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BPK 205 Chapter Notes -Renal Function, Macula Densa, Afferent Arterioles


Department
Biomedical Physio & Kines
Course Code
BPK 205
Professor
Parveen Bawa

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Chapter 19 (Multiple choice and essay type)
1. (a) Draw and explain the structure of a typical nephron all the way to the collecting
ducts. [20 minutes, 1 page of
writing + one figure]
Afferent arteriole transfers blood to renal corpuscle. Blood travels through
glomerulus in the Bowman’s capsule, entering the nephron as filtrate. The
glomerulus capillaries join to form the efferent arteriole.
Filtered fluid flows from Bowman’s capsule into proximal tubule
oPrimary fxn of proximal tubule is bulk reabsorption of isosmotic fluid.
Cells transport solutes out of lumen, and water follows by osmosis
then into loop of Henle.
oDescending portion of loop: more solute reabsorbed than water. When
filtrate leaves loop, it is now hyposmotic relative to plasma
Then it ascends to the distal tubules
From distal tubules to the collecting duct
Filtrate in Collecting ducts travels down from cortex to medulla and drains
into renal pelvis
oDistal tubules and collecting duct is where fine regulation of salt and
water balance takes place under control of several hormones
(secretion and reabsorption occurs here in these two regions)

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(b) Now draw the vascular system related to each part of the nephron. [15 minutes,
draw additional parts on the same
figure as above]
Peritubular capillaries surround both tubules. Vasa recta surrounds loop of henle
where it dips into medulla. Passage of solutes and molecules between these two
types of capillaries is mediated be interstitial fluid.
2 .What is juxtaglomerular apparatus? What three types of cells/structures comprise
the JGA and what are their
functions?Draw the corpuscle and indicate where these structures are.[20 minutes, 1
page including figure of the
corpuscle].
Juxtaglomerular apparatus is the region where the distal tubule comes in contact
with the afferent and efferent arterioles.
Macula densa and Granular cells comprise it.
Granular Cells (aka juxtaglomerular cells
oSmooth muscle cells in walls of afferent arterioles
oSynthesize, store, and release enzyme renin
oRenin causes production of angiotensin II for vasoconstriction
Macula Densa
oRegion of specialized epithelial cells in wall of distal tubule around
bowman capsule

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oIncreased NaCl in distal tubules causes constriction of afferent
arterioles via paracrine agents
3. Define Glomerular Filtration Rate.What factors does GFR depend on? [20
minutes, 1 page of writingplus figure]
Glomerular Filtration Rate: Volume of fluid filtered into Bowman’s Capsule per unit
time. Usually around 125 mL/min or 180 L/day.
Factors
Pressure
oHigh hydrostatic pressure of blood flowing through glomerular
capillaries pushes plasma out
oColloidal osmotic pressure of proteins in capillaries favors fluid back
into capillaries
oBowman capsule has fluid that creates fluid pressure. Fluid pressure
opposes filtration from capillaries
oNet outward osmotic pressure and large pores in fenestrated
capillaries allow sufficient plasma volume to filter out into Bowman’s
capsule
Filtration coefficient
oDetermined by surface area available for filtration
oDetermined by permeability of membranes
Depends on size of filtration slits
Angiotensin II and prostaglandins may act on podocytes and
mesangial cells, changing size of filtration slits and permeability
of the slits.
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