Ch 25 Urinary Part 2 Flashcards
What are the 2 classes of nephrons?
Cortical and Juxtamedullary
Where are the cortical nephrons located?
entirely in cortex and are more numerous
Why are juxtamedullary nephrons important? What do they do?
important in the production of the urine
What consists of the juxtamedullary nephrons?
- long nephron loops deeply invaded in the medulla
- thick and thin acesending limbs
What do the mansa dansa cells do?
they act as chemoreceptors that monitor NaCl concentration of filtrate entering DCT
What do the Granular cells do?
smooth muscles cells that secrete renin. They act as mechanoreceptors that sense blood pressure in the afferent arteriole.
What does the extraglomerular do? (mesengial)
passes signals between mansa densa cells and granular cells
What does the afferent arteriole supply?
The glomerulus
What drains the glomerulus?
the efferent arteriole
What does the glomerular filtration do?
produces cells and protein free filtrate
What does tubular reabsorption do?
moves substances from filtrate back to blood (glucose)
What does tubular secretion do?
moves substances from blood that couldn’t pass through the filtration membrane into the filtrate
Urine is produced from _____
Filtrate
Filtrate is produced via ____
glomerular filtration
The percent of blood plasma entering glomeruli that becomes glomerular filtrate
filtration fraction (16-20 % is normal)
In the filtration membrane blood comes in the
larger afferent arteriole
What happens when the filtration membrane is constricted?
its shunts and cuts of blood meaning less fluid
What does the glomerular capsule space do in the membrane filtration?
caputures filtrate that escapes from glomerulus
What are the 3 layers of the filtration membrane
capillary endothelium
basement membrane
foot processes of podocyte of glomerular capsule
What does the capillary endothelium do?
contains fenestrations that blocks blood cells
What doe the basement membrane do?
it blocks all the smallest proteins
What do the foot processes of podocytes do?
they are little spaces with with filtration slits and slit diaphragm that block macromolecules (large proteins, polysaccharides)
What is filtration (in membrane) ?
flow of liquid through a membrane due to hydrostatic pressure (pressure inside capillaries that pushes through filtration membrane)
Who holds greater volume of fluid? Capillaries of filtration membrane of glomeruli?
filtration membrane of glomeruli
What molecules does the filtration membrane allow to pass?
has to be smaller than 3nm
water, glucose, amino acids, nitrogenous wastes
Why are plasma proteins remained in the blood?
to maintain colloid osmotic pressure
prevents water loss of capsular space
proteins in filtrate indicate membrane problem
Hydrostatic pressure in glomerular capillaries
glomerular blood pressure
55 mm HG
What does the hydrostatic pressure in the glomerular capillaries do?
forces fluid out of glomerulus into glomerular capsule space
Hydrostatic pressure in capsular space
filtrate pressure in capsule
15 mm Hg
What does the hydrostatic pressure do in capsular space?
pushes back into glomerulus
colloid osmotic pressure in capillaries
pull of proteins in blood 30 mmHg
What is the net filtration pressure?
sum of forces
If pressure was higher than normal, would the NFP go up or down?
Up to produce more urine
What is the glomerular filtration rate?
vol of filtrate formed per min by kidneys
What is the GFR ( glomerular filtration rate) proportional to?
Net filtration pressure
total surface area available for filtration
filtration membrane permeability
What does tubular reapsorption do?
quickly reclaims most of the tubular contents (filtrate) and returns them to blood
Where does tubular reasporbtion occur?
In renal tubules
What is Tubular secretion?
reabsorption in reverse
forces things from blood INTO filtrate
What does tubular secretion occur?
in the PCT to contron blood ph
What is the transcellular route for tubular reabsorption?
- transport across the apical membrane
- diffusion across the cytosol
- Transport across the basolateral membrane
- movement through the interstitial fluid and into capillary
Paracellular route for tubular reabsorption
- movement through leaky tight junctions particularly in PCT
- movement through the interstitial fluid into capillary
What happens during the tubular reabsorption of Na?
allows water and other solutes to be reabsorbed
What is sodium potassium pump? (Location, Function)
located in the basolateral membrane
pumps Na into intersitial space
uses 6% daily ATP (active transport process)
Na K pump establishes concentration gradient for..
secondary active transport
Organic nutrients that reabsorbed by secondary active transport and are cotransported with Na +
glucose, amino acids, some ions and vitamins
Tubular reabosrption of water/nutrients via active/passive transport steps
- at Basolateral membrane Na+ is pumped via Na K pump. Active transport creates concentration gradients that drive…
- Downhill Na+ entry at the apical membrane
- Reabsporion
Tubular reabosrption of water/nutrients via active/passive transport steps
- at Basolateral membrane Na+ is pumped via Na K pump. Active transport creates concentration gradients that drive…
- Downhill Na+ entry at the apical membrane
- Reabsporion of organic nutrients and ions by contransport at apical membrane
- Reabsorption of water by omosis via aquaporins. water reabosorption increases the concentration of solutes that are left behind. these solutes can then be reabsorped as the move down gradients
- lipid soluble substances diffused by transcellular route
- Various ions (Cl Ca K) and urea diffuse by paracellular route
When carriers for a solute is saturated, excess is exerted into ___.
urine
Transport maximum
exists for every reabosrbed susbtance and reflects the number of carriers in renal tubules that are available
What is hyperglycemia and what does it lead to regarding transport maximum
leads to high blood glucose levels that exceed Tm , and glucose spills over into urine
Filtrate volume that is reabosorbed in PCT
65 % of filtrate vol is reabsorbed
H20, Na+ and HCO3-
Glucose, amino acids, and other nurtrients
What does the PCT secrete?
H+ and NH4+ and some drugs
The descending limb absorbs…
water
What does the DCT absorb?
Na+ (aldestrone) and Ca+ (parathyroid)
What does the DCT secrete?
K+ by aldostrone
What does the ascending limb absorb?
Na+ K+ Cl-
What does the ascending limb secrete?
urea
What does the collecting duct absorb?
H20 (by ADH)
Na+ (by Aldosterone) Cl- follows
Urea (increased by ADH)
What does the collecting duct secrete?
K+ by aldosterone
