Renal Structure and Function

Question 1

What is tubular secretion?

Answer 1

tubular secretion is the transfer of materials from the peritubular capillaries to the renal tubular lumen

Question 2

What is the formula for excretion rate?

Answer 2

ER = (filtration rate- reabsorption rate) + secretion rate

Question 3

Describe sympathetic input regulation in controlling the micturition reflex.

Answer 3

sympathetic input relaxes the detrusor muscle via the B-3 receptor (Gs-cAMP)

Question 4

Describe autoregulation of blood in the kidneys.

Answer 4

2 responses:

Myogenic responses: the intrinsic property of smooth muscle is to contract when stretched

Tubuloglomerular feedback TGF:
high delivery of sodium ion to macula densa > adenosine and ATP secretion > vasoconstriction of afferent arteriole > decreases renal BF and GFR

Vasodilation occurs when there is decreased sodium delivery

Question 5

Be able to reproduce a chart on the changes in glomerular cap pressure, peritubular cap pressure, and the nephron plasma flow when there is constriction of efferent arteriole, dilation of efferent arteriole, constriction of afferent arteriole, dilation of afferent arteriole.

Answer 5

Question 6

What is normal GFR?

Answer 6

120 mL/min or 180 L/day

Question 7

What is the formula for net filtration pressure of the glomerulus.

Answer 7

net filtration pressure = filtration forces - absorption forces

Question 8

What are substances freely filtered by the kidney?

Answer 8

major electrolytes: sodium, chloride, potassium, bicarb

metabolic waste products: urea, creatinine

metabolites: glucose, amino acids, organic acids (ketone bodies)

non-natural substances: inulin, PAH (p-aminohippuric acid)

Lower weight proteins and peptides: inulin, myoglobin

Question 9

What is the pathology of nephrotic syndrome?

Answer 9

there is marked disruption of the filtering membrane. As a result plasma proteins pass through the membrane and are eliminated in the urine

Question 10

What are some clinical signs of nephrotic syndrome?

Answer 10

• marked proteinuria > 3.5 g/day (because of disrupted glomerular membrane systems
• edema (loss of plasma oncotic pressure
• hypoalbuminemia (albumin lost to the urine)
• lipiduria (lipid in urine)
• hyperlipidemia (increased lipid synthesis in the liver)

Question 11

What is the pathology behind nephritic syndrome?

Answer 11

there is an inflammatory disruption of the glomerular membrane system. This disruption allows proteins and cells to cross the filtering membrane

Question 12

Clinical signs of nephritic syndrome?

Answer 12

proteinuria < 3.5 g/day (evidence of disrupted membrane)

hematuria (disrupted membrane)

oliguria (inflammatory infiltrates reduce fluid movement across membrane

HTN (inability of kidney to regulate the extracellular volume

azotemia (inability to filter and excrete urine)

Question 13

What does filtration fraction mean?

Answer 13

fraction of the material entering the kidney that is filtered

Question 14

What is the normal filtration fraction for a freely filtered substance?

Answer 14

20%

Question 15

FF formula?

Answer 15

FF = GFR/RPF

Question 16

What is normal RPF?

Answer 16

600 mL/min

Question 17

How does FF affect oncotic pressure in the peritubular capillary (πPC)

Answer 17

The greater the FF the higher the oncotic pressure in the peritubular capillaries because FF represents loss of protein free fluid into the Bowman’s space

Question 18

Be able to predict what will happen to GFR, RPF, FF and glomerular filtration pressure with afferent constriction and efferent constiction.

Answer 18

See figure shown.

Question 19

Stimulation of SNS to the kidneys cause vasoconstriction of the arteriole with the most effect on which arteriole?

Answer 19

afferent arteriole

Question 20

Angiotension II has greater effect on which arteriole?

Answer 20

the efferent