Quiz 2 Flashcards
1
Q
-it gets rid the body of waste materials that are either ingested or produced by metabolism.
-To control the volume and composition of the body fluids. A balance between the intake and output is maintained in large part by the kidneys.
A
Kidney
2
Q
is the dilated blind end of the nephron and consists of the invaginated capillary tuft called as the glomerulus.
A
The Glomerular Capsule (Bowman’s Capsule)
3
Q
coalesce to form the efferent arteriole which conducts blood away from the glomerulus and is returned to the systemic circulation through the renal vein.
A
The Capillaries
4
Q
The area between the glomerular tuft and the Bowman’s capsule is known as the______________ and it is the site of collection of the glomerular filtrate which is directly funneled into the proximal tubule.
A
Bowman’s space
5
Q
is lined by a layer of epithelial cells.
A
Glomerular Capsule
6
Q
is continued from the glomerular capsule by proximal tubule which is composed of proximal convoluted portion and the proximal straight portion.
A
The Nephron
7
Q
within the cortex and the straight portion extends about halfway into the outer medulla.
A
Convoluted Portion
8
Q
consists of descending thin limb, which is continuous from the proximal straight tubule, the ascending thin limb that terminates at the junction of the inner and outer medulla (cortical nephrons lack a thin ascending limb) and the ascending thick limb that returns to the glomerulus of origin in the cortex and passes between the afferent and efferent arterioles.
A
The Loop of Henle
9
Q
The distal tubule, connecting tubule and cortical collecting tubule are collectively referred to as
A
Distal Convoluted Tubule
10
Q
• Mammalian kidney has two principal types of nephrons and are classified based on_______________________
A
-Location of their glomeruli and based on Depth of penetration of the loops of Henle into the medulla.
11
Q
nephrons with glomeruli in the outer and middle cortices are called
A
cortical nephrons.
12
Q
• They are associated with the loop of Henle that extend to the junction of the cortex and medulla or into the outer zone of the medulla, e.g., Marine aquatic mammals.
A
cortical nephrons.
13
Q
• Those nephrons with glomeruli in the cortex close to the medulla are known as____________________
A
juxtamedullary nephrons.
14
Q
They are associated with loops of Henle that extend more deep into the medulla, e.g., mammals in arid region desert animals such as Kangaroo and rat.
A
juxtamedullary nephrons.
15
Q
• Blood flow to the kidneys is normally ____ of the cardiac output. •
A
22%
16
Q
enters the kidney and branches to form the interlobar arteries, arcuate arteries, interlobular arteries and afferent arterioles which lead to the glomerular capillaries, where large amount of fluid and solutes (except plasma proteins) are filtered to begin urine formation.
A
The Renal Artery
17
Q
coalesce to form the efferent arteriole which leads to a second capillary network, the peritubular capillaries surrounding the renal tubules
A
distal ends of the capillaries of each glomerular
18
Q
is unique, in that it has two capillary beds-
o Glomerular capillaries and
o Peri-tubular capillaries, separated by efferent arterioles which help to regulate the hydrostatic pressure.
A
Renal Circulation
19
Q
The glomerulus has a high pressure of _____ Hg and peritubular capillaries have a low pressure of 13 mm Hg which helps in rapid fluid filtration.
A
60 mm
20
Q
empty into vessels of the venous system which run parallel to the arteriolar vessels and progressively form the interlobular vein, arcuate vein, interlobar vein and renal vein.
A
Peritubular Capillaries
21
Q
The glomerulus has a high pressure of 60 mm Hg and peritubular capillaries have a low pressure of______ Hg which helps in rapid fluid filtration.
A
13 mm
22
Q
The peritubular capillaries branches to form the_________ into the medulla and lie side by side with the loops of Henle.
A
Vesa Recta
23
Q
return toward the cortex and empty into the cortical veins, similar with the loops of Henle
A
Vesa Recta
24
Q
are associated with long looped nephrons. They play an essential role in the formation of concentrated urine.
A
Vesa Recta
25
is brought about by vasoconstriction initiated by reflexes through the vasomotor centre in the medulla and pons. Increased sympathetic tone elicits renin secretion from granular cells and enhances sodium reabsorption from nephron segments
RENAL BLOOD FLOW AND GLOMERULAR FILTRATION RATE
26
are more dense than the other epithelial cells and are collectively called as macula densa.
Contact Epithelial Cells
27
marks beginning of the distal tubule.
Macula Densa
28
The smooth cells of the afferent and efferent arterioles that make contact with the macula densa are specialized smooth muscle cells and are called as
Juxta glomerular cells
29
have secretory granules that contain renin, a proteolytic enzyme.
Juxta glomerular cells
30
The space between the macula densa and the afferent and efferent arterioles and the space between the glomerular capillaries is known as
mesangial region/Extra glomerular mesangial cells or Lacis cells.
31
are involved in feed back mechanism that assist regulation of renal blood flow and glomerular filtrate rate.
JG cells
32
is the quantity of GF formed each minute in all the nephrons of both the kidneys/kg body weight. In humans it is about 125 ml/min. Total quantity of GFR formed /day = 180 L. Over 99% of the filtrate is reabsorbed in the tubules, the remainder passing into the urine.
Glomerular Filtration Rate
33
is the volume of blood delivered to the kidneys per unit time
Renal Blood Flow
34
is the percentage of the renal plasma flow that becomes Glomerular Filtrate. The normal plasma flow through both the kidneys is 650 ml/min but the normal GFR in both the kidneys is 125 ml/min, hence the average filtration fraction is 19%.
Filtration Fraction
35
• Three factors that determine the filtration pressure are
Glomerular pressure,
Plasma colloidal osmotic pressure (COP) and Bowman’s capsular pressure.
36
is affected by the rate of blood flow through the nephrons. Since a very large portion of plasma is filtered through the glomerular membrane, the COP in the glomerulus is high which opposes further filtration.
Glomerular Filtration Rate
37
a portion of plasma fluid is not filtered until new plasma flows into the glomerulus. Greater the plasma flow, greater the filtration rate.
Effect of renal blood flow on GFR
38
• But when blood stagnates in the glomerulus for a prolonged period, increase in plasma COP occurs which causes a
fall in GFR
39
Effect of sympathetic stimulation on GFR
• Mild to moderate stimulation of sympathetic nerves causes
afferent arteriolar constriction and decreases GFR.
40
Effect of sympathetic stimulation on GFR
Strong sympathetic stimulation causes great reduction in the glomerular blood flow and glomerular pressure resulting in fall of GFR to zero level.
glomerular blood flow and glomerular pressure resulting in fall of GFR to zero level.
41
Effect of arterial pressure on GFR
When arterial pressure increases from 100 to 200mm Hg______________________ occurs automatically by autoregulation, thus prevents a major rise in glomerular pressure (GP) and GFR increases to only 15-20%.
afferent arteriolar constriction
42
• Two theories have been proposed to explain autoregulation-______________ and ______________
Myogenic Theory and JG Theory in animals.
43
According to this theory, the increase in BP would expand an artery and it would respond by contracting. In this way, RBF would be decreased and glomerular HP reduced. The reduced glomerular HP reduces GFR.
Myogenic Theory
44
A reduction in BP causes less tension and blood vessel would dilate to increase RBF and glomerular HP with subsequent increase in GFR. That is, when arterial pressure rises, arterioles are stretched, once stretched, arterioles contract forcefully. This decreases RBF to normal level. A decrease in arterial pressure dilates the blood vessels which increases RBF and GFR.
Myogenic Theory
45
contains renin (a proteolytic enzyme). Renin is released when- Reduced GFR, Reduced glomerular pressure and Increased sympathetic stimulation of kidneys.
• Juxta glomerular apparatus (JGA)
46
causes reduced sodium concentration in the tubular fluid as it flows past the macula densa and this low sodium causes release of renin from JGA.
Reduced GFR
47
is rapidly converted to angiotensin II by converting enzyme which is present in high concentration in the lungs.
Angiotensin I
48
is a powerful vasoconstrictor and causes vasoconstriction throughout the body thereby increasing the BP. Some amount of Angiotensin II is formed in the glomerulus, i.e. in the JG cells.
Angiotensin II
49
causes marked constriction of efferent arteriole which increase glomerular pressure and also GFR but decreases RBF. Increase in pressure increases GFR but decrease in blood flow decreases GFR and in effect there is a less change in GFR.
Angiotensin II
50
• Decreased blood flow to peritubular capillaries decreases peritubular pressure, which causes
increased tubular reabsorption,
51
is also associated with the JG theory of autoregulation
The mechanism of tubulo glomerular feedback (TGF)
52
refers to alteration in GFR with changes in the tubular flow rate.
Tubule-glomerular feedback
53
• It is mediated by the macula densa cells of the JG apparatus. These cells sense changes in the sodium and chloride to their region. If GFR is increased because of increased glomerular HP there will be increase in macula densa flow and sodium and chloride delivery intiates a response that returns GFR and macula densa flow towards the normal by afferent arteriole constriction (which lowers glomerular HP).
Tubule-glomerular feedback
54
• Three processes are involved in the formation of urine in the nephrons-
Glomerular filtration,
Tubular reabsorption,
Tubular secretion.
55
is the fluid that is filtered through the glomerular membrane into the Bowman’s capsule.
• Glomerular filtrate
56
are relatively impermeable to proteins so that the filtered fluid, glomerular fluid (GF) is essentially protein free and devoid of cellular elements.
Glomerular Capillaries
57
The glomerular capillary membrane has three layers:
o Endothelium of the capillary
o Basement membrane
o A layer of epithelial cells (podocytes) surrounding the outer surface of the capillary basement membrane
58
are perforated by thousands of small holes called fenestrae.
The endothelial cells lining the glomerulus
59
• Surrounding the endothelium is ________________composed of a meshwork of collagen and proteoglycan fibrillae which can filter large amount of water and small solutes.
the basement membrane
60
• The final layer contains epithelial cells called ________ lining the outer surface of the glomerulus. These cells are not continuous but consists of many finger-like projections which form slit pores through which glomerular filtrate filters.
podocytes
61
Reasons for high degree of selectivity
• Size of the molecule: Pores in the membrane allow molecules with a diameter up to 8 nm.
• Pores are lined with a strong negative charges and electrostatic repulsion of the protein molecules (proteins are electronegative) prevent their filtration.
62
is the net pressure forcing the fluid through the glomerular membrane equals to the glomerular pressure minus sum of glomerular colloidal osmotic pressure and capsular pressure.
Filtration Pressure
63
Transport of fluid from the Bowman’s capsule to the renal pelvis is accomplished by a difference in the hydrostatic pressure.
Tubular Transport
64
is the transport of solute from the peritubular capillaries to the tubular fluid.
Tubular Secretion
65
plays a major role than the secretion in the formation of urine. More than 90% of the water in the GF is reabsorbed as it passes through the tubules. Some substances such as sodium, glucose and amino acids are almost completely reabsorbed so that their concentration decreases almost to zero before the fluid becomes urine so that they are conserved by the body and not excreted and lost by the urine.
Reabsorption
66
Basic mechanisms of absorption is by two process –
Active transport and Passive transport.
67
• Transport by a carrier for a single compound (e.g., sodium) and is unidirectional.
Uniport
68
• Transport of two compounds on the same carrier in the same direction (e.g., sodium plus glucose, or sodium plus amino acid).
Symport or co-transport
69
• Movement of a compound in one direction driven by the movement of a second compound in opposite direction (e.g., Na2+ and H+ antiport).
Antiport or counter transport
70
are actively transported from the interior of the tubular epithelial cells to the peritubular space across the basal membrane. Therefore, intra-cellular Na2+ is lowered, creating a chemical gradient for Na2+ (lumen concentration higher) between the tubular lumen and tubular epithelial cell.
Sodium Ions
71
is established for these substances and they are reabsorbed down their concentrated gradient. The extent of their reabsorption depends on the permeability of the tubular epithelium for the solute.
• A chemical concentration gradient
72
are synthesised in the epithelial cells and diffuse into the tubular fluid.
Ammonium ions
73
65% of the reabsorption and secretion take place. Only 35% of the GF leaves the proximal tubule.
Proximal Tubules
74
is less permeable to water and more permeable to urea.
Ascending limb of Loop of Henle
75
• Final concentration of urine takes place in the
collecting tubule.
76
collecting tubule has two functional units
cortical and medullary portion.
77
is impermeable to urea and medullary portion is moderately permeable to urea
Cortical portion
78
Permeability of collecting tubule to water is determined by the concentration of (hormone) in the blood.
Antidiuretic hormone (ADH)
79
Reabsorption and secretion in different regions of tubules
• Water transport is by osmotic diffusion.
o Proximal tubule: 65% reabsorption.
o Loop of Henle: 15%.
o Distal tubule: 10%.
o Collecting duct: 9.3%.
o Urine: 0.7%.
80
provides an expandable reservoir for urine, which is continuously flowing from pelvis of the kidney through ureters.
Urinary Bladder
81
is the process in which the urinary bladder empties when it becomes filled with urine.
Micturition
82
is secreted continuously though at a varying rate and it passes through the collecting ducts into the pelvis of the kidney and carried to the urinary bladder by the ureters.
Urine
83
contain muscles capable of contraction, which helps in propulsion of urine along the tube into bladder
The Ureters
84
increases frequency, and sympathetic stimulation decreases frequency of peristalsis of ureters.
• Parasympathetic stimulation
85
• Parasympathetic stimulation increases frequency, and __________decreases frequency of peristalsis of ureters.
sympathetic stimulation
86
is the elevated level of waste products in the blood, particularly nitrogen-containing compounds like urea and creatinine.
Uremia or azotemia
87
is the chief nitrogenous end product of protein metabolism and is excreted by the kidneys in the urine of mammals. It is also found in the blood and lymph.
Urea
88
is a toxic condition that occurs due to retention of urea is the blood.
Uremia
89
Increased urine formation
• Diuresis:
90
: Increased excretion of urine. It may be due to the deficiency of ADH
Polyuria
91
Reduced excretion of urine
Oliguria
92
Complete cessation of urine formation
Anuria
93
Difficult or painful micturition
Dysuria
94
Slow dropwise painful discharge of urine caused by spasm of urethra and bladder
Stranguria
95
is the measurement of the kidney’s ability to remove substances from the plasma.
Renal clearance
96
are used to determine Renal Blood Flow (RBF), Renal Plasma Flow (RPF), Glomerular Filtration Rate (GFR), Filtration Fraction (FF) and how different substances are handled by the kidney tubules (reabsorbed or secreted) and to compare the kidney function values for diagnostic purposes.
Clearance measurements
97
is used to express the ability of the kidneys to clean or clear the plasma of various substances. e.g., If the plasma passing through the kidneys contains 1 mg of a substance in each ml and 1 mg of this substance is also excreted into the urine each minute, then 1 ml/min of the plasma is cleared of the substance.
Plasma Clearance
98
is an excellent measure of kidney function and the clearance rate of different substances are determined by analyzing the concentration of substance simultaneously in plasma and urine and measuring the rate of urine formation.
Plasma Clearance
99
is another polysaccharide used to estimate GFR.
Mannitol
100
In clinical conditions it can be used to measure GFR and kidney functions. __________ is freely filtered and not reabsorbed by the tubules.
Creatinine
101
is the total amount of substance in the plasma that passes through the kidneys each minute.
Plasma load of a substance
102
Renal mechanism of urine formation and Permeability of the tubules
• Renal mechanism of urine formation
• Renal mechanism of concentrated and dilute urine formation-
• Concentrated urine
103
Permeability of the tubules
High permeability for water and no permeability for sodium, chloride and urea
Descending limb of Loop of Henle
104
Permeability of the tubules
No permeability for water, highly permeable to sodium, chloride and moderately permeable to urea.
Ascending thin limb of Loop of Henle
105
Permeability of the tubules
Permeable to sodium, chloride, low permeability to water and urea.
Ascending thick limb of Loop of Henle
106
Permeability of the tubules
Permeable to sodium, chloride and low permeability for water and urea.
Distal tubule
107
Permeability of the tubules
Sodium reabsorption is stimulated by aldosterone and water and urea reabsorption by ADH.
Cortical collecting tubule,
outer medullary collecting duct and
inner medullary collecting duct:
108
exists where the inflow of fluid runs parallel to, counter to, and in close proximity to the outflow for some distance. These characteristics are common to the anatomical arrangements of the Loops of Henle and vasa recta. In the kidney, two counter current systems operate-
A counter current system of tubules or vessels
109
Counter current mechanism of kidney
Loops of Henle
Counter current multiplier
110
Counter current mechanism of kidney
Vasa recta
Counter current exchanger
111
is permeable to solutes and so the solutes diffuse into the medullary interstitial fluid with retention of water in the tubule, thereby diluting the tubular fluid. This creates a small osmotic gradient between the tubular and peritubular fluids (interstitial fluid). This osmotic gradient is being multiplied vertically by counter current flow in the descending thin limb (permeable for water and not for solutes).
The ascending thick limb of the Loop of Henle
112
Countercurrent exchanger- Vasa recta
is a counter current system in which transport between the outflow and inflow is entirely passive. Vasa recta is permeable to water and solutes through out their length.
Countercurrent exchanger
113
Countercurrent exchanger- Vasa recta
water is drawn by osmosis from the plasma of vasa recta to the hyperosmotic peritubular fluid (created by counter current multiplier) and the solutes diffuse from the peritubular fluid into the vasa recta.
descending limb of the vasa recta
114
Countercurrent exchanger- Vasa recta
solutes diffuse back into the peritubular fluid and water is drawn by osmosis back into the vasa recta. Net result is that the solutes responsible for medullary gradient are mostly retained in the medulla and the vasa recta carry only slightly more solutes than are brought to them.
115
is a mechanism for concentration of urea in the medulla. Urea is concentrated in collecting tubule and diffuses through the walls of collecting tubule into the medullary interstitial fluid. From there, it is reabsorbed in the Loop of Henle and flows with tubular fluid in the ascending limb through distal tubule into collecting tubule and again out of the collecting tubule into the medullary interstitial fluid. Urea circulates several times before it flows into the urine and it causes urea to accumulate in high concentration in medullary interstitium. This counter current multiplier system helps in concentration of urine and also ensures constant excretion of urea when urine output is low.
Recirculation of urea
