Lecture 35: Controlling and Coordinating the urinary system

Question 1

What are the major functions of the kidneys?

Answer 1

= Excretion
= Homeostasis
= Hormones
= Metabolism

Question 2

How do the kidneys regulate metabolism?

Answer 2

GLUONEOGENESIS: synthesis of glucose from amino acid precursor occurs in the kidneys (and liver)

AMMONIS NH3: synthesised and secreted in the kidneys, and has a hole in N balance and pH balance

Question 3

How do the kidneys regulate homeostasis?

Answer 3

ACID-BASE: synthesis of HCO3 and excretion of non-volatile acids
FLUID BALANCE: urine output which can be adjusted to maintain volume and osmolarity
ELECTROLYTE BALANCE: Renal control of Na+, K+, Ca2+ and PO4. Most electrolytes are kept in balance by what we excrete rather than what we absorb
e.g high K+ intake = excretion by kidneys gradually increased

Question 4

Explain kidney secretion ? What do they excrete?

Answer 4

WATER and ELECTROLYTES: surplus water and electrolytes need to be excreted to maintain homeostatic balance (especially ECF composition/volume)
METABOLIC waste products: Hormones, bile pigments and nitrogenous waste (urea, uric acid)
FOREIGN SUBSTANCE: Toxins and drugs

Question 5

What are some examples of hormones which the kidney regulates and produces ?

Answer 5

EPO, calcitriol, renin, dopamine, kallikrein, prostaglandins

Question 6

The kidneys produce erythropoietin, how do the kidneys do this?

Answer 6

• Low oxygen levels are detected by the kidneys
• Kidneys release EPO in response to low O2 levels
• Stimulates bone marrow to produce more RBC’s
• Chronic renal failure —-> anaemia

Question 7

The kidneys activate vitamin D to its active form, how do they this?

What is vitamin D essential for ?

Answer 7

The active form of Vit. D is CALCITRIOL. The enzyme; renal enzyme 1-hydroxylase found in the kidney converts inactive vitamin D to calcitriol.
- Calcitirol is important for calcium balance and bone mineralisation

Question 8

What are the three nephron processes ?

Answer 8

Filtration = creates a plasma-like filtrate of the blood
Reabsorption = removes useful solutes form the filtrate and returns them to the blood
Secretion= Adds additional wastes from the blood to the filtrate

Question 9

Different processes occur in different parts of the nephron. What occurs in the?

• Glomerulus
• Proximal tubule
• Distal tube
• Collecting duct

Answer 9

Glomerulus: filtration
Proximal tubule: bulk reabsorption
Distal tubule: fine-tuning of electrolytes
Collecting duct: fine-tuning of water reabsorption