Chapter 27 - Glomerular Filtration

Question 1

Glomerular filtrate composition

Answer 1

• protein-free
• devoid of cellular elements
• similar concentration of salts and organic molecules as the concs in plasma

Question 2

(True/False)

Fatty acids are completely filtered in the glomerular

Answer 2

False

low-molecular weight substances such as calcium and fatty acids are not completely filtered in the glomerulus do to it being partially bounded to plasma proteins

Question 3

Glomerular filter fluid rate is determined by:

Answer 3

(1) the balance of hydrostatic and colloid osmotic forces acting across the capillary membrane

(2) the capillary filtration coefficient (Kf) , the product of permeability, and filtering surface area of the capillaries

Question 4

High filtration rate of the glomerulus is due to

Answer 4

• high glomerular hydrostatic pressure
• large capillary filtration coefficient

Question 5

GFR of an average adult human

Answer 5

125 ml/min or 180L/day

Question 6

Fraction of renal plasma flow that is filtered

Answer 6

0.2

20% of plasma flowing through the kidney that is filtered

Question 7

Filtration fraction

Answer 7

filtration fraction = GFR / Renal plasma flow

Question 8

3 major layers of the glomerular capillary membrane - as the filtration barrier

Answer 8

(Lumen)

(1) endothelium of the capillary with fenestrae

(2) basement membrane

(3) a layer of epithelial cells (podocytes) surrounding the outer surface of the capillary basement membrane

Question 9

ALL LAYERS of the glomerular capillary wall provide a (1) barrier to filtration of plasma protein and

(2) a means to rapid filtration of water and most solutes in the plasma

Answer 9

A. Capillary endothelium
(1) fixed negative charges
(2) holes or fenestrae

B. Basement membrane
(1) strong negative electrical charges from proteoglycans
(2) collagen and proteoglycan fibrillae meshwork with large spaces

C. Epithelial cells - podocytes
(1) negative charges
(2) gaps (slit pores) along the footlike processes (pedicles)

Question 10

Filterability:
(1) 100% -
(2) 75% -
(3) 0% -

Answer 10

(1) substance is filtered as freely as water
(2) substance is filtered only 75% as rapidly as water
(3) substance is not filtered

Question 11

Pore size of glomerular membrane

Answer 11

8nm

Question 12

Proteins excreted in urine

Answer 12

proteinuria or albuminuria

Question 13

(True/False)

The cause of minimal change nephropathy are unclear but are partially related to an immunological response and abnormal T-cell secretion of cytokines - injuring podocytes and increasing premeability

Answer 13

True

Question 14

GFR

Answer 14

GFR = (Kf) x (net filtration pressure)
Where net filtration is the sum of osmotic forces (PG - PB - πG + πB)

Question 15

Osmotic forces in the glomerulus:
1.) PG
2.) PB
3.) πG
4.) πB

Answer 15

1.) hydrostatic pressure in the glomerulus - favors filtration (60mmHg)

2.) hydrostatic pressure in the bowman’s capsule - opposes filtration (18mmHg)

3.) colloid osmotic pressure of the glomerulus - opposes filtration (32mmHg)

4.) colloid osmotic pressure of the bowman’s capsule - favors filtration (0mmHg)

Question 16

Net filtration pressure

Answer 16

10mmHg

Question 17

Kf of the glomerulus

Answer 17

12.5 ml/min/mmHg of filtration pressure
400 times as high as Kf of most capilliaries

Question 18

distention and dilation of the renal pelvis and calyces

Answer 18

hydronephrosis

Question 19

Osmotic pressure of plasma in:
(1) afferent arteries
(2) glomerular capillaries
(3) efferent arteries

Answer 19

(1) 28 mmHg
(2) 32 mmHg
(3) 36 mmHg

Question 20

Two factors that influence the glomerular capillary colloid osmotic pressure:

Answer 20

(1) the arterial plasma colloid osmotic pressure
(2) fraction of plasma filtered by the glomerular capillaries - filtration fraction

Question 21

INCREASED GLOMERULAR CAPILLARY COLLOID OSMOTIC PRESSURE () GFR

Answer 21

DECREASES

Question 22

INCREASED GLOMERULAR HYDROSTATIC PRESSURE () GFR

Answer 22

INCREASES

Question 23

Primary means for physiological regulation of GFR

Answer 23

changes in glomerular hydrostatic pressure

Question 24

Glomerular hydrostatic pressure is determined by

Answer 24

1.) arterial pressure
2.) afferent arteriolar resistance
3.) efferent arteriolar resistance

Question 25

Donan Effect

Answer 25

the higher the protein concentration, the more rapidly the colloid osmotic pressure rises because of the interaction of ions bound to the plasma proteins

Question 26

combined blood flow through both kidneys in a 70 kg man

Answer 26

1100 ml/min or about 22% of the cardiac output

Question 27

percent of total body weight of 2 kidneys combined

Answer 27

0.4%

Question 28

(True/False) The arterial-venous extraction of oxygen in the kidneys is low but is twice the rate of the brain

Answer 28

True

Question 29

Renal oxygen consumption varies in proportion to ()

Answer 29

renal tubular sodium reabsorption

Question 30

Renal Blood Flow

Answer 30

Question 31

Renal vein pressure

Answer 31

3 to 4 mmHg

Question 32

GFR arterial pressure range

Answer 32

80 to 170 mmHg

Question 33

(True/False) Blood flow in renal medulla accounts for only 1% to 2% of total renal blood flow

Answer 33

True

Question 34

Activation of sympathetic nerve fibers in the renal arteries lead to

Answer 34

decrease renal blood flow and GFR

Question 35

Norepinephrine, epinephrine, and endothelin (1) renal blood vessels and (2) GFR

Answer 35

(1) constrict (2) decrease

Question 36

(True/False) Angiotensin II preferentially constricts efferent arterioles raising glomerular hydrostatic pressure while reducing renal blood flow

Answer 36

True

Question 37

Endothelin-Derived nitric oxide (1) renal vascular resistance and (2) GFR

Answer 37

(1) decreases (2) increases

Question 38

In afferent arterioles of the kidneys, (1) and (2) are released to counteract the vasoconstrictor effects of angiotensin II

Answer 38

(1) nitric oxide (2) prostaglandins

Question 39

Prostaglandins and Bradykinin (1) renal vascular resistance and (1) GFR

Answer 39

(1) decreases (2) increases

Question 40

Tubular reabsorption is () leaving 1.5L/day to be excreted in urine

Answer 40

178.5 L/day

Question 41

The juxtaglomerular complex is composed of

Answer 41

(1) macula densa cells in the initial portion of the distal tubule (2) juxtaglomerular cells in the walls of the afferent and efferent arterioles

Question 42

Macula densa cells sense

Answer 42

sodium chloride delivery to the distal tubule

Question 43

Decrease in sodium chloride concentration (detected by the macula densa) intiates

Answer 43

(1) decrease resistance to blood flow in the afferent arterioles - raises glomerular hydrostatic pressure (2) INCREASES RENIN RELEASE FROM THE juxtaglomerular cells of the afferent and efferent arterioles

Question 44

GFR changes by only a few percentage points, even with large fluctuations in arterial pressure between ()

Answer 44

75 - 160 mmHg

Question 45

Answer 45

Question 46

Myogenic mechanism

Answer 46

the ability of individual blood vessels to resist stretching during increased arterial pressure to prevent an excessive increase in renal blood flow and GFR