Lecture 31: Urine Composition, functions of the kidney, and basic nephron processes Flashcards
How much normal urine do we produce in a day?
1.5L/day
What percentage of urine is water?
95% - 98%
What are three metabolic wastes that our body excretes through our urine?
creatinine
urea
uric acid
What is present in the urine that can determine the pH?
H+, NH3
What ions are present in the urine?
Na+, K+
Does normal urine contain drugs and toxins?
yes
What 10 things are present in normal urine?
water creatinine urea uric acid H+ NH3 K+ Na+ drugs toxins
What things do you expect in pathologic urine (6)
glucose protein blood haemoglobin leucocytes bacteria
What does normal urine look, taste and smell like?
- looks clear, light or dark amber look
- tastes acidic (not sweet)
- smells unremarkable
What does pH depend on and what is the approximate pH for a vegetarian and meat eater?
diet
vegetarians: pH up to 7.2
meat eaters: pH 4.8
What does pathological urine look, taste and smell like?
- looks golden, red, brown, blue
- taste sweet
- smells like fruit or rotten
What 5 things can we look for in a urinalysis?
red blood cells spez. gravity glucose protein pH
What is spez. gravity?
it gives an indication where the osmotic value of association is
Is blood present in plasma and urine?
no, neither
What is the range of spez. gravity in the plasma and urine?
285 - 300 mOsmol/L in plasma
50 - 1335 mOsmol/L in urine
Is glucose present in the plasma and the urine?
yes in the plasma but not in the urine
What is the pH range in the plasma and the urine?
plasma: 7.4
urine: 4.5 - 8.0
What are 9 functions of the kidney?
- ________ production
- M________
- G________
- _______ regulation
- excretion of ______, endogenous _______ and _________
- reabsorption of ________
- _____/______ homeostasis
- ________ homeostasis
- hormone production
- metabolism
- gluconeogenesis
- pH regulation
- excretion of drugs, endogenous metabolites and toxins
- re-absorption of nutrients
- salt/ion homeostasis
- water homeostasis
What two things determine blood pressure and why?
Na+ and H2O because these two determine the blood volume
Why is it important that the kidneys produce hormones, using EPO as an example?
What does chronic renal failure mean in terms of the number of red blood cells and haemoglobin in the blood?
- low O2 levels are detected by the kidneys
- the kidney releases EPO which stimulates the bone marrow to produce more red blood cells
- chronic renal failure means that there are low levels of red blood cells/ haemoglobin in the blood
What is meant by the metabolism function of the kidneys?
the kidneys convert compounds into water soluble compounds
What is meant by the gluconeogenesis function of the kidneys?
the kidneys want to convert amino acids to glucose in the fasting mode
Why is it important to maintain Na+ and K+ homeostasis?
- to maintain normal blood pressure
- to maintain a normal resting membrane potential
What can happen if K+ concentration gets too high?
it can lead to hyperkalemia which can cause death
How does the excretion of lipid soluble and water soluble drug from the kidney differ?
- lipid soluble is excreted by the kidneys after metabolisation in the liver
- water soluble is excreted directly by the kidneys
Why does vomiting increase the pH of the blood?
Because acid is being removed from the body so the blood is basic
Why does diarrhoea change blood pH?
because HCO3- is being removed from the body so the blood is acidic
How do the lungs and the kidneys control pH of the blood?
HCO3- concentration in the blood is controlled by the lungs (exhalation of CO2) and kidneys by reabsorption of HCO3- or secretion of H+ ions
What are the three basic processes of the nephron?
filtration
secretion
re-absorption
What is filtration?
when small molecules pass through to create a plasma-like filtrate of the blood
What is reabsorption?
this is when useful solutes are removed from the filtrate and returned into the blood
What is secretion?
additional wastes from the blood are added to the filtrate
What is the difference between excretion and secretion of the kidneys?
excretion = filtration - reabsorption + secretion
excretion is what the final product it
secretion is when additional wastes are added to the filtrate from the blood
What are three different ways that different molecules are released by the body? Give examples
- some substances need to be filtered and then partly reabsorbed (Na+/K+)
- some substances need to be filtered and then entirely reabsorbed (glucose)
- some substances need to be filtered and actively secreted so they are completely removed from the body (PAH)
What process takes place in the glomerulus in the nephron?
filtration
What process takes place in the proximal tubule in the nephron?
bulk reabsorption of Na+ and K+, secretion of metabolites, drugs and toxins
What process takes place in the distal tubule in the nephron?
fine tuning of electrolytes/water reabsorption
What process takes place in the collecting duct in the nephron?
fine tuning of electrolytes/water reabsorption
Where is the only place that glucose is reabsorbed?
in the proximal tubule
Where is K+ reabsorbed and where is it secreted?
is it reabsorbed in the proximal tubule and secreted in the collecting duct
Water is reabsorbed in most parts of the nephron. Where is it not?
not in the ascending nephron
Drugs and toxins are mostly excreted by _______ ________ not _______
active secretion
filtration
Big molecules are not even _________
filtered
