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SFIII Test 3 > Glomerular Filtration I > Flashcards

Glomerular Filtration I Flashcards

1
Q

What are the two types of glomerular mesangial cells and their functions?

A

Phagocytic - keeps glomerular membranes clean and functional

Nonphagocytic - functions as a contractile cell to regulate the surface area for filtration

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2
Q

What are the three layers of the glomerular membrane?

A

Endothelium - fenestrated capillary freely permeable even to large molecules

Basement membrane - Barrier to large proteins and lipids

Epithelium - composed of specialized cells called podocytes that form filtratio slits

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3
Q

What is glomerulonephritis?

A

Renal disease with bilateral inflammatory changes in the glomeruli

Characterized by decreased urine production, presence of blood and protein in urine, and edema

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4
Q

What is nephrotic syndrome?

A

Nonspecific disorder

Severe proteinuria, hypoalbuminemia, hyperlipidemia, generalized edema

Caused by various disorders that damage the glomeruli

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5
Q

What are the slit diaphragm proteins?

A

Nephrin, NEPH-1, P-Cad, FAT, Podocin

Mutations in encoding genes can cause nephrotic syndrome

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6
Q

What is nephritic syndrome?

A

Clinical syndrome characterized by:

Edema, Hypertension, Hematuria

Elevated serum creatinine, Azotemia, Oliguria

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7
Q

What is the structure of the tubule?

A

Made up of a single layer of epithelial cells with tight junctions between adjacent cells

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8
Q

What is the structure of the proximal tubule and its functions?

A

Connected to Bowman’s Capsule

Major site of reabsorption of filtered fluid

Apical membrane has extensive, non-motile brush border

Basolateral membrane consists of multiple infoldings and lined with mitochondria

Interdigitation with neighboring cells not tight, allows for large lateral intercellular spaces or channels

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9
Q

What is the structure and function of Henle’s loop?

A

Hairpin loop that allows fluid in the descending and ascending portions to influence each other

Configuration results in countercurrent direction of flow of the tubular fluid

Loops are close together and can influence electrolyte and water transport

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10
Q

What is the structure and function of the distal tubule?

A

Returns to cortex and makes contact with the afferent and efferent arterioles of the parent renal corpuscle

Site of the juxtaglomerular apparatus (JGA)

Shorter than the proximal tubule

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11
Q

What are the three cell types of the juxtaglomerular apparatus?

A

Macula densa cells

Granular cells

Extraglomerular mesangial cells

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12
Q

What are macula densa cells?

A

Specialized epithelial cells in the thick ascending limb of the loop of Henle/early distal tubule

Provide information on flow, volume, or NaCl concentration of tubular fluid to the JGA

Interdigitate with the other two cell types of the JGA

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13
Q

What are granular cells?

A

Differentiated smooth muscle cells in the walls of the afferent (predominantly) and efferent arteriole

Secretes Renin

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14
Q

What are extraglomerular mesangial cells?

A

Aka lacis or polkissen cells

Phagocytic activity, continuous with the intraglomerular mesangial cells

Communicate with granular cells via gap junctions

Impermeable to water

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15
Q

What is the collecting tubule system?

A

Connecting tubule, initial portion of cortical collecting duct, and cortical and medullary collecting duct

Receives tubular fluid from distal tubules on its course from the cortex to the inner medulla

Sit of “fine tuning” of tubular fluid composition which results in fine control of the ECF fluid composition

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16
Q

What types of cells line the collecting tubule system?

A

Principal cells

Intercalated cells

17
Q

What is the function of principal cells?

A

Responsive to hormones:

ADH

ANP

Aldosterone

18
Q

What is the function of intercalated cells?

A

a intercalated cells - H+ secretion

B intercalated cells - HCO3 secretion

19
Q

What are the two types of nephrons?

A

Coritcal (or superficial)

Juxtamedullary

20
Q

Describe cortical nephrons

A

7/8 of all nephrons

Glomeruli lie in outer 2/3 of cortex

Short Loops of Henle, rarely penetrate the medulla

Have no thin ascending loop of Henle

21
Q

Describe juxtamedullary nephrons

A

1/8 of all nephrons

Glomeruli lie in inner 1/3 of cortex and are larger

Loops of Henle are long; thin segment of loop may reach the tip of the papillae

Number of JM nephrons and their Loops of Henle directly correlates with the capacity to make concentrated urine

22
Q

What is the nerve supply to the kidney?

A

NO vagal innervation

Sympathetic innervation to:

Smooth muscle of efferent and afferent arterioles (vasoconstriction

Granular cells - increase renin secretion

Basement membrane - enhances Na reabsorption

23
Q

Describe the organization of the blood supply in the kidneys

A

Renal artery –> Interlobar artery –>arcuate artery –>Interlobular artery

Veins accompany arteries

24
Q

What is glomerular filtration?

A

The bulk-flow of esentially protein-free plasma from the glomerular capillaries into Bowman’s capsule

No active transport

Permeability selective

25
Q

What is tubular secretion?

A

Transfer of materials from the peritubular-capillary plasma to the tubular lumen

Highly selective

Both active and passive transport processes

Occurs throughout the length of the nephron

26
Q

What is tubular reabsorption?

A

Transfer of materials from the lumen of the tubule to the peritubular-capillary plasma

Highly selective

Both active and passive transport processes

Occurs throughout the length of the nephron

27
Q

How much blood flow do the kidneys get?

A

About 1200ml/min

Represents about 20% of cardiac output

28
Q

What glomerular filtration rate?

A

How much blood passes through the glomeruli each minute

Normal GFR is about 90-130ml/min

Best overall index of kidney function

Significant decrease indicates renal insufficiency or renal failure

29
Q

What is the filtration fraction?

A

GFR divided by the renal plasma flow

FF = GFR/RPF

30
Q

What factors affect GFR?

A

Ultrafiltration coefficient

Glomerular capillary pressure

Pressure in Bowman’s space

Average colloid osmotic pressure in the glomerular capillaries

31
Q

What factors increase the ultrafiltration coefficient (Kf)?

A

ANP - causes relaxation of the mesangial cells, increasing surface area and therefore Kf

32
Q

What factors decrease the ultrafiltration coefficient?

A

ADH - contraction of mesangial cells, decreased surface area, lower Kf

ANG II - see above

Pathologic changes - thickening of the filtration barrier, destruction of the glomerular capillaries

33
Q

How does the pressure in Bowman’s space affect GFR?

A

Increase in Bowman’s pressure decreases urine flow

Pb increases with increases urine flow or in pathological obstruction of the tubules

34
Q

What two mechanisms are responsible for autoregulation in the kidneys?

A

Myogenic mechanism

Tubuloglomerular feedback mechanism

SFIII Test 3 (12 decks)

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