CH 26 Flashcards
(233 cards)
1
Q
what are general functions of the urinary system?
A
- removes wastes from blood
- regulates composition, pH, volume, osmolarity, pressure of blood
- produces hormones
2
Q
what is blood osmolarity?
A
total concentration of dissolved solutes present in blood
3
Q
what are wastes that the kidneys can excrete?
A
nitrogenous wastes:
- urea
- uric acid
- creatinine
- urobilin
- ammonia
- drugs
- toxins
4
Q
which ions can the kidneys control the amount present in blood?
A
- Na+
- Cl-
- Ca2+
- HPO4 2-
5
Q
how do the kidneys regulate blood pH?
A
- control H+ excreted into urine
- conserve HCO3 -
6
Q
what are some hormones the kidneys can produce
A
- calcitriol
- erythropoietin
7
Q
how do the kidneys regulate blood glucose levels?
A
through gluconeogenesis:
kidneys convert glutamine into glucose
8
Q
why is right kidney more inferior than left kidney?
A
liver displaces it
9
Q
what is the hilum of the kidney?
A
notch containing attachment to ureters, and blood, lymphatic, and nerve supply
10
Q
what are the three layers of the kidneys? from deep to superficial
A
- fibrous capsule
- perirenal fat capsule
- renal fascia
11
Q
what is fibrous capsule?
A
collagen-rich sheet
- maintains kidney shape
- protects kidneys from mechanical injury
12
Q
what is perirenal fat capsule?
A
fatty tissues
- protect kidney from trauma
- anchors kidney within retroperitoneal cavity
13
Q
what is renal fascia?
A
collagen + elastin rich CT
- anchors kidneys to surrounding organs and abdominal wall
14
Q
what is the parenchyma?
A
functional portion of kidneys, consisting of renal cortex + pyramids
- contains nephrons
15
Q
what is urine inside collecting ducts and papillary ducts called?
A
filtrate; further reabsorption can still occur
16
Q
what is fluid inside the major and minor calices called?
A
urine; no further reabsorption occurs
17
Q
describe pathway of urine through kidneys to ureters
A
Collecting ducts → Papillary Ducts → Minor calices → Major calices → Renal pelvis → Ureter
18
Q
what is the renal sinus?
A
depression in the side of the kidney
- where hilum of kidney is nestled into
19
Q
what is cardiac output?
A
total amount of blood pumping out of ventricles per unit time (L/min)
20
Q
Describe arterial blood pathway in kidney
A
Renal artery → Segmental artery → Interlobar artery → Arcuate artery → Cortical Radiate artery → afferent glomerular arteriole → glomerulus → efferent glomerular arteriole → peritubular capillaries
21
Q
Describe venous blood pathway in kidney
A
peritubular capillaries → cortical radiate vein → arcuate vein → interlobar vein → renal vein
22
Q
what is a kidney lobe?
A
a renal pyramid
- associated renal column on either side
- associated renal cortex
23
Q
how are glomerular capillaries different from other capillaries?
A
they lie between two sets of arterioles, no venule
24
Q
which division of the ANS innervates the kidneys?
A
the sympathetic division
25
Describe innervation of kidneys:
lateral grey horn of SC → lumbar splanchnic nerve → renal ganglion → renal plexus
26
what do vasomotor nerves that innervate kidneys do?
constrict the arteriole smooth muscle
27
what is the renal corpuscle?
filters blood plasma
28
what is the glomerular capsule
double-walled epithelial sheath around glomerulus that keeps filtrate inside nephron and sends it to the PCT
29
what is glomerulus
capillary network where blood is filtered
30
what is the renal tubule
where fluid filtered through glomerulus flows into and may be reabsorbed back into the body
31
what are cortical nephrons?
short nephron loops in renal cortex and outer renal medulla
- blood supply is by **peritubular capillaries**
- 80-85% of nephrons
32
what are juxtamedullary nephrons?
long nephron loops that reach deepest regions of the renal medulla
- blood supplied by peritubular capillaries + **vasa recta**
- 15-20% of nephrons
33
why are the walls of a nephron thin?
- single epithelial cell layer
- facilitates **exchange** btwn blood and filtrate
34
what cells compose the visceral layer of the glomerular capsule?
**podocytes**- simple squamous e.
- pedicels wrap around endothelial cells of the glomeruli
35
what cells compose the parietal layer of the glomerular capsule?
-simple squamous e.
36
what is histology of the PCT
simple cuboidal e.
- microvilli on apical surface
37
what is histology of nephron loop's thin ascending limb
simple squamous e.
38
what is histology of the nephron loop's descending limb
simple squamous e.
39
what is the histology of nephron loop's thick ascending limb
simple cuboidal/low columnar
- more cytoplasm needed b/c they fxn in secretion
40
what is histology of DCT
simple cuboidal e.
41
what is histology of last DCT and CD
simple cuboidal e.
- principal cells
- microvillous intercalated cells
42
what are macula densa
columnar cells part of ascending limb of nephron loop
- contains chemoreceptors that detect increased [Na+] in blood
43
what are juxtaglomerular cells
modified smooth muscle cells on walls of afferent glomerular arteriole
- detect low blood pressure and secrete renin
44
what are principal cells
simple cuboidal e. cells in collecting ducts
- express receptors for **ADH** and **Aldosterone**
45
what are intercalated cells
microvillous simple cuboidal e. cells in DCT and CD that regulate blood pH by secreting H+ and reabsorbing HCO3-
46
why are injured nephrons not replaced
you are born w/ all nephrons you will ever have
47
how do kidneys grow if you are born w/ all nephrons you will ever have
nephrons grow by increasing size and capacity
48
what is a hypertrophic kidney?
an increased size kidney
- more susceptible to renal failure
a hypertrophic kidney usually develops when an individual loses one kidney, so the remaining one increases capacity and size to make up for the loss, but it becomes more susceptible to renal failure
49
what is glomerular filtration
blood plasma and small enough dissolved substances get filtered into the glomerular capsule
50
what is tubular reabsorption
water, ions, and other substances get reabsorbed from renal tubule lumen into peritubular capillaries and ultimately into systemic circulation
51
what is tubular secretion
wastes, drugs, excess ions secreted from peritubular capillaries into renal tubule, ultimately making their way into urine
52
what is the filtration fraction
portion of blood plasma that filters out of afferent glomerular arterioles (16-20% in healthy adults)
53
what are the three barriers filtered substances cross during glomerular filtration?
1. glomerular endothelial cells
2. basal lamina of glomerulus
3. pedicel's slit membrane
54
how do glomerular endothelial cells fxn in glomerular filtration
large fenestrations permit all (except RBCs) to exit capillaries
- regulated by mesangial cells
55
what are mesangial cells
cells btwn efferent and afferent arterioles that **contract to regulate filtration**
56
how does basal lamina of glomerulus fxn in glomerular filtration
collagen + ANIONIC glycoproteins permit water + small solutes out of capillaries but **REPEL negatively-charged plasma proteins**
57
what are pedicels
foot-like processes of podocytes
58
what is a flitration slit
spaces btwn pedicels
59
how does slit membrane fxn in glomerular filtration
only *very small* molecules can pass through, prevents filtration of medium-sized proteins
- water
- ions
- glucose
- vitamins
- amino acids
- ammonia
- urea
60
why does filtration at renal corpuscle occur in larger volumes than at systemic capillaries?
- glomerular capillaries have large SA for exchange
- very permeable, leaky filtration membrane
- glomerular capillary blood pressure is high
61
why are efferent glomerular arterioles smaller in diameter than afferent glomerular arterioles
- to increase vascular resistance in efferent glomerular arterioles, leading to high blood pressure in the capillaries
62
how do mesangial cells regulate surface area glomerular capillaries have
mesangial cells contract= decreased SA
mesangial cells relaxed= increased SA
63
what is bulk flow?
net movement of solutes down **fluid pressure gradients** into out of blood, regardless of solute's conc. gradient
64
what is capsular hydrostatic pressure
pressure of glomerular filtrate on basement membrane of glomerular capillaries
- promotes reabsorption
65
what is glomerular blood hydrostatic pressure
pressure of blood plasma on walls of glomerular capillaries
- promotes filtration
66
what is blood colloid osmotic pressure
pull of solutes in blood (especially blood proteins) on fluids outside glomerular capillaries
- promotes reabsorption
67
what is the formula for net filtration pressure in the nephrons?
GBHP - (CHP+BCOP)
68
does net filtration or net reabsorption occur from glomerular capillaries?
net filtration, GBHP is greater than CHP and BCOP combined
69
what determines the rate of glomerular filtration?
anything that also determines the net filtration pressure, blood pressure, blood volume in systemic circulation
70
what happens if GFR is excessively high?
insufficient time for reabsorption, loss of important substances in urine
71
what happens if GFR is excessively low?
nearly all filtrate is reabsorbed and wastes will not be excreted
72
what will hemorrhage do to NFP?
Blood volume decreases, blood pressure decreases, NFP decreases because glomerular BHP also decreases
73
what will hemorrhage do to GFR?
systemic BHP decreases, glomerular BHP decreases, so GFR decreases
74
how can GFR be controlled?
- adjusting blood volume entering glomeruli
- altering glomerular capillary surface area
75
what are 3 mechanisms that control GFR?
1. renal autoregulation
2. neural regulation
3. hormonal regulation
76
how is renal autoregulation carried out?
- kidneys must maintain constant blood flow even if conditions are changed (e.g. during exercise) so renal autoregulation ensures systemic blood pressure remains constant
77
what are the two renal autoregulation mechanisms?
1. myogenic mechanism
2. tubuloglomerular feedback
78
what is the stimulus in myogenic mechanism?
- **stretching of afferent glomerular arteriole walls**
- increased blood flow through afferent glomerular arterioles
- increased glomerular filtration
79
what are the receptors for myogenic mechanism?
stretching of the walls of afferent glomerular arterioles stimulates arteriolar **constriction**
- less perfusion to the arterioles
80
what is the net physiological response of myogenic mechanism?
- blood flow decreased
- GBHP back to homeostatic levels
81
what is the stimulus for tubuloglomerular feedback?
increased GFR, rapid delivery of Na+ and Cl- to macula densa cells
82
what are the receptors for tubuloglomerular feedback?
the **macula densa cells** detect increased delivery of Na+, CL-, and water, they are chemoreceptors
83
what is the control center of the tubuloglomerular feedback?
**juxtagomerular apparatus** decreases secretion of nitric oxide
84
what are the effectors of the tubuloglomerular feedback?
**afferent glomerular arterioles** vasoconstrict (b/c less nitric oxide to vasodilate)
85
what is the net physiological response of the tubuloglomerular feedback?
decrease in GFR
86
which one is faster? myogenic mechanism or tubuloglomerular feedback?
myogenic mechanism
- tubuloglomerular feedback involves signals sent to multiple cells in sequence
87
what is the major stimulus of neural regulation in the kidneys?
increase in activity level of renal sympathetic nerves that release norepinephrine
88
what **type of neurotransmitter** binds to what **type of adrenergic receptors** on target cells in neural regulation of the kidneys?
sympathetic fibres of renal nerves release **norepinephrine** that bind **α-1** adrenergic receptors
89
what is the net physiological response of neural regulation of the kidneys?
when NE binds α-1 receptors on afferent glomerular arterioles, they **vasoconstrict and GFR decreases**
90
what are the effectors of neural regulation?
afferent glomerular arterioles
91
what does decreases renal perfusion lead to?
-decreased urinary output
- reallocation of blood flow to other organs
92
what are the two hormones that control glomerular filtration rate?
- Angiotensin II
- Atrial Natriuretic Peptide
93
what is major stimulus of Angiotensin II in controlling GFR?
**decreased blood volume/pressure** stimulates production of Angiotensin II
94
what are the effectors of Angiotensin II on GFR?
**constriction** of afferent and efferent glomerular arterioles
95
what is the net physiological response of Angiotensin II on GFR?
decreased GFR
96
what is the stimulus of Atrial natriuretic peptide on controlling GFR
**stretching of atrial walls** stimulates production of ANP
97
what are the effectors of Atrial natriuretic peptide on controlling GFR
**mesangial cells** in glomerulus **relax**, increasing surface area for filtration
98
what is the net physiological response of atrial natriuretic peptide on controlling GFR
increase of GFR
99
what are the two routes for reabsorption in the tubules?
1. **paracellular reabsorption**: between adjacent tubule cells into the peritubular capillaries
2. **transcellular reabsorption**: through individual tubule cells into peritubular capillaries
100
what is the apical membrane of the tubules?
the microvillous membrane facing the tubular lumen
101
what is the basolateral membrane of the tubules?
the membrane that faces interstitial fluid outside of the tubules
102
what cell junctions join the adjacent cells?
tight junctions
103
where are tight junctions leaky in the tubules?
in the proximal convoluted tubules, where fluid is permitted to leak between tubule cells
104
how do ions and fluid move across membranes?
thorugh transporters either at apical or basolateral membranes of the tubules
105
where is Na+-K+ ATPase located on renal tubule cells?
on basolateral membrane
106
why is there no Na+-K+ ATPase on the apical membranes?
to ensure **unidirectional** transport of Na+
- it is constantly reabsorbed into blood
107
what is the difference between a primary active transporter and a secondary active transporter?
Primary: directly uses ATP hydrolysis to powere movement of solutes AGAINST their conc. gradient
Secondary: uses electrochem gradients of one ion DOWN its conc gradient to power movement of another solute AGAINST its conc. gradient
- no ATP
108
what is the difference between a symporter and an antiporter?
symporter: two things move in same direction
anitporter: two things move in opposite direction
109
what are two ways water is reabsorbed into blood?
1. obligatory water reabsorption
2. facultative water reabsorption
110
what is obligatory water reabsorption?
- occurs in PCT + descending limb
- osmotic movement of water following solutes
- water moves down its conc. gradient
- where salt goes, water follows!
111
what is facultative water reabsorption?
- occurs in late DCT and CD
- controlled by ADH
- increased permeability to water by principal cells
112
where is the majority of water reabsorbed in the nephrons?
in the PCT via obligatory water reabsorption
113
where is the major site of Na+ reabsorption?
in the PCT
114
what proteins reabsorbed Na+ at PCT?
Na+-glucose symporters in apical membrane
Na+-H+ antiporters in apical membrane
115
how is faciliated diffusion of HCO3- out of tubule cells into blood possible?
by increasing intracellular HCO3-
116
how many ions of HCO3- and Na+ are reabsorbed per 1 H+ secreted?
1 of HCO3-
1 of Na+
117
what protein allows water to be reabsorbed in PCT?
aquaporin-1 on both apical and basolateral membranes
118
how does aquaporin-1 allow for water reabsorption at PCT
aquaporin-1 makes PCT highly permeable to water, allowing transcellular reabsorption to occur in addition to the paracellular reabsorption already happening in PCT
119
how does Cl- being present in high concentration affect reabsorption of other ions?
increasing negative charge of IF by Cl- promotes diffusion of cations along same route
120
how does ammonia accumulate in IF?
ammonia is product of deamination of amino acids
121
why is there little water reabsorption in the nephron loop?
the cells there are impermeable to water
122
what protein promotes Cl- reabsorption in the thick ascending limb?
Na+-K+-2Cl- symporters in apical membrane
123
why is secretion of K+ back into the tubular lumen by K+ leak channels important?
to promote paracellular reabsorption of cations by increasing negative charge of IF
124
why does K+ diffuse back into tubular lumen after Na+-K+-2Cl- symporters transport K+ into cytoplasm of tubular cells?
leak channels present in apical membranes allow faciliated diffusion of K+ into lumen
125
what is the net reabsorption into vasa recta because of K+ leak channels?
1 Na+ and 2 Cl-, no K+ reabsorbed
126
why does osmolarity of fluid in tubule lumen decrease as fluid flows toward ascending limb?
ascending limb is virtually impermeable to water so it stays in tubular lumen, but it is permeable to ions so they are reabsorbed and removed from tubular lumen
127
what protein facilities sodium and chloride reabsorption in the DCT
Na+-Cl- symporters
128
what part of the nephron does PTH affect?
early DCT
129
how does PTH affect cells of the early DCT?
binds receptors on the tubular cells, stimulating reabsorption of Ca2+ when blood calcium levels are low
130
what hormones do principal cells in late DCT and CD possess receptors for?
ADH, Aldosterone
131
what do the principal cells in the late DCT and CD do?
reabsorb Na+, secrete K+
132
why does K+ secretion vary in the principal cells?
- dietary intake of K+ varies
- blood levels of K+ varies
K+ simply follows concentration gradient
133
what is the main source of K+ excreted in urine? what channel on what membrane of the principal cells?
apical leak K+ channels on principal cells
(basolateral leak K+ channels put K+ back into IF)
134
what do intercalated cells do?
reabsorb HCO3- and K+, secrete H+
regulates blood PH
135
what are the five hormones that regulate reabsorption and secretion?
- Angiotensin II
- Aldosterone
- Antidiuretic Hormone
- Atrial Natriuretic Peptide
- Parathyroid Hormone
136
how does angiotensin II regulate reabsorption and secretion?
1. decrease GFR by vasoconstriction of afferent arteriole
2. stimulate Na+-H+ antiporters in PCT
3. stimulate aldosterone release
137
what proteins does Angiotensin II affect in PCT?
Na+-H+ antiporters
138
how does aldosterone regulate reabsorption and secretion?
stimulates principal cells to reabsorb more Na+, secrete more K+
- facultative water reabsorption increases
139
what is the net physiological response due to Aldosterone?
increased blood volume and blood pressure
140
how does ADH regulate reabsorption and secretion
- increased permeability of principal cells to water
- stimulates expression of aquaporin-2 at apical membranes
- increased facultative water reabsorption
141
stimulus of ADH regulation of nephrons?
increased osmolarity blood plasma and IF
142
receptors for ADH regulation of nephrons?
osmoreceptors in hypothalamus send nerve impulses to hypothalamus and post. pit
143
control centre for ADH regulation of nephrons?
hypothalamus and post. pit.
- increases ADH release
144
effectors for ADH regulation of nephrons?
principal cells of collecting ducts and late DCT
- increased water permeability, increased facultative water reabsorption
145
net physiological response to ADH regulation of nephrons?
decrease in blood plasma osmolarity
146
how does normal hydration modulate ADH levels?
normally hydrated = normal ADH lvls
- 99% water reabsorbed, 1& excreted as **hyperosmotic urine** (1-2L/day)
147
how does dehydration modulate ADH levels?
dehydrated = high ADH lvls
- 99.8% water reabsorbed
- 0.2% excreted, urinary output very low (400mL/day)
- urine is concentrated, hyperosmotic
148
what is hyperosmotic urine?
urine with higher concentration of solute than blood
149
how does overhydration modulate ADH levels?
overhydrated = low ADH lvls
- 80% reabsorbed, 20% excreted
- dilute, hypoosmotic urine (up to 36L/day)
150
what hormones does ANP suppress?
Aldosterone and ADH
151
how does ANP affect reabsorption and secretion in the tubules?
- inhibits NA+ reabsorption in PCT and CD
- suppressed Aldosterone and ADH secretion
152
what are the effects of ANP in the context of tubular secretion and reabsorption?
- natriuresis
- diuresis
- decreased blood volume and pressure
153
what is natriuresis?
increased Na+ excretion in urine
154
what is diuresis?
increased urinary output
155
what stimulates PTH release from dense principal parathyroid cells?
low blood Ca2+ levels
156
what are the effectors of PTH?
- tubule cells in DCT, reabsorbing more Ca2+
- tubule cells in PCT to reabsorb less HPO4 3-, increase free Ca2+ in blood
157
what does urinary output and excretion depend on?
fluid intake, hormone levels (like ADH)
158
why do kidneys still eliminate wastes as urine even when fluid intake is low or excess fluid is lost?
body still produces waste, no matter the conditions
159
why does IF in renal medulla have higher osmolarity than blood plasma?
countercurrent flow
160
what is countercurrent flow?
fluid in a tube runs in one direction and fluid in another, nearby, parallel tube runs in opposite direction
161
what are two types of countercurrent flow?
- countercurrent multiplication
- countercurrent exchange
162
what mechanism **establishes** osmotic gradient across renal cortex into renal medulla?
countercurrent multiplication
163
why does Na+ and CL- accumulate in the medullary IF during reabsorption?
Na+-K+-2Cl- symporters in thick ascending limb sets up osmotic gradient in the renal medulla
- water is impermeable here
164
what is countercurrent multiplication?
the opposite and parallel arrangements of the two nephron loop limbs and their difference in permeabilities **MULTIPLY** the concentration of ions in the medullary IF
165
why is countercurrent multiplication needed when ADH levels are high?
ESTABLISHES the renal medullary osmotic gradient, which is crucial producing concentrated urine
166
what is urea recycling?
urea diffuses out of medullary portion of CD, diffusing into descending and thin ascending limbs
167
how does urea recycling assist countercurrent multiplication?
urea is recycled and increases in concentration in the renal medulla during reabsorption
168
what is countercurrent exchange?
passive flow of water and solutes from the interstitial fluid of the renal medulla into the blood of the vasa recta
169
why is countercurrent exchange needed when ADH levels are high?
MAINTAINS the renal medullary osmotic gradient, which is crucial producing concentrated urine
170
what is the benefit of blood flowing slowly in the vasa recta?
allows maximal exchange of solutes, water, etc. with the surrounding interstitial fluid of the renal medulla
171
what direction do solutes move as blood flows through descending portion of the vasa recta?
solutes move from renal medullary IF INTO blood
172
what direction do solutes move as blood flows through ascending portion of the vasa recta?
solutes move out of blood INTO renal medullary IF
173
what is the importance of countercurrent exchange in addition to maintaining the renal medullary osmotic gradient?
ensures that oxygen and nutrients still reach renal medullary cells **without changing** the osmolarity of the renal medulla IF
- doesn't disturb osmotic gradient in renal medulla
174
what is urinalysis?
the collection and interpretation of urinary output volume and its physical, chemical, and **microscopic** characteristics
175
how do blood tests allow us to analyze function of the kidneys?
examining composition of blood to see if kidneys are filtering properly
176
what are two indicators in blood that show abnormal kindey functioning?
1. blood urea nitrogen
2. plasma creatinine
177
what is blood urea nitrogen?
presence of urea, nitrogen in blood
- increases when glomerular filtration fails
- result of amino acid deamination
178
how do you treat blood urea nitrogen?
decrease dietary protein intake
179
what is plasma creatinine?
product of creatine phosphate catabolis by muscles
- increases when renal function is compromised
180
what is renal plasma clearance?
volume of blood "cleared" of a substance per unit time (mL/min)
181
what does renal plasma clearance tell us?
the rate of excretion in urine for a particular substance
182
S = (U*V)/P
U = [substance] in urine
P = [substance] in plasma
V = urine flow rate
183
why does the renal plasma clearance of **creatinine** closely approximate a norma GFR?
creatinine is not reabsorbed
184
why is para-aminohippuric acid used to measure renal plasma flow?
it is cleared by kidneys in one pass
185
what is renal plasma flow?
volume of plasma passing through kidneys
186
what are the ureters?
tubes that carry urine from renal pelvis to urinary bladder
187
how do the ureters carry urine to the urinary bladder?
1. peristaltic contractions
2. gravity
3. fluid pressure pushes urine in one way
188
what allows the ureters to expand as they fill with urine?
the mucosa is made of urothelium
189
what is the histology of the muscular layer of the ureters? from deep to superficial
1. longitudinal layer
2. circular layer
distal 1/3 of ureters have additional outer longitudinal layer
190
what is the function of the adventitia of the ureters?
- connects ureters to other tissues
- anchors ureters in pelvic cavity
191
what is the urinary bladder?
expandable organ that stores urine
192
what is important about how the ureters connect to the urinary bladder obliquely?
- forms a **physiological valve**
- as urinary bladder fills, pressure pushes the oblique openings closed to prevent urine backflow
193
what is the full volume of the urinary bladder?
~700-800mL but it usually doesn't get that full
194
why is the volume of the urinary bladder smaller in females?
the full urinary bladder pushes against the uterus
195
what is the trigone?
inferior, triangular area inside urinary bladder containing stretch receptors
- formed by the two ureteral openings and the internal urethral orifice
196
why does the urinary bladder have rugae?
allows expansion of urinary bladder as it fills
197
what is the function of the internal urethral sphincter?
involuntarily controls opening and closing of urethra, permitting passage of urine into urethra but preventing backflow of urine back into the urinary bladder
198
what is the function of the external urethral sphincter?
voluntarily controls opening and closing of urethra
199
where is the external urethral sphincter?
in the deep muscles of the perineum
200
what is the external urethral orifice?
opening of urethra to outside, allows expulsion of urine
201
what is the detrusor muscle?
muscular layer of urinary bladder consisting of:
1. inner longitudinal layer
2. intermediate circular layer
3. outer longitudinal layer
202
what is the function of the detrusor muscle?
provides tone as urinary bladder fills
203
what does the circular layer of the detrusor muscle form at the inner urethral orifice?
the internal urethral sphincter
204
what is the micturition reflex?
spinal reflex controlling urination
205
what is the stimulus for the micturition reflex
volume in urinary bladder reaches 200-400mL
206
what is the receptors for the micturition reflex?
stretch receptors in urinary bladder wall detect distension
207
what is the control centre for the micturition reflex?
stretch receptors send nerve impulses to **micturition centre** in sacral spinal cord
208
what is the output for the micturition reflex?
nerve impulses through:
1. **parasympathetic fibres** to internal anal sphincter, detrusor muscle
2. inhibitory somatic motor fibres to skeletal muscle of external urethral sphincter
209
what are the effectors of the micturition reflex?
detrusor muscle - contracts
internal urethral sphincter - relaxes
external urethral sphincter - relaxes
210
what is the net response for the micturition reflex?
urination
- pressure on fluid within urinary bladder increases
- internal urethral orifice now open
211
what is the urethra?
terminal passage for urine from urinary bladder to exterior of body
- also discharges semen in males
212
what is the histology of the urethra's mucosa in MALES
- urothelium in proximal end
- stratified columnar / pseudostratified columnar epithelium in distal end
213
what is the prostatic urethra
portion of urethra going through prostate in males
214
what is the muscular layer of the prostatic urethra?
mostly circular smooth muscle, forms internal urethral sphincter
215
what is the muscular layer of the membranous urethra?
mostly circular skeletal muscle, forms external urethral sphincter
216
what is the membranous urethra?
portion of uretrha going through deep perineal muscles
217
what is the spongy urethra?
portion of urethra going through corpus spongiosum penis
218
what is the histology of the urethra's mucosa in FEMALES
- urothelium in proximal end
- pseudostratified/stratified columnar in intermediate
- nonkeratinized stratified squamous in distal end
219
what is the histology of the muscular layer of the urethra in FEMALES
- outer skeletal muscle
- inner smooth muscle
220
what systems does the urinary system cooperate with?
- blood buffers
- blood
- liver
- lungs
- sweat glands
- digestive system
221
how does urinary system and blood buffers cooperate?
both blood and kidneys bind excess H+ in blood to prevent blood pH changes
222
how does urinary system and blood cooperate?
blood transports wastes to appropriate organs for storage, processing, elimination at kidneys
223
how does urinary system and liver cooperate?
liver detoxifies drugs to prepare wastes for excretion at kidneys
224
how does urinary system and lungs cooperate?
both excrete CO2 waste upon exhalation
225
how does urinary system and sweat glands cooperate?
both dissipate heat and excrete water, CO2, urea, and salts
226
Imagine the discovery of a new toxin that blocks renal tubule reabsorption but does not affect filtration. Predict the short-term effects of this toxin.
Without reabsorption, initially 105–125 mL of filtrate would be lost per minute, assuming normal glomerular filtration rate. Fluid loss from the blood would cause a decrease in blood pressure, and therefore a decrease in GBHP. When GBHP dropped below 45 mmHg, filtration would stop (assuming normal CHP and BCOP) because NFP would be zero.
227
For the following urinalysis results, indicate whether you should be concerned or not and why: (a) dark yellow urine that is turbid;
a. Although normally pale yellow, urine color can vary based upon concentration, diet, drugs, and disease. A dark yellow color would not necessarily indicate a problem, but further investigation may be needed. Turbidity or cloudiness can be caused by urine that has been standing for a period of time, from certain foods, or from bacterial infections. Further investigation is needed.
228
For the following urinalysis results, indicate whether you should be concerned or not and why: (b) ammonia-like odor of the urine;
b. Ammonia-like odor occurs when the urine sample is allowed to stand.
229
For the following urinalysis results, indicate whether you should be concerned or not and why: (c) presence of excessive albumin;
c. Albumin should not be present in urine (or be present only in very small amounts) because it is too large to pass through the filtration membranes. The presence of high levels of albumin is cause for concern as it indicates damage to the filtration membranes.
230
For the following urinalysis results, indicate whether you should be concerned or not and why: (d) presence of epithelial cell casts;
d. Casts are hardened masses of material that are flushed out in the urine. The presence of casts is not normal and indicates a pathology.
231
For the following urinalysis results, indicate whether you should be concerned or not and why: (e) pH of 5.5;.
e. The pH of normal urine ranges from 4.8 to 8.0. A pH of 5.5 is in normal range.
232
For the following urinalysis results, indicate whether you should be concerned or not and why: (f) hematuria.
f. Hematuria is the presence of red blood cells in the urine. It can occur with certain pathological conditions or from kidney trauma. Hematuria may occur if the urine sample was contaminated with menstrual blood.
233
Bruce is experiencing sudden, rhythmic waves of pain in his groin area. He has noticed that, although he is consuming fluids, his urine output has decreased. From what condition is Bruce suffering? How is it treated? How can he prevent future episodes?
Bruce has developed renal calculi (kidney stones), which are blocking his ureters and interfering with the flow of urine from the kidneys to the urinary bladder. The rhythmic pains are a result of the peristaltic contractions of the ureters as they attempt to move the stones toward the urinary bladder. Bruce can wait for the stones to pass, can have them surgically removed, or can use shock-wave lithotripsy to break apart the stones into smaller fragments that can be eliminated with urine. To prevent future episodes, Bruce needs to watch his diet (limit calcium) and drink fluids, and may need drug intervention.
