Chapter 14- Urinary System Flashcards
(180 cards)
1
Q
What are the kidney’s functions?
A
maintain H2O balance and proper osmalarity of body fluids
Regulate ECF ions
Maintain plasma volume
Maintain acid-base balance
Eliminating metabolic waste
Produce erythropoietin and renin
Converting Vit D to its active form
2
Q
What does the urinary system consist of?
A
- urine forming organs
- Structures that carry urine from kidney to outside body
3
Q
What are the urine forming organs?
A
Kidneys
4
Q
What are the structures that carry urine from kidneys to outside the body?
A
Ureters
Urinary bladder
Urethra
5
Q
What is each kidney supplied with (blood vessels)?
A
A renal artery and a renal vein
6
Q
What do the kidneys act on to produce urine?
A
Plasma
7
Q
What is the basic anatomy of the kidney?
A
Outer cortex and inner medulla, urine drains into the renal pelvis (medial inner core of kidney)
8
Q
What are the ureters function?
A
Carry urine from kidneys to the bladder
9
Q
What are the ureters walls made from?
A
Smooth muscle
10
Q
What is the urinary bladder’s function?
A
Temporarily store urine
-Periodically empties to the outside of the body
11
Q
What is the anatomy of the bladder?
A
Hollow, distensible, smooth muscle-walled sac
12
Q
What is the urethra function?
A
Convey urine to the outside of the body
13
Q
What is the nephron?
A
Functional unit of the kidney
14
Q
How many nephrons per kidney
A
~1 million nephrons/kidney
15
Q
What are the two coponents of the nephron?
A
- Vascular component
- Tubular component
16
Q
What creates the two distinct regions of the kidney (Outer cortex, inner medulla)?
A
Arrangement of nephrons
17
Q
What is the appearance of the outer region: renal cortex?
A
Granular
18
Q
What is the inner region: renal medulla made up of?
A
Striated triangles called renal pyramids
19
Q
What makes up the Vascular component?
A
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
20
Q
What makes up the tubular component?
A
Bowman’s capsule
proximal tubule
Loop of Henle
Distal tubule and collecting duct/tubule
Juxtaglomerular apparatus
21
Q
What is the Juxtaglomerular apparatus?
A
Part of nephron that produces substances involved in the control of kidney function
-Made up of efferent and afferent arterioles, and the distal convoluted tubule
22
Q
What is the glomerulus?
A
Ball of capillaries that filters water and solutes as the blood passes through it
23
Q
What arterioles deliver blood to glomerulus?
A
Renal artery—-> Afferent arterioles
24
Q
What arterioles transports blood away from glomerulus?
A
Efferent arterioles
25
What do efferent arterioles break down into?
Peritubular capillaries ----> Renal vein
-Surround tubular part of nephron
26
What is the tubular component?
Hollow, fluid-filled tube formed by a single layer of epithelial cells
27
What are the parts of the Loop of Henle?
1. Descending limb
2. Ascending limb
28
Where do all nephrons originate?
Cortex
29
What specifically give the granular appearance of the cortex?
Glomeruli
Bowman's capsule
30
What are the kinds of nephrons?
1. Cortical
2. Juxtamedullary
31
What kind of nephrons are 80% of nephrons?
Cortical
32
Where do glomeruli of cortical nephrons lie?
Outer layer of cortex
33
Where do glomeruli of juxtamedullary nephrons lie?
inner layer of cortex
34
What is the Juxtamedullary nephrons function?
Preform most of urine concentration
20% are this type
35
What efferent arterioles belong to Juxtamedullary nephrons?
Long looping vasa recta
36
What efferent arterioles belong to cortical nephrons?
peritubular capillaries
37
What are the three basic kidney processes?
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
38
How much is filtered through glomerular filtration?
180L/day
39
How much is reabsorbed through tubular reabsorption?
178.5L/day
40
How much of cardiac output do the kidneys receive?
20-25%
41
What is the total blood flow through the kidneys?
1L/min
42
How much of the plasma that enters the glomerulus is not filtered?
80%
43
Where does the non-filtered plasma leave the glomerulus?
Through the efferent arteriole
44
What are the 3 layers of the glomerular membrane?
1. Glomerular capillary wall
2. Basement membrane
3. Inner layer of Bowman's capsule
45
What kind of capillary is the Glomerular capillary wall?
Fenestrated
46
Why is the Glomerular capillary wall fenestrated?
More permeable to water and solutes than any other capillary in the body
47
What does the inner layer of the Bowman's capsule consist of?
Podocytes that encircle the glomerulus tuft
48
What do podocytes surround?
Basement membrane of the glomerulus
49
What do podocytes terminate in?
Foot processes
50
What are the clefts between podocytes called?
Filtration slits
51
What is the purpose of filtration slits?
They are where the filtrate enters the Bowman's capsule
52
What kind of process is Glomerular filtration?
Passive process
53
What kind of pressure forces the fluids/solute through a membrane in glomerular filtration?
Hydrostatic pressures
54
Why are Glomeruli efficient filters?
-Filtration membrane has a large surface area
-Very permeable to water and solutes
-Glomerular pressure is higher than other capillaries
55
What are the 3 physical forces involved in Glomerular filtration?
1. Glomerular capillary blood pressure
2. plasma-colloid osmotic pressure
3.Bowman's capsule hydrostatic pressure
56
What magnitude is Glomerular capillary blood pressure?
55mmHg
57
What magnitude is Plasma-colloid osmotic pressure?
30mmHg
58
What magnitude is Bowman's capsule hydrostatic pressure?
15mmHg
59
What is Glomerular capillary blood pressure?
Fluid pressure exerted by blood within
glomerular capillaries
60
What does Glomerular capillary blood pressure depend on?
Resistance to blood flow offered by afferent and efferent arterioles
61
What is the major force producing glomerular filtration?
Glomerular capillary blood pressure
62
What is Plasma-colloid osmotic pressure caused by?
Caused by unequal distribution of plasma proteins across glomerular membrane
63
What is the effect of Glomerular capillary blood pressure?
Favours filtration
-forces fluid out of globular capillary into bowman's capsule
64
What is the effect of Plasma-colloid osmotic pressure?
Opposes filtration
-Draws fluid into capillaries and out of the bowman's capsule
65
What is Bowman's Capsule Hydrostatic Pressure?
Pressure exerted by fluid in initial part of tubule
66
Bowman's Capsule Hydrostatic Pressure function?
Push fluid out of bowman's capsule
67
What is the effect of Bowman's Capsule Hydrostatic Pressure?
Opposes filtration
-Draws fluid into capillaries and out of the bowman's capsule
68
What is Net filtration pressure?
The difference between force favouring filtration and forces opposing filtration
Favouring= Glomerular Capillary BP
Opposing= Plasma-colloid pressure and Bowman's Capsule Hydrostatic pressure
69
What is the formula for Net filtration pressure?
Net fil. pres.= glomerular capillary blood pressure – (plasma-colloid osmotic pressure + Bowman’s capsule hydrostatic pressure)
--> 55mmHg- (30mmHg+15mmHg)= 10mmHg
70
How much of plasma in filtered through glomerular filtration?
20%
71
Does glomerular filtration filter proteins?
No it is protein-free
72
How many millilitres is filtered per minute with glomerular filtration?
125mL/min
73
What does glomerular filtration rate depend on?
1. Net filtration pressure
2. Available glomerular surface area
3. How permeable the glomerular membrane is
74
What are unregulated influences on the GFR?
Plasma-colloid osmotic pressure
Bowman's capsule hydrostatic pressure
-They are constant but can change (NOT CONTROLLED)
75
What can cause the Plasma-colloid osmotic pressure to change?
Severely burned patient
Dehydrating diarrhoea
76
How does a severely burned patient affect the GFR?
GFR increases
77
How does dehydrating diarrhoea affect the GFR?
GFR decreases
78
What can cause the Bowman's Capsule hydrostatic pressure to change?
Obstructions like kidney stones
79
What pressure is controlled to adjust the GFR and suit the body's needs?
Glomerular capillary blood pressure
80
What pressures remain constant?
Plasma-colloid osmotic pressure and Bowman’s capsule hydrostatic pressure
81
What are the 2 major control mechanisms on glomerular blood pressure to alter GFR?
1. Autoregulation
2. Extrinsic sympathetic control
82
What is the purpose of auto regulation?
It aims to prevent spontaneous changes in GFR
-GFR kept within a narrow range despite changes in BP
83
Autoregulation is what kind of regulatory mechanism?
Intrinsic
84
How does auto regulation work?
Changing the diameter of the afferent arteriole which changes BP in glomerular capillary
85
If no auto regulation mechanisms what would happen to GFR?
Increase BP increase GFR
Decrease BP decrease GFR
86
What happens when the afferent arteriole undergoes vasoconstriction? (blood flow to glomerulus decreases)
Decrease glomerular capillary BP ---> Decreases Net filtration pressure --> Decreases GFR
87
What happens when the afferent arteriole undergoes vasodilation? (blood flow to glomerulus increases)
Increase glomerular capillary blood pressure ---> increases net filtration pressure ---> Increase GFR
88
What are the two intrarenal mechanisms that contribute to auto regulation?
1. Myogenic mechanism
2. Tubuloglomerular feedback TGF
89
What is myogenic mechanism?
Stretch causes afferent arteriole smooth muscle to contract when BP is increased
-less stretch=relaxation
90
What is the macula densa?
Area of specialised tubular cells that monitor the NaCl concentration of the tubular fluid
91
What is Tubuloglomerular feedback?
Mechanism that involves the juxtaglomerular apparatus that allows the nephron to monitor salt level and use ATP and adenosine to regulate GFR
92
What does adenosine constrict?
Afferent arteriole
93
What happens to the TGF when salt increases (caused by GFR increase)?
1. Macula Dense cells release ATP and degrade to adenosine.
2. Afferent arteriole constricts (bc of adenosine)
3. Glomerular blood flow is reduced and GFR lowers
94
Do increases in BP that occur normally like from excercise affect GFR?
No, GFR doesn't increase/decrease
-prevents needless loss of water and solutes
95
What is the purpose of extrinsic sympathetic control on GFR?
It aims to regulate arterial blood pressure long-term
96
What overrides auto regulation mechanisms?
Extrinsic sympathetic control
-Deliberate change in GFR despite normal BP range
97
What mediates extrinsic control and where is the input sent to?
Sympathetic nervous system sends input to afferent arterioles
98
What extrinsic control reduces urine output?
Barorecptor reflex
e.g Blood loss decrease plasma volume
99
What substances are filtered by the kidneys?
Water
Sodium
Glucose
Urea (waste)
Phenol (waste)
100
What is tubular secretion?
The transfer of substances from tubular lumen into peritubular capillaries
-highly selective and variable process
101
What 5 barriers do reabsorbed substances cross during tubular secretion?
1. Leave tubular fluid by crossing luminal membrane
2. Pass through the cytosol, to get from one side of the tubular cell to the other
3.Cross basolateral membrane (enter interstitial fluid)
4.Diffuse through interstitial fluid
5.Penetrate capillary wall to enter blood plasma
102
All tubular fluid components are the same concentration as in plasma, EXCEPT for?
Proteins
103
Where does waste material go?
It isn't reabsorbed into blood so it stays in the tubule
104
What are the two types of reabsorption?
Passive: No energy, down electrochemical gradient
Active: energy needed, against electrochemical gradient
105
What is the essential mechanism for Na+ reabsorption?
Na-K ATPase pump
-Active transport
106
How much of the kidney's total energy is spent on Na transport?
80%
107
What follows reabsorbed sodium by osmosis?
Water
108
What mainly effected by water following reabsorbed sodium?
Has an effect on blood volume and blood pressure
109
Why is Na reabsorption important?
If body Na is controlled, ECF water volume is controlled which controls blood volume and blood pressure
110
What other substances are coupled to the movement of Na reabsorption?
Glucose, amino acids and Cl-
111
What is the most abundant cation in filtrate and ECF?
Sodium Na+
112
Where is the fine tuning of Na reabsorption carried out? (too much or too little Na)
Distal tubule
Too much Na--->Less reabsorbed, more excreted in urine
Too little Na--->More reabsorbed
113
What do ECF volume changes affect?
Blood pressure
114
How is Na reabsorption fine-tuned?
RAAS
115
What is RAAS?
Renin-angiotensin-aldosterone system
Most important Hormone system involved in Na regulation through use of Juxtaglomerular apparatus granular cells
116
What do JGA granular cells release?
Renin
117
What is Renin?
Hormone that helps regulate BP and maintain normal sodium levels
118
What does Renin do?
Converts angiotensinogen into angiotensin I
119
What is angiotensin-converting enzyme?
Enzyme that converts Angiotensin I into angiotensin II
120
What does Angiotensin II stimulate the secretion of?
Aldosterone
121
What are the functions of the RAAS?
1. Increases Na absorption, promotes water retention (negative feedback system)
2. Potent constrictor of systemic arterioles
3.Stimulates thirst
4. Stimulates vasopressin secretion
122
What is aldosterone?
Hormone that acts on last portion of distal convulsed tubules and collecting ducts
123
What does aldosterone do?
Increases apical membrane Na channels
Creates more basolateral Na/K ATPase pumps
124
What happens to Na reabsorption when there is Low ECF volume and Low BP?
More renin is released which leads to more aldosterone released. More aldosterone=more Na reabsorbed and greater volume in ECF
125
What happen when there is High ECF volume in Na reabsorption?
Less renin is released which leads to less aldosterone released. Less aldosterone= Less Na reabsorbed and more body volume lost in urine
126
What is Atrial Natriuretic peptide (ANP)
Hormone opposite to aldosterone, it INHIBITS Na reabsorption
127
What secretes ANP?
Atria
128
What is ANP secreted in response to?
Being stretched by Na retention
Expansion of ECF volume
Increase is arterial pressure
129
What does ANP release promote?
1. Natruresis (Loss of Na)
2. Diuresis (Increase urine production)
3. Hypotensive effects
All help to correct the OG stimulus that brought about release of ANP (negative feedback)`
130
What is reabsorption of glucose and amino acids dependent on?
Sodium, they are reabsorbed by secondary active transport
131
How much water reabsorbed is UNCONTROLLED?
80%
65%- reabsorbed in proximal tubule
15%-Reabsorbed in loop of henle
132
How is the other 20% of water reabsorbed in a controlled way?
Under hormonal control of Vasopressin or ADH
133
What do the proximal tubule and loop of henle contain to allow water reabsorption?
Aquaporins (water channels)
134
How is bulk flow enhanced?
increased plasma colloid osmotic pressure of peritubular capillaries
135
Which part of the nephron regulates H2O reabsorption via vasopressin?
Distal portion
136
What happens to waste products the more water is reabsorbed?
Waste products become more concentrated, remain in tubular fluid and are excreted in urine
137
Why can't waste products be reabsorbed?
They cannot permeate the tubular wall
138
Where is Hydrogen secreted?
proximal, distal and collecting tubules
139
Where are potassium ions secreted?
Only is distal and collecting tubules under the control of aldosterone
140
Why is potassium ion secretion important?
Keeps plasma K at appropriate concentration to maintain normal membrane excitability
141
Where are organic ions secreted?
Only in proximal tubules
142
What is potassium ion secretion?
Movement of K from capillaries to interstitial fluids into tubular cell via the pump and out via ion channels into urine
143
Where are K channels located?
1. Basolateral membrane (proximal tubule and loop of Henle)
2. Luminal membrane (Distal portions)
144
What happens to K if channels are on basolateral membrane?
K is recycled
145
What happens to K is channels are on luminal membrane?
K is secreted
146
What two separate things does aldosterone dually control?
K secretion and Na reabsorption
147
What does Dual control mean?
If one pathway is activated it still affects the other one
148
If the aldosterone pathway is activated for decreased Na what would happen to K concentrations?
They would decrease
149
What is the Body fluids osmolarity when there is normal fluid balance and solute concentration?
300mOsm/L
=body fluids (ECF) are Isotonic
150
When there is too much H2O relative solutes?
ECF is hypotonic
Cells>ECF
-too dilute
151
When there is a water deficit relative to solutes?
ECF is hypertonic
Cells
152
What does the kidneys urine secretion concentration depend on?
Body's state of hydration
153
Where is the vertical osmotic gradient maintained?
Interstitial fluid of renal medulla
154
What is the vertical osmotic gradient?
Concentration of interstitial fluid of the medulla of each kidney and progressively increases
300mOsm/L ---> 1200mOsm/L
155
What does the vertical osmotic gradient follow?
Hairpin loop of Henle deeper and deeper into medulla
deeper=higher mOsm/L
156
What establishes the medullary vertical osmotic gradient ?
Countercurrent multiplication system
157
What is Countercurrent multiplication ?
Fluid in one tube flows the opposite way in
the adjoining tube
158
What is the descending limb highly permeable to?
Water
159
What is the descending limb NOT highly permeable to?
Sodium
160
What does the ascending limb actively transport out of the tubular lumen and into the surrounding interstitial fluid?
Sodium chloride NaCl
161
What is the ascending loop impermeable to?
Water
-Water doesn't follow salt via osmosis
162
What is the role of Vasopressin?
increases the permeability of the tubule cells to water
163
Where is 65% if water reabsorption obligatory?
proximal tubule
164
Why does water reabsorption vary in the distal tubule and collecting duct?
It is based on secretion of vasopressin
165
Where is vasopressin produced and released?
produced in the hypothalamus
and released from the posterior pituitary
166
What does vasopressin act on?
Distal tubule
Collecting duct
167
How does Vasopressin work on tubule cells?
cyclic AMP mechanism
168
What happens to urine excretion during a water deficit?
vasopressin is increased so H2O can b reabsorbed by peritubular capillaries and conserved for odies
-small quantity of Concentrated 1200mOsm/L urine leaves collecting tubules
169
What happens to urine excretion during a water excess?
Vasopressin is decreased so no water is reabsorbed in collecting tubule and large quantity of dilute urine is excreted 100mOsm/L
170
What is osmotic diuresis?
Increased urine production containing increased excretion of water AND solute
171
In diabetes mellitus what solute is excreted?
Glucose (not reabsorbed as it excels reabsorption capacity)
-Sweet urine
172
What is water diuresis?
Increased urine with little increased solute
Caused by: excess water intake or diabetes insipius
173
What is Micturition?
The action of urinating
174
What controls micturition (urine release)?
Sphincters:
1. Internal urethral sphincter
2. External urethral sphincter
175
What is the internal urethral sphincter made from?
Smooth muscle
176
What controls the internal urethral sphincter?
parasympathetic nervous system contracts it
Relaxed bladder causes it to close
177
What is the external urethral sphincter made from?
Skeletal muscle
-Its under voluntary control, somatic motor
178
Elimination of urine is a combination of what?
reflex and voluntary control
179
During reflex control urine in bladder stimulates what?
Stretch receptor
180
What allows urine to pass though urethra?
Relaxation of external sphincter muscle
