Urinary V Lecture Flashcards
Ureter is specialized to ____
transport urine to bladder
the ureter has 3 layers:
- mucosa : transitional epithelium and lamina porporia
- muscularis: inner longitudinal, and outer circular smooth muscle
- adventitia: outer CT layer holding ureter in place
urine stretches muscularis layer stimulating ….
peristalic waves
peristalic waves:
waves of contraction which propel urine toward bladder
(regardless of gravitational pull)
only operate one way
signaled by urine stretching muscularis (bladder filling)
urinary bladder is specialized for….
urine storage
the urinary bladder has 3 layers:
- mucosa: transitional epithelium. stratified (barrier) lamina propria
- muscularis: detrusor muscle- extensive smooth muscle layers (contract to void urine)
- adventitia or serosa: outer CT layer
transitional epithelium
creates a barrier- has the ability to stretch or flatten depending on the fullness of the bladder
rugae:
when the bladder is empty, the wall is thrown into folds called rugae. these folds dissapear when the bladder is full (stretched)
detrusor muscle:
smooth muscle in wall stretches and thins allowing for stretching w/o increasing internal pressure.
under control of autonomic nervous system.
what is the capacity of the urinary bladder
500-1000 ml
trigone:
triangular region formed by openings of ureters and urethra
(site of persistent infections)
Urethra:
carries urine out of body
differences: urethra: m/f
F: 3-4 cm long
M: 20 cm long, 3 regions
urinary sphincters:
- internal urethral sphincter smooth muscle controlled by ANS
- external urethral sphincter: skeletal muscle, voluntary- controlled by somatic NS
micturition:
the act of emptying the urinary bladder
micturition is a …..
spinal reflex with CNS influence
role of nervous system (2 parts) in micturition
- parasympathetic nervous system: contracts detrusor muscle, relaxes internal urtheral sphincter
- sympathetic nervous system: active during bladder filling, relaxes detrusor and contract internal urethral sphincter to prevent voiding
micturition: involuntary reflex
- urine fills the bladder and stretches its wall
- stretch receptors send a signal via sensory afferent fibers from the sacral portion of the spinal cord
- parasympathetic efferent fibers stimulate detrusor muscle to contract and the internal urethral sphincter to relax causing micturition
micturition: voluntary control from CNS
- interneurons in the spinal cord commincate the “full bladder” signal to the micturition center of the pons
- if micturition is appropriate, the cerebral cortex facilitates this process and allows external sphincter to relax: urine is voided.
Look at slide about CNS determining urine storage or emptying
do it, now.
urinary incontinence:
inability to control urination
when the higher brain (pontine storage center) is controlling micturition it is acting on the spinal efferents how…
- decreasing parasympathetic activity
- increases sympathetic activity
- increases somatic motor nerve activity
pontine storage center
the part of the higher brain that allows or inhibits micturition at appropriate times.
urinary retention:
bladder unable to expel urine.
(general anesthesia, hypertrophy of prostate in. men
urine output:
the result of all the processes that take place in the kidney.
excretion:
the process of eliminating waste
excretion equation
excretion= filtration - reabsorption + secretion
excretion equation is important because:
- tells us how a substance behaves
ex. pain medication: when to dose - measures kidney function
ex. checks for failure
Tubular reabsorption:
PCT
reabsorption of all nutrients, many electrolytes, most sodium (NA+) and water (obligatory water reabsorption)
tubular reabsorption:
Descending limb of nephron loop
reabsorption of solutes (Na+, K+, Cl-)
tubular reabsorption:
DCT and/or collecting duct:
regulated reabsorption/ secretion
1. ADH
2. Aldosterone
3. Atrial natriuretic peptide (ANP)
4. parathyroid hormone
antidierectic hormone in regulation
stimulates aquaporin synthesis increasin water reabsorption
(regulates water reabsorption)
Aldosterone in regulation
stimulates synthesis of Na+ channels (apical) and Na+/K+ ATPase (basolateral) increasing Na+ reabsoprtion
ANP in regulation
inhibits Na+ reabsorption (opposite of aldosterone)
parathyriod hormone in regulation:
increases Ca+ reabsorption
what things are reabsorbed in proximal tubule
- nutrients (glucose, amino acids)
- vitamins
- electrolytes (NA, K+, Cl-)
- bicarbonate ions
- H2O
obligatory reabsorption:
reabsorption of water in proximal tubule
65% of water filtered
secretion is always active transport and requires
ATP
reabsorption moves water and solutes from…
filtrate to blood
if there was no reabsorption in the proximal tubule which valuable substance would be lost
a. hydrogen ions
b. nitrogenous waste
c. glucose
d. drugs
c. glucose
what percent of glucose is reabsorbed?
100%
reabsorption in which substances pass between adjacent tubular cells is called:
paracellular route
where does most of the reabsorption of water, nutrients, electrolytes, and bicarbonate ion occur?
proximal convoluted tubule (PCT)
PCT cells are the most active reabsorbers because
lined with simple cuboidal epithelium that has extensive microvilli on its apical border and many mitochondria
reabsorbs all glucose and amino acids, 65% of water and electrolytes mostly by nephron loop.
(rest of renal tube also reabsorbs but less so)
the process of reabsorption returns substances to which structure(s)?
peritubular capillaries and vasa recta
water reabsorption is always:
a passive process.
follows solutes by osmosis, and can. use transcellular or paracellular route.
aquaporins:
transmembrane proteins, act as water channels that allow water passage across the epithelial cell plasma membrane.
why would bicarbonate (HCO3) be reabsorbed?
the body needs it to help control pH.
when bicarbonate ion is reabsorbed, hydrogen ion (H+) is secreted into the filtrate.
these nephrons are responsible for establishing the medullary osmotic gradient.
juxtamedullary nephrons
because long nephron loops extend into medulla and are surrounded by vasa recta
countercurrent exchanger:
vasa recta
counter current exchange and multiplier between vasa recta and nephron loop achieves 2 main tasks:
- water reabsorption (between 15-25% of the remaining water)
- create and maintain medullary concentration gradient
the. thick ascending limb of the nephron loop is permeable to
ions such as Na and Cl.
(contains active transport pumps for these ions and is NOT permeable to water)
what is the consequence of the selective reabsorption of sodium and chloride in the ascending loop of Henle?
an osmotic gradient is established in the kidney medulla
osmolarity at deepest part of the medulla?
1200 mOsm
osmolarity at the borderof the cortical-medullary border?
300 mOsm
the thin ascending limb of the nephron loop is permeable to
water
NOT salt or other solutes
as filtrate moves down the descending limb of the nephron loop:
its concentration increases.
(filtrate loses water but not solutes)
why does water leave the kidney tubule as the filtrate travels down the thin descending loop of Henle?
because of the osmotic gradient in the interstitium of the medulla
in which part of the nephron will the filtrate have the highest solute concentration (i.e. highest osmolarity?)
at the hairpin turn of the nephron loop
what drives the activity of the Na-Cl pumps in the ascending limb of the loop?
the high concentration of the filtrate
if the filtrate concentration is lower than normal at the turn of the nephron loop:
active transport in the thick ascending limb will be less efficient.
countercurrent multiplier:
creates the medullary osmotic gradient
refers to the actions of the nephron loop.
NaCl reabsorption in ascending lim promotes water absorption in the descending limb, in turn makes it easier for NaCl to be reabsorbed in ascending limb by pumps.
POSITIVE FEEDBACK LOOP
what is the purpose of the countercurrent exchange performed by the vasa recta?
it maintains the medullary osmotic gradient
countercurrent: flows in the opposite direction.
blood flows in opposite directions within neighboring, parallel capillaries.
exchange: salts being exchanged for water
the distal tubule is a site for
reabsorption and secretion
what is diuresis?
the loss of water in urine
what control water reabsorption in the distal tubule?
hormones
what 2 hormones increase reabsorption of water in the distal tubule and collecting ducts?
anti-diurectic hormone (ADH) and aldosterone
ADH increases water reabsorption by:
stimulating the insertion of aquaporins into the plasma membranes of the medullary collecting duct epithelial cells.
which of the following hormones causes sodium reabsorption in the distal tubule?
aldosterone
( and K secretion)
which would be a potassium sparing durg?
water lose and decrease potassium in kidneys.
a drug that blocks the effect of aldosterone
which hormone conserves water by causing aquaporins to be inserted in the epitheleal cells of the collecting ducts?
ADH
what is the medullary concentration (osmotic) gradient?
the deeper you go in the medulla, the higher the concentration of salts or ions
an increase in urine volume is usually accompanied by _____ in urine concentration
a decrease
more water but same amount of solute so concentration will decrease
if there was no medullary concentration ;(osmotic) gradient the kidneys would produce
large amount of dilute urine
what if ADH is not present?
a large amount of dilute urine is formed
furosemide “loop dieretics” inhibit pump for the active reabsorption of Na and Cl. what happens to urine?
large amount of urine produced
list the structures in order : urine passing through as it is excreted:
collecting duct, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, urethra
which of the following promotes the formation fo dilute urine:
decreased osmolarity of extracellular fluids
where is the vasa recta blood osmolarity the highest?
deep in the medulla
(at the hairpin turn)
ultrfiltrate (filtrate) formed in glomerulus:
produced in the renal corpuscle of the nephron
similar to blood plasma (no proteins)
has the same osmolarity as blood plasma
how is the PCT different than the DCT
Water reabsorption always happens in the proximal convoluted tubule (it is obligatory) but it is regulated in the distal convoluted tubule.
