Kidney Flashcards
Nephron
Functional unit of the kidney which begins at Bowman’s capsule
Contained in kidney cortex and medulla
Kidney has a million nephrons
Urethra vs Ureters
Urethra takes urine out of the body and 2 ureters carry the urine from the kidney.
Parts of the kidney
Bowman’s capsule- surrounds the glomerulus and collects filtrate
Glomerulus is capillaries where blood is filtered
Proximal tube reabsorption and secretion occurs
Descending loop is when water is reabsorbed
Ascending loop is when ion are reabsorbed
Distal tube reabsorption and secretion occurs
Collecting duct is where urine is received
Nephron’s ability to exchange materials with the blood
Afferent vs Efferent
Afferent arteriole takes blood toward the kidney and the glomerulus, it decreases blood supply but it’s wider to maintain high blood pressure
Efferent arteriole goes out of the kidney, narrower to help pressure gradient
Function of the kidney requires filtration, reabsorption and secretion
Filtration happens at the Bowman’s capsule with glomerulus
Reabsorption happens at proximal, loop of henle, distal and collecting duck
Secretion occurs at proximal, distal and collecting tube
Less than 1% of the filtered plasma is secreted as urine
1-100% of plasma volume enters afferent arteriole from and gets filtered
80% goes out of the efferent arteriole to peritubular capillaries
-20% falls into bowman’s capsule and is filtered through the tubule
-19% is reabsorbed
-more than 99% of plasma entering kidney returns to systemic circulation
-less than 1% is excreted
Glucosuria
Glucosuria is when glucose appears in urine
Glucose has to be transported back into the peritubular capsule
GFR based on time
How fast material moves from the plasma to the urine the 2.75 L
(excretion rate)/ X concentration in plasma
-Hydrostatic pressure is the blood pressure
-Colloid osmotic pressure is due to proteins in plasma but not the Bowman’s capsule
-Fluid pressure is the filtrate in the Bowman’s capsule
Net filtration
Hydrostatic pressure- colloid osmotic pressure- pressure of fluid
How many times per day is plasma filtered?
Every 20 minutes or 72x/Day
Vasocontraction and vasodilation in the afferent arteriole vs efferent arteriole
Vasoconstriction in the afferent arteriole decreases renal blood flow, capillary blood pressure and GFR while increasing resistance in the afferent arteriole.
Vasodilation in the afferent arteriole increases renal blood flow, capillary blood pressure and GFR while decreasing resistance in the afferent arteriole.
Vasoconstriction in the efferent arteriole increases resistance while increasing the hydrostatic blood pressure, GFR and lowers the renal blood flow
Vasodilation in the efferent arteriole increases renal blood flow while decreasing GFR, hydrostatic blood pressure and resistance.
Explain how an increase in hydrostatic pressure in the Bowman’s capsule would affect GFR?
An increase in hydrostatic pressure in the bowman’s capsule would decrease GFR because it opposes the filtration pressure gradient from the glomerulus into Bowman’s capsule.
It will make it harder for fluids and solute to fall into the Bowman’s capsule.
How would you increase GFR at the two arterioles
In the Afferent arteriole, vasodilation would increase GFR by increasing renal blood flow and hydrostatic blood pressure.
In the Efferent arteriole, vasoconstriction would increase GFR by decreasing the renal blood flow but increasing hydrostatic blood pressure.
GFR is the standard for measuring kidney efficiency
What are the formula
Clearance refers to rate at which material is removed from blood and appears in the urine.
-Filtration rate of X= X in plasma X GFR
-Excretion rate of X= urine flow X X in urine
-Clearance rate of X= Excretion rate of X mg/min / X in plasma mg/ml
What factors affect GFR
-Changes in renal blood flow, blood pressure
-Arteriole constriction (afferent vs efferent)
-Changes in protein concentration, dehydration, osmolarity
-Changes in hydrostatic pressure within Bowman’s capsule
Clearance rate of inulin vs glucose
Inulin clearance is equal to GFR because with inulin, the filtration and excretion rate are the same which means that there is no net reabsorption or secretion.
With glucose, all of it is absorbed which means that the filtration rate is higher than the excretion rate so there is a net reabsorption rate which means that glucose is filtered and reabsorbed
What is the normal glucose clearance rate
It’s zero because glucose should not be secreted
Penicilin vs urea
Penicillin is cleared from the plasma and into urine faster than inulin
It is secreted and excreted while urea is reabsorbed and excreted.
What happens when filtration is higher than excretion or of excretion is higher than filtra
If filtration rate is higher than excretion rate then there is a net reabsorption
If Excretion rate is greater than the filtration rate then there is a net secretion.
Osmoregulation involves the digestion, integument and respiratory systems as well as the kidney
Volume is gained by ingestion and IV which makes the GFR keep happening and it can be adjusted through afferent or efferent arteriole.
Volume is loss in the urine and vasopressin regulates water reabsorption and kidneys only conserve volume not replace it.
Volume is also loss from lungs, skin, digestive tract.
Osmolarity changes as the filtrate moves through the loop of Henle.
-At the descending limb, isosmotic fluid leaving leaving the proximal tubule becomes more concentrated. Water leaves due to osmolarity of blood, it’s salty outside.
-At the ascending limb, solute leave the tubule and create an hyposmotic fluid.
-At the distal tubule, permeability to water and solute is regulated by hormones as well as in the collecting duct.
-Final urine osmolarity depends on reabsorption in the collecting duct.
Cortex vs medulla osmolarity
The cortex top part is isosmotic to plasma but the medulla becomes progressively more concentrated
Nephron tubules are interwoven with a set of peritubular capillaries which form a portal system
Vasa recta allows transfer from tubule to blood
Renal countercurrent multiplier increases the efficiency of of water absorption
The vaso recta is more hypertonic at the descending limb which increases water leaving the tubule and casing a hypertonic filtrate. At the ascending limb water doesn’t leave because the channel is impermeable to water no aquaporins channels, ions leave and are reabsorbed leaving a hypoosmotic filtrate.
