Renal Physiology

Question 1

controls the ability of the kidney to clear waste products and maintain the body’s water and electrolyte balance

Answer 1

nephrons

Question 2

describe nephrons

Answer 2

controls the ability of the kidney to clear waste products and maintain the body’s water and electrolyte balance

Question 3

types of nephrons

Answer 3

Cortical nephrons - located in the cortex of the kidneys and remove waste products and reabsorb nutrients

Juxtaglomerular nephrons extend into the medulla of the kidney and concentrate the urine

Question 4

Renal blood flow

Answer 4

Renal artery,
Afferent arteriole,
Efferent arteriole,
Proximal convoluted tubule capillaries,
Vasa recta / Loop of Henle,
Distal convoluted tubule capillaries,
Renal vein.

Question 5

normal renal blood flow is

Answer 5

approx. 1200 mL/min

Question 6

normal plasma flow is

Answer 6

approx. 600 to 700 mL/min

Question 7

nephron functions in the production of urine

Answer 7

Glomerular filtration,
Renal tubular reabsorption,
Renal tubular concentration,
Renal tubular secretion.

Question 8

describe glomerular filtration

Answer 8

nonselective filtration of plasma substances with MWs less than 70,000 daltons (MW of albumin is 67,000 daltons)

Filtration pressure is controlled by the renin-angiotensin aldosterone system (RAAS)

Question 9

Describe Renal tubular reabsorption

Answer 9

passive transport reabsorbs water and urea

active transport reabsorbs glucose, amino acids, chloride, and sodium.

Question 10

renal tubular concentration happens in

Answer 10

the ascending and descending loops of Henle

Question 11

Describe Renal tubular secretion

Answer 11

removes nonfiltered waste products from the blood to the filtrate and maintains the acid-base balance in the body.

substances such as medications are bound to plasma carrier proteins and are too large to be filtered.

In the tubules, they dissociate from the carrier protein and are then secreted into the filtrate.

Small hydrogen molecules are easily filtered and must be returned to the blood. In the filtrate they combine with phosphate ions or ammonia secreted by the renal tubular cells are secreted back to the blood.

Small bicarbonate ions needed for the acid-base buffering system are also easily filtered. They combine with the hydrogen molecules , producing bicarbonate (carbonic acid?) that can be secreted back into the blood.

Question 12

normal value of glomerular filtration rate (GFR)

Answer 12

120 mL/min, with some variance for body size

Question 13

classic test for GFR

Answer 13

creatinine clearance, which requires timed urine specimen

*calculated GFR estimates (eGFR) do not require a timed urine specimen

Question 14

creatinine clearance formula

Answer 14

C= UxV//P

formulas may use serum creatinine and combinations of age, sex, ethnicity, blood urea nitrogen, and serum albumin.

Question 15

measurement of serum markers: a small molecule produced at a constant rate by all nucleated cells

Answer 15

Cystatin C

Question 16

describe Cystatin C

Answer 16

measurement of serum markers: a small molecule produced at a constant rate by all nucleated cells

It is completely filtered, reabsorbed and then broken down by the renal tubular cells. Serum level remains constant unless the GFR decreases causing the serum level to rise.

Question 17

primary tests for renal tubular reabsorption

Answer 17

serum and urine osmolarity

Question 18

measures the ability of the kidney to respond to body hydration

Answer 18

the free water clearance test

Question 19

describe the free water clearance test

Answer 19

measures the ability of the kidney to respond to body hydration

formula: Cosm = Uosm x V // P osm

Question 20

detects the inability of the proximal convoluted tubule to secrete hydrogen molecules

Answer 20

Tubular secretion test: Titratable acidity

Question 21

describe Titratable acidity

Answer 21

Tubular secretion test: detects the inability of the proximal convoluted tubule to secrete hydrogen molecules

Question 22

detects the inability to produce ammonia in the proximal and distal convoluted tubules

Answer 22

Urinary ammonia

Question 23

describe urinary ammonia

Answer 23

Tubular secretion test: detects the inability to produce ammonia in the proximal and distal convoluted tubules