Formation Of Urine ( Slide 44 - 164 ) Flashcards
1
Q
- Formation of urine in the nephrons
- Three processes are involved in the formation of urine in the nephrons:
A
Glomerular filtration, Tubular reabsorption, Tubular secretion
2
Q
What is the fluid that is filtered through the glomerular membrane into the Bowman’s capsule?
A
Glomerular filtrate
3
Q
What are relatively impermeable to proteins so that the filtered fluid, glomerular fluid (GF) is essentially protein free and devoid of cellular elements?
A
Glomerular capillaries
4
Q
The glomerular capillary membrane has three layers:
A
- Endothelium of the capillary
- Basement membrane
- A layer of epithelial cells (podocytes) surrounding the outer surface of the capillary basement membrane
5
Q
The endothelial cells lining the glomerulus are perforated(holes) by thousands of small holes called?
A
fenestrae
6
Q
Surrounding the endothelium of glomerular capillaries is the basement membrane composed of a meshwork of ? and ? which can filter large amount of water and small solutes
A
collagen and proteoglycan fibrillae
7
Q
The final layer of glomerular capilliaries 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
A
podocytes
8
Q
Therefore, Glomerular Filtrate must pass through three different layers before it enters the?
A
Bowman’s capsule
9
Q
What are completely impermeable to glomerular membrane?
A
plasma proteins
10
Q
Size of the molecule: Pores in the glomerular membrane allow molecules with a diameter upto?
A
8 nm
11
Q
What are lined with a strong negative charges and electrostatic repulsion of the protein molecules (proteins are electronegative) prevent their filtration?
A
Pores
12
Q
The energy for the filtration is provided by the ? in the form of hydrostatic pressure of the blood inside the glomerular capillaries and the colloidal osmotic pressure of the fluid within the Bowman’s space through the capillary membrane into the Bowman’s capsule
A
heart
13
Q
Colloid osmotic pressure in the blood and the hydrostatic pressure in the Bowman’s space oppose?
A
filtration
14
Q
What pressure in the Bowman’s capsule is negligible due to very low protein content
A
colloidal osmotic pressure
15
Q
What pressure in the glomerular capillaries increases, since 1/5th of the fluid portion of the plasma in the capillaries filters into the capsule increases the protein concentration about 20% as blood passes from arterial to venous end of the glomerular capillaries
A
colloidal osmotic pressure
16
Q
What 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?
A
Filtration pressure
17
Q
Transport of fluid from the Bowman’s capsule to the renal pelvis is accomplished by a difference in the hydrostatic pressure
A
Tubular transport
18
Q
What reabsorption involves transport of water and solutes from the tubular fluid to the peritubular capillaries?
A
Tubular reabsorption
19
Q
What is the transport of solute from the peritubular capillaries to the tubular fluid?
A
Tubular secretion
20
Q
What plays a major role than the secretion in the formation of urine?
A
Tubular reabsorption
21
Q
What percentage of the water in the GF is reabsorbed as it passes through the tubules?
A
90%
22
Q
Basic mechanisms of absorption is done by two process:
A
Active transport and Passive transport
23
Q
What part of tubular wall have a brush border at the luminal surface?
A
Tubular epithelial cells
24
Q
Tubular epithelial cells have a brush border at the luminal surface. It is composed of ? which increases surface area of the lumen.
A
microvilli
25
The base of the tubular epithelial cell rests on the?
basement membrane
26
Tubular epithelial cells are attached to each other near the brush border forming?
tight junction or zona occludens
27
Sodium, glucose, amino acid, calcium, potassium, phosphate and urate ions are actively transported. They are transported through?
carrier proteins
28
Transport by a carrier for a single compound (e.g., sodium) and is unidirectional
Uniport
29
Transport of two compounds on the same carrier in the same direction
Symport or co-transport
30
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
31
What percentage of Na2+ is reabsorbed in the proximal tubule
65%
32
About 65% of Na2+ is reabsorbed in the?
proximal tubule
33
About 65% of Na2+ is reabsorbed in the proximal tubule. The energy required for this mechanism is derived from the ? located in the basolateral membrane of the proximal tubule epithelial cells.
Na2+-K+ ATPase (sodium pump)
34
What compound 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
35
What compound is readily diffuses from the tubular lumen to the peritubular space through tight junction between tubular epithelial cells because of transepithelial electrical potential difference (lumen negative) created by Na2+ transport.
Chloride ion
36
What component in the cell can diffuse through the basolateral membrane to the peritubular space or move into the tubular lumen in counter transport to Cl– diffusion into the cell?
HCO3– (bicarbonate ion)
37
Glucose and amino acid are reabsorbed by?
symport or co-transport
38
Glucose and amino acid are reabsorbed by symport or co-transport. They are coupled with specific carriers that require Na2+ binding and diffuse into the cell. Inside the cell Na2+ and glucose or amino acid separates from the carrier. The Na2+ is actively transported by ? to the peritubular space.
Na2+ – K+ ATPase
39
Glucose and amino acid are reabsorbed by symport or co-transport. They are coupled with specific carriers that require Na2+ binding and diffuse into the cell. Inside the cell Na2+ and glucose or amino acid separates from the carrier. The Na2+ is actively transported by Na2+ – K+ ATPase to the peritubular space. .Glucose and amino acids are then transported by?
facilitated diffusion
40
After the diffusion of solute (Na2+, Cl– , HCO3–, glucose, amino acid) into the peritubular space, what is established? where by a greater osmotic pressure is present in the peritubular space.
osmotic gradient
41
After the diffusion of solute (Na2+, Cl– , HCO3–, glucose, amino acid) into the peritubular space, an osmotic gradient is established, where by a greater osmotic pressure is present in the peritubular space. Therefore, what diffuses from the peritubular lumen and tubular cells into the peritubular space?
water
42
What compound its permeability for the proximal tubule is much less than that of water and more than 50% of the amount of it in the GF continues beyond the proximal tubule?
Urea
43
What compound with a molecular weight of less than 69,000 are reabsorbed in the proximal tubule and not lost in the urine?
Proteins
44
Proteins are reabsorbed by ? and subsequently degraded by cellular lysosomes to amino acids.
endocytosis
45
The amino acids move from the cell to the peritubular space by?
facilitated diffusion
46
What are hydrolyzed at the luminal brush border of proximal tubule and the resultant amino acids is taken into the cell by co-transport mechanism?
Small peptides
47
Several substances are transported from the peritubular capillaries into the interstitial fluid and then to the tubular lumen via the tubular epithelial cells.
Tubular secretion
48
What transport is unique, in that it is reabsorbed in some parts of the tubule and secreted in others? It is reabsorbed in the convoluted portion of proximal tubule and secreted in the straight portion of proximal tubule. It is secreted and reabsorbed in the distal nephron.
K+ transport
49
What ions are synthesised in the epithelial cells and diffuse into the tubular fluid?
Ammonium ions
50
65 % of the reabsorption and secretion take place in what tubule?
Proximal tubule
51
What percentage of the GF leaves the proximal tubule?
35%
52
Permeability of the epithetical cells of descending limb of Loop of Henle is great and occurs by what diffusion? It is highly permeable to water and moderately permeable to urea and Na2+.
simple diffusion
53
What part of loop of henle is less permeable to water and more permeable to urea?
Ascending limb of Loop of Henle
54
They have rudimentary brush border and cells adapted for Na2+ transport against concentration gradient. They are impermeable to water and urea
Thick segment of Loop of Henle and distal tubule
55
active absorption of Na2+ and active secretion of K+ is controlled by?
aldosterone
56
Final concentration of urine takes place in the?
collecting tubule
57
collecting tubule has two functional units:
cortical and medullary portion
58
Portion of collecting tubule that is impermeable to urea?
Cortical portion
59
Portion of collecting tubule that is moderately permeable to urea?
medullary portion
60
Permeability of collecting tubule to water is determined by the concentration of ? in the blood.
Antidiuretic hormone (ADH)
61
Large amount of ADH causes collecting tubule to be highly permeable to?
water
62
In the absence of ADH, very little of ? is reabsorbed in collecting tubule.
water
63
What percentage is reabsorbed in proximal tubule?
65%
64
What percentage is reabsorbed in Loop of Henle?
15%
65
What percentage is reabsorbed in Distal tubule?
10%
66
What percentage is reabsorbed in Collecting duct?
9.3%
67
What percentage of the original water is left in urine, which is excreted?
0.7%
68
What percentage of urea is reabsorbed?
50%
69
What solute is not reabsorbed but some quantities are secreted in proximal tubule?
Creatinine
70
What provides an expandable reservoir for urine, which is continuously flowing from pelvis of the kidney through ureters?
Urinary bladder
71
What is the process in which the urinary bladder empties when it becomes filled with urine?
Micturition
72
What 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
73
What contain muscles capable of contraction, which helps in propulsion of urine along the tube into bladder?
ureters
74
As urine collects in the pelvis, pressure increases which initiates what contraction? beginning from pelvis and spreading down along the ureters to force urine towards bladder.
peristaltic contraction
75
What stimulation increases frequency of peristalsis of ureters?
Parasympathetic stimulation
76
What stimulation decreases frequency of peristalsis of ureters?
sympathetic stimulation
77
At the junction of ureter with bladder, what valve is present which prevents reflux of urine from bladder?
ureterovesicular valve
78
distended. Out flow of urine into the urethra is prevented by ? at the neck of the bladder
sphincters
79
When the pressure in the bladder reaches what mm of water? contraction of bladder wall begins, relaxation of sphincter occurs and urination or micturition occurs
150 mm
80
What nerve fibers leave from spinal cord in 2nd to 4th lumbar nerves to the posterior mesentric ganglion and postganglionic fibres reach the bladder through hypogastric nerves?
preganglionic sympathetic fibres
81
In all mammals, what nerves cause contraction of whole bladder and they are main motor nerves? They are inhibitory to internal sphincter.
parasympathetic nerves
82
What are present in the bladder walls that are stimulated during contraction of urinary bladder?
Receptors
83
What flow through urethra helps to maintain bladder contraction and relaxation of external sphincter?
Urine flow
84
What is the elevated level of waste products in the blood, particularly nitrogen-containing compounds like urea and creatinine?
Uremia or azotemia
85
What 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
86
What is a toxic condition that occurs due to retention of urea in the blood?
Uremia
87
Increased urine formation
Diuresis
88
Increased excretion of urine. It may be due to the deficiency of ADH
Polyuria
89
Reduced excretion of urine
Oliguria
90
Complete cessation of urine formation
Anuria
91
Difficult or painful micturition
Dysuria
92
Slow dropwise painful discharge of urine caused by spasm of urethra and bladder
Stranguria
93
What is the measurement of the kidney’s ability to remove substances from the plasma?
Renal clearance
94
What is used to express the ability of the kidneys to clean or clear the plasma of various substances?
Plasma clearance
95
A substance to measure GFR must be freely filtered at the glomerulus and,should not be reabsorbed or secreted by the tubular epithelium after it enters,the nephron. What is a fructose polysaccharide that is the substance that is most commonly used?
Inulin
96
What is another polysaccharide used to estimate GFR aside from insulin?
Mannitol
97
What is freely filtered and not reabsorbed by the tubules. In some species (not in dogs) about 10% is secreted by the tubules. It can’t be used in birds because it is either secreted or reabsorbed from the tubules to a greater extent.
Creatinine
98
What is used to measure renal plasma flow?
Para Amino Hippuric acid (PAH)
99
What urine is formed by passive water reabsorption from the tubules while many solutes in the tubular fluid are absorbed by active process?
Concentrated urine
100
What urine is formed by absorption of solutes alone and excretion of water in the urine?
Dilute urine
101
Dilution or concentration of urine depends on hypertonicity/osmolality of the interstitial fluid in the?
renal medulla
102
Dilution of the tubular fluid by the thick ascending limb and distal tubules by solute reabsorption which allows formation of?
dilute urine
103
For generating ?, two factors are essential:
- Reabsorption of osmotically active substance by the tubules into the medulla.
- Removal of water from the interstitium by the vasa recta.
hypertonic medullary fluid
104
Normal osmolality of the GF as it enters the proximal tubule is?
300 milli osm/L
105
osmolality in the medullary interstitial fluid is higher reaching a maximum in the inner most regions of the medulla, it increases from?
300 milli osm/L to 1200 milli osm/L
106
the cause for accumulation of sodium chloride in medulla is what flow ? through vasa recta which helps to prevent removal of sodium chloride from the interstitial fluid
sluggish blood flow
107
What system of tubules or vessels 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.
counter current system
108
In the kidney, two counter current systems operate:
- Counter current multiplier– Loops of Henle
- Counter current exchanger– Vasa recta
109
Continued active secretion by the ascending thick limb, concentration of tubular fluid in the descending thin limb and diffusion from the lumen of the ascending thin limb into the medullary interstitial fluid establishes a vertical osmotic gradient. Therefore, each time sodium chloride makes the circuit around the Loop of Henle, this multiples the concentration of sodium chloride in the medulla and hence, Loop of Henle is called as?
Counter current multiplier
110
What 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
111
Blood flow in the vasa recta i ? because an increased rate of medullary blood flow results in decreased time required for diffusion of solute from the ascending limb back to peritubular fluid resulting in gradual loss or wash out of medullary gradient.
sluggish
112
What is a mechanism for concentration of urea in the medulla?
Recirculation of urea
113
What is concentrated in collecting tubule and diffuses through the walls of collecting tubule into the medullary interstitial fluid?
Urea
114
When there is excess of water in the body and a reduction in plasma osmolarity, kidneys can excrete a ? with a concentration as low as 50 mOsm/L. This can be achieved by reabsorbing only the solutes and not water in the distal parts of the nephron.
dilute urine
115
For formation of a ? two basic requirements are essential:
- High level of ADH which increases the permeability of distal tubule and collecting tubule to water.
- High osmolarity of the renal medullary fluid which provides osmotic gradient for reabsorption of water in the presence of ADH.
concentrated urine
116
As fluid flows into the cortical collecting tubule, the amount of water reabsorption is dependent on plasma concentration of ADH. In the presence of high concentration of ADH the cortical collecting tubule becomes highly permeable to water and large amounts of water are?
reabsorbed
117
What is synthesised in the cell bodies of hypothalamic nuclei (supraoptic nuclei) and transported to nerve fibre endings in the posterior lobe of the pituitary where it is stored in the secretory granules. Its release in the blood is controlled by osmoreceptors in the hypothalamus that are close to the supraoptic nuclei. It regulates water conservation.
ADH
118
Fear and pain also causes release of?
ADH
119
What regulates K+ and Na+ concentration. It acts on tubules causing Na+ reabsorption and K+ excretion?
Adrenal cortex
120
Renin is activated by reduced circulating blood volume as in hemorrhage. Decreased sodium concentration in the distal convoluted tubule and sympathetic stimulation also causes release of renin
Renin – Angiotensin – Aldosterone system
121
excretion of in urine is regulated at the proximal tubule by the action of parathyroid and thyrocalcitonin from thyroid?
Ca2+ and PO4
122
What causes decrease in PO4 reabsorption and increase in PO4 excretion in urine. This increases mobilisation of Ca2+ from bone and absorption from intestine resulting in increased plasma Ca2+ level and decreased Ca++ excretion.
Parathyroid hormone (PTH)
123
Myocardial cells of the atria release the ? when the atria are stretched during high volume of blood.
Atrial natriuretic peptide
124
What hormones are produced from kidney regulates erythropoiesis?
Erythropoietin
125
What hormone is produced from kidney acts as blood pressure lowering agents?
Prostaglandin
126
The normal blood pH is?
7.4
127
Any disturbance in the H+ ion concentration leads to imbalance of?
pH
128
Three primary buffer systems are involved in regulation of H+ ion concentration in the body fluids to prevent?
alkalosis or acidosis
129
Three primary buffer systems are involved in regulation of H+ ion concentration in the body fluids to prevent alkalosis or acidosis:
- Chemical acid base buffer systems
- Respiratory regulation of acid base balance
- Renal control of acid base balance
130
- When there is a change in the H+ ion concentration, the body fluids react immediately to minimize the change. Chemical buffers act by converting either strong acids or bases into weaker acids or bases.
Chemical acid base buffer systems
131
This is the most important buffer system in the body. It combines with H+ ions to form carbonic acid in the tubular fluid, which then dissociates to CO2 and H20. The CO2 formed is removed by the lungs and the HCO3– formed in the cells is reabsorbed from the filtrate to the blood.
Bicarbonate
132
It plays a major role in buffering renal tubular fluid and ICF. The two main elements of this chemical buffer are HPO4 2- (base) and H2PO4– (weak acid). Hydrogen ions from strong acids are captured by converting a weak base to a weak acid and strong base captured by conversion of a weak acid to a weak base.
phosphate buffer
133
It is an intracellular buffer present in high concentrations in the blood. Hemoglobin molecule forms the second most important blood buffer and is present in the form of proteinate ions (Hb–). These basic ions, with their weak acids (HHb) form a buffer pair. When an acid is added to the blood.
Protein buffer
134
What is formed by the hydrolysis of glutamine in the presence of enzyme glutaminase in the tubular cells which freely diffuses into luminal fluid and continues with H+ ions to form NH4 + ions. This NH4 + ions combines with chloride ions and is excreted as ammonium chloride in the urine.
Ammonia
135
What system acts as the second line of defense against acid base disturbances?
respiratory system
136
What regulate acid-base balance by excreting either an acidic or basic urine?
kidneys
137
What ions are secreted in the proximal tubule, thick ascending loop of Henle and distal tubule by sodium hydrogen counter transport
H+ ions
138
The filtered what ions ? are not easily reabsorbed across the tubular membrane. The bicarbonates combines with H+ ions to form H2CO3 which then dissociates to form Co2 and H2O. This CO2 moves across the tubular membrane and diffuses immediately into the tubular cell.
bicarbonate ions
139
When excess of ? are secreted, only a small fraction of is excreted in the ionic form (H+) in the urine and the remaining H+ ions combines with buffers such as phosphate and ammonia buffer in the tubular fluid as urine can be acidified to a pH of about 4.5.
H+ ions
140
This buffer system is composed of ammonia (NH3 ) and ammonium ion (NH4+).
Combination of excess H+ with ammonia buffer system
141
The pH of the ? is determined by the rate of conjugate base to their weak acids.
ECF
142
The total amount of buffer base in whole blood including HCO3, Hb and other bases of lesser importance is called ?. These bases are known as metabolic components determining blood pH
buffer base (B.B)
143
The gain of strong acid or loss of base from the ECF is known as?
metabolic acidosis
144
What will be present in metabolic acidosis?
Acidemia
145
there is failure of HCO3– reabsorption and loss in the urine?
Renal acidosis
146
pancreatic juice containing HCO3 is not reabsorbed and is lost
Diarrhoea
147
This process involves the gain of base (OH or HCO3 ions) or loss of strong acid by ECF.
Metabolic alkalosis
148
If excretion of CO2 by the lungs falls below the rate of CO2 production in the body, what develops?
respiratory acidosis
149
When alveolar hyperventilation occurs, the expiration of CO2 may exceed the rate of its production within the body.
Respiratory alkalosis
150
What is a major constituent of all living things. Most of the ions and molecules that make up living matter have chemical and physical relationships with it.
Water
151
What is inversely proportional to the body water content?
Body fat
152
It is in any chemical that dissociates to ions when dissolved in a solution?
electrolyte
153
What is the major cation of ECF?
Sodium
154
If ECF sodium rises, it stimulates the release of ECF and thirst. Water gained by this mechanism, dilutes the ECF thereby restoring normal sodium level. This increases the blood volume and a slight increase in BP, which in turn increases the GFR and excretion of excess sodium and water there by restoring the ECF volume to its normal level.
Short term Control (ADH-Thirst Control System)
155
A deficiency of sodium in the ECF causes increased excretion of water due to inhibition of the release of ADH. A decline in osmolality decreases the GFR with a subsequent increase in reabsorption of sodium and water
Long term Control (Salt hunger/ Sodium ingestion)
156
Many sodium deficient animals have a strong behavioural drive to salt to replace the deficiency of sodium. This is called as ? and is commonly seen in ruminants
salt hunger
157
What is the major cation of intra cellular fluid and about 89% of the total body content?
Potassium
158
What ions are balanced electrically with the chloride and bicarbonate ions?
sodium ions
159
The excretion or reabsorption of sodium ions is accompanied by?
chloride ions
160
In the birds, the ureters transport the urine to the ?, which is the common collection site for digestive, reproductive and urinary organs.
cloaca
161
Avian kidneys are characterized by having two major types of nephrons:
- Reptilian type and
- Mammalian type
162
What are located in the cortex and it lacks the loop of Henle. It has no capacity to concentrate the urine, i.e., there is no tubular transport system and whatever solute and water is present in the filtrate, directly passes to the cloaca.
reptilian type nephrons
163
Type of nephrons have well defined loop of Henle. It has the capacity to concentrate the urine. In this tubular transport system is present.
Mammalian type
164
An unique feature of avian kidney is its ? which provides an extra branch of blood flow to the renal tubules along with peritubular capillaries. Venous blood from vein gives one branch to the kidney and this branch provides the microcapillaries which perfuse the tubules along with peritubular capillaries.
Renal Portal System (RPS)
165
The metabolic end product of protein and amino acids in reptiles and birds is the?
uric acid
166
What is formed in liver and also in kidneys from ammonia. Uric acid is freely filterable at the glomerulus, and it is also secreted by the tubules
Uric acid
167
Renal response to ADH in birds is similar to that of the mammals. In addition to the action of ADH on the tubular cells it also controls the functioning of reptilian and mammalian type of nephrons.
Concentration of avian urine
168
What urine when mixed with faeces is cream coloured and contains thick mucous. The precipitated uric acid is mixed with mucus and mucus facilitates the carrying of uric acid in the urine.
Birds urine
