Chapter 14 - Urinary System Flashcards
1
Q
Kidney Functions
A
-maintaining stable ECF volume
-electrolyte composition
-osmolarity
-waste elimination
-H₂O balance
-plasma volume
-acid-base balance
-erythropoietin and renin production
-converting vitamin D to active form
2
Q
Osmolarity Maintenance
A
-solute concentration
-through regulating H₂O balance
-prevents osmotic fluxes that could cause shrinking or swelling of cells
3
Q
Plasma Volume Maintenance
A
-long-term regulation of arterial blood pressure
-through NaCl and H₂O balance
4
Q
Erythropoietin
A
-hormone that stimulates red blood cell production
5
Q
Renin
A
-enzymatic hormone
-triggers a chain reaction important in salt conservation
6
Q
Renal Pelvis
A
-where formed urine drains
-in the medial inner core of each kidney
7
Q
Ureters
A
-smooth muscle walls
-exits kidney at medial border
-carry urine to the bladder
8
Q
Urethra in Females is _____ and _______.
A
straight; short
9
Q
Urethra in Males
A
-longer and curving
-2 functions a) urine elimination b) semen passageway
10
Q
Nephron
A
-functional unit of the kidney
~1 million nephrons/kidney
-regulate water and solute
-2 components: a) vascular b) tubular
11
Q
Renal Cortex
A
-located in the outer region of the nephron
-granular appearance
12
Q
Renal Medulla
A
-inner region of the nephron
-made of renal pyramids (striated triangles)
13
Q
Juxtaglomerular Apparatus
A
-intersection of the afferent and efferent arterioles and the distal convoluted tubule
-the DCT passes between the arterioles
14
Q
Vascular Component
A
-glomerulus is the dominant part
15
Q
Glomerulus
A
-a tuft of capillaries
-filters protein-free plasma into the tubular component
16
Q
Path of Blood
A
-renal artery, afferent arterioles, glomerulus, efferent arteriole, peritubular capillaries, venules, renal vein
17
Q
Peritubular Capillaries
A
-surround the tubular part
-supply the renal tissue
-exchange fluid with tubular lumen
18
Q
_____ arterioles are the only in the body to drain from capillaries?
A
efferent
19
Q
Tubular Component
A
-hollow, fluid-filled tube
-single layer of epithelial cells
-begins at the glomerulus and ends at the renal pelvis
20
Q
Bowman’s Capsule
A
-part of the tubular component
-collect the glomerular filtrate
-double walled
21
Q
Proximal Tubule
A
-part of the tubular component
-lies entirely in the cortex
-coiled
-uncontrolled reabsorption and secretion
22
Q
Loop of Henle
A
-part of the tubular component
-U-shaped that dips into the medulla
-ascending (NaCl) and descending (H2O) limbs
-establishes and osmotic gradient
-controls urine concentration
23
Q
Juxtaglomerular Apparatus
A
-vascular AND tubular component
-produces substances in controlling kidney function
24
Q
Distal Tubule
A
-lies in cortex
-controlled reabsorption (Na+ and H₂O) and secretion (K+ and H+)
25
Collecting Duct
-where distal tubule empties
-brings urine to renal pelvis
26
Cortical Nephrons
-glomeruli lie in the outer cortex layer
-80% of nephrons
27
Juxtamedullary Nephrons
-glomeruli lie in the inner cortex layer
-long looped nephron
-establishes osmotic gradient
-most of urine concentration
28
Vasa Recta
-part of juxtamedullary nephrons
-long vascular loops
29
Glomerular Filtration
-180L/day
-1st step in urine formation
-protein-free fluid passes through 3 layers of the glomerular membrane
30
The 3 Glomerular Layers
1. Glomerular capillary wall: more permeable to water and solutes than anywhere in the body
2. Basement membrane
3. Inner Bowman's Capsule layer
31
The glomerular capillary wall is made of __________ capillary
fenestrated
32
The inner Bowman's capsule layers consists of ______ that encircle the glomerulus
podocytes
33
Podocytes
-role in glomerular filtration
-terminate in foot processes
-surround basement membrane
34
Filtration Slits
-clefts between the foot processes
-where filtrate enters the Bowman's capsule
35
Glomerular filtration is a ________ process where ________ ________ force fluids and solute through a membrane.
passive; hydrostatic pressures
36
Filtration Membrane
-has a large surface area
-is very permeable to water and solutes
37
Glomerular pressures is ______ vs other capillaries.
-higher
-180L/day vs 20L/day (all other capillary beds combined)
38
Glomerular Filtration: Forces
-recall bulk flow
-3 physical forces involved
39
Glomerular Capillary Blood Pressure
-outward direction
-55 mmHg
-afferent vs efferent resistance
-filtration along entire capillary length
-favours filtration
40
Plasma-colloid Osmotic Pressure
-inward direction
-30 mmHg
-high due to more water being filtered
-opposes filtration
-caused by unequal distribution of plasma proteins across the membrane
41
Bowman's Capsule Hydrostatic Pressure
-into the outside
-15 mmHg
-opposes filtration
-pressure exerted by fluid in initial part of tubule
-pushes fluid out of Bowman's capsule
42
Net Filtration Pressure Equation
-glomerular capillary bp - (plasma-colloid osmotic + Bowman's capsule hydrostatic) = net pressure
-favours filtration
-55-(30+15)=10mmHg
43
Glomerular Capillary Blood Pressure
-the fluid pressure exerted by blood in glomerular capillaries
-depends on: resistance to flow by afferent and efferent arterioles
44
Glomerular Filtration Rate (GFR)
-depends on net filtration pressure, surface area, permeability
45
Unregulated GFR Influences
-pathological changes in plasma-colloid osmotic pressure and Bowman's capsule hydrostatic pressure
46
Changes in Plasma-colloid Osmotic Pressure
-affect GFR
-due to: a) severely burned patient (↑GFR) b) diarrhea (↓GFR)
47
Changes in Bowman's Capsule Hydrostatic Pressure
-affect GFR
-due to obstruction (ie. kidney stone)
48
Controlled GFR Influences
-glomerular capillary bp adjusted to suit body needs
49
Autoregulation
-prevent spontaneous GFR changes
-kidneys maintain a constant blood flow despite driving changes in BP
-done by adjusting resistance to flow
-a myogenic mechanism
-TGF
50
Myogenic Mechanism
-used in autoregulation
-property of vascular smooth muscle
-contraction in response to stretch (increased pressure)
51
Tubuloglomerular Feedback
-used in autoregulation
-involves the Juxtaglomeruluar apparatus
-granular cells and macula densa which release ATP to induce vasoconstriciton (vv.)
52
Macula Dense
-detects changes in salt levels of fluid flowing past and stimulates release of ATP
-ATP degrades to adenosine and constricts the afferent arteriole
-this will decrease blood flow and hence GFR
53
Extrinsic Sympathetic Control
-long term BP regulation
-sympathetic input to afferent arterioles
-override autoregulation
54
Baroreceptor Reflex
-responds to a fall or rise in BP to sympathetically vasoconstrict or vasodilate
-affects heart and blood vessels (renal too!)
55
Vasoconstriction______ blood flow to the glomerulus and ______ GFR
decreases, reduces
56
Vasodilation______ blood flow to the glomerulus and ______ GFR
increases, increases
57
Will natural BP increases/decreases affect GFR?
-No
-ie. exercise
-this prevents the needless loss of water and solutes
58
Kidneys receive ___-___% of cardiac output
20 to 25
59
Blood flows through the kidneys at about _L/min
1
60
___% of plasma leaves the glomerulus not filtered
80
61
Tubular Reabsorption
-178.5L/day
-the transfer of substances from tubular lumen into peritubular capillaries
-a highly selective and variable process
-must cross 5 barriers
62
____% of water is reabsorbed and ____% is excreted
99; 1
63
____% of sodium is reabsorbed and ____% is excreted
99.5; 0.5
64
____% of glucose is reabsorbed and ____% is excreted
100; 0
65
____% of urea is reabsorbed and ____% is excreted
50; 50
66
____% of phenol is reabsorbed and ____% is excreted
0; 100
67
Path in Transepithelial Transport
luminal cell membrane, cytosol, basolateral cell membrane, interstitial fluid, capillary wall
68
Passive Reabsorption
-no energy is required
-substances move down the electrochemical/osmotic gradient
69
Active Reabsorption
-occurs if any of the substances being transported requires energy
-movement against the electrochemical gradient
70
What % of Na+ is absorbed at the proximal tubule?
67%
71
What is the role of Na+ reabsorption at the proximal tubule?
-reabsorbing glucose, amino acids, H2O, Cl-, urea
72
What % of Na+ is absorbed at the ascending limb of the loop of henle?
25%
73
What is the role of Na+ reabsorption at the ascending loop of henle?
-kidney's ability to produce urine of varying concentrations
74
What % of Na+ is absorbed at the distal and collecting tubules?
8%
75
What is the role of Na+ reabsorption at the distal and collecting tubules?
-variable
-subject to hormonal control
-regulating ECF volume
76
Na+ K+ ATPase Pump
-located on basolateral membrane
-essential for Na+ reabsorption
77
What % of total energy is spent by kidneys for Na+ transport?
80%
78
Water + Sodium = BFFs
-water follows reabsorbed sodium
-follows by osmosis
-main effects: a) ECF water volume b) blood volume c) blood pressure
79
Na+ reabsorption is almost always _____ transport
active
80
Co-Transporters
-move glucose, amino acids, Cl-
-generated by the electrochemical gradient
-coupled passive entrance as a result of active Na+ pumping
81
Fine-tuning of Na+ reabsorption is carried out in the _______ ________.
distal tubule
82
Too much body Na+, _____ is reabsorbed and hence ______ is excreted in urine.
less; more
83
Too little body Na+, _____ is reabsorbed and hence ______ is excreted in urine.
more; less
84
Renin-angiotensin-aldosterone System (RAAS)
-important for fine-tuning of Na+ regulation
85
Granular Cells and Na+ Reabsorption
-detect sodium load, change in pressure, volume
-lead to release of the Renin hormone
86
Renin coverts angiontensinogen (inactive) into ________________.
angiotension I
87
Angiotension I is converted to angiotension II (active) by _________-__________ enzyme.
angiotensin-converting
88
Angiotension II stimulates the secretion of ___________.
aldosterone (released by adrenal cortex)
89
Aldosterone Action
-acts of kidneys, DCT and collecting ducts
-this will increase Na+ reabsorption (Cl- follows)
-H2O is conserved
-ECF volume and arterial BP decrease
90
Increased Na+ reabsorption promotes _______ retention.
-water
91
The RAAS acts as a +/- feedback system.
negative feedback loop
92
Functions of the RAAS
-water retention
-constricting systemic arterioles
-stimulates thirst
-vasopressin secretion
93
Where does aldosterone act?
-on the last portion of the distal convoluted tubules and collecting ducts
94
What does aldosterone do?
-increase apical Na channels
-increases Na+/K+ ATPase pumps
95
Aldosterone Negative Feedback Loop
low ECF volume or low BP, more renin, more aldosterone, more Na reabsorption, increased ECF volume
96
Atrial Natriuretic Peptide (ANP)
-inhibits Na+ reabsorption
-opposes aldosterone
-decreases Na+ reabsorption
-decreases RAAS action
97
ANP Secretion
-secreted by atria in response to: a) being stretched (Na+ retention increased blood volume) b) expansion of ECF volume c) increased arterial pressure
98
Glucose and Amino Acid Reabsorption
-done by sodium dependent secondary active transport
99
Water Reabsorption
-80% is uncontrolled: 65% by proximal tubule 15% by loop of henle
-20% is controlled by vasopressin
100
ADH/Vasopressin
-Anti Diuretic Hormone
-regulates water reabsorption
-produced in the hypothalamus and released from the posterior pituitary
-acts on distal tubule and collecting duct
101
Aquaporine
-water channels
102
How is bulk flow enhanced?
increased plasma colloid osmotic pressure of peritubular capillaries
103
Regulated Water Reabsorption
-in distal portion of the nephron
104
Waste Products
-increase in concentration as water is reabsorbed
-cannot permeate tubular wall are are excreted in urine
105
Tubular Secretion
-the transfer of substances from peritubular capillaries into the tubular lumen
-tubules can selectively add some substances to filtrate
106
H+ Secretory Systen
-regulates acid-base balance
107
Where is H+ secreted?
-proximal, distal, collecting tubules
108
K+ Secretory System
-maintain normal membrane excitability in muscles and nerves
-K+ moves from capillaries to interstitial fluid
109
All filtered __ is reabsorbed
K+
110
Where is K+ secreted?
-only in distal and collecting tubules
-under control of aldosterone
111
Organic Ion Secretory System
-more efficient elimination of foreign organic compunds
112
Where are organic ions secreted?
-only in the proximal tubule
113
If on the basolatereral membrane, K+ is__________.
-recycled
-proximal tubule and loop of henle
114
If on the luminal membrane, K+ is ________.
-secreted
-distal portions
115
K+ Deficiency
-may be caused by aldosterone pathway activated by Na+
116
Isotonic
-the inside and outside are equal
117
If the concentration in the ECF is greater than in the cells: ECF __________
hypertonic
-water deficit
118
If the concentration in the ECF is less than in the cells: ECF __________
Hypotonic
-too much water in the ECF
119
Vertical Osmotic Gradient
-established in the interstitial fluid of the medulla
-the gradient exists between the tubular lumen and the surrounding interstitial fluid
-the gradient starts in the cortex (300) and increases as it moves into the medulla (1200)
120
Countercurrent Multiplication
-established the vertical osmotic gradient
-fluid in one tube flows the opposite way in the adjoining tube
121
Which limb of the loop of henle is permeable to H2O?
-the descending limb
122
Which limb of the loop of henle is used for NaCl reabsorption?
-the ascending limb (it is impermeable to water)
123
Water reabsorption is ________ in the distal tubule and collecting duct
variable, based on the secretion of ADH
124
Action of Vasopressin
1. ADH binds with receptor sites on basolateral membrane
2. cAMP second messenger system activated
3. cAMP increases membrane permeability to H2O, water channels are inserted into the membrane
4. water enters through the water channel
125
Dehydration
-small volume of concentrated urine excreted
-reabsorbed H2O picked up by peritubular capillaries and conserved for the body
-vasopressin secretion increases
126
Water Excess
-large volume of dilute urine
-no H2O reabsorbed
-excess H2O eliminated
-vasopressin secretion decreases
127
Diuresis
-increased urine production
128
Diabetes Mellitus
-sweet pee
-glucose in urine
-the filtered load exceeds reabsorption capacity
129
Diabetes Insipidus
-ADH deficiency
-produce 25-30L of urine per day
-always drinking water
130
Internal Urethral Sphincter
-smooth muscle (parasympathetic)
-relaxed bladder causes closure
131
External Urethral Sphincter
-skeletal muscle
-under voluntary control
