Chapter 14- Urinary System Flashcards
(137 cards)
1
Q
What is the urinary system?
A
kidneys and structures carrying urine for elimination
2
Q
What are the 2 distinct regions of the kidney?
A
- Renal cortex
- Renal medulla
3
Q
8-18 conical masses whose bases reside at the junction and tip of the papilla
A
renal pyramids
4
Q
What is a nephron?
A
a functional unit of the kidney
5
Q
What are the 2 types of components of a nephron?
A
Tubular and vascular
6
Q
what is the glomerulus?
A
a vascular component of the nephron that filters large volumes of plasma into tubular components
7
Q
what are afferent arterioles?
A
the renal artery subdivided into small vessels that deliver blood to the glomerulus.
8
Q
what is the efferent arterioles?
A
a vascular component of the kidneys that are formed by capillaries rejoining. Their main function is to act as a passageway for unfiltered blood to leave the glomerulus.
9
Q
what are the peritubular capillaries?
A
A second set of capillaries that form from the efferent arterioles. They are the site for exchange between tubular systems and blood.
10
Q
What is the tubular component of the nephron?
A
A hollow fluid filled tube formed by a single layer of epithelial cells
11
Q
list the segments of the tubular component
A
- bowman’s capsule
- Proximal tubes
- Loop of henle
- Distal tubule
- Collecting duct
12
Q
What segment of the tubular component of a nephron surrounds the glomerulus to collect filtrate from capillaries.
1. bowman’s capsule
2. Proximal tubes
3. Loop of henle
4. Distal tubule
5. Collecting duct
A
1.
13
Q
What is the tubular component that collects urine from up to 8 nephrons into a duct to empty into the renal pelvis
1. bowman’s capsule
2. Proximal tubes
3. Loop of henle
4. Distal tubule
5. Collecting duct
A
5
14
Q
What is the tubular component that is highly coiled and lies within cortex.
1. bowman’s capsule
2. Proximal tubes
3. Loop of henle
4. Distal tubule
5. Collecting duct
A
4
15
Q
What is the tubular component that filtered fluid enters second and is highly coiled/convoluted within the cortex
1. bowman’s capsule
2. Proximal tubes
3. Loop of henle
4. Distal tubule
5. Collecting duct
A
2
16
Q
What is the tubular component that is a hairpin loop that dips into the renal medulla
1. bowman’s capsule
2. Proximal tubes
3. Loop of henle
4. Distal tubule
5. Collecting duct
A
3
17
Q
What are the 2 types of nephrons?
A
Cortical and juxtamedullary
18
Q
Cortical nephrons are the most abundant type of nephrons
True/False
A
True
19
Q
Compare and contrast the two types of nephrons
A
Cortical nephrons have glomerulus that lie in the outer layer of the renal cortex with loops of Henle that dip only slightly into the renal medulla. Juxtamedullary nephrons have glomerulus that only stay in the inner parts of the renal cortex and have loops of Henle that dip far into the renal medulla.
20
Q
What are vasa recta?
A
They are a structure that is formed by pertibular capillaries of juxtamedullary nephrons only. They run alongside the Henle loop.
21
Q
cortical nephrons have vasa recta
True/False
A
False.
Their peritubular capillaries entwine around the henle loop but do not form a vasa recta.
22
Q
Do the proximal/distal tubules of juxtamedullary nephrons have vasa recta?
A
No, the peritubular capallaries just intertwine with the structures like in the cortical nephrons.
23
Q
What are the 4 basic nephron functions?
A
Glomular filtration
Tubular reabsorbtion
Tubular secretion
Urine excretion
24
Q
Describe what globular filtration is
A
The process of blood being filtered through glomular capillaries in the glomerulus into the Bowmans capsule.
25
How much blood that enters the kidney gets filtered?
20%
26
Describe what tubular reabsorbtion is
As the “filtrate” flows through the tubules the substances that the body wants get returned to the peritubular capillaries
27
Describe what Tubular Secretion is.
The secretion of solutes from the peritubular capillaries into the proximal/distal tubules
28
Why do we need a second mechanism of selective transfer (aka tubular secretion)
Not sure….read 497
29
Define urine excretion
The elimination of substances from the body in the urine.
30
List the 3 layers that make the glomerular membrane
1. Glomerular capillary wall
2. Basement membrane
3. Podocytes
31
Describe the glomerular capillary wall
A single layer of flattened endothelial cells that are perforated by many pores.
32
What are fenestrations?
Pores between endothelial cells and on endothelial cells
33
What purpose do the fenestrations on the glomerular capillary walls serve?
They make the layer 100x more permeable than capillaries in other places
34
Describe the basement membrane
Layer composed of glycoproteins and collegen between the glomerulus and Bowmans capsule. The composition allows it to filter out smaller proteins.
35
What kind of charge does the basement membrane have and how does it effect filtration?
It has a negative charge and which blocks small protiens that also have negative charges.
36
Describe podocytes
Epithelial cells that surrounds the glomerular
37
What is the 1st step of urine formation?
Ultra filtration
38
What is ultra-filtration?
Passive movement of fluid from the glomerular capillaries into the Bowmans space.
39
The fluid that moves during ultra-filtration has proteins in it.
True/False
False it is protein free
40
List the factors that influence filtration
Size of particle being filtered
Charge of particle being filtered
Starling forces
41
How are glomerular capillaries different from any other capillary?
Filtration across the capillaries that make up the glomerulus are generally the same as filtration with any other capillary except
1. Glomerular capillaries are more permeable so more fluid gets filtered for a lower pressure
2. The forces are set up so that they filter across the entire capillary which other capillaries don’t do.
42
What is oncotic pressure?
Osmotic pressure exerted by proteins in a vessel (tubules) plasma that draws in water.
43
What is hydrostatic pressure?
The general principle that describes the pressure exerted by a stationary fluid on an object
44
Oncotic pressure and hydrostatic pressure work together
True/false
False
They oppose each other
45
What is osmosis?
The transport of water across a membrane in relation to impermeable solute.
46
What do starlings forces describe?
The movement of water between capillaries and tissues
47
List the forces that influence filtration.
1. Glomerular capillary hydrostatic BP
2. Plasma-colloid oncotic pressure
3. Bowmans capsule hydrostatic pressure
4. Bowmans capsule oncotic pressure
48
What is glomerular capillary hydrostatic pressure?
It is one of the forces involved in glomerular filtration. Specifically it is the pressure exerted by blood within the capillaries and favors filtration.
49
Why is glomerular capillary pressure higher than the pressure found in other arteries?
The afferent arteriole leading into the glomerulus has a large diameter compared to the efferent arteriole exiting the glomerulus. Because the blood can flow faster than it can flow out the pressure is higher. This is the main force to push fluid out of the glomerulus into the bowmans capsule.
50
What is plasma oncotic pressure?
Plasma membrane proteins are in the glomerular capillaries and cannot filter into the Bowman’s Capsule. So the concentration of H2O is higher in the Bowman’s Capsule. Osmosis creates a pressure that wants water to flow into the glomerular capillaries. This is a force that opposes filtration. “Pressure caused by the unequal distribution of plasma proteins across the glomerular membrane. “
51
What is Bowman’s capsule hydrostatic pressure?
The pressure exerted by fluid in the initial parts of the tubule. It is a force that pushes fluid out of the Bowman’s capsule which therefore opposes filtration.
52
What is the net filtration pressure for filtration?
It is 10 mm Hg, as it is the difference of the pressure between forces favoring filtration and opposing filtration.
53
What is the Glomerular Filtration Rate?
The actual rate of filtration that depends on the net filtration, surface area, and permeability.
54
List where the pressure favors filtration.
Bowmans Capillary, afferent arteriole, efferent arteriole
55
List where the pressure favors reabsorbtion
Peritubular capillary
56
What are the 2 types of control for making adjustments to the Glomerular Filtration rate?
Sympathetic and Auto-regulation
57
Describe general control of the GFR
The one thing that can be reliable controlled to alter the GFR is the glomerular capillary pressure. The pressure in the glomerular capillaries depends on the systemic arterial pressure and the resistance from the afferent arteriole. If afferent resistance increases then less blood flows into the glomerular capillaries which decrease the GFR.
58
In theory…
How would an increase in arterial pressure affect the GFR?
Why would this be bad?
GFR would increase
This would be bad because that would mean that with any small fluctuation in arterial pressure the GFR would also experience changes when we want there to be constant filtration.
59
Describe auto-regulation.
It is the mechanism that maintains constant GFR despite arterial blood pressure changes. It does this by vasocontricting/vasodialating as needed in response to the afferent arteriole pressure.
60
If the afferent arteriole blood pressure increase what would happen to the GFR?
How would auto-regulation counter this?
An increase in BP is an increase in blood flow. The GFR would also increase but the auto-regulation mechanism would trigger vasoconstriction to inhibit blood flow in to the glomerulus to compensate.
61
Briefly describe sympathetic control of the GFR.
Long term regulation of blood pressure by the sympathetic nervous system.
(Activate sympathetic => vasoconstriction)
62
What are the two mechanisms that contribute to auto-regulation?
Myogenic and tubuloglomerular
63
What is the myogenic mechanism?
Using the property of smooth muscle that responds to stretch by contracting. So if the afferent arteriole is stretched it will automatically retract.
64
What is tubuloglomerular feedback?
An autoregulation mechanism that senses the change in salt.
65
If there is an increase in afferent arteriole blood pressure describe how tubuloglomerular feedback reacts.
An increase in blood pressure means an increase in blood that gets filtered into the distal tubule. With that comes an increase in salt. Specifically that salt increase will be detected by Macula Densa in the distal tubule. The Macula Densa will release ATP that will trigger the vasoconstriction of the afferent arterioles. The constriction with decrease flow into glomerular capillaries and decrease blood filtered to normal.
66
What gets filtered out of the blood via the glomerulus?
Everything except proteins
67
If everything gets filtered out of the blood how do we get any nutrients?
Things get reabsorbed very selectively
68
Where does reabsorption occur?
The tubules
69
Slide 15 has a picture. Label all the parts of the tubule.
70
List the barriers in order that a substance has to travel across to get reabsorbed into the capillaries. (Transepithelial transportation)
Luminal cell membrane, cytosol, basolateral cell membrane, interstitial fluid, capillary cell wall
71
Transepithelial transportation is passive
True/false
False
It can be active or passive. Specifically we actively reabsorb Na+.
72
How is Na+ actively transported?
With a Na+/K+ ATP pump out the basolateral cell membrane.
73
Where is the one place Na+ cannot be reabsorbed?
Decending loop of henle
74
What role does sodium (Na+) reabsorbtion in the proximal tubules play?
Assists in the reabsorbtion of other molecules
75
What role does reabsorbtion in the distal/collecting tubules play?
Key role in regulating the ECF volume which affects long term blood pressure control.
76
What role to granular cells play in GFR control?
They are the cells that sense the drop in arterial blood pressure by detecting stretch.
77
What is the main hormonal regulatory system for Na+.
Renin-angiotensin aldosterone system (RAAS)
78
What are the 3 inputs that granular cells respond to with increased renin secretion?
1. Stretch
2. Decrease in NaCl (this is done by the macula Densa cells)
3. Drop in BP
79
List the RAAS mechanism beginning with renin and ending with aldosterone.
Renin converts angiotensinogen into angiotensin I. Angiotensin-converting enzyme turns angiotensin I into angiotensin II in the lungs. Angiotensin II triggers the release of aldosterone from the adrenal cortex.
80
Where does aldosterone get released?
The adrenal cortex. It acts on the principal cells in the distal and collecting tubules.
81
How does aldosterone trigger increase of Na+ reabsorption.
It promote the insertion of more Na+ leak channels into the luminal membrane and more Na+/K+ channels into the basolateral side.
82
What does aldosterone act on?
Principle cells in the distal/collecting tubules
83
How do more leak channels and more Na+/K+ channels increase Na+ reabsorption and water retention?
The increase in leak channels allows for more Na+ to leak into the cell dividing the interior of the distal/collecting tubule (urine channel) and the peritubular capillary (regular blood supply). From there the Na/K pump can pump the Na out of the cell to the capillary. That is the increase in Na reabsorption. (Not sure about the water retention)
84
What will passively travel with Na+?
Cl- because they are usually bound.
85
RAAS is a negative feedback loop.
True/false
True
The release of renin is triggered by a drop in Na, drop in BP, and drop in blood volume. But when salt increases again those triggers go away stopping the release of renin.
86
Describe natriuretic peptides
Peptides produced by the heart that cause more Na+ and H2O to be excreted in the urine.
87
The reabsorption of glucose and amino acids is done with
Secondary active transport
88
How is glucose reabsorbed?
A symporter carrier
89
What is a symport carrier?
A co-transporter in the plasma membrane that transport molecules in in the same direction as the driving ion
90
The concentration of glucose inside the cell is the same as the concentration of glucose in the plasma. How then is glucose passively transported?
The Na+ gradient drives Na+ down it’s gradient into the plasma using the symporter channels that bind glucose at the same time and release it to the plasma even though it’s against it’s concentration gradient.
91
Where does glucose reabsorption take place?
Proximal tubule
92
When the all carrier protein binding sites are occupied and the rate of transport of a substance is maxed.
Tubular Maximum
93
What happens to extras substance when the tubular maximum is reached?
It is excreted in the urine
94
The plasma concentration at which the tubular maximum is reached and the substance is excreted in the urine.
Renal threshold
95
80% of water reabsorption is unregulated
True/false
True
96
Water is reabsorbed _________
Passively
It follows Na+
97
Where does water reabsorption occur?
65% in the proximal tubule
15% in the loop of henle
20% in the distal tubules
98
Where is water reabsorption actually regulated?
The AQP-2 channels in distal tubules by hormones
99
What hormone helps regulate water reabsorption
Vasopressin
100
Water can also diffuse out of the cell via osmosis because in the peritubular capillaries the amount of proteins is lower and the amount of water is lower than in the tubules
True/false
False
While water does diffuse out of the cells lining the tubules into the capillaries it is because in the capillaries there are more protiens and less water.
101
What is urea?
A waste product from the breakdown of proteins
102
Why does urea get reabsorbed?
H2O gets reabsorbed a lot so then there is not a lot of water compared to urea in the tubule. By the end of the tubule the concentration of urea is so big that it is diffuses down its concentration gradient into the capillaries
103
How much urea is reabsorbed?
50%
104
What does vasopressin do?
Increases the permeability of the distal and collecting tubules to H2O
105
How does vasopressin increase H2o reabsorption?
Insertion of AQP-2 channels into luminal membrane
106
Without vasopressin what would be impermeable to water?
Collecting ducts and distal tubule
107
What are the most important substances secreted by the tubules?
H+ ions, K+ ions, and organic ions
108
Why is the secretion of H+ ions important?
Maintains the acid-base balance
109
_____ are secreted into tubular fluid through intercalated cells
H+ ions
110
______ secretion occurs in the distal and collecting tubules in the principal cells
K+
111
How does K+ secretion work?
When the Na+/K+ pump transfers Na+ out of the cell it also transfers K+ into the cell. This creates a high concentration in the cell that diffuses into the tubule through a leak channel. This also keeps K+ concentration low in the interstitial fluid which promotes K+ to come out of the blood.
112
What is the most important regulator of K+ secretion
Alsosterone, I think because aldosterone regulates the reabsorbtion of Na+ which is inversely proportional to K+ intake
113
The volume of plasma completely cleared of a substance by the kidneys
Plasma clearance
114
What is clearance rate?
The amount of blood that gets reabsorbed without a given substance.
115
What is plasma clearance?
The volume of plasma completely cleared of a substance by the kidneys per minute
116
What does a clearance rate equal to the GFR indicate?
That the substance was not reabsorbed. AKA all the substance was discarded.
117
What is an example of a substance that does not get reabsorbed?
Insulin/creatine
118
What does a clearance rate of 0 mean?
That a substance was fully reabsorbed
119
What does a GFR greater than the clearance rate mean?
The substance was partially reabsorbed
120
The substance was partially reabsorbed
121
What does it mean if the clearance rate is greater than the GFR
The substance is both filtered and secreted
122
In theory the concentration of our urine should be in in equilibrium with the concentration of the rest of our body. Explain why.
The driving force for H2O absorption throughout the tubules is the osmotic gradient between the tubular lumen and the interstitial fluids. If the interstitial fluids had an osmolarity equal to the rest of the body then water would diffuse until in equilibrium between the structure.
123
If your kidneys worked like they are theoretically supposed to why would that be bad?
We would have no way to get rid of extra water and no way to hold on to water if we were low.
124
What allows us to produce kidneys at ranging concentrations
Vertical osmotic gradient
125
What establishes the vertical osmotic gradient?
Long juxtamedullary nephrons
126
Does the medulla or the cortex have a lower concentration of H2O
Medulla
It is a osmolarity of 600-1200 which means there is less water/more solutes
127
Where does fluid in the descending loop of Henle come from?
The proximal tubule
128
Where does the fluid leaving the ascending loop of Henle go?
The distal tubules
129
The descending loop of henle is permeable to _______ but not _______
H2O Na+
130
The ascending loop of Henle is impermeable to ________ but actively transports _________
H2O Na+
131
Why is the descending loop so permeable to H2O
There an abundant amount of AQP-1 channels always open
132
Describe countercurrent multiplication
The ascending limb actively pumps Na+ out but water can’t follow which gives it a higher concentration of H2O (lower osmolarity). This also makes the osmolarity in the interstitial fluids high. This pull water from the descending limb into the interstitial fluid. Eventually an equilibrium is reached with high osmolarity (less water) in the descending loop and low osmolarity (more water) in the ascending loop. As new fluids enter the process above is repeated until the osmolarity are more extreme. (Reading pg 522 helped me understand)
133
Which 2 tubules are impermeable to H2O?
How can they become permeable?
Collecting and distal
Vassopressin
134
Acid-base balance refers to…
The regulation of free hydrogen ions
135
136
The majority of reabsorption occurs in the….
Proximal tubule
137
Where does most of the variable reabsorption occur?
Distal and collecting ducts
