Sugars (presence of sugars in urine can indicate disease)

Amino acids (loss of amino acids occurs in disease of proximal tubule

Question 10

What are kidneys involved in excretion of?

Answer 10

Waste products and drugs

• Nitrogenous waste from protein metabolism (urea, creatinine)

Drugs can accumulate if kidneys aren’t functioning properly –> toxic effects

Question 11

Where is creatinine released from?

Answer 11

Muscle

Question 12

What are creatinine levels used to indicate?

Answer 12

Kidney function

Question 13

How are the kidneys involved in RBC production (erythropoiesis)?

What can patients with kidney disease develop?

Answer 13

Kidneys release EPO (erythropoietin) hormone which prompts bone marrow to make RBCs

Anaemia

Question 14

What is release of EPO stimulated by?

Answer 14

Hypoxia

Question 15

What is recombinant erythropoietin?

Answer 15

Stimulate release of RBCs which decreases need for blood transfusions

(used by athletes for doping)

Question 16

How do the kidneys control calcium and phosphate levels?

Answer 16

Kidneys secrete activated form of vitamin D

Question 17

How does active vitamin D control calcium and phosphate levels?

Answer 17

Facilitate intestinal absorption of calcium, although it also stimulates absorption of phosphate and magnesium ions.

In the absence of vitamin D, dietary calcium is not absorbed well

• Increases Ca formation
• Decreases Ca excretion
• Increases excretion of phosphorus

Question 18

Where is vitamin D activated?

Answer 18

Produced in skin and taken in from diet –> converted to active form in liver (1st stage) and kidneys (2nd stage)

Question 19

What glands control calcium metabolism?

Answer 19

Parathyroid glands

Question 20

What happens when parathyroid glands sense low calcium?

Answer 20

2ary hyperparathyroidism

Secrete PTH which goes to bones –> causes bones to release calcium and phosphorus –> increased blood calcium

This can lead to brittle bones

Question 21

How can kidney disease lead to brittle bones?

Answer 21

• Not producing activate vitamin D
• Poor calcium absorption
• Parathyroid glands sense low calcium and secrete PTH
• PTH causes bones to release calcium and phosphorus to increase blood calcium
• Brittle bone disease

Question 22

What happens if parathyroid glands are overactive for too long? What does this lead to?

Answer 22

Become autonomous –> no longer respond to drugs

3ary hyperparathyroidism

Question 23

How do the kidneys control blood pressure?

Answer 23

Secrete renin

Renin converts angiotensinogen –> angiotensin I

Question 24

What is blood pressure like of patients with kidney disease?

Answer 24

High blood pressure

Question 25

Normal range of sodium?

Answer 25

133-146 mmol/L

Question 26

Normal range of urea?

Answer 26

2.5-7.5 mmol/L

Question 27

Normal range of creatinine?

Answer 27

Female –> 60-93 μmol/L

Male –> 64-104 μmol/L

Question 28

Normal range of bicarb?

Answer 28

22-29 mmol/L

Question 29

Normal range of chloride?

Answer 29

95-108 mmol/L

Question 30

During urinalysis, what is looked for in kidney disease?

Answer 30

• pH (acidic in disease)
• Haematuria (blood in urine not normal)
• Proteinuria (proteins in urine not normal)
• Glucose (diabetes)
• Nitrites (infection)
• Leucocytes (infection)

Question 31

What is the normal protein/creatinine ratio in the urine?

Answer 31

< 13.0

Question 32

What is the normal albumin/creatinine ratio in the urine?

Answer 32

< 3.0

Question 33

How do the kidneys control blood pressure?

Answer 33

Juxtaglomerular apparatus is situated on afferent glomerular arterial secretes renin

Question 34

What is renin release controlled by?

Answer 34

• Sympathetic tone
• Pressure changes in the afferent arterioles
• Chloride and osmotic concentration

Question 35

What is effect of renin?

Answer 35

Converts angiotensinogen to angiotensin I (which is converted to the vasocontrictor angiotensin II)

Question 36

How are the kidneys involved in RBC production (erythropoiesis)?

Answer 36

Erythropoietin is produced by fibroblasts in the renal interstitium

This stimulates the production of erythropoiesis in response to hypoxia

This results in the production of red blood cells

Question 37

How are the kidneys involved in bone metabolism?

Answer 37

Naturally occurring vitamin D (cholecalciferol) requires hydroxylation in both the liver (to form 25-hydroxy cholecalciferol), and the kidney (to form 1,25-hydroxy cholecalciferol)

1,25-hydroxy cholecalciferol is the activated form of vitamin D
important for gastrointestinal calcium absorption

Failure to absorb calcium results in hypocalcaemia and increased secretion of parathyroid hormone. This in term can result in secondary
hyperparathyroidism (bone disease).