Filtration, Secretion, Reabsorption
Definition of secretion.
Material enters nephron lumen after renal capsule
what are the functions of all of these structures?
glomerulus- filtration
PCT- reabsorption
DLOH- reabsorption of water but not ions
ALOH- reabsorption of ions (Na) but not water
DCT- sodium/potassium concentration in filtrate is regulated
CD- water reabsorption is regulated
What is the first regulator and what does it occur?
pH control and in the proximal convoluted tubule
Where is most of bicarbonate reabsorbed?
PCT
Diabetes insipidus
malfunctioning ADH or receptor
reduced reabsorption of water up to 5-10 L urine produced per day
large urine volume plus increased thirst (symptoms mimic diabetes mellitus except no elevated glucose conc. in urine)
Define filtration.
selective removal; blood to the lumen at the renal capsule
According to the glomerular filtration rate, how often is your blood volume filtered?
every 45 minutes
What does pH control contribute to help regulate renal functions?
H+ secretion, bicarbonate reabsorption, and production of new bicarbonate
What is the body's response to alkalosis/acidosis?
alkalosis- decreased reabsorption of bicarbonate, decreased excretion of H+, lungs decrease rate of breathing (hypoventilation)
acidosis- nearly all bicarbonate reabsorbed, new bicarb produced by kidney, increased excretion of H+, more bicarb produced (if necessary from glutamine), hyperventilation, and increased urine buffering by phosphate buffer and ammonia.
what does ADH primarily regulate?
total body water
Define reabsorption.
material return to blood from nephron lumen
List the percentages of NaCl reabsorption, glucose and amino acid reabsorption, and water reabsorption in the proximal convoluted tubule.
65%, 100%, and 65%
What is the bicarbonate equation?
HCO3- + H+ (two directional arrow) H2CO3 (two directional arrow) CO2 + H2O
Explain the failsafe mechanism.
If pH is too acidic (uncontrolled diabetes) new bicarb and ammonia can be produced from the amino acid glutamine.
What does aldosterone directly and indirectly effect?
directly- Na/K concentration
indirectly- water concentration
regulator of BP
Reabsorption- proximal convoluted tubule
secretion- distal convoluted tubule
filtration- glomerulus
300 mOsm and 1200 mOsm
What are the three regulators of blood pH and what is normal urine pH?
buffers (especially bicarbonate), renal system, respiratory system
6.0
How much of the reabsorption of Na is regulated and unregulated?
90% total reabsorption in PCT and ALOH but unregulated
8% unregulated in DCT
98% is unregulated and 2% is regulated by aldosterone
What is diuresis?
increased urine volume
What is the ascending loop of Henle impermeable to?
water because it has tight junctions
At the end of the collecting duct, what is the environment that contributes to the medulla?
hyperosmotic
what enzyme allows the production of new bicarbonate?
carbonic anhydrase (CA)
How much of K+ reabsorption is regulated and unregulated?
secretion regulated in DCT
90% reabsorption PCT unregulated
10% reabsorbed in DCT if no aldosterone secretion is more importan than reabsorption
what do Loop diuretics, Osmotic diuretics, and ACE inhibitors do?
loop- inhibit sodium/potassium pumps in ALOH and inhibit NaCl reabsorption
osmotic- mannitol is filtered but not reabsorbed and increases osmolarlity of filtrate
ace- inhibit conversion of angiotensin I to II and inhibits aldosterone release