1
Q
Why are kidneys retroperitoneal structures?
A
separated from abdominal cavity by their peritoneum envelope
positioned behind peritoneum / outside & behind abdominal cavity
2
Q
Indented area on concave edge of kidney; where ureter, blood vessels, nerves, & lymphatics enter/leave kidney
A
Renal hilus
3
Q
Expanded origin of ureter within kidney; receives final discharge of urine from collecting ducts
A
Renal pelvis
4
Q
Muscular tube that conveys urine from renal pelvis to urinary bladder
A
Ureter
5
Q
Caudal continuation of neck of bladder; conveys urine from bladder to exterior
A
Urethra
6
Q
Functional boundary between bladder & urethra; composed of skeletal muscle encircling urethra
A
External sphincter
7
Q
Smooth muscle in neck of bladder, mixed w/ elastic tissue, acts as what?
A
Internal sphincter
8
Q
Medullary portions of collecting tubules
A
Collecting ducts
9
Q
Do large‐breed dogs have significantly greater numbers of nephrons than small‐breed dogs?
A
No
large kidney size in large dogs have large nephrons rather than more nephrons
10
Q
Besides their location, what differentiates Juxtamedullary Nephrons from Cortical Nephrons?
A
Depth of penetration of loops of Henle into medulla
Juxtamedullary Nephrons: long loops of Henle that extend deeply into medulla, sometimes reaching renal pelvis
Cortical Nephrons: short loops of Henle that extend only to junction of cortex & medulla or into outer zone of medulla
11
Q
Have long loops of Henle that extend deeply into medulla, sometimes reaching renal pelvis
A
Juxtamedullary Nephrons
12
Q
Have short loops of Henle that extend only to junction of cortex & medulla or into outer zone of medulla
A
Cortical Nephrons
13
Q
Will tubular fluid from both cortical and juxtaglomerular nephrons be subjected to medullary influence associated with concentrating urine?
A
Yes
tubular fluid of all nephrons is emptied into shared collecting ducts that proceed through medulla to renal pelvis. therefore, final output of each nephron is subjected to same factors affecting urine concentration, regardless of influence of different nephron types on tubular fluid
14
Q
What is the progressive order of vessels as blood enters the afferent arterioles and exits via renal veins? (8)
(AKAG EPVC)
A
1.) Renal Artery
2.) Kidney
3.) Afferent arterioles
4.) Glomerulus
5.) Efferent arterioles
6.) Peritubular capillaries
7.) Renal Veins
8.) Caudal vena cava
15
Q
What are the components of the nephron (in order) from the glomerulus to the inner medullary collecting duct? (10)
(GBPDA DCCOI)
A
1.) Glomerulus
2.) Bowman’s capsule
3.) Proximal tubule
4.) Descending Limb of Loop of Henle
5.) Ascending Limb of Loop of Henle
6.) Distal tubule
7.) Connecting tubule
8.) Cortical collecting tubule
9.) Outer medullary collecting duct
10.) Inner medullary collecting duct
16
Q
Be aware where the distal tubule begins and the location of its output. Is the influence of the distal tubule in the cortex or in the medulla?
A
Cortex
distal tubule begins beyond macula densa. thick segment of ascending limb of loop of Henle returns to its glomerulus of origin in cortex, passes between afferent & efferent arteriole, and proceeds from there as distal tubule to its cortical collecting tubules. distal tubule resides entirely in renal cortex.
17
Q
Collective name for thickened tubular epithelial cells making contact with its glomerulus of origin? It marks the beginning of the distal tubule.
A
Macula densa
18
Q
Specialized smooth muscle cells that make contact with the thickened tubular epithelium of the thick ascending limb that is making contact with its glomerulus of origin? These cells are located in afferent arteriole & contain secretory granules that contain renin (proteolytic enzyme).
make contact with the macula densa
A
Juxtaglomerular (JG) Granular Cells
19
Q
Space between macula densa, afferent & efferent arterioles, and glomerular capillaries? Consists of mesangial cells & mesangial matrix.
A
Mesangial Region
20
Q
Secrete matrix & glomerular basement membrane, provide structural support, have phagocytic activity, secrete prostaglandins, exhibit contractile activity, and can influence blood flow through glomerular capillaries
A
Mesangial Cells
21
Q
What are the 3 components of the juxtaglomerular apparatus?
A
1.) Macula densa
2.) JG granular cells
3.) Extraglomerular mesangial cells
22
Q
Also known as Lacis Cells, located outside the glomerulus and between the macula densa and the JG granular cells
A
Extraglomerular mesangial cells
23
Q
- assists in regulation of renal blood flow & glomerular filtration rate
- associated with regulation of blood flow & filtration fraction for nephron
- associated with secretion of renin, an enzyme involved in formation of angiotensin II
A
Juxtaglomerular apparatus
24
Q
What division of the autonomic nervous system provides innervation to the kidneys?
A
Sympathetic (Adrenergic) Division of ANS
25
What structures are innervated? - 3
- renal vasculature
- all segments of nephron
- JG granular cells
26
What changes are invoked by Efferent Renal Sympathetic Nerve Activity (ERSNA)? - 3
- renal haemodynamics
- tubular ion & water transport
- renin secretion
27
Significance of renal sympathetic nerves having functionally specific groups of fibers versus a homogeneous group of fibers?
* Each fiber group can target specific renal functions: e.g., afferent/efferent arterioles, tubular Na⁺ reabsorption, renin secretion.
* Allows precise regulation of renal blood flow, GFR, and Na⁺/water balance.
* Homogeneous fiber group would activate all renal responses together, reducing fine-tuned control.
Bottom line: functional specificity → coordinated and selective renal regulation
28
Are sensory (afferent) fibers intermixed with motor (efferent) fibers in the renal nerves?
Yes
renal nerves serve as a communication link between the central nervous system and the kidneys
29
Responses occurring in 1 kidney as result of intervention on same (ipsilateral) or opposite (contralateral) kidney that are mediated by neurohumoral mechanisms
Renorenal reflex
30
Response to obstruction to ureteral flow in right ureter (4)
1.) mechanosensitive neurons are activated -> reflex decrease in contralateral ERSNA
2.) contralateral diuresis & natriuresis
3.) ipsilateral impairment of urine flow & solute excretion
4.) increase in contralateral urine flow & solute excretion -> unchanged total urine flow & solute excretion
31
3 processes associated with urine formation?
1.) Glomerular Filtration
2.) Tubular Reabsorption
3.) Tubular Secretion
32
Fluid part of the blood from which glomerular filtrate is formed
Plasma
33
Ultrafiltrate of plasma that appears in Bowman's capsule as result of glomerular filtration
Glomerular fitrate
34
Created when glomerular filtrate enters nephron tubules because of compositional changes that occur immediately as result of reabsorption from tubular lumen & secretion into tubular lumen
Tubular fluid
35
Tubular reabsorption & tubular secretion continue throughout the length of the nephrons & collecting ducts, so that tubular fluid becomes _____ when it enters renal pelvis
urine
36
Follow the pathway of fluid from plasma in the afferent arteriole through the several components of the nephron to its final discharge from the urethra (13)
(AKGBP HD CtCd RUUU)
1.) Afferent arteriole
2.) Kidney
3.) Glomerulus
4.) Bowman’s casule
5.) Proximal tubule
6.) Loop of Henle
7.) Distal tubule
8.) Collecting tubule
9.) Collecting duct
10.) Renal pelvis
11.) Ureter
12.) Urinary bladder
13.) Urethra
37
Refers to the rate at which blood flows to the kidneys
Renal Blood Flow (RBF)
38
Refers to the part of the RBF that is plasma
Renal Plasma Flow (RPF)
39
Rate at which glomerular filtrate is formed
Glomerular Filtration Rate (GFR)
40
Ratio of GFR to RPF and is the fraction of plasma flowing through the glomerulus that becomes glomerular filtrate
Filtration Fraction (FF)
41
Which variable (RBF, RPF, GFR, or FF) represents the largest volume?
Renal Blood Flow (RBF)
42
In an 11.35 kg dog in a normal state of hydration, what are the following approximate values for kidney function:
Renal blood flow: 300 ml/min
Renal plasma flow: ___ ml/min
Glomerular filtration rate: __ ml/min
approximate value for percentage of glomerular filtrate that's excreted as urine: ___%
Renal plasma flow: 180 ml/min
Glomerular filtration rate: 45 ml/min
approximate value for percentage of glomerular filtrate that's excreted as urine: 1.05%
43
As it affects urine concentration, the outcome is influenced by:
A.) Cortical nephrons
B.) Juxtamedullary nephrons
C.) Both cortical and juxtamedullary nephrons
Both Cortical & Juxtamedullary Nephrons
44
Thin descending limb, thin ascending limb, & thick ascending limb of loop of Henle:
A.) Have the same lumen diameter
B.) Have the same epithelial cell thickness
C.) Have a lumen diameter corresponding to the limb being thin or thick
Same lumen diameter
45
Innervation to the kidney is provided by?
Functionally specific groups of fibers with both motor (efferent) and sensory (afferent) activity
46
The following values were obtained in a renal physiology laboratory where RBF, RPF, GFR, and FF were being measured but their identity has been lost: 16mL/min per kg; 3.36mL/min per kg; 8.64mL/min per kg; 0.35. Their reassigned identity should be?
1.) RBF: 16mL/min/kg
2.) GFR: 3.36mL/min/kg
3.) RPF: 8.64mL/min/kg
4.) FF: 0.35
47
What would be the response of a renorenal reflex following a left ureteral obstruction?
Mechanoreceptors in the left kidney activate a reflex to increase activity of the right kidney
48
High-pressure system with high hydrostatic pressure favouring filtration; resembles arterial end of muscle capillary
Glomeruli
49
Low-pressure system with low hydrostatic pressure favouring reabsorption; represents venous end
Peritubular capillaries
50
Which one b/w glomeruli & peritubular capillaries resembles arterial end of muscle capillary and which one represents the venous end?
Glomeruli - similar to arterial end of a typical muscle capillary
Peritubular capillaries - similar to the venous end
51
What factors associated with the intravascular lysis of erythrocytes would give rise to hemoglobinuria and/or acute renal shutdown? (3)
- Normal intravascular lysis of erythrocytes
- Excessive intravascular lysis
- High tubular haemoglobin concentration coupled with continued water reabsorption
52
Factor associated with intravascular lysis of erythrocytes that results in haemoglobin being bound by plasma haptoglobin, preventing leakage at the glomerulus due to the increased size of the combined molecule
Normal intravascular lysis of erythrocytes
53
Factor associated with intravascular lysis of erythrocytes that causes unbound haemoglobin to appear in the urine (haemoglobinuria)
Excessive intravascular lysis
54
Factor associated with intravascular lysis of erythrocytes that can cause haemoglobin to precipitate and block tubules, leading to acute renal shutdown
High tubular haemoglobin concentration coupled with continued water reabsorption
55
How does efferent arteriolar constriction increase the FF?
It increases glomerular hydrostatic pressure (HP) and reduces renal blood flow (RBF) --- decreasing RBF while maintaining GFR will increase FF
56
How does poor kidney perfusion relate to greater access to filtration of large molecules?
Change the electrostatic charge of the glomerular membrane which allows molecules previously restricted from filtration to be filtered & enter capsular space
57
Tubuloglomerular feedback mechanism fo regulation of RBF and GFR
- Decreased GFR slows flow rate in the loop of Henle -> increased reabsorption of Na & Cl in ascending limb of loop of Henle
- Macula densa senses decreased NaCl concentration -> signals decrease in resistance to blood flow in afferent arterioles -> raises glomerular HP & help return GFR to normal.
- Macula densa signal also increases renin release from JG cells
- Renin increases formation of Angiotensin I -> Angiotensin II
- Angiotensin II constricts Efferent arterioles -> increase glomerular HP & glomerular filtration (return GFR to normal)
58
What is the role of renin in the autoregulation of RBF and GFR?
- Converts plasma angiotensinogen to angiotensin I.
- Angiotensin I is converted to angiotensin II by ACE
- Angiotensin II constricts efferent arterioles, increasing glomerular hydrostatic pressure & glomerular filtration (return GFR to normal)
59
Why is reabsorption of fluid from tubules into the peritubular capillaries analogous to reabsorption that occurs at the venous end of a muscle capillary?
Peritubular capillary dynamics favour reabsorption, in contrast to filtration at glomerulus. This occurs because protein not filtered at glomerulus contributes to a greater colloidal osmotic pressure (COP) in peritubular capillary than in tubular fluid.
60
How do reductions in peritubular capillary HP & elevations in peritubular capillary COP relate to greater tubular reabsorption?
These conditions favour movement of fluid from tubules into peritubular capillaries
61
What are 3 mechanisms whereby 65% of Na+ reabsorption occurs in the proximal tubules?
1.) Cotransport of Na+ with glucose or amino acids
2.) Countertransport with H+
3.) Chloride-driven Na+ transport in more distal portions of the proximal tubules
62
What are the mechanisms and location that account for 25% of Na+ reabsorption?
1.) ~25% of tubular load of Na+ is reabsorbed in ascending thick segment of loop of Henle (medullary and cortical)
2.) Na entry occurs via a Na+–K+–2Cl– carrier in luminal membrane (cotransport)
3.) Na+ is actively extruded across basolateral surfaces by Na+/K+‐ATPase, and Cl– diffuses passively to maintain electrical neutrality
63
What is important about the flexibility accorded Na+ reabsorption in the distal nephron?
Allows for increased Na+ reabsorption in collecting duct if an increased load is delivered; accommodation for hypovolemia & its associated declining blood pressure
64
What accounts for 65% of water reabsorption in the proximal tubules? Note the limitations for urea and other nonactively reabsorbed solutes.
Na⁺ reabsorption creates osmotic gradient, causing water to follow. Urea and other nonactively reabsorbed solutes become concentrated, but since tubule is less permeable to urea than water, 50%+ of filtered urea remains in tubule.
65
What are the mechanisms for the reabsorption of proteins and peptides?
Proteins/Polypeptides → reabsorbed by endocytosis, degraded in lysosomes to amino acids → amino acids exit via facilitated diffusion
Small peptides → hydrolyzed at the brush border → amino acids enter cells via cotransport
66
What are the 2 methods associated with H+ secretion? How is K+ secretion related to dietary intake of K+?
H⁺ secretion:
1.) Countertransport (Na⁺–H⁺ exchange) in proximal and distal tubules.
2.) Active secretion by intercalated cells in the collecting duct.
K⁺ secretion & diet:
- Low K⁺ intake → increased K⁺ reabsorption.
- High K⁺ intake → increased K⁺ secretion.
67
What is the relationship of transport maximum to diabetes mellitus?
Plasma glucose increases due to lack of insulin, raising tubular glucose load. When this exceeds Tm, glucose is not fully reabsorbed & appears in urine (glycosuria).
Retained glucose increases tubular osmotic pressure, causing water to remain in tubules, leading to increased urine volume (polyuria).
68
What is the significance of the property of the proximal tubule known as glomerulotubular balance?
maintain consistent proportion of filtrate reabsorption in proximal tubule, irrespective of changes in glomerular filtration rate (GFR); ensure distal nephron is not overwhelmed by drastic changes in GFR, allowing it to maintain proper control over final urine composition
- Consistent Fractional Reabsorption
- Regulation at Low GFR
- Regulation at High GFR
69
Which one of the following would have the highest values for hematocrit and plasma protein concentration?
A.) Blood in the afferent arterioles
B.) Tubular filtrate
C.) Blood in the efferent arteriole
Blood in the efferent arteriole
70
Generally speaking, protein molecules are normally restricted from filtration through the glomerular membrane because of?
Their size and polyanionic nature
71
Plasma glucose concentration of 300mg/dL and a urinalysis that is positive for glucose has been found in a dog. Which one of the following would be a likely clinical sign?
Polyuria and Polydipsia
72
Because of a decrease in GFR, the tubular fluid in the loop of Henle has been slowed allowing greater reabsorption of sodium and chloride ions in the ascending loop of Henle. The macula densa senses the decrease in sodium concentration. Which one of the following responses occurs?
Afferent arteriole dilation, release of renin, and efferent arteriole constriction
73
Hemoglobin that arises from intravascular lysis of erythrocytes will be?
Be bound to haptoglobin as long as the lysis is not severe, but if lysis is excessive, haptoglobin becomes saturated and unbound hemoglobin may be filtered and appear in urine, a condition known as hemoglobinuria
74
Prepares ISF of renal medulla, so tubular fluid of proximal tubules entering medullary loop of Henle can be modified before returning to distal tubule. Modification of tubular fluid (after it leaves proximal tubule) for conservation or elimination of water depends on very high osmolality in ISF of renal medulla.
Countercurrent system
75
What characteristics of the descending limb of the loop of Henle would cause the osmolality of the tubular fluid at the hairpin turn to be high?
Permeable to water but impermeable to solutes
- water diffuses by osmosis to the higher osmotic pressure of the ISF, which increases the solute concentration (mostly NaCl) while approaching the hairpin turn of the loop of Henle
76
What factors in the thin and thick segments of the ascending limb of the loop of Henle cause the tubular fluid to become diluted before it enters the distal tubule?
Thin segment:
Permeable to NaCl and impermeable to water, so NaCl diffuses into the ISF due to the concentration gradient, and water remains in the tubule.
Thick segment:
NaCl is actively transported to the ISF, and water continues to be retained.
77
How does the recirculation of urea assist the countercurrent multiplier system?
Helps maintain high solute concentration in ISF of kidney medulla. Urea diffuses from inner medullary collecting ducts into ISF & then into thin segments of ascending limbs of the loops of Henle. Assist osmotic gradient as well and ensure urea excretion when urine output is low.
78
What would happen to the vertical medullary gradient in the medulla if the countercurrent exchanger system did not exist?
Blood from descending limbs of vasa recta would return directly to renal vein instead of counterflowing into ascending limb, solute of renal medulla would be quickly removed instead of being retained
79
During periods of diuresis, how does urea contribute to medullary washout?
- Greater amount of urea filtered is excreted
- Lesser amount is recirculated
- Contribution of urea to medullary osmolality is decreased (diminishes ability to concentrate tubular fluid in collecting ducts)
80
What are the factors that contribute to the low osmolality of the tubular fluid at the end of the distal tubule?
- Na⁺ and Cl⁻ removal in the ascending limb of the loop of Henle while water remains in the tubule.
- Continued active NaCl transport in the distal tubule.
- Low permeability to water and urea in the distal tubule
81
What are the target cells of ADH?
Cortical Collecting Tubules and Medullary Collecting Ducts
82
How responsive is the rate of ADH secretion to deviations in plasma osmolality?
1%
83
What would the urine‐to‐plasma osmolal ratio be if the osmolality of the innermost region of the medulla was 1200mosmol and there was an extreme need for water conservation?
urine-to-plasma osmolal ratio of ~ 4:1
84
Urinalysis would reveal dilute urine with a lower-than-normal specific gravity
Diabetes Insipidus
85
Urinalysis would likely show a higher-than-normal specific gravity and test positive for glucose
Diabetes Mellitus
86
Why is polydipsia a clinical sign of both diabetes insipidus and diabetes mellitus?
Compensatory mechanism for the polyuria (formation and excretion of a large volume of urine) observed in both conditions, helping to overcome the water deficit
87
What are some causes of impaired urine concentrating ability associated with chronic renal failure?
- Increased solute excretion
- Medullary washout
- Reduced responsiveness to ADH
88
Which one of the following nephron parts is associated with the establishment of a high salt concentration in the medulla of the kidney?
Loop of Henle
89
Loss of solute (Na+ , Cl– ) and retention of water that occurs in the ascending limb of the loop of Henle causes the tubular fluid to be _________ as compared with plasma.
Hypotonic
90
With regard to the tubular transport of urea
During excretion, there is recirculation of some from the inner medullary collecting ducts to the ascending thin limb of the loop of Henle
91
Which one of the following is not associated with diabetes mellitus?
A.) Increased urine formation
B.) Renal threshold for glucose is exceeded
C.) Increased thirst
D.) Lack of antidiuretic hormone (ADH)
Lack of antidiuretic hormone (ADH)
92
When antidiuretic hormone from the posterior pituitary is released in greater amounts, what will happen to the fluid in the collecting ducts of the kidney?
A.) It will become more dilute
B.) It will remain the same
C.) It will become more concentrated
More Concentrated
93
Detection of increased osmoconcentration of the ECF by osmoreceptors in the hypothalamus would result in:
A.) More concentrated urine
B.) More dilute urine
C.) No change in urine concentration
More concentrated urine
94
Which part of the loop of Henle has the lowest osmolality (greatest dilution)?
A.) Ascending thin limb
B.) Descending thin limb
C.) Ascending thick limb
D.) Hairpin loop
Ascending thick limb
95
Where in the loop of Henle does urea permeability begin and end?
A.) Begins and ends in the thin ascending limb
B.) Begins in the thin ascending limb and ends at the end of the thick ascending limb
C.) Begins and ends in the thick ascending limb
D.) There is permeability for urea throughout the loop of Henle
Begins and ends in the thin ascending limb
96
Movement of solute and water between the vasa recta and the ISF occurs by:
A.) Passive diffusion for water and urea and active transport for NaCl
B.) Passive diffusion for water and NaCl and active transport for urea
C.) Passive diffusion for water, urea, and NaCl
Passive diffusion for water, urea, and NaCl
97
A diuretic that interferes with the cotransport of NaCl in the thick segment of the ascending limb of the loop of Henle would:
A.) Decrease the osmolality of the tubular fluid
B.) Predispose (tendency for) to medullary washout
C.) Further concentrate the medullary ISF
D.) Reduce the excretion of urea
Predispose (tendency for) to medullary washout
98
What is the response to hyperosmolality with regard to thirst and antidiuretic hormone (ADH) release? What would be the response to hypoosmolality?
Hyperosmolality:
↑ Plasma osmolality → stimulates thirst and increases ADH release, leading to increased water intake and water reabsorption.
Hypoosmolality:
↓ Plasma osmolality → suppresses thirst and decreases ADH release, leading to increased water excretion.
99
How is the regulation of [Na+] related to ECF volume expansion and ECF volume depletion?
ECF expansion → ↑ Na⁺ excretion (natriuresis) to reduce volume.
ECF depletion → ↓ Na⁺ excretion, conserve Na⁺ to restore volume.
100
Where are the principal receptors located that respond to acute changes in blood volume?
- Atrial stretch receptors in the left and right atria.
- Carotid and aortic baroreceptors also respond to pressure/volume changes.
101
What are the 3 levels of ERSNA activity in response to hypovolemia?
Mild hypovolemia → slight ↑ ERSNA.
Moderate hypovolemia → moderate ↑ ERSNA, enhanced renin release.
Severe hypovolemia → maximal ↑ ERSNA, strong vasoconstriction, maximal renin release.
102
What are the effects of the left atrial stretch reflex initiated by hypervolemia?
↑ atrial pressure → ↓ sympathetic outflow → ↑ Na⁺ and water excretion (diuresis/natriuresis)
103
What is the stimulus for the release of ANP in hypervolemia and what is its role in reducing intravascular volume?
↑ atrial stretch
promotes natriuresis, diuresis, and vasodilation → reduces intravascular volume.
104
What action of diuretics promotes diuresis?
inhibit tubular Na⁺ reabsorption → water follows → ↑ urine output.
105
How is the ECF [Na+] regulated?
- Controlled by renal Na⁺ excretion in response to ECF volume and arterial pressure changes
- Hormones like aldosterone and ANP modulate Na⁺ reabsorption/secretion
106
Why is the regulation of ECF [K+] critically controlled?
Small changes in [K⁺] profoundly affect membrane potential, impacting cardiac and neuromuscular function
107
What provides for the regulation of ECF [K+] and what is the stimulus for its production?
- Renal excretion and cellular uptake provide regulation.
- Stimulus: ↑ ECF [K⁺] triggers aldosterone release from adrenal cortex → promotes K⁺ secretion in distal nephron.
108
What is the role of parathyroid hormone following its secretion in response to low ECF [Ca2+]?
↑ Ca²⁺ reabsorption in kidney, ↑ Ca²⁺ mobilization from bone, ↑ intestinal Ca²⁺ absorption via vitamin D activation.
109
What is the effect of parathyroid hormone on phosphate excretion?
Increases phosphate excretion (phosphaturia) in the kidney, preventing hyperphosphatemia during Ca²⁺ mobilization
110
The renin–angiotensin–aldosterone system is effective in the adjustments needed for the correction of?
Hypovolemia
111
Volume receptors in the left atrium are stretched during hypervolemia that results from increased Na+ intake. Which one of the following is influential in the return to normal?
A.) Aldosterone
B.) Inhibition of ERSNA and release of ANPC ADH
Inhibition of ERSNA and release of ANPC ADH
112
Extracellular fluid Na+ concentration is regulated by:
A.) Osmoreceptor–ADH system and thirst mechanism
B.) Aldosterone mechanism
Osmoreceptor–ADH system and thirst mechanism
113
Detection of increased osmoconcentration of the ECF by osmoreceptors in the hypothalamus would by followed by:
A.) Secretion of ADH, more dilute urine, suppression of thirst, and loss of water
B.) Secretion of ADH, more concentrated urine, stimulation of thirst, and water retention
Secretion of ADH, more concentrated urine, stimulation of thirst, and water retention
114
Which one of the following hormones promotes the tubular reabsorption of Na+ and the tubular secretion of K+?
A.) Antidiuretic hormone
B.) Secretin
C.) Aldosterone
D.) Oxytocin
Aldosterone
115
What prevents backflow of urine from the bladder to the ureters?
Ureterovesical junction
116
How are the sacral spinal cord and brainstem reflexes coordinated to allow for storage of the urine while it is formed?
- Sympathetic nerves relax detrusor and contract internal sphincter.
- Somatic nerves keep external sphincter contracted.
- Pontine micturition center inhibits voiding reflex during filling.
117
What are the events associated with the initiation and maintenance of micturition?
- Bladder fills → stretch receptors fire → afferent signals to sacral cord and pontine center.
- Pontine center coordinates: detrusor contraction + sphincter relaxation → urine voiding.
118
Do the sympathetics have a role in micturition?
inhibit detrusor, contract internal sphincter → promote storage, not voiding
119
How do spinal injuries relate to urinary incontinence?
- Supraspinal lesions: loss of voluntary control → reflex (spastic) bladder.
- Sacral lesions: flaccid bladder → overflow incontinence.
120
What term describes the clinical sign associated with FUS?
Dysuria / Stranguria
(difficulty/painful urination)
121
Why is urine normally yellow in color?
Urochrome (from hemoglobin breakdown)
122
What appears to be the purpose for the secretion and presence of mucus in horse urine?
Lubricates urethra and may protect urinary tract epithelium.
123
What is the principal nitrogenous constituent of mammalian urine and where is it formed?
Urea - formed in the liver via the urea cycle from ammonia derived from amino acid metabolism
124
What are the features of creatinine that make it useful in the renal clearance formula for measuring kidney function?
Freely filtered, not reabsorbed, minimally secreted → reflects glomerular filtration rate (GFR) accurately
125
Why do diseased kidneys have a lower renal clearance than normal kidneys?
Reduced GFR, damaged nephrons → less filtration and clearance of solutes
126
Would a plasma concentration for creatinine of 6mg/dL be of concern?
Significant elevation → indicates severe renal dysfunction
127
Why are osmolal clearance values useful for evaluating diuretics?
Evaluates concentration/dilution ability of kidneys and effectiveness of diuretics on water and solute excretion
128
Tubular fluid is transported from Bowman’s capsule to the renal pelvis by:
A.) Action of cilia
B.) Peristalsis
C.) Hydrostatic pressure gradient
D.) Bucket brigade
Hydrostatic pressure gradient
129
The principal nitrogenous constituent of mammalian urine is:
A.) Amino acids
B.) Uric acid
C.) Urea
D.) Ammonia
Urea
130
The most probable reason for the abundant secretion of mucus in the kidney pelvis and upper part of the ureter in the horse is that it:
A.) Provides a carrier for the carbonates and phosphates and prevents their collection in the renal pelvis
B.) Prevents irritation from highly alkaline urine
C.) Reduces friction for passage of urine
Provides a carrier for the carbonates and phosphates and prevents their collection in the renal pelvis
131
A renal clearance for urea of 50 mL/min means that:
A.) 50 mL of the RPF are completely cleared of their urea, and the remainder continue through the kidney with none extracted
B.) 50 mL of filtrate are formed each minute, and all of the urea is excreted
C.) Each milliliter of the RPF contributes urea to that which is excreted, but the amount excreted in the urine each minute would require all of the urea in 50 mL of the RPF
Each milliliter of the RPF contributes urea to that which is excreted, but the amount excreted in the urine each minute would require all of the urea in 50 mL of the RPF
132
Creatinine clearance evaluations provide an estimate of:
A.) Functional renal mass
B.) Amount of protein metabolism
C.) Muscle mass
D.) Ability to concentrate urine
Functional renal mass
133
Which division of the autonomic nervous system is associated with micturition?
A.) Sympathetic
B.) Parasympathetic
C.) Both sympathetic and parasympathetic
Parasympathetic
134
Which one of the following statements about creatinine is not true?
A.) The amount produced depends on the mass of muscle in the body and is very constant from day to day
B.) Creatinine is a nitrogenous byproduct of muscle metabolism
C.) Creatinine production depends on the amount of protein metabolism and therefore is variable
D.) High plasma concentrations of creatinine are a first indication of kidney disease
Creatinine production depends on the amount of protein metabolism and therefore is variable
135
Sacral center reflex emptying of the urinary bladder (without brain stem and cerebral cortex control) will be?
frequent and incomplete
136
Which one of the following terms most accurately describes a clinical sign of feline urologic syndrome (FUS)?
A.) Stranguria
B.) Oliguria
C.) Polyuria
D.) Anuria
Stranguria
137
The usual yellow color of urine is derived from:
A.) Carotene
B.) Uric acid
C.) Bilirubin
D.) Urea
Bilirubin
138
Visualize the division of the kidneys into lobes and lobules and the structural detail of a lobule.
Each lobe has multiple lobules, each with nephrons draining into a central medullary cone/collecting duct
139
What are the two nephron types associated with avian kidneys?
1. Cortical (Mammalian-type) – short loops of Henle, less concentrated urine.
2. Medullary (Reptilian-type) – long loops of Henle, can concentrate urine.
140
Where is the location of each nephron type within a lobule?
- Cortical nephrons: superficial cortex.
- Medullary nephrons: deep cortex/medulla.
141
What is lacking in the reptilian nephron that makes it incapable of concentrating urine?
No loop of Henle
142
Where are the loops of Henle of the mammalian nephrons located within a lobule?
extend into the medulla of the lobule
143
What structures are located in the medullary cone?
Collecting ducts
Loops of Henle
Vasa recta
144
Would the tubular fluid from reptilian nephrons be exposed to the osmotic gradient in the medullary cone on its exit from the kidney?
No
reptilian nephrons bypass the gradient → dilute urine
145
What is the origin and distribution of renal portal blood?
Hindlimb/caudal body venous blood → renal portal vein → kidney cortex/tubules
146
What structure controls the amount of renal portal blood that perfuses the kidney?
Renal portal valve
147
Under control conditions, which nephron type provides the greatest volume of filtrate?
Mammalian-type nephrons
148
What would be an approximate osmolality of ureteral urine when birds are dehydrated?
~1200–1600 mOsm/kg
149
What is the principal nitrogenous constituent of avian urine?
Uric acid
150
What is the value of having two sources of blood perfusing the tubules?
Adequate perfusion for filtration and tubular metabolism
151
What is the value of having uric acid precipitated in the tubules?
Conserves water
152
What organs in birds are sites for the conversion of ammonia to uric acid?
Liver and Renal tubules
153
How do the effects of angiotensin II in birds vary from the effects in mammals?
vasoconstriction & may enhance medullary nephron reabsorption
154
What is the role of aldosterone on the kidney?
↑ Na⁺ reabsorption, ↑ K⁺ excretion → helps conserve water
155
What are the effects of atrial natriuretic peptide?
↓ Na⁺ reabsorption, ↑ natriuresis and diuresis, ↓ blood volume
156
What hormone is involved in the regulation of calcium and phosphorus?
Parathyroid hormone (PTH)
157
Where is the major location for the post‐renal modification of ureteral urine?
Cloaca / Urodeum
158
Which one of the following nephron components is lacking in reptilian nephrons?
A.) Proximal tubule
B.) Loop of Henle
C.) Distal tubule
D.) Collecting duct
Loop of Henle
158
What is the apparent function of mucus that is present in avian feces?
Lubricates and protects lower urinary and digestive tracts
159
Renal portal system blood is:
A.) Venous blood
B.) Arterial blood
Venous blood
160
Reptilian nephron tubular fluid bypasses the medullary cones where it could otherwise become concentrated. True or False?
False
161
Which avian nephron is associated with the countercurrent mechanism?
Mammalian type
162
Renal portal blood enters the vascular supply perfusing the renal tubules at the level of the:
A.) Glomerulus
B.) Peritubular capillaries
C.) Vasa recta
Peritubular capillaries
163
The principal nitrogenous component of avian urine
Uric acid
164
Uric acid precipitates in the renal tubules in order to?
Avoid obligation of water excretion
165
Ammonia is converted to uric acid in birds in where?
liver and kidneys
166
Location for the greatest post‐renal modification of ureteral urine
Colon
167
Secrete only NaCl and serve an extrarenal osmoregulatory function
Salt glands (Nasal glands)
Vet. Systemic Physiology Lec.
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