ch 26: urinary Flashcards
describe the flow of urine
urine flows from the kidneys, through the ureters, to the bladder, out through the urethra
describe the ureters
25-30 cm in length. transport urine from the kidney to the urinary bladder, primarily by peristalsis
describe the innermost layer of the ureter
- The mucosa layer: innermost layer; formed of a transitional epithelium (can stretch) and lamina propria (has elsatic fibers, and lymphatic tissue)
mucus is secreted to prevent the cells from coming in contact w/ acidic urine
3 layers of wall of the ureters
- the mucosa layer
- the muscularis layer
- the adventitia layer
describe the muscularis layer of the ureter
contains a longitudinal layer and circular layer of smooth muscle cells; peristalsis contributes to urine flow
describe the adventitia layer of the ureters
it’s the outermost layer
consists of connective tissue that anchors the ureters in place.
Contains blood vessels and nerves to supply the ureters
what is the trigone
the area is bordered by 2 ureteral openings and one urethral opening
what are the 3 layers of the wall of the bladder
- the mucosa layer
- the muscularis layer
- the adventitia
describe the mucosa layer of the bladder
inner most layer
formed of a transitional epithelium and lamina propria (has elastic fibers and lymphatic tissue). Mucus is secreted to prevent the cells from coming in contact with the acidic urine
describe the muscularis layer of the bladder
(detrusor muscle)
composed of 3 layers of smooth muscle; outer longitudinal, middle circular and longitudinal inner
function of rugae in bladder
permits expansion of the bladder
circular smooth muscle vs circular skeletal muscle in the bladder
circular smooth muscle forms te internal urethral sphincter; under involuntary control
circular skeletal muscle forms the external urethral sphincter; under voluntary
describe the adventitia
the outermost layer of the bladder. It consists of loose connective tissue that anchors the bladder in place.
Which of the following is a funnel-shaped area
where the openings for the ureters and the
urethra are found in the urinary bladder?
a) Detrusor
b) Rugae
c) Trigone
d) Lamina
c) Trigone
how does urination occur (receptors and pathways)
- stretch receptors detect stretching when the volume exceeds 200-400 mL
- sensory neuron carries information to the spinal cord (S2-S4)
- pre-ganglionic neuron carries motor impulses to the bladder
- post-gangionic neuron stimulates the detrusor muscle to contract
- sensory impulses are relayed to the cerebral cortex (via the thalamus) for awareness of fullness
- cerebral cortex can initiate voiding or delay it occurrence by controlling the external urethral sphincter (skeletal muscle)
Which part of the urine elimination pathway is
under voluntary control?
a) Internal urethral sphincter
b) External urethral sphincter
c) Detrusor muscle
d) a and b
b) external urethral sphincter
Which region of the spinal cord contains the
center of the micturition reflex?
a) Pelvic
b) Sacral
c) Thoracic
d) Lumbar
b) sacral
Which branch of the nervous system carries
motor impulses of the micturition reflex?
a) Parasympathetic
b) Sympathetic
c) Somatic
d) Spinal
a) parasympathetic
in females the urethra length
4 cm in length.
what are the 2 layers the wall of the female urethra
- The mucosa layer is the innermost layer. It goes from transitional epithelium to nonkeratinized stratified squamous epithelium.
The lamina propria has elastic fibres and blood vessels
- the muscular consists of circular smooth muscle
describe the male urethra
The male’s urethra is much longer
than the female’s urethra (~20 cm).
It goes through the prostate
(prostatic urethra), then through the deep muscles of the perineum
(intermediate urethra), and through
the penis (spongy urethra)
what are the 2 layers in the wall of the male urethra
- The mucosa layer is the inner most layer. It goes from transitional epithelium to pseudostratified columnar epithelium to nonkeratinized stratified squamous epithelium. The lamina propria has
elastic fibers, and blood vessels. - The muscularis consists of smooth muscle fibers in the prostatic urethra (internal
sphincter), and skeletal muscle in the intermediate urethra (external sphincter)
describe the kidneys
The kidneys are found just above
the waist between the
peritoneum and the wall of the
abdomen; they are
retroperitoneal organs (along with
the adrenal glands & the ureters).
The kidneys are protected by
the 11th & 12th ribs.
what are the renal functions?
Filtration, reabsorption, secretion = Excretion of waste products
1.1 Regulation of water and electrolyte balance
blood ionic composition Na+, K+, Ca+2, Cl- and phosphate ions
1.2 Regulation of acid-base balance (blood pH)
1.3 Regulation of blood volume and pressure conserving or eliminating water
2. Endocrine functions
2.1 Secrete erythropoietin (stimulate RBC production)
2.2 Renin (enzyme) → regulates aldosterone levels
2.3 Calcitriol (activated form of vit D) → promotes intestinal calcium absorption
3. Gluconeogenesis
how are lobes, pyramids and papilla related
A kidney contains 8-18 lobes. A
lobe is formed of a pyramid
(medulla), the overlying area of
renal cortex, and one half of each
adjacent renal column.
Papilla = apex of pyramid
what is a nephron and where are they found
a nephron is the functional unit of the kidney
nephrons are found in the renal cortex and the renal medulla
a kidney has over 1 million nephrons each composed of a corpuscle and tubule
describe the path of urine drainage
Many nephrons drain into
a collecting duct, which
drain into papillary ducts,
which further converge
into minor calyces (one per
lobe) and major calyces (2
3 per kidney). Urine drains
into a single, large renal
pelvis, then into the ureter
to the bladder
what are nephrons made of and what happens there
a kidney has over 1 million nephrons each composed of a corpuscle and a tubule
the renal corpuscle is where blood plasma is filtered
what happens in the renal tubule
substances get reabsorbed into the blood
cortical nephrons vs juxtamedullary nephrons
80-85% of nephrons are cortical
nephrons; the tubule doesn’t
go deep into the medulla
15-20% of nephrons are juxtamedullary
nephrons. The tubule goes deep into the medulla. They allow for excretion of very
dilute or very concentrated urine (see later)
Juxtamedullary nephrons:
a) Make up about 80-85% of the nephrons within the kidney.
b) Allow regulation of blood volume and pressure.
c) Have renal corpuscles located in the outer portion of the renal
cortex.
d) Have very short nephron loops.
e) Have very thick descending nephron loops.
b - more space for osmosis
what are nephrons composed of?
Vascular component –
connects to circulatory system and is made
of 2 arterioles
◦ Afferent arteriole (carries unfiltered blood) enters the high pressure (glomerular capillaries)
◦ Efferent arteriole (carries filtered blood) branches to form low-pressure peritubular
capillary bed
Tubular component –
connects to circulatory system and
elimination functions of kidney
what are peritubular capillaries
As solutes flow through the
renal tubules, they get
reabsorbed from the tubules
into peritubular capillaries
what are the 3 basic processes that the nephron and collecting ducts perform
- In the renal corpuscle, blood plasma flowing through the glomerulus gets filtered into
the glomerular capsule. - All along the renal tubule and collecting duct, water, ions, and other substances get
reabsorbed from the renal tubule lumen into the blood - substances such as wastes, drugs, and excess ions get secreted from the blood into the
renal tubule. These substances ultimately make their way into the urine.
where does filtration of blood start
Filtration of blood
starts at renal
corpuscle made of:
Glomerulus
Glomerular (aka
Bowman’s) capsule
blood flows from the afferent arteriole into the ______
glomerular capillaries
plasma filtered from the glomerular capillaries enters the ____ of the _________
capsular space ; glomerular capsule
Blood leaving the afferent arterioles flows
next into which of the following vessels?
a) Glomerulus
b) Capsular space
c) Efferent arteriole
d) Interlobular vein
e) Peritubular capillaries
A
Glomerular (Bowman’s) capsule consists of:
a) Tightly packed cuboidal and smooth muscle cells
b) The space that contains tubular filtrate
c) The two layers of cells that enclose the capsular space
d) The glomerular capillaries
e) Macula densa and juxtaglomerular cells
C
what are the two layers of the glomerular capsule? describe them
- the parietal layer which consists of a simple squamous epithelium; it forms the wall of the capsule
- The viceral layers which consists of a modified simple squamous epithelium. podocytes are cells wrapped around the capillaries`
what are podocytes
cells wrapped around the capillaries
filtered substances move from the blood stream through 3 barriers. What are they? What does it form
fenestration of glomerular cells, basal lamina and slit membrane
forms an ultrafiltrate of urine
describe the ultrafiltrate of urine
chemical composition
like plasma, but no proteins (too large)
what is the point of filtration?
The principle of filtration is to force fluids and solutes
through membrane by hydrostatic pressure
fenestration of glomerular endothelial cells vs basal lamina vs slit membrane
Fenestration of glomerular
endothelial cells prevents filtration of
blood cells but allows all components
of blood plasma to pass through
The basal lamina of glomerulus prevents
filtration of larger proteins
Slit membrane between pedicels prevents
filtration of medium-sized proteins
Which part of the nephron loop is
responsible for filtration?
a) Renal corpuscle
b) Proximal convoluted tubule
c) Distal convoluted tubule
d) Collecting duct
A
Which of the following parts of a nephron
does NOT contain filtrate?
a) Renal corpuscle
b) Renal tubule
c) Glomerulus
d) Glomerular capsule
C
describe the flow of filtrate starting at the glomerular capsule
- filtrate leaves the glomerular capsule and enters the proximal convoluted tubule (PCT)
- filtrate then goes though the nephron loop
- the last section of the tubule id the distal convoluted tubule (DCT)
- Nephron drains into collecting ducts
what reabsorbs over 99% of filtered substances
nephrons
where are most substances reabsorbed from
from the proximal convoluted tubule; the rest of the nephron does the fine-tuning
where are substances reabsorbed into?
the peritubular capillaries
describe the principle of filtration
to force fluids and solutes through a membrane
by pressure - is the same in glomerular capillaries as in capillaries elsewhere
in the body
what is the net filtration pressure (NFP)?
The net filtration pressure (NFP) is the total of all pressures that promote
either filtration or reabsorption
3 steps in net filtration pressure
Glomerular blood hydrostatic
pressure (GBHP) promotes
filtration (55 mmHg)
Capsular hydrostatic pressure (CHP)
opposes filtration (15 mmHg)
Blood colloid osmotic
pressure (BCOP) opposes
filtration (30 mmHg)
Which of the following pressures drives fluid
from the glomerulus into the capsular space?
a) Capsular hydrostatic pressure
b) Blood colloid osmotic pressure
c) Glomerular hydrostatic pressure
d) a and b
c
what is glomerular filtration rate (GFR). What happens if it’s too high or too low?
Amount of filtrate formed in all renal corpuscles of both kidneys / minute
◦ average adult rate is 105-125 mL/min
Homeostasis requires constant GFR
◦ too high - useful substances are lost due to the speed of fluid passage through
nephron (not enough reabsorption)
◦ too low - sufficient waste products may not be removed from the body
what is the GFR directly related to? What do you need to do to change the GFR
The GFR is directly related to the net filtration pressure; any change in the net
filtration pressure will affect GFR
To alter the GFR,
1. you can adjust blood flow into and out of the glomerulus
2. you can alter the glomerular capillary surface area available for filtration
describe the myogenic mechanism
A systemic increase in BP stretches the wall of the afferent arteriole
In response, smooth muscle cells contract, reducing the diameter of the
afferent arteriole
The opposite takes place under low blood pressure – fewer stretching causes the
relaxation of smooth muscle, leading to an increase in the diameter of the
arteriole (increase in GFR)
describe tubuloglomerular feedback
When the GRF is too high (due
to elevated systemic BP), fluid
flows too rapidly through the
renal tubule, causing
inadequate reabsorption
In response, the macula densa (from the
DCT) inhibits the release of NO (NO is a
vasodilator), resulting in vasoconstriction
of the afferent arteriole
describe the neural regulation of GFR
Blood vessels of the kidney are supplied by sympathetic
fibers that release norepinephrine; this causes
vasoconstriction of afferent arterioles
At rest, renal BV are maximally dilated because
sympathetic activity is minimal; at rest, renal
autoregulation prevails
With high sympathetic stimulation (e.g., during exercise or hemorrhage),
vasoconstriction of afferent arterioles reduces GFR
lowers the urine output (keeps water in blood vessels)
diverts blood flow to other tissues
describe the hormonal regulation of GFR
Angiotensin II is a potent vasoconstrictor that narrows both the afferent and
efferent arterioles, reducing the GFR
Remember: the renin-angiotensin
aldosterone pathway increases the
blood pressure; by reducing the
GFR, more water stays in the body
describe the renin-angiotensin-aldosterone pathway
Renin leads to the production of angiotensin II, which:
Causes constriction of afferent
and efferent arterioles,
thereby decreasing the GFR
Enhances the
reabsorption of Na+, Cl-
and water in the PCT
Promotes the production
of aldosterone from the
adrenal cortex
Reabsorption of which of the following
ions is an action of aldosterone?
a) Sodium
b) Potassium
c) Calcium
d) Phosphorus
a
what does atrial natriuretic peptide (ANP) do?
Atrial natriuretic peptide (ANP) is released by heart cells when there is too much stretching of the atria (due to increased blood volume)
ANP causes the glomerular mesangial cells to relax, increasing
the capillary surface area available for filtration, thereby
increasing the GFR
A large increase in blood volume promotes the release of atrial natriuretic
peptide (ANP) from the heart (due to overstretching of the atrial wall)
what does ANP inhibit
ANP inhibits the reabsorption
of Na+ and water in PCT and in
the collecting ducts
what does ANP increase
Increases GFR by relaxing
mesangial cells, thus increasing
capillary surface area for filtration
ANP suppresses the secretion of which hormones
aldosterone and ADH
Renin directly activates which of the following?
a) Aldosterone
b) Angiotensin
c) ADH
d) Sympathetic tone
e) a and b
B
When a person goes into shock, urine output
a) Decreases
b) Increases
c) Remains constant
a
describe tubular resorption
Transport across membranes
can either be active or passive
Passive transport includes
diffusion and facilitated
diffusion. In paracellular
reabsorption, substances
diffuse between the cells
Active transport includes primary
and secondary active transport.
describe reabsorption in the PCT
Na+ antiporters reabsorb Na+ and
secrete H+ (for elimination
through urine)
Na+ symporters help
reabsorb substances from
the tubular filtrate (glucose, HPO4, and SO4, ions, amino acids and lactic acid)
Bicarbonate ions
(HCO3-) are reabsorbed
Cl-, K+, Ca2+, Mg2+ and urea
become more concentrated
in the 2nd half of PCT, and
thus diffuse into
peritubular capillaries
(facilitated diffusion)
osmosis is promoted in the
PCT; ~ 65% of water is
reabsorbed in the PCT
reabsorption in the nephron loop
The nephron loop reabsorbs
50% of the remaining water
(~15% of total water), and 2/3
of the remaining Na+ and Cl- ions
reabsorption in the thick ascending limb of the nephron loop
The thick ascending limb of
the nephron loop is
relatively impermeable to
water, and pumps Na+ and
Cl- from tubular fluid to
interstitial fluid; solutes get
reabsorbed, but water
doesn’t
reabsorption in the thin descending limb of the nephron loop
The thin descending limb of the
nephron loop is permeable to
water and relatively
impermeable to solutes; water
gets reabsorbed there, but
solutes do not
steps in reabsorption in the nephron loop
- Na+ and Cl- are pumped out of the ascending limb nto the interstitial fluid.
Since osmosis doesn’t
take place, the tubular
concentration of solutes
decreases as Na+ and Cl-
ions are being pumped
out - As Na+ and Cl- are being pumped out, osmolarity of interstitial fluid
increases - High osmolarity in the interstitial fluid drives water out of the
descending limb
4.As water gets out, solute concentration increases in the
descending limb
- The higher concentration of
solutes accelerates pumping from the ascending limb
reabsorption in the distal convoluted tubule (DCT)
Once the tubular fluid reaches the DCT, it represents a reduced volume of tubular fluid at
low solute concentration; only 15-20% of initial filtrate volume reaches the DCT. The DCT reabsorbs ~10-15% of the remaining water
Urea and other organic wastes were not
pumped out of the ascending limb, so they now
represent a significant proportion of the remaining solutes
As fluid flows along the DCT, reabsorption of
Na+ and Cl- continues due to Na+/Cl- symporters;
these pumps are controlled by aldosterone
The DCT serves as the major site
where parathyroid hormone
stimulates reabsorption of Ca2+
reabsorption in the collecting ducts
The collecting ducts contribute to the
reabsorption of more Na+ and Cl- ions,
as well as Ca2+, HCO3- and some urea
Which part of a nephron is responsible for
reabsorbing all organic nutrients from filtrate?
a) Renal corpuscle
b) Nephron loop
c) Proximal convoluted tubule
d) Distal convoluted tubule
e) c and d
C
water reabsorption where?
Water is reabsorbed in PCT, the
descending limb of the loop, and
the DCT and the collecting ducts.
~85% of water is reabsorbed
through obligatory reabsorption;
whenever solutes are reabsorbed,
water follows
regulation of water reabsorption
Concentration and volume of urine depends on
facultative reabsorption; facultative reabsorption
is regulated by antidiuretic hormone (ADH)
ADH stimulates the insertion of aquaporin-2
channels into the membrane of the DCT and collecting ducts. Aquaporin-2 channels promote the reabsorption of water, producing a small volume of concentrated urine
Anti-diuretic hormone:
a) Increases urine production
b)Is secreted in response to high blood pressure
c) Concentrates urine
d)Is released by the adrenal gland
C
Which process contributes to pH regulation?
a) Glucose reabsorption
b) Secretion of H+ ions
c) Constriction/relaxation of arterioles
d) Water reabsorption
B
regulation of blood volume and osmolarity (hormones)
Aldosterone, Angiotensin II, Natriuretic Peptides, Urodilatin
Alter blood volume without affecting blood osmolality
Aldosterone and Angiotensin II increase sodium and water reabsorption,
whereas natriuretic peptides and urodilatin inhibit their reabsorption
For aldosterone and angiotensin II to be released renin must be released first
◦ Renin is released:
◦ Decreased blood flow to the kidneys
◦ Reduced serum sodium levels
◦ Activation of sympathetic nerves to the juxtaglomerular cells
for natriuretic peptides to be released
Atrial cells in the heart must be overstretched by excessive blood volume
◦ Inhibits all the actions of Angiotensin II
◦ Results in loss of sodium and water in the urine
for urodilatin to be released
Distal and collecting tubule cells identify increased circulating volume
◦ It is very similar in structure and function to natriuretic peptides
◦ Inhibits Na+ and water reabsorption
parathyriod hormone
PTH causes the reabsorption of Ca2+ from DCT
PTH is released from the parathyroid glands when blood
calcium levels are low
diuretics
Exert effect by blocking reabsorption of sodium at specific sites in the renal tubules
Exert osmotic effects that prevent water reabsorption in water-permeable parts of
nephron
◦ Loop diuretics, thiazide diuretics,
potassium-sparing diuretics, osmotic diuretics
◦ ACE inhibitors inhibit the formation of
Angiotensin II and aldosterone
a) Angiotensin II
b) ADH
c) Aldosterone
d) Angiotensin II and Aldosterone
e) Angiotensin II, Aldosterone, and ADH
D
Facultative reabsorption of water due to ADH
occurs in which of the following structures?
a) Collecting ducts
b) Distal convoluted tubule
c) Proximal convoluted tubule
d) Nephron loop
e) a and b
E
Which substance(s) will cause a decrease in
urine output?
a) Natriuretic Peptide
b) Aldosterone
c) ADH
d) a and b
e) b and c
E
If the urinary excretion rate of a drug such as penicillin
is greater than the rate at which it is filtered at the
glomerulus, how else is it getting into the urine?
a) Movement through intercellular clefts into the glomerular
capillaries
b) Active transport
c) Blood colloid osmotic pressure
d) Tubular reabsorption
e) Tubular secretion
E
