Urinary System Anatomy and Physiology (CH 14)
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1
What are the three core functional pillars of the urinary system?
Fluid & electrolyte homeostasis, waste & toxin excretion, and endocrine production
2
Which hormone produced by the kidneys regulates blood pressure?
Renin
3
Which hormone secreted by the kidneys stimulates red blood cell production?
Erythropoietin
4
Which vitamin is converted into its active form by the kidneys?
Vitamin D
5
What are the four primary anatomical components of the urinary system?
Kidneys, ureters, urinary bladder, and urethra
6
What is the outer, granular-appearing region of the kidney called?
Renal cortex
7
What is the inner, striated-appearing region of the kidney called?
Renal medulla
8
What structure at the medial inner core of the kidney collects urine after it is formed?
Renal pelvis
9
Approximately how many nephrons are present in each human kidney?
About 1 million nephrons
10
What constitutes the functional unit of the kidney?
The nephron
11
What are the vascular components of a nephron?
Afferent arteriole, glomerulus, efferent arteriole, and peritubular capillaries
12
What are the tubular components of a nephron?
Bowman's capsule, proximal tubule, loop of Henle, distal tubule, and collecting duct
13
What percentage of all nephrons are cortical nephrons?
80%
14
Where do the glomeruli of juxtamedullary nephrons lie?
Inner layer of the cortex
15
Which type of nephron is primarily responsible for establishing the medullary osmotic gradient to concentrate urine?
Juxtamedullary nephron
16
What structure produces substances involved in the control of kidney function where the vascular and tubular components meet?
Juxtaglomerular apparatus
17
What is the mathematical formula for urinary excretion (\$E\$)?
\$E = F - R + S\$
18
In the urine excretion formula \$E = F - R + S\$, what does each letter represent?
\$E\$ = Excretion, \$F\$ = Filtration, \$R\$ = Reabsorption, \$S\$ = Secretion
19
What is the average volume of glomerular filtrate produced per day?
180 Liters (about 47 gallons)
20
How many times per day is total plasma volume filtered by the kidneys?
~65 times per day
21
How much fluid is reabsorbed daily out of the 180 L filtered?
178.5 Liters
22
What is the average daily volume of urine excreted under normal conditions?
1.5 Liters per day
23
What percentage of the plasma entering the glomerulus is filtered into Bowman's capsule?
~20%
24
What percentage of plasma entering the glomerulus remains unfiltered and exits via the efferent arteriole?
80%
25
What is the direction of fluid movement during tubular reabsorption?
From the tubular lumen into the peritubular capillary blood
26
What is the direction of fluid movement during tubular secretion?
From the peritubular capillary blood into the tubular lumen
27
How much more permeable to water and solutes is the glomerular capillary wall compared to ordinary capillaries?
100 times more permeable
28
What percentage of plasma proteins normally cross the glomerular membrane into Bowman's capsule?
Only ~1%
29
Why is healthy urine normally protein-free?
Filtered proteins are reabsorbed and degraded into amino acids in the proximal tubule
30
What is the primary driving physical force favoring glomerular filtration?
Glomerular capillary blood pressure
31
What is the normal value of glomerular capillary blood pressure?
55 mm Hg
32
What is the value of plasma-colloid osmotic pressure opposing filtration?
30 mm Hg
33
What is the value of Bowman's capsule hydrostatic pressure opposing filtration?
15 mm Hg
34
What is the normal net filtration pressure in the glomerulus?
10 mm Hg
35
What effect does vasoconstriction of the afferent arteriole have on glomerular filtration rate (GFR)?
Decreases GFR
36
What effect does vasodilation of the afferent arteriole have on glomerular filtration rate (GFR)?
Increases GFR
37
What percentage of total resting cardiac output do the kidneys normally receive?
20% to 25%
38
How does the afferent arteriole respond to an increase in systemic arterial blood pressure during autoregulation?
It constricts
39
How does the afferent arteriole respond to a decrease in systemic arterial blood pressure during autoregulation?
It dilates
40
To be reabsorbed from filtrate into plasma, how many distinct barriers must a substance cross?
5 distinct barriers
41
What are the five barriers of transepithelial transport during tubular reabsorption?
Luminal cell membrane, cytosol, basolateral cell membrane, interstitial fluid, and capillary wall
42
What active transport mechanism on the basolateral membrane drives sodium (\$Na^+\$) reabsorption?
\$Na^+\$- \$K^+\$ ATPase pump
43
What percentage of filtered sodium is reabsorbed in the proximal tubule?
67%
44
What percentage of filtered sodium is reabsorbed in the loop of Henle?
25%
45
What percentage of filtered sodium is reabsorbed in the distal and collecting tubules under hormonal control?
8%
46
Which three stimuli trigger the secretion of renin from the kidneys?
Decreased \$NaCl\$, decreased ECF volume, and decreased arterial blood pressure
47
What circulating inactive plasma protein does renin convert into angiotensin I?
Angiotensinogen
48
What enzyme converts angiotensin I into angiotensin II?
Angiotensin-converting enzyme (ACE)
49
Which endocrine gland does angiotensin II stimulate to release aldosterone?
Adrenal cortex
50
What is the primary action of aldosterone on the distal nephron?
Stimulates \$Na^+\$ reabsorption and \$K^+\$ secretion
51
How does sodium retention lead to the expansion of extracellular fluid (ECF) volume?
\$Na^+\$ osmotically holds more \$H_2O\$ in the ECF
52
What cardiac chambers secrete atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)?
Cardiac atria secrete ANP; cardiac ventricles secrete BNP
53
What stimulus triggers the release of ANP and BNP?
Stretch of the cardiac chambers due to elevated \$Na^+\$, ECF volume expansion, and high BP
54
What is natriuresis?
The excretion of sodium in the urine
55
What effect do natriuretic peptides have on the renin-angiotensin-aldosterone system?
They inhibit it
56
How are glucose and amino acids reabsorbed across the luminal membrane in the proximal tubule?
By \$Na^+\$-dependent secondary active transport via symport carriers
57
What is the tubular maximum (\$T_m\$) for glucose?
375 mg/min
58
What is the normal filtered load of glucose under resting physiological conditions?
125 mg/min
59
What term describes the maximum rate of active substance transfer by tubular carriers?
Tubular maximum (\$T_m\$)
60
What active process drives the passive reabsorption of chloride (\$Cl^-\$), water (\$H_2O\$), and urea in the proximal tubule?
Active sodium (\$Na^+\$) reabsorption
61
Through which specific aquaporin channels does water exit the proximal tubule cells into the lateral spaces?
AQP-1 water channels
62
What drives water from the lateral spaces into peritubular capillaries in the proximal tubule?
Hydrostatic pressure
63
What is the clinical significance of renal hydrogen ion (\$H^+\$) secretion?
Regulation of systemic acid-base balance
64
Which hormone regulates potassium ion (\$K^+\$) secretion in the distal and collecting tubules?
Aldosterone
65
What are the primary functions of the organic ion secretory systems in the proximal tubule?
Elimination of non-filterable organic ions, rapid removal of foreign compounds, drugs, and food additives
66
What percentage of filtered water is obligatorily reabsorbed in the proximal tubule?
65%
67
What percentage of filtered urea is passively reabsorbed in the proximal tubule?
50%
68
Which hormone controls variable water reabsorption in the distal tubule and collecting duct?
Vasopressin (antidiuretic hormone)
69
On which membrane of principal cells are vasopressin \$V_2\$ receptors located?
Basolateral membrane
70
What intracellular second-messenger pathway is activated when vasopressin binds its receptor?
Cyclic AMP (cAMP) pathway
71
Which aquaporin channels are inserted into the luminal membrane in response to vasopressin?
AQP-2 water channels
72
Which aquaporin water channels are permanently located on the basolateral border of principal cells?
AQP-3 or AQP-4 water channels
73
What parasympathetic reflex causes the bladder to contract during micturition?
Activation of bladder wall stretch receptors stimulating parasympathetic nerves
74
What happens to the internal urethral sphincter when the bladder contracts?
It mechanically opens
75
Under which type of nervous system control is the external urethral sphincter?
Voluntary control (somatic motor neurons from the cerebral cortex)
76
Does urination occur when the motor neuron to the external urethral sphincter is stimulated or inhibited?
Inhibited
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