-
Kidney drops into pelvis. Why?
- Nephroptosis
- kidneys are retroperitoneal - outside peritoneal membrane
- drop when not enough fat to hold up
-
which kidney is lower? why?
-
3 functions of urinary system
- excretion
- elimination
- homeostatic regulation
-
excretion v. elimination
- removal or organic wastes from body fluids
- v.
- discharge of waste from body
-
6 homeostatic functions of urinary system
- 1. regulates blood volume and blood pressure
- 2. regulates plasma ion concentrations
- 3. helps stabilize blood pH
- 4. conserves important nutrients
- 5. assists liver in detoxifying poisons
- 6. gluconeogenesis
-
what organs produce urine?
size?
-
what organs make up the urinary tract?
- ureters
- urinary bladder
- urethra
-
process of eliminating urine
-
result of nephroptosis
kinked ureters/blood vessels
-
study of urinary system
nephrology
-
doctor of urinary system
-what other system?
- urologist
- also male reproductive system
-
how does the urinary system regulate blood volume/pressure?
- adjust how much water lost in urine
- release erythropoetin and renin --> stimulates production of angiotensis
-
the urinary system helps regulate the concentration levels of which ions? how?
- Sodium, Potassium, chloride (control how much lost in urine)
- Calcium (synthesis of calcitriol)
-
US works with which system to stabilize blood pH? How?
- Respiratory
- controls loss of H+ and bicarbonate ions in urine
-
what product does the US turn to glucose to help regulate homeostasis?
glutamine
-
what 3 structures protect/stabilize kidneys?
- fibrous capsule (collagen, covers entire surface)
- perinephric fat capsule (adipose, surrounds renal capsule)
- renal fascia (outer layer, anchors kidneys)
-
what anchors the kidneys to surrounding structures?
renal fascia
-
what are the functional units of the kidneys? what occurs here?
- nephrons
- tubular structures in each renal lobe
- -filtration and urine production, secretion/resorption
-
what occurs in the kidneys during sympathetic innervation?
- vasoconstriction
- -rate of urine formation adjusted by changing blood flow/volume at nephron
- -renin released
-
What does renin do?
- raises blood pressure
- -Restricts loss of water and salt in urine by stimulating reabsorption at nephron
- -stimulates production of angiotensin II
- -stimulates thirst center
-
two main parts of nephron and function
- renal corpuscle- filters blood plasma
- renal tubule- converts filtrate to urine
-
what makes up the renal corpuscle?
- glomerulus
- glomerular capsule around it
- -cup-shaped structure
-
what kind of cell is wrapped around the capillaries of the glomerulus?
- podocytes
- - have "feet" called pedicles
- -"visceral epithelium"
-
what delivers blood to the glomerulus? What removes it? Where does it go from there?
Afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries -> small venules -> venous system
-
describe the size of afferent and efferent arterioles and why it is important
- Afferent are wider, efferent smaller
- creates pressure gradient so that filtration will occur
-
How does high blood pressure affect the glomerulus?
- causes more blood to flow through -> more filtration
- glomerulus is overworked and wears out
-
what is the fluid called when it's in the renal corpuscle and renal tubule?
Blood
-
What is the glomerulus?
A ball of capillaries where filtration occurs (goes into renal corpuscle)
-
What is the fluid called once it enters the renal corpuscle?
filtrate
-
What can't filter through and is thus not found in filtrate?
-
Where does filtrate go after leaving the renal corpuscle?
Renal tubule
-
Three functions of the renal tubule
- Reabsorb nutrients from filtrate
- -glucose and water soluble vitamins
- Reabsorb water
- -90% of water in filtrate is reabsorbed
- -Secrete waste products that didn't get into renal corpuscle at glomerulus (drugs, toxins, etc)
-
What will happen if you don't produce enough ADH/have enough ADH receptors? Resulting disease?
- Reabsorption won't occur
- -> Polyurea
- ->Diabetes insipidus
-
Why doesn't glucose enter your urine? If it does, what is happening, what is it called, and what disease might you have?
- gets reabsorbed at renal tubule
- Too much glucose in bloodstream -> can't reabsorb it all
- Glycosuria
- Diabetes Mellitus
-
Sweet urine
Associated disease
- Glycosuria
- Diabetes Mellitus
-
What are the three segments of the renal tubule?
Proximal convoluted tubule (PCT)
nephron loop (loop of Henle)
Distal convoluted tubule (DCT)
-
Where does the most reabsorption of glucose and ions take place?
Proximal convoluted tubule in renal tubule
-
Once the fluid enters the renal tubule, what is it called?
Tubular fluid
-
Tubular fluid passes from PCT -> nephron loop ->DCT -> _________________
Collecting duct
-
function of collecting ducts
- receive fluid from many nephrons
- many collecting ducts merge to become larger papillary duct
-
Once the fluid enters the collecting ducts, what is it called?
Urine
-
Recap: What are the different names, and associated locations, for the fluid that passes through the urinary system?
- Enters glomerulus: blood
- Renal corpuscle: filtrate
- Renal tubule: tubular fluid
- Collecting duct: urine
-
The renal corpuscle is made up of the glomerulus and the glomerular capsule around it. What is between the two?
Capsular space
-
function of descending limb of nephron loop
reabsorption of water from tubular fluid
-
function of ascending limb of nephron loop
- reabsorption of ions
- -helps make concentration gradient at medulla
-
Two kinds of nephrons; which is more common?
- Cortical nephrons- 85%
- -short
- Juxtamedullary nephrons- 15%
- -long
-
Where does blood go from the efferent arteriole of the nephron loops in cortical nephrons?
In Juxtamedullary nephrons?
Peritubular capillaries
in Juxt: to vasa recta
-
How does aldosterone cause the reabsorption of water?
- Increases number of Na+/K+ antiporters
- -> reabsorbs sodium
- -> water follows
-
The longer loop of Henle in the Juxtamedullary nephron allows it to do what?
conserve more water
-
What forms the outer wall of the renal corpuscle?
glomerular capsule
-
What drives filtration?
Pressure from heart, size difference between afferent and efferent arterioles
-
What role do podocytes of the glomerulus play in filtration?
- shaped like an octopus with feet wrapped around capillaries
- feet = "pedicels"
- Between the feet are filtration slits
- -
anything smaller than 3 nm can pass through freely into capsular space
-
Bacterial infection in glomerulus
Glomerulonephritis
causes damage to filtration membrane - allows things that are too big to filter out
-
Cell that helps control the diameter of the vessel in glomerulus
Mesangial cell
-
What kind of capillaries are the glomerular capillaries?
Fenestrated (large pores)
-
What kind of filtration occurs at the renal corpuscle? What solutes enter the capsular space?
- passive
- glucose, free fatty acids, amino acids, vitamins
- -also water
-
what percentage of solutes that are filtered out end up in urine?
-
Where does most reabsorption occur?
Proximal Convoluted Tubule
-
Where is the entrance to the PCT located? What does it have to distinguish it?
- opposite where the afferent and efferent arterioles are
- microvilli
-
Where do substances that are reabsorbed in the PCT go?
Back to blood
-
what absorbs materials from tubular fluid and releases them into peritubular fluid?
tubular cells
-
Peritubular fluid is a kind of ____
Interstitial Fluid
-
what gets reabsorbed at the PCT?
- the good stuff: elecrolytes, fatty acids, amino
- acids, glucose, vitamins
-
Two segments of each limb of the nephron loop and their function
- Thick segment: reabsorbs solutes
- Thin segment: reabsorbs water
- -ascending and descending limb both have thick and thin segments-
-
which segment of the nephron loop is absent in the cortical nephron? What does this imply?
- Thin segment
- Cortical loops not as effective at reabsorbing water
-
Kangaroo rats have more __________, so they can reabsorb more water
Juxtamedullary nephron loops (with thin segments)
-
what controls reabsorption rates?
hormones
-
Aldosterone:
Targets
Effects
- Nephron loop, DCT, Collecting ducts
- Raise blood volume
- Reabsorb sodium, secrete potassium
- --> increase chlorine and water reabsorption (follow sodium)
- Reduce urine volume
-
Angiotensin II:
Target
Effects
Afferent/Efferent arterioles, PCT
- Reduce water loss (raise blood volume)
- stimulates thirst
- vasoconstriction
- stimulates aldosterone and ADH secretion
-
ADH:
Target
Effects
- Collecting duct
- water reabsorption (inserts aquaporins)
- reduce urine volume
- increase concentration of urine
-
ANP/BNP:
Targets
Effects
- Afferent/Efferent arterioles, Collecting duct
- Dilate afferent, constrict efferent --> drive filtration
- Increase GFR
- inhibit renin, ADH, aldosterone
- increase urine, decrease blood volume
-
Calcitonin:
Targets
Effects
- DCT
- synergistic to parathyroid hormone
-
Calcitriol:
Target
Effects
- DCT
- synergistic to parathyroid hormone
-
Epenephrine/Norepenephrine function
- induce renin secretion -> angiotensin II -> raise blood pressure
- -reduce GFR/urine volume
-
Parathyroid hormone:
Target
Effect
- PCT, DCT, nephron loop
- Promotes calcium reabsorption in loop and DCT
- Increase phosphate excretion by PCT (no crystals)
- promotes calcitriol
-
What is GFR?
- Glomerular Filtration Rate
- amount of filtrate former per minute by the two kidneys combined
-
what happens if the GFR is too high?
- fluid flows too rapidly, can't reabsorb enough water/solutes
- excrete more urine, risk dehydration/electrolyte depletion
-
What happens if GFR is too low?
fluid moves too slowly through tubules, reabsorb waste that should be eliminated
-
Slit that admits renal nerves, blood vessels, lymphatics, ureter into kidney
hilum
-
part of nephron that filters blood plasma
renal corpuscle (glomerulus and glomerular capsule)
-
part of nephron that converts filtrate to urine
renal tubule (PCT, nephron loop, DCT, CD)
-
what part of nephron loop has high metabolic activity and what causes it?
- thick segments (active transport of salts)
- lots of mitochondria
-
Flow of fluid from formation of glomerular filtrate to urine leaving the body:
- Glomerular capsule
- -> PCT
- -> Nephron loop
- -> DCT
- -> Collecting duct
- -> Papillary duct
- -> Minor calyx
- -> Major calyx
- -> Renal pelvis
- -> Ureter
- -> Urinary bladder
- -> Urethra
-
4 stages of converting blood plasma to urine
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
- Water conservation
-
Compare blood plasma to filtrate
Very similar composition, but filtrate has no proteins
-
Compare tubular fluid to filtrate
substances are removed/added by tubular cells
-
What changes does urine undergo once it enters the collecting duct?
Not much- change in water content
-
What is glomerular filtration anyway?
water and some solutes in blood pass from capillaries in glomerulus into capsular space of the nephron
-
What is the Glomerular Hydrostatic Pressure (pressure pushing blood out of glomerulus)?
50 (much higher than other capillaries)
-
COP in glomerular filtrate
not significant --> no proteins
-
Capsular Hydrostatic Pressure (pushing back on glomerulus)
15 (most ICF pressure is negative i.e. not pushing back)
-
BCOP in glomerulus (pushing back in)
25
-
Why is it important to maintain a net filtration of 10 mm Hg in the glomerulus?
Prevent buildup of toxins
-
Describe net filtration pressure in glomerulus
- 50 (HP out) - 25 (BCOP in) - 15 (CsHP in) = 10 mm Hg out
- -> just filtrating, not reabsorbing fluid in glomerulus
-
How much urine is excreted per day?
1-2 liters
-
why is maintaining blood pressure so important in the glomerulus?
Controls the Glomerular Filtration Rate -> ensures that the right amount of filtration/reabsorption occurs
-
how is the autoregulation of the GFR carried out?
by changing diameters of arterioles/capillaries in response to changes in blood pressure/flow (smooth muscle stretch repsponse)
-
how is the GFR autoregulated if there is reduced blood flow?
- Create higher pressure gradient
- dilate afferent arteriole and glom. capillaries, constrict efferent
-
how is the GFR autoregulated if there is increased blood flow/pressure?
- Create lesser pressure gradient
- walls of afferent arterioles are stretched, causing smooth muscle to contract
- ->constrict afferent arterioles, difference with efferent is less -> less gradient, less filtration
-
what cells release renin
juxtaglomerular cells (JGA)
-
when afferent arteriole is constricted, the GFR increases/decreases
decreases (less difference in pressure)
-
Describe results of Renin-Angiotensin-Aldosterone mechanism
- BP drops -> JGA releases renin
- stimulates production of angiotensin II
-vasoconstriction at efferent arteriole raises glomerular BP and GFR (makes sure filtration continues)
-lowers BP in peritubular capillaries -> increases reabsorption of NaCl and water (raise BP)
-stimulates aldosterone (sodium and water reabsorption)
-stimulates ADH (water reabsorption)
-stimulates thirst center
-
tubular reabsorption
removes useful solutes from filtrate, returns them to blood
*Reabsorption = back to blood
-
tubular secretion
removes wastes from blood, adds them to filtrate
-
water conservation
removes water from urine, returns it to blood, concentrates urine
-
what is the most abundant cation in filtrate?
sodium
-
Why is sodium so important?
- It creates an osmotic and electrical gradient
- Drives reabsorption of water and solutes
-
Name some things sodium can symport with
glucose, amino acids, lactate
-
what is pumped out of the cell and into tubular fluid when sodium is pulled in (antiporter with sodium)? What does this do?
Hydrogen (eliminates acid from body fluids)
-
what hormone activates the Na+/H+ antiporter?
Angiotensin II
-
What prevents sodium from accumulating in the epithelial cells?
- Sodium/Potassium pumps (active transport)
- pumps sodium into ICF, returns to bloodstream
-
what ion follows sodium? why?
chloride, negatively charged, attracted to positive sodium
-
true or false: the kidney removes all toxic urea from the blood
How does this relate to urea concentration of urine?
- false: removes about half, reabsorbs about half (40-60%)
- reabsorbs 99% of water, so urine has higher concentration of urea
-
how much creatine is reabsorbed?
None- it is all secreted into the tubule and goes into urine
-
99% of water is reabsorbed; how much of that occurs in the PCT?
Why does this occur?
What is this called?
2/3
reabsorption of solutes/salt there makes tubular cells hypertonic to tubular fluid, water follows (osmosis via aquaporins)
obligatory water reabsorption
-
Constant rate of water reabsorption, not controlled by hormones
- obligatory water reabsorption
- PCT, descending limb
-
hormone controlled water reabsorption
- facultative water reabsorption
- DCT and CD
-
how do water and solutes get reabsorbed into peritubular capillaries?
osmosis and solvent drag
-
the maximum rate of reabsorption due to limited number of transport proteins is called the ___________
transport maximum
-
glycosuria is a sign of what disease?
diabetes mellitus
-
two functions of tubular secretion
- remove wastes from blood (includes drugs/medications)
- maintain acid-base balance
-
Primary function of nephron loop
generate osmotic gradient that enables the collecting duct that enables the collecting duct to concentrate the urine and conserve water
makes it really dilute- pushes out solutes and brings in water
-
secondary function of nephron loop
reabsorb Na+, K+, Cl- and water
-
describe solute concentration at various stages of nephron loop
1) Entering loop
2) descending limb
3) bottom of loop
4) ascending limb
5) entering DCT
-
what controls reabsorption of water and salts in the DCT and CD?
hormones: facultative reabsorption
-
what stimulates aldosterone secretion in the DCT?
blood sodium concentration falls, increase of potassium level
-
4 effects of ANP/BNP
dilate afferent, constrict efferent -> increase GFR
inhibit renin/aldosterone
inhibit ADH
inhibit salt reabsorption
-
What prompts ADH?
dehydration, rising blood osmolarity
-
How does ADH raise blood volume?
inserts more aquaporins at collecting duct for more reabsorption
-
Parathyroid hormone is released in response to high/low blood calcium levels?
low
-
What does parathyroid hormone do in the PCT? DCT/thick segment of nephron loop?
- PCT: inhibit phosphate reabsorption
- DCT/thick: increase calcium reabsorption
-
when urine enters upper CD, it is hyper/hypo/iso-tonic to blood plasma. When leaves it is ______.
- Enters: isotonic
- Leaves: hypertonic (4x more concentrated)
-
What two things cause water to leave the collecting duct, thereby concentrating the urine?
- ECF is very hypertonic, water leaves via osmosis
- CD is more permeable to water than solutes
-
Water diuresis
Very hypotonic (dilute) urine from drinking a lot of water
-
What hormone is released when you're dehydrated?
- ADH -increase water reabsorption
- add more aquaporins
-
What happens to ADH when you're really well hydrated?
Suppressed, aquaporins are removed for less permeability to water/reabsorption
-
Does increasing the GFR result in more or less urine production? Why? What hormone causes this to happen
- More: less time for reabsorption -> more urine
- --> ANP/BNP
If GFR is low, more time for reabsorption -> less urine
-
-
What creates urea?
breakdown of proteins
-
What creates creatinine?
creatine phosphate is broken down in muscles for extra ATP
-
What creates uric acid?
breakdown of nucleic acids (DNA, RNA)
-
What happens if there's a buildup of uric acid/Resulting disease? What is this a result of?
Kidney failure -> buildup -> super saturation -> crystals ->
Gouty Arthritis
-
Is renal threshold higher for glucose or amino acids?
glucose
-
Amino acids in urine
- proteinuria
- after high protein meal
-
what makes pee yellow?
urobilinogen
-
what effect do ACE inhibitors have on BP?
decrease (inhibit Angiotensin II production)
-
Glomerulonephritis
lose proteins that should be reabsorbed -> reduced BCOP -> edema
-
Where is fluid most concentrated? Most dilute?
Concentrated: bottom of nephron loop and in collecting duct
Dilute: top of nephron loop/beginning of DCT
-
What happens to filtration/reabsorption rates in kidney/liver failure?
there aren't any proteins so there's a low BCOP to push back in, so filtration is normal but reabsorption rates are low
-
what two sunstances can be measured in urine to evaluate GFR?
creatinine, insulin
-
What causes the medulla to have such a high (4x) osmolarity (salt concentration)?
"occurs between two parallel segments of nephron loop"
Countercurrent multiplier
-
What does the countercurrent multiplier do (2 benefits)
helps reabsorb solutes and water before tubular fluid reaches DCT/CD
Establishes concentration gradient for water reabsorption in CD
-
prolonged stimulation of what hormone causes hypokalemia?
aldosterone (pumps Na+ in, K+ out)
-
why can alkalosis be caused by prolonged aldosterone stimulation?
sodium can be antiporter with bicarbonate -> pump Na+ in, bicarbonate out -> bicarbonate builds up in blood, makes it alkaline
-
Lack of ADH/ADH receptors -->
- polyurea
- Diabetes insipidus
-
Polyurea is a sign of ________
Diabetes insipidus
-
what happens to the thirst center with age?
not as sensitive to angiotensin II -> drink less
-
Two names for urination
Diuresis, micturition
-
what do diuretics target?
ascending loop -> stop reabsorption of solutes -> less osmosis -> lots of clear pee
-
what is the function of the vasa recta?
returns water and solutes back to blood
-
what is the normal pH for urine?
4.5-8 (avg 6)
-
Is reabsorption in PCT active or passive? What does this cause?
- Active
- Osmotic water flow out of tubular fluid -> reduce volume of filtrate
- -obligatory
-
In thick ascending limb, is transport of solutes active or passive?
Active
-
Where does urine go upon leaving the collecting ducts?
- Minor calyx
- Major calyx
- Renal pelvis
- Ureter
- Urinary bladder
- Urethra
-
what's a pyelogram?
- Tests for kidney function
- inject dye
- check for blockage, kidney stones, cancer
-
what kind of epithelium do the ureters and urinary bladder have?
transitional epithelium (allows for stretch and recoil)
-
size difference in male and female bladders
same; females can't expand as much due to uterus
-
Benign Prostatic Hypertrophy
- Prostate grows and constricts urethra
- -> urine backs up
always feels like you have to pee but can't fully void bladder
-
what part of the bladder acts as a funnel, channeling the urine from the bladder into the urethra?
Trigone
-
two urethral sphincters- voluntary or involuntary?
- Internal urethral sphincter- smooth muscle -> involuntary
- External urethral sphincter- skeletal muscle -> voluntary
-
what muscle causes the bladder to contract?
- Detrusor muscle
- (in muscularis layer)
-
how long is the male urethra?
8-20 cm (7-8 in)
-
3 parts of male urethra
- Prostatic urethra
- membranous urethra
- spongy urethra (in penis)
(PMS)
-
length of female urethra
3-5 cm (1-2 in)
-
what act permits micturition?
voluntary relaxation of external urethral sphincter
-
what part of the brain is responsible for the micturition reflex?
Pons
-
What is the micturition reflex?
- baroreceptors (stretch receptors) in bladder stimulate sensory fibers
- -> pons
- -> efferent nerves of bladder
- -> detrusor muscle contraction
- -> sensation to thalamus
- -> voluntary relaxation of external sphincter causes relaxation of internal sphincter
-
what causes the relaxation of the internal urethral sphincter?
voluntary relaxation of the external sphincter
-
what volume of urine in bladder triggers micturition reflex?
>500 mL
-
why don't infants have voluntary control over micturition?
nerves aren't myelinated yet
-
inability to control urination voluntarily
incontinence
-
what is the first sign of normal incontinence with age? what causes it?
- leaking
- weakened muscle tone
-
what can cause incontinence?
Alzheimer disease, stroke, loss of muscle tone
-
what changes take place in the urinary system with age?
- fewer functional nephrons
- reduced GFR -> less urination
- reduced sensitivity to ADH
- problems with micturition reflex
-
What four systems are part of the larger excretory system?
- Urinary system
- Integumentary system (sweat)
- Respiratory system (Co2)
- Digestive system
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