10:13 Intro to the Kidney Flashcards
what are the three main roles of the kidneys?
Homeostatsis; Eliminate soluble wastes; Make endocrine products.
how do the kidneys maintain homeostasis?
regulate blood and extracellular fluid: water, ions, acid-base
how do the kidneys eliminate soluble wastes
eliminate metabolic wastes; eliminate toxins and drugs (sometimes after liver modification, e.g. glucuronidation)
How does the kidney act as an endocrine organ?
Renin: (angiotensinogen proscessing); Erythropoietin; Vitamin D2 and D3
what does Renin do?
Regulates Kidney function; Up blood [NaCL], volume, and pressure
what does erythropoietin do?
cytokine for CFU-E (increase RBCs)
what do vitamin D2 and D3 do?
Ca2+ regulation
Big Picture: how do the kidney support homeostasis?
by using a filter (the basement membrane between the capillaries and the bowman’s space) to adjust blood chemistry by exchanging water, salts, and other low MW solutes, acids/base between blood and filtrate tubule.
what are the key structures of the kidney? (atonomy)
outside renal cortex; medullary rays (extend from the medulla to the outside cortex); medulla (pyramids), renal column (between the medulla); renal papilla (at the base of the pyramids); minor calyces (smallest collecting ducts); major clyces; renal pelvis (large collecting space); ureter
what is the difference in the Juxtamedullary and Cortical nephrons?
the Juxtamedullary extend all the way down in the pyramid into the medulla. the cortical do not extend so deep; the justamedullary have Vasa Recta (Regenerative salt exchanger)
where does the processed urine get depositied?
in the calyces that feed to the ureter
how to see the cortex vs. the medulla in the microscope
the cortex: circular renal corpuscles and tubes; medulla has only tubes.
Describe the function of the Renal Corpuscle
Form initial filtrate (180-200) liters of fluid a day. the small capillary forces the blood out through increased blood pressure.
The function of the rest of the nephron after the renal corpuscle
the rest of the job is to get all but 1 liter of the 180-200 liter/day back to the body and continuously adjust blood compostion
location where we recover 65% initial filtrate
PCT (primary convoluted tubule)
Where in the nephron do we form the high salt [] of the medulla
in the loop of Henle
where do we selectively recover NaCl and secrete H+ and HCO3-
The collecting Tubules and Ducts
Where do we selectively recover water?
in the late distal tubule, collecting tubules and ducts
where do we regulate filtrate formation?
Juxtaglomerular apparatus, JGA
what are the main components returned to the blood from the nephron filtrate?
3Lbs. of NaCl and 1/2 pound of glucose returned to blood/day
what lines the inside of the glomerulus?
parietal cells, or the simple low epithelial and the visceral cells around the capillary bed.
what is the filtration unit of the kidney?
the renal corpuscle
what is the hole where the blood vessels come into the renal corpuscle (bowman’s capsule)
the vascular pole
what is the space between the capillary bed and the wall of the renal corpuscle?
the urinary space or bowman’s space.
what is the pole where the bowman’s capsule connects to the urinary?
urinary pole
what are the cells that surround the capillaries in the glomerular, and how are they structured?
Primary secondary and tertiary branches of the podocyte cells wrap around the capillary and extend interlocking pedicles to create filtration slits where the filtration of the blood happens
Endothelial cells of the capillary, podocytes hugging them, what other cell types are in the glomerulus?
mesangial cells (pericyte - like) also present in the glomerulus involved in turning over basal lamina, controlling capilalry diameter, and signaling. activities altered by disease that affect filtration like diabetes.
what are the constituents of the glomerulus?
the podocytes surrounding the endothelial cells, and the mesangial cells.
describe the movement of blood filtrate in the glomularus
blood is in very high pressure and is pushed out the thick basal lamina and between the filtration slits of the podocytes and into the urinary space.
what are the three layres of filtration in the glomularus?
fenestrated endothelium; thick basal lamina; filtration slits
what is the constiuents of the filtrate
mostly the plasma minus the cells and large protiens. (therefore very little protein)
what ist he protien that acts as a net between the filtration slits?
nephrin
how much blood plasma moves accross the 3 layers of filtration into the urinary space?
20%, limited by the oncotic pressure
what is the first duct after the urinary space?
proximal convoluted Tubule (PCT): primary recovery
returns ca. 120-130 l/day to blood (65%)
proximal convoluted tubule
longest section of nephron, most common component of cortex
proximal convoluted tubule
the epithelium of the Proximal convoluted tubule
look alot like the epithelium of the intestines: apical microvilli, ZO+ZA, basolateral Na, K-ATPase
what makes the PCT structure and function different from the intestines?
systems to exrete organic acids and bases
what is the main function of the PCT epithelium?
resorb ca. 65% of inital filtrate volume, using Na+ gradient, including amino acids, glucose, PO4, Ca, HCO3
the condition of the resorbed fluid
isosmotic and enters pertubular capillaries
how do we get protiens that leak into the filtrate back out into the blood?
reabsorb proteins via pinoytosis at the base of microvilli of the apical side of the PCT epithelium. then broken down and sent to the blood as amino acids.
secrete specific acids and bases into the fitrate, can occur after modifiaction by the liver
the epithelium of the PCT
perform the hydroxylase reaction that creats vitamin D2 and D3
The epithelium of the PCT
the majority of components present i the filtrate of the kidney tubules arrive there form the blood primarily due to
blood pressure
what situatio favors the reabsorption of fluid form the filtrate in cortical kidney tubules back to the blood in peritubular capillaries?
High oncotic pressure of blood in peritubular capillaries
what are the straight tubules of the kidney after the initail blood filtration?
medullary rays of Proximal straight tubules
how to identify the proximal tubules in the kidney?
tall cells faily large cells, therefore few nuclei
a counter current multiplier system
Loop of henle – a system that uses the counterflow of two loops to establish and utilize a concentration gradient.
large number of aquaporins present, therefore very permiable to water. not so permiable to ions.
Thin descending limb
no aquaporin and impermeable to water, but actively pump out ions to make the medula very salty (high osmolarity)
Ascending Thick limb
Describe the changes in osmolarity through the loop of henle
the descending loop allows watter out and not ions, therefore the filtrate becomes hypertonic. The ascending loop pumps ions out and no water (set gradient for descending) and makes the filtrate hypotonic coming out of the medulla!
is more water or salt recovered in the loop of henle?
25% of NaCl is recovered, but only 10% of the water.
what pharmacutical targets does the loop of henli present?
Diuretics, inhibit a Na,K,Cl (NKCC) co-transporter to inhibit this transport of ions accross the thick ascending limb. This lowers the osmotic gradient of the medulla and therefore resorbs less water in the DL, therefore more water through the loops and is peed out!
supply most of the deep loops and provide most of the high salt in the medulla
juxtamedullary corpuscles
Describe the Cortical Nephrons
cortical: short loop; further from the corticomedullary junction, efferent arteriole supplies peritubular capillaries.
describe the Juxtamedullary nephron
long loop of henle; glomerulus close to coricomedullary junction; efferent arteriole supplies vasa recta.
what is the result of the countercurrent multiplier system?
remove a ton of water at first and then remove a ton of salt afterwards to give a much reduced volume of very hypotonic fluid
How do the thick and thin loops of henle differ in the microscope
cells surrounding an empty lumen are either very low or cubiodal.
The macula densa
the thick hyperplasia of cells from the thick ascending loop that touch the original corpuscle from whence the tubule came
help to turn over the basement membrane and keep it cleen and maintain the epithelium
pericytes
resorb some Ca2+ and NaCl, Target of Thiazide diuretics, not a major target of aldosterone (except at the end?)
Distal convoluted tubles
The microscopic view of the distal convoluted tubule
simple cuboidal cells, no fuzy lining of microvilli etc.
The track of the filtrate trough a nephron to the toilet?
through the three layers of filter, urinary space, urinary pole; proximal convoluted tubule; thick descending loop, thin descending loop; thin asscending loop; ascending thick loop; past macula densa of the juxtaglomerular apparatus (JGA); Distal convoluted tubule; connecting tubule; collecting tubules, collecting ducts; papillary ducts, area cribosa, minor calyx, major calyx, renal pelvis, ureter, bladder, urethra, toilet!
stimulates Na channel open on the apical side of the CT/CD and incrrese the Na, K-ATPase in basolateral membranes pumping ions out of the filtrate!– water will follow this reabsorption of ions
Aldosterone
what is the net result of aldosterone
sodium resorption, water resorption, increase fluid in body, and blood stream, increasing blood pressure.
inserts aquaporin in the membrane of collecting duct cells, water moves from the filtrate to the body
Antidiuretic hormone (ADH)
havn’t had much to drink how is my ADH level?
High
how does BP change with fluid level?
more fluid retained, therefore the BP goes up
where is ADH made and retained?
made in the hypothalamus and stored in the pituitary
how does the level of ADH relate to the concentration of the urine?
High ADH means concentrated urine; Low ADH means Dilute Urine
ADH is also known as:
arginine vasopressin (AVP)
how does the osmolarity relate to the position of the filtrate in the tubule?
Initially it is 300 mOsm (isotonic); in the thick descending it becomes hypertonic (600 mOsm). in the thin descending loop it is very hypertonic (1200 mOsm). in the thick ascending loop it becomes hypotonic (120 mOsm).
how does the filtrate move from the Collecting duct to the minor Calyx?
It moves through the Urothelium lined papillary ducts and through small openings at the area cribosa into the minor calyx
what would remove a low molecular weight acid drug in the renal system.
the proximal convoluted tubules, that have specific import elements to remove organic bases and acids from the blood.
where does the filtrate become hypotonic?
in the thick ascending limb
the components of the juxtaglomerular apparatus, JGA
Extraglomerular mesengial cells; Juxtaglomerular cells (specialized smooth muscle cells of the afferent arteriole); Macula densa.
specialized smooth muscles cells that contain the protease Renin
Juxtaglomerular cells of the afferent arteriole
The rate of filtrate moving through the Bowman’s capsule into the PCT
GFR
The ideal rate of filtration that allows removal of unwanted element and recovery of wanted elements
this is known as the ‘set point’.
Two general types of regulation of the GFR
Intrinsic mechanism (tubuloglomerular feedback and myogenic control) and Extrinsic mechanisms (sympathetic, adrenal, Renin-angiotensin)
how does the GFR relate to the comparative BP of the aA and eA?
the differential constriction of the afferent and efferent arterioles of the RC control the blood pressure in the RC which is the driving force for the formation of the GFR!
feedback that says we need more filtrate or less filtrate
tubuloglomerular feedback