Tubular Reabsorption and Tubular Secretion Flashcards
tubular reabsorption
returns filtered water and filtered solutes back to the bloodstream
interstitial fluid pressure
helps drive water back into peritubular capillaries
blood hydrostatic pressure
relatively low in the peritubular capillaries, which reduces resistance to reabsorption
plasma proteins are not filtered
which raises blood colloid osmotic pressure in peritubular capillaries
total plasma volume filters through the renal tubules every
22 minutes
substances can be reabsorbed from the filtrate along
one of two possible routes
transcellular route
allows substances to pass from filtrate across epithelial cells of tubule through cytoplasm, into interstitial fluid
paracellular route
allows substances to “leak” out of filtrate through “tight” junctions between epithelial cells
substances that get reabsorbed from the filtrate
are taken into the peritubular capillaries
blood retains its plasma proteins
so water gets drawn into capillaries by osmosis
solvent drag
occurs when dissolved solutes enter capillaries by following water
primary active transport
uses ATP energy to pump substances into capillaries
secondary active transport
uses energy from ionic electrochemical gradient to pump substances into capillaries
symporters
can move two or more substances across a membrane in same direction
antiporters
can move two or more substances across a membrane in opposite directions
transport maximum (Tmax)
describes the reabsorption limit of a renal tubule due to the number of transport proteins that are available
each particular solute has its own Tmax when
all of its transporters are occupied
Tmax is high for glucose and
other substances that body needs to retain
tubular secretion
removes substances form the peritubular capillaries and adds them to the filtrate
most tubular reabsorption occurs in the
proximal convoluted tubule
sodium reabsorption creates an
osmotic gradient and an electrical gradient to drive the reabsorption of water and other solutes
sodium ions reabsorbed by symporters
in first portion of PCT along with glucose, amino acids, phosphate ions
sodium ions reabsorbed by antiporters
that transport hydrogen ions out
most abundant cations in filtrate
sodium ions
chloride ions get reabsrobed
because they follow sodium ions due to electrical attraction