Chapter 17 - The Kidney

Question 1

Kidneys:

Answer 1

lie on either side of the vertebral column below the diaphragm and liver.

Question 2

Ureters:

Answer 2

urine produced in the kidneys is drained into a cavity known as the renal pelvis and then is channeled from each kidney via long ducts called ureters.

Question 3

Urinary bladder:

Answer 3

storage sac for urine, and its shape is determined by the amount of urine it contains. Has a muscular wall known as the detrusor muscle.

Question 4

Renal cortex:

Answer 4

reddish brown and granular in appearance because of its many capillaries.

Question 5

Renal medulla:

Answer 5

the deeper region is striped in appearance due to the presence of microscopic tubules and blood vessels

Question 6

Renal pyramids:

Answer 6

8 to 15 conical renal pyramids compose the medulla

Question 7

Renal columns:

Answer 7

separate the renal pyramids

Question 8

Minor calyx:

Answer 8

each pyramid project into a small depression called a minor calyx

Question 9

Major calyx:

Answer 9

several minor calyces unite to form a major calyx

Question 10

Renal pelvis:

Answer 10

the major calyces then join to form the funnel-shaped renal pelvis. The renal pelvis collects urine from the calyces and transports it to the ureters and urinary bladder.

Question 11

Nephron:

Answer 11

the functional unit of the kidney responsible for the formation of urine.

Question 12

Tubules:

Answer 12

a nephron consists of small tubes, or tubules, and associated blood vessels.

Question 13

Afferent arterioles:

Answer 13

a number of interlobular arteries radiate from the arcuate arteries into the cortex and subdivide into numerous afferent arterioles, which are microscopic.

Question 14

Renal artery  interlobar arteries  arcuate arteries  afferent arterioles

Answer 14

Renal artery  interlobar arteries  arcuate arteries  afferent arterioles

Question 15

Glomeruli:

Answer 15

the afferent arterioles deliver blood into glomeruli, capillary networks that produce a blood filtrate that enters the urinary tubules.

Question 16

Efferent arteriole:

Answer 16

the blood remaining in a glomerulus leaves through an efferent arteriole

Question 17

Peritubular capillaries:

Answer 17

efferent arterioles deliver blood into another capillary network known as the peritubular capillaries, which surround the renal tubules.

Question 18

Peritubular capillaries  interlobular veins  arcuate veins  interlobar veins  renal vein.

Answer 18

Peritubular capillaries  interlobular veins  arcuate veins  interlobar veins  renal vein.

Question 19

Glomerular (Bowman’s) capsule:

Answer 19

surrounds the glomerulus. The glomerular capsule and its associated glomerulus are located in the cortex of the kidney and together constitute the renal corpuscle.

Question 20

Proximal convoluted tubule:

Answer 20

filtrate that enters the glomerular capsule passes into the lumen of the PCT. The wall of the PCT consists of a single layer of cuboidal cells containing millions of microvilli. 70-80% of reabsorption occurs here.

Question 21

Loop of Henle:

Answer 21

fluid passes from the PCT to the loop of Henle.

Question 22

Ascending & descending limbs:

Answer 22

this fluid is carried into the medulla in the descending limb of the loop and returns to the cortex in the ascending limb of the loop.

Question 23

Distal convoluted tubule:

Answer 23

back in the cortex, the tubule again becomes coiled and is called the DCT. The DCT is shorter than the PCT and has relatively few microvilli and terminates as it empties into a collecting duct.

Question 24

Collecting duct:

Answer 24

receives fluid from the DCTs of several nephrons. Fluid is then drained by the collecting duct from the cortex to the medulla as the collecting duct passes through a renal pyramid.

Question 25

Summarizes the functions of the nephrons.

Answer 25

Urine = filtration – reabsorption + secretions

Question 26

What kind of capillaries make up the Glomerulus?

Answer 26

Fenestrated capillaries.

Question 27

The epithelial cells that make up the wall of Bowman’s Capsule (Glomerular Capsule) are also called the fenestrae. Why this name? What is the specialized structure that they have?

Answer 27

As a result of these large pores, glomerular capillaries are 100 to 400 times more permeable to plasma water and dissolved solutes than are the capillaries of skeletal muscle.

Question 28

Why is the filtered fluid called an “ultrafiltrate”?

Answer 28

The fluid that enters the glomerular capsule is called ultrafiltrate because it is formed under pressure – the hydrostatic pressure of the blood.

Question 29

What does “Autoregulation” mean? Of what use is it? What is the mechanism of autoregulation?

Answer 29

1. The ability of the kidneys to maintain a relatively constant glomerular filtration rate (GFR) in the face of fluctuating blood pressure is called renal autoregulation. Afferent arterioles dilated when the mean arterial pressure falls toward 70 mmHg, and the afferent arterioles constrict when the mean arterial pressure rises above normal. 2. Two general mechanisms are responsible for renal autoregulation: (1) myogenic constriction of the afferent arteriole, due to the ability of the smooth muscle to sense and respond to an increase in arterial pressure; and (2) the effects of locally produces chemicals on the afferent arteriole, which is part of a process called tubuloglomerular feedback.

Question 30

Know the process of glucose reabsorption. How are most other solutes reabsorbed?

Answer 30

1. Glucose and amino acids in the blood are easily filtered by the glomeruli into the renal tubules. This occurs in the proximal tubule by secondary active transport, which is mediated by membrane carriers that co-transport glucose and Na+. 2. Glucose appears in the urine – a condition called glycosuria – when more glucose passes through the tubules than can be reabsorbed. 3. The proximal tubule reabsorbs most of the filtered salt and water, and most of the remainder is reabsorbed across the wall of the collecting duct under ADH stimulation.

Question 31

When solutes are reabsorbed, what happens to the water in the tubules?

Answer 31

Water follows the salt out of the tubular filtrate into the peritubular capillaries by osmosis. Osmosis of water cannot occur if the tubular fluid and surrounding interstitial fluid are isotonic to each other. In order for water to be reabsorbed by osmosis, the surrounding interstitial fluid must be hypertonic.

Question 32

Be able to describe the “Countercurrent Multiplier” system.

Answer 32

The interaction that occurs between the descending limb and the ascending limb of the loop of Henle in the kidney. This interaction results in the multiplication of the solute concentration in the interstitial fluid of the renal medulla. It increases the concentration of renal interstitial fluid from 300 mOsm in the cortex to 1200 – 1400 mOsm in the inner medulla. (1) The extrusion of sodium chloride from the ascending limb makes the surrounding interstitial fluid more concentrated. Multiplication of this concentration is due to the fact that (2) the descending limb is passively permeable to water, which causes its fluid to increase in concentration as the surrounding interstitial fluid becomes more concentrated. (3) The deepest region of the medulla reaches a concentration of 1400 mOsm.

Question 33

Of what use is the build up of a high salt concentration in the depths of the renal medulla (pyramids)?

Answer 33

The great hypertonicity of the renal medulla is critical because it serves as the driving force for water reabsorption through the collecting ducts, which travel through the renal medulla to empty their contents of urine into the renal pelvis

Question 34

What does ADH do to the collecting duct?

Answer 34

When ADH is present, the collecting duct becomes more permeable to water, and thus more water is drawn out by osmosis into the hypertonic renal medulla and peritubular capillaries.

Question 35

How does the ADH do to the collecting duct relate to the build up of a high salt concentration in the depths of the renal medulla (pyramids)

Answer 35

ADH stimulates the fusion of these vesicles with the plasma membrane and the insertion of the aquaporin channels into the plasma membrane.

Question 36

What kinds of nephrons have very long Loops of Henle?

Answer 36

The increased length of the loop of Henle in juxtamedullary nephrons extends deep into the inner medulla and helps sustain a steep osmotic gradient in the medullary interstitial fluid that allows for the creation of concentrated urine.

Question 37

concept of “Clearance”

Answer 37

Renal clearance refers to the ability of the kidneys to remove molecules from the blood plasma by excreting them in the urine. Because of renal clearance, the concentrations of these substances in the blood leaving the kidneys (renal vein) is lower than their concentrations in the blood entering the kidneys (renal artery).

Question 38

What volume of plasma has been completely cleared/cleaned of solute?

Answer 38

Plasma has 100mg of Z per 100ml. After passing through the kidneys, venous plasma has 0.5 mg/ml (removed 50%). If I filter 100 ml/min, then it’s “as if” I cleaned 50 ml completely and didn't touch the other 50 ml. Amount = concentration (mg/ml) X Volume (ml) = mg Amount in urine = amount removed from plasma (Conc. Of Z) x (Vol. of Urine) = (Conc. Of Z in plasma) X (Vol. of Plasma cleaned)

Question 39

What compounds are use to measure GFR and RPF (renal plasma flow)?

Answer 39

1. Inulin is a polysaccharide of fructose that is filtered by the human kidneys but neither reabsorbed nor secreted. The clearance rate of injected inulin is thus used to measure the glomerular filtration rate. CInulin = GFR = 120 ml/min 2. PAH (para-aminohippuric acid) is a substance used to measure total renal plasma flow because its clearance rate is equal to the total rate of plasma flow to the kidneys. PAH is filtered and secreted by the renal nephrons but not reabsorbed. CPAH = RPF = 625 ml/min 3. Renal blood flow = 1200 ml/min

Question 40

Know the role Aldosterone plays in Sodium and Potassium reabsorption.

Answer 40

Aldosterone stimulates Na+ reabsorption and K+ secretion in the late distal tubule and cortical collecting duct.

Question 41

The mechanisms that control the secretion of Aldosterone.

Answer 41

1. Aldosterone secretion is stimulated directly by a rise in blood K+ and indirectly by a fall in blood volume. 2. Decreased blood flow and pressure through the kidneys stimulates the secretion of the enzyme renin from the juxtaglomerular apparatus. 3. Renin catalyzes the formation of angiotensin I, which is then converted to angiotensin II. 4. Angiotensin II stimulates the adrenal cortex to secrete aldosterone.

Question 42

What is the relationship between sodium, potassium, and hydrogen ion?

Answer 42

1. In the distal tubule, K+ and H+ are secreted in response to the potential difference produced by the reabsorption of Na+. High concentrations of H+ may therefore decrease K+ secretion, and vice versa, helping to reestablish the proper ratio of these ions in the extracellular fluid. 2. Acidosis (increased H+ plasma concentration) increases the secretion of H+ and reduces the secretion of K+ into the filtrate. Alkalosis (lowered plasma H+ concentration) increases the renal secretion of K+ into the filtrate, and thus the excretion of K+ in the urine.

Question 43

What is the maximum acidity (pH) of the urine?

Answer 43

4.5.

Question 44

What role do buffers play in getting rid of H+?

Answer 44

In order for more H+ to be excreted from acidic urine, the acid must be buffered without changing the pH. The buffering action of phosphates (HPO42–) and ammonia (NH3) provide the means for excreting most of H+ in the urine.