Urinary System, Lecture 2 Flashcards
Renale Tubule - wall and surrounding area
areas
- tubular lumen: inside area of renal tubule
- epithelial cell: cells making up wall of renal tubule
- interstitial fluid: extracellular fluid surrounding renal tubule
- blood vessel: peritubular capillaries
tubular epithelial cell membranes
- apical: between tubule lumen and inside and inside tubular epithelial cell
- basolateral: between inside tubular epithelial cell and interstitial fluid
tight junction
- connections point between adjacent epithelial cells
Tubular Reabsorption/Tubular Secretion
once filtered: regulation
- how much to keep?
- how much to eliminate?
tubular reabsorption
- renal tubule to peritubular capillaries
- mechanism for retaining substances
- moving from inside lumen to peritubular capillaries
- things we want to keep inside the body
tubular secretion
- peritubular capillaries to renal tubule (lumen) -> opposite
- mechanism for eliminating waste and foreign substances/removing excess
- taking out anything we do not want in the body
Passive Movement - Basics
- high to low solute concentration (towards the low cause that is where more concentration is needed)
- moving “down” or “with” gradient
- membrane moving through -> semipermeable (allows some things to move (fairly freely) while some cannot)
-> simple diffusion, facilitated diffusion and osmosis
Passive Movement - simple diffusion
simple diffusion
- move straight through membrane (permeable to it)
- just moves from high to low moving directly through membrane
- just diffusion can mean ‘simple’ diffusion
Passive Movement - facilitated diffusion
facilitated diffusion
- needs a membrane protein to provide passage (transporter)
my notes:
- not going straight through membrane, something creates pathway (tunnel or channel)
- ex. ion key to move through to door while other do not
- binds onto the membrane protein, changing membrane protein and releases on other side
- still passive moving from high to low
- membrane protein embedded in wall allowing something to pass through
Passive Movement - osmosis
- specifically for water
- involves an aquaporin (specific membrane protein) to provide passage
- aquaporin imbedded in the wall that allows for water to get through
- if osmosis is going from low to high, water is going from high to low
- same movement
Active Movement - basics
- low to high solute concentration (reverse of passive)
- moving “up” or “against” gradient (trying to go upstream or up the current (river analogy))
- at least 2 ions moving together:
◦ same direction - cotransport or symporter
◦ opposite direction - counter transport or
antiporter
◦ need both to move (ions) - primary (if they say just active transport means primary)
◦ ATP (adenosine triphosphate) breakdown
provides direct energy to “pump” across
membrane
◦ both ions moving “up” their gradients
◦ use the energy directly (directly breaking
something down and using its energy)
◦ both ions will be moving same way from low to
high - secondary
◦ move in response to conditions created by
primary
◦ an ion will moving “down” its gradient while
another moves “up” its gradient
◦ use energy indirectly
◦ ions moving in opposite directions
Tubular Reabsorption/Tubular Secretion (proximal tubule cells)
- '’X” can be glucose or amino acids
proximal tubule: - location for bulk of reabsorption
◦ 65% sodium reabsorbed (most thing respond to
what sodium is doing - follow sodiums lead)
◦ 100% glucose reabsorbed
◦ 100% amino acids reabsorbed - secretion of hydrogen (variable amount) - can be high or low depending on what needs to be done
(diagram to go with it)
Tubular Reabsorption/Tubular Secretion (tubular epithelial cells - water)
- obligatory water reabsorption - water that moves following solutes (obliged to follow)
- lots of aquaporins in proximal tubules so water can move freely
- sodium movement creates change is osmotic pressure gradient (altered solute concentration)
◦ if you have less particles that is going to decrease
osmolarity
◦ higher osmolarity as the particles arrive
somewhere else - water will move by osmosis in response to this changed osmotic pressure gradient
- obligatory water reabsorption includes 65% water reabsorbed in proximal tubule
- the two percentages tend to be pretty close as water follows blindly
- one of the key things that follows sodium is water
Tubular Reabsorption/Tubular Secretion (other ions following water (proximal tubule cell))
- water movement that followed sodium alters other ion solute concentration gradients (creates gradients for these ions)
- these ions can move by simple diffusion in latter half of proximal tubule
- as these ions move they alter osmotic pressure gradients (like sodium did) and draw even more water along
- basically: sodium moves - water follows - other ions move - more water follows
- fairly early in tubule (proximal)
Tubular Reabsorption/Tubular Secretion (ascending loop of Henle cell)
ascending loop of Henle
- 25% sodium is reabsorbed
- 35% chloride reabsorbed
- 25% potassium reabsorbed
- no water movement
descending loop of Henle
- 15% of water reabsorbed
obligatory water reabsorption
- total: ~80%
◦ 65% in proximal tubule
◦ 15% in descending loop of Henle
(diagram notes - memorize)
Tubular Resorption/Tubular Secretion (distal tubule and collecting duct cell)
- 6-9% sodium reabsorbed
- secretion of potassium (variable amount adjusted for dietary intake, hormonal levels)
◦ can secrete more of it if diet is more in K or it can
be less if intake is less
◦ hormones - control quite a bit - hormones can
turn these processes up and down
◦ back in proximal tubule everything moved pretty
easily now there is more control
facultative water reabsorption - adapting to need
(how much more do we reabsorb of water) - variable amount; hormone regulated
- under normal hydration conditions:
◦ 19% reabsorption
◦ 1% urinary excretion (1-2 L/day)
