RENAL 1- MCC

What are the three main processes by which kidneys produce urine?

Filtration, reabsorption, and secretion.

How many nephrons are in each kidney?

Approximately 1 million.

What are the main homeostatic functions of the kidney?

Water/electrolyte balance, blood pressure regulation, acid-base balance, and waste excretion.

What are the three regions of the kidney?

Cortex (outer), medulla (middle), papilla (inner).

What is the functional unit of the kidney?

The nephron.

Define the two types of nephrons and their key differences?

Superficial (cortical): Short loops of Henle, lower filtration rate, ~85%. Juxtamedullary: LONG loops of Henle, higher filtration rate, fewer amount nephrons

What is the site of filtration, and terminal end of, in the nephron?

Glomerulus.

Which nephron segment performs most reabsorption? What kind of solutes?

Proximal convoluted tubule (PCT). Na/H20/glucose

Which segment is the major site of secretion and hormonal regulation?

Distal convoluted tubule (DCT).

What is the final site for reabsorption and hormonal regulation?

Collecting duct.

What effect does sympathetic stimulation have on RBF?

Alpha-1 mediated vasoconstriction, decreases RBF.

How does angiotensin II (at low/high levels) affect GFR?

Low: increase GFR (efferent constriction). High: decrease GFR (both afferent and efferent constriction).

What is the role of prostaglandins and dopamine in RBF?

Vasodilation of AA; protective of RBF under sympathetic stimulation.

What are the two types of autoregulation of RBF?

Myogenic regulation and tubuloglomerular feedback.

What are the three layers of the filtration barrier?

Endothelium, glomerular basement membrane (GBM), podocytes.

What size molecules are freely filtered?

<5000 Da or <4 nm.

What does the GBM repel?

Negatively charged proteins.

What diseases affect the GBM? Result in?

Alport syndrome (type IV collagen mutation within GBM), progressive kidney disease, Goodpastures syndrome (autoimmune attack on type IV collagen of GBM), glomerulonephritis.

What is the formula for GFR using Starling forces?

GFR = Kf[(Pgc - Pbs) - Pigc]

What happens to GFR with afferent arteriole constriction? RPF?

decrease GFR, decrease RBF

What is the gold standard for measuring GFR? Why?

Inulin clearance. Freely filtered, with no absorption in gut nor reabsorb or secret. 

What is the clinical standard for measuring GFR? Why?

Creatinine clearance. freely filtered, from muscle breakdown; also secreted by peritubular capillaries so slight overestimation

What is reabsorption?

Movement of substances from tubule back into blood.

What is secretion? What transport process does it use? What ion powers it?

Movement of substances from blood into tubule. Active transport; Na+

Where does most secretion occur?

Distal convoluted tubule (DCT).

What transporters are involved in glucose reabsorption? What kind of transport do they each use?

Apical: SGLT2 (early PCT), SGLT1 (late PCT). Basolateral: GLUT2 (early/late), GLUT1 (late). Secondary active, facilitation diffusion

What is Tm in glucose reabsorption?

Tubular transport maximum, max rate of reabsorption.

What causes glucosuria in diabetes?

Plasma glucose exceeds Tm, increased glucose appears in urine.

How is urea reabsorbed? WHAT MUST WE REMEMBER ABOUT H2O?

facilitated diffusion = passive reabsorption; facilitated by UT1 transporter. UREA ABSORPTION FOLLOWS WATER REABSORPTION

What is PAH used to measure? Why?

Renal plasma flow (RPF); because totally filtered/secreted, no reabsorption

What is the primary function of the glomerulus?

Filtration of plasma to form ultrafiltrate, removing water and small solutes while retaining large proteins and blood cells.

What is a function that the kidney and liver share?

gluconeogenesis

loop of henle primarily absorbs?

water and salt

what and where is the JG apparatus?

macula densa of thick ascending LOH/DCT, and JG/granular cells of AA

ANP has what effect on GFR and how? For what purpose?

increases GFR, vasodilates AA and constricts EA; dump extra volume

How do NSAIDS hurt kidneys

NSAIDS attacks PGE; that means no vasodilation, so can constrict AA which leads to less blood flow in kidneys

What does myogenic feedback look like?

AA stretches > Ca released > smooth muscle constricts > increased resistance to blood flow

What does tubuloglomerular feedback look like?

Macula densa in DCT taste salt and flow, sends infro to JG/granular cells in AA for renin release

filtration barrier is described as? impermable to?

fenestrated; large proteins, WBC, RBC, negative charges (d/t GBM)

podocytes described as having, and let what size molecules thru?

interdigitated foot processes, filtration slits; molecules < 5000 Da or < 4nm; bigger than that present in filtrate is big bad!

function of glomerular mesangial cells

engulf macromolecules stuck in GBM

filtration equilibrium occurs at what end of glomerular capilllary?

end of capillary

RBF vs GFR?

RBF (renal blood flow) is the total volume of blood flowing through the kidneys, while GFR (glomerular filtration rate) is the volume of fluid filtered by the kidneys' glomeruli per minute. RBF is the larger, overall blood supply, while GFR is a specific measure of kidney function that represents how much plasma is filtered from that blood.

What would constricting EA do to GFR? RPF?

increase GFR, decrease RPF

define excretion

sum of filtration, reabsorption, and secretion

Net transport of a substance depends on?

filtration rate, concentration in plasma, percentage in plasma NOT bound to protein

What do each SGLT require to move? Where does it get it's secondary active transport energy?

SGLT 2 in early PCT requires 1 Na, SGLT1 in late PCT requires 2 Na. From Na/K ATPase maintaining Na gradient