Urinary - Formation Of Urine Flashcards
What are the three steps?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What is glomerular filtration rate (GFR)?
Measures how well the kidneys filter blood
How does blood pressure effect filtration? (Normal bp? Low bp?)
Normal bp = normal filtration
Low bp = pressure differential not great enough to cause filtration (results in low urine production)
How do juxtaglomercular nephrons help when glomerular bp falls?
Releases renin to regulate bp
- Glomerular filtration
Blood pressure forces blood into the glomerulus -> bowman’s capsule collects filtrate (fluid filtered from the blood)
Filtration stops if bp is too low
- Tubular reabsorption
Useful substances are reabsorbed from the filtrate back into the blood in the peritubular capillaries
What useful substances are reabsorbed?
- water
- glucose
- amino acids
- ions
Where does most reabsorption occur?
PCT
Are nitrogenous waste products reabsorbed?
No, they are poorly reabsorbed
How much water does PCT reabsorb?
60-70%
How much organic substances does PCT reabsorb?
99-100%
How much sodium and chloride ions does PCT reabsorb?
60-70%
How much water does the nephron loop reabsorb?
25%
How much sodium and chloride ions does the nephron loop reabsorb?
20-25%
What influences the reabsorption of water for the distal comvulated loop? What percent of water?
Influenced by ADH
5%
What is ADH?
Regulates water balance in the body
What influences the reabsorption of sodium ions in the distal convoluted tubules?
Aldosterone
What is aldosterone?
Regulates bp and electrolyte balance
How much water does collecting system reabsorb? Influenced by what? What is sodium reabsorption influenced by?
9%
ADH and aldosterone
What is obligatory water reabsorption and facultative water reabsorption?
Two ways kidneys reabsorb water from filtrate back into bloodstream
What is obligatory water reabsorption? Percent?
Collects 85% of water
Automatic process not controlled by hormones
Occurs in PCT and descending loop of henle
What is facultative water reabsorption?
Water reabsorption regulated by ADH
Occurs in distal convoluted loop & collecting ducts
- Tubular secretion: reabsorption in reverse (this process is important for what?)
Important for getting rid of substances not already in filtrate
AND
Materials move from PCT into renal tubules
What are materials that move from PCT into renal tubules?
Creatinine & hydrogen + potassium ions
