Chapter 25 the urinary system Flashcards
what are the three functions of the urinary system?
waste removal
maintain blood volume
regulate blood chemistry
what is the general function of the kidneys?
site of filtration
site of urine production
how much blood do the kidneys filter?
1.2 L of blood per minute
entire volume of blood is filtered 60x per day
what do the kidneys have in abundance to aid in their function?
abundance of mitochondria and use 20% of body’s oxygen to produce ATP in order to have energy to filter blood and concentrate urine
what is the location of the kidneys? which is lower? why?
between T12 and L3
right is lower because it is crowded by liver
what are the layers of the kidneys called? deep to superficial
fibrous capsule
perirenal fat capsule
renal fascia
what is the fibrous capsule’s structure/function?
transparent inner layer
stops spread of infections from surrounding regions into kidneys
what is the perirenal fat capsule’s structure/function?
thick middle layer
cushions and holds kidneys in place
what is the renal fascia’s structure/function?
dense fibrous connective tissue
anchors
what is renal ptosis? and what can this cause?
kidneys drop due to severe weight loss
can prevent urination flow
what is found in the cortex of the kidneys?
made mostly of blood vessels
what is found within the renal medulla?
renal tubes
what is the renal pelvis?
central cavity that collects urine
what are the major and minor calyces of the kidneys?
minor: is the tube directly leading out of the renal pyramids
major: is the joining of several minor calyces
name the order of urine flow starting with renal pyramid
what is a nephron? how many of them are there?
structural and functional units of the kidneys in producing urine
1 million per kidney
what is the structure/function of the glomerulus?
ball of capillaries
site of blood filtration
how many glomerulus per nephron?
1
what is the structure/function of the afferent arteriole?
feeds into the glomerulus
larger diameter
contains “dirty” blood
what is the structure/function of the efferent arteriole?
leaves glomerulus
smaller diameter
contains filtered blood
where do solutes go that cannot travel through the filtration membrane?
back out the efferent arteriole
why is the efferent arteriole called that instead of a venule?
because it leads to another capillary bed (peritubular capillary)
what is the structure/function of the peritubular capillaries?
branch from the efferent arteriole
surround renal tubules
collect solutes reabsorbed by kidneys
what is the location and function of the glomerular capsule?
is the cup surrounding the glomerulus
receives filtrate from glomerulus
what is the location and function of the proximal convoluted tube?
closest convoluted tube to the glomerulus
site of most reabsorption
what is the location and function of the nephron loop?
composed of descending/ascending loop
allows production of concentrated and dilute urine
creates counter current multiplier
what is the location and function of the distal convoluted tube?
furthest convoluted tube from the glomerulus
fine tunes ion reabsorption
what is the location and function of the collecting duct?
last chance to modify chemical composition of urine
drains into renal pelvis
how many nephrons drain into a single collecting duct?
many nephrons drain into the same collecting duct
what is food called when leaving the mouth heading to the stomach?
bolus
what is food called when leaving the stomach?
chyme
what is fluid leaving the collecting ducts of kidneys called?
urine
what is fluid called when leaving the glomerulus?
filtrate
what are the two classes of nephrons?
cortical nephrons
Juxtamedullary nephrons
which class of nephrons is most common?
cortical nephrons (85%)
what is the difference of structure of the cortical vs Juxtamedullary nephrons?
cortical nephrons are mostly located in cortex
Juxtamedullary have long nephron loops which plunge deep into medulla
what is the purpose for Juxtamedullary nephrons?
critical for generating concentration gradients
what is the location/function of the Juxtaglomerular complex
region of tubule where ascending limb of nephron loop contacts afferent arteriole
function: regulates the rate of filtrate formation/ systemic blood pressure
what types of cells are found in Juxtaglomerular complex?
macula densa cells
granular cells
what is the location/ function of the macula densa cells?
location: form wall of ascending nephron loop at the juxtaglomerular complex
function: contain chemoreceptors that sense concentration of NaCl then signal for vasoconstriction/dilation
what is the location/function of granular cells within the juxtaglomerular complex?
location: Large smooth muscle cells lining afferent arteriole
function: contain mechanoreceptors sensing changes in MAP
false; aim for the right
what are the three processes that the renal tube uses to control urine composition? what occurs in each step?
glomerular filtration - control what solutes enter renal tube
tubular reabsorption - save valuable solutes push them back into peritubular capillaries
tubular secretion - pump waste directly into renal tubule from peritubular capillaries
what type of capillary is the glomerulus?
fenestrated capillaries
what are the layers of the glomerular filtration membrane?
- endothelium of glomerular capillaries
- visceral membrane of glomerular capsule
- basement membrane in between
what is the structure of the visceral membrane of the glomerular capsule?
made of podocytes
slits between podocytes allow for fluid to enter capsule
what is the function of the basement membrane within the glomerular filtration membrane?
prevents passage of anything greater than 5 nm
explain how fluid moves out of the glomerulus and into the renal tube?
blood pressure in glomerulus is high for capillaries (55 mmHg) and pressure in capsule is lower (15 mmHg) allowing fluid to go from high to low
explain how the glomerular filtration rate is regulated
intrinsic and extrinsic mechanisms
what is the GFR? what is the average rate?
Glomerular filtration rate - Volume of filtrate formed per
minute
125 mL/min
how much urine is produced each day?
1.5 L
what is involved in the intrinsic controls of GFR? specifically the Myogenic response
myogenic response - automatic response to constrict when vessel is stretched and relaxes when not stretched (triggering vasodilation)
what is involved in the intrinsic controls of GFR? specifically the tubuloglomerular feedback
*macula densa cells cause granular cells to release NO/ATP
what is involved in the extrinsic controls of GFR? specifically which nervous system?
sympathetic nervous system will cause vasoconstriction decreasing GFR
what is involved in the extrinsic controls of GFR? specifically the renin-angiotensin?
granular cells release renin when triggered by:
- SNS causing vasoconstriction
- macula densa cells sensing low GFR
- reduced stretch in afferent arteriole
what does renin convert to?
angiotensin II
where does the majority of reabsorption occur? how does its structure aid in this?
proximal convoluted tubule
has microvilli to increase surface area
what is the goal of tubular reabsorption?
recover valuable solutes from glomerular filtrate
(electrolytes/ water/ organic/ nutrients)
what is the animal that is able to secrete solid uric acid crystals?
desert rat (so good at saving water)
what is the shape of wombat poop?
cubes
how does tubular reabsorption take place?
active transport
what types of exact nutrients are reabsorbed?
100% organic nutrients
HCO3-
Na+
Cl-
K+
what is the effect of high/low GFR on tubular reabsorption?
high: not enough time to reabsorb everything (high content NaCl)
low: wastes will begin to be reabsorbed (low NaCl)
where does tubular secretion mostly occur?
proximal convoluted tubule
(can also occur in DCT)
what is tubular secretion?
movement from peritubular capillaries to renal tube
what types of substances can be in tubular secretion?
drugs too big to cross filtration membrane
urea that was reabsorbed
potassium to balance osmolarity
H+ or HCO3- to maintain pH
what did Sawa have nightmares about in school?
loop of Henle
what is the location and function of the counter current multiplier?
location: nephron loop
function: allows formation of concentration gradients/ used to concentrate or dilute urine
which type of nephron is the counter current the strongest?
long nephron loops of juxtamedullary nephrons
the descending/ascending limb is permeable to what?
descending: water (impermeable to salt)
ascending: NaCl (not permeable to water)
what is the starting and ending value of the osmolarity within the descending tubule of the nephron loop?
starts at 300 mOsm (same as blood)
ends at 1200 mOsm (increases with the leaving of water)
what is the starting and ending value of the osmolarity within the ascending tubule of the nephron loop?
starts: 1200 mOsm
ends: 100 mOsm
at equal levels on a picture of the nephron loop, what is the difference in mOsm of descending/ascending loop?
difference of 200 mOsm
which limb of the nephron loop creates the osmolarity gradient?
ascending limb pushes salt out (which creates the gradient for water to come out of the descending limb)
what is the number going in to the nephron loop in mOsm? coming out?
in: 300 mOsm
out: 100 mOsm
how does the osmotic gradient create dilute urine?
happens when body is well hydrated
collective duct is kept relatively impermeable to water (no need to save extra water)
how does the osmotic gradient create concentrated urine?
occurs when dehydrated
cells in collecting duct open aquaporins (water channels) in order to reabsorb water in peritubular capillaries
what are the hormones that enable insertion of aquaporins in the collecting duct?
ADH (antidiuretic hormone)
what happens to the mOsm of the collecting duct when dehydrated?
increases back to 1200 mOsm because water is leaving to be reabsorbed
what are diruetics?
chemicals that increase urinary output
how do osmotic diuretics work? example?
hold water in renal tube because concentration within renal tube is so high so water remains to dilute the solutes
ex: glucose in diabetics
how does caffeine work as a diuretic?
by inhibiting sodium reabsorption thereby inhibiting water from being reabsorbed
how does alcohol work as a diuretic?
inhibits ADH release that trigger aquaporin release so water remains in collecting duct
what is the renal clearance rate? what is the acronym associated with it?
volume of plasma that is cleared of a particular substance per minute
C
what is the renal clearance rate (C) equal to?
GFR = 125 mL/min
what is the color of urine come from?
urochrome
what does pink or brown urine indicate?
ingestion of some foods (beets)
presence of bile pigments or blood
what might cloudy urine indicate?
microbes
what is the pH of urine?
6
what can acidic urine indicate?
large amount of protein/ whole wheat diet
what can highly basic urine indicate?
vegetarian diet
prolonged vomiting
bacterial infection
what is the chemical composition of urine?
water
urea
uric acid
creatinine
electrolytes (ions)
what is renal calculi?
crystals of calcium, magnesium or uric acid within kidneys (kidney stones)
what causes renal calculi?
urine retention
infection
alkaline pH
what size renal calculi can pass? what occurs if it cannot?
< 5 mm
hydronephrosis (need lithotripsy to remove)
what is another word for urination?
micturition
how is it that astronauts can urinate still in space? is gravity not involved?
no, layers of smooth muscle in ureter wall contract to propel urine to bladder
is the bladder intra/retroperitoneal?
retroperitoneal on pelvic floor
what does bladder have to allow for stretch?
rugae
where in the bladder is a common site for infection? why?
trigone of bladder
because it is close to the opening of the urethra
what min/max size can bladder hold?
800 - 1000 mL
what muscle contracts to expel urine?
detrusor muscle
what are the regions of the male urethra called?
prostatic urethra (within prostate)
intermediate/ membranous
spongy (within length of penis)
which section of male urethra does ejaculatory ducts empty?
prostatic urethra
where is the urethrae muscle in the male urethra?
intermediate urethra
why do women get more urinary infections than men?
the urethra is shorter
it is closer to anal opening (near potential fecal bacteria)
what are the two sphincters responsible for release of urine? which is voluntary/involuntary?
internal urethral sphincter: involuntary
external urethral sphincter: voluntary
why is pH regulation so important?
protein shape is determined by charge interactions of molecules (charge of molecules is determined by pH)
name an example of how pH affects specific protein function?
correct shape of hemoglobin can only be accomplished within certain pH range, otherwise it will fail to correctly bind to oxygen
what is the normal pH of arterial blood? venous blood? why different?
arterial: 7.4
venous: 7.35
because venous blood contains wastes and the wastes are acidic
what is acidosis? its pH range?
pH is lower than normal because it has more H+ molecules
< 7.35 in arterial blood
what is alkalosis? its pH range?
blood pH is higher than normal because it has fewer H+ molecules
> 7.45
what is the job of buffers in the body? what are the names of the types of buffer systems we have in the body?
to resist pH changes
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system
which buffer system is the most important? where is is primarily used?
bicarbonate buffer system
in extracellular fluid
what is the bicarbonate buffer system, how does it maintain pH?
made of carbonic acid and bicarbonate (acid/base pair)
they are H+ sponges, can either soak up H+ or squeeze out H+ to increase/decrease pH
what is the alkaline reserve?
all the bicarbonate dissolved in plasma (pH only decreases when all this reserve is used up)
where is the phosphate buffer system used?
urine
intracellular fluid
how does the phosphate buffer system work?
similar to the bicarbonate buffer system (soaks up/ lets go of H+)
what is the protein buffer system?
amino acids contain acid/base pair
where is protein buffer system used?
both intracellular and extracellular fluid
how does breathing regulate pH?
increase breathing rate also increases pH
what happens to blood pH when hyperventilating?
increases pH
what is the problem with using breathing to regulate pH?
only eliminates carbonic acid (so if the body’s pH is raised due to other acids like linoleic etc, than it won’t work)
what other organ can regulate pH in addition to the lungs?
kidneys rid of acids to lower pH
what is metabolic acidosis? caused by?
lower than 7.35
too much alcohol consumption (metabolized into acetic acid)
starvation (produce fatty acids and ketone bodies)
what is metabolic alkalosis? caused by?
pH higher than 7.45
excessive vomiting (parietal cells secrete bicarbonate into blood while reproducing HCl)
antacid overdose (same thing happens but caused by excessive base consumption)
what is respiratory acidosis? caused by?
low blood pH due to altered breathing
- shallow breathing
- poor gas exchange (COPD)
what does poor ventilation lead to?
respiratory acidosis
what is respiratory alkalosis? caused by?
high blood pH due to altered breathing
- hyperventilation
what is renal tubular acidosis? caused by?
low blood pH due to kidney not being able to secrete acids or reabsorb bicarbonate
what two organs are involved in the compensation of pH?
kidneys and lungs
explain how compensation functions to maintain a normal pH when excess acid or base is being produced?
if respiratory regulation of pH fails, renal system will try to compensate and vice-versa
COPD patients have respiratory acidosis, what happens to their urine pH?
urine pH will decrease because it is ridding of acids within the body to lower the acidic blood pH
