each kidney is supplie by the renal artery arising from the aorta
divides into a few segmental arteriesfurther divides into interlobar arteries,travel between the pyramids
branches again form the arcuate arteries, which travel along the base of the pyramids
then these give rise to the interlobular arteriesafferent arterioles , leads to the glomerulus
blood leaves the glomerulus by the efferent arterioles, which then lead to the pertiubular capillaires, then to the interlobular veins, arcuate veins, interlobar veins, and renal vein, there are NO segmental veins
2 sets of arterioles, 2 sets of capillaries - coritcal nephron ( peritubular capillaries ) and the juxamedullary nephron ( vasa recta)
describe the structure of the renal corpsucle of the nephron:
renal corpuscle: consists of the glomerulus and the glomerular (Bowman) capsule
glomerular (Bowman) capsule: 2 layers - parietal (outer) layer - simple squamous epithelium, and visceral (inner) layer that consists of podocytes
capsular space: separtes the 2 layers by a filtrate collector
fxn: filters the blood plasma
describe the strcutre of a nephron and explain the physiological function of each nephron component:
renal tubule: a duct that leads away from the glomerular capsule
Fxn: convert the filtrate into urine
proximal convoluted tubule (PCT): arises from glomerular capsule, a great deal of absorption occurs here
nephron loop (loop of Henle): long U shaped protion, descending and ascending limb, thick segment engaged in active transports, and thin segments is permable to water
distal covoluted tubule (DCT): the end of the nephron
collecting duct: receives fluid from the DCT of several nephrons
distinguish between the cortical and justameduallary nephrons on the basis of location, strcutrue and fxn:
cortical nephrons
location: beneath the renal capsule, close to the kidney surface, in cortex
strcutre: short nephron loops, or none
fxn:
juxtamedullary nephrons:
location: in the medulla
structure: long nephron loops
fxn: maintaining an osmotic gradient inthe medulla that helps the body conserve water
Trace the flow of urine though kidney and out of the body:
glomerular capsule
proximal convoluted tubule
nephron loop
distal convoluted tubule
collecting duct
papillary duct
minor calyx
major calyx
renal pelvis
ureter
urinary bladder
urethra
identify the 3 basic steps/stages of urine formation in the nephron:
converts blood plasma to urine
glomerular filtration, tubular reabsorption, tubular secretion, and water conservation
glomerular filtrate: fliud in capsular space, similar to blood plasma, NO PROTEINS
tubular fluid: fluid from PCT to DCT, substaces are added/removed by tubules
urine: fluid in the collecting duct, little alteration
describe the filtration membrane:
fenestrated endothelium of the capillary: large filtration pores, highly permeable, but small enough to exclude blood cells from filtrate
basement membrane: gel-like, small pores, excludes molcules larger than 8nm, and negatively charged particles
filtration slits: podocytes, allows molecules about 30nm wide between them
most molecules smaller than 3 nm can pass
molecules that can pass are: water, electrolytes, glucose, fatty acids, amino acids, mitrogenous wastes, and vitamins
molecules turned back: blood cells, plasma proteins, large anions, protein-bound minerals and hormones, most molecules >8nm in diameter
describe how infections or trauma can affect the filtration membrane:
can allow albumin or blood cells to filter through
proteinuria (albuminuria): kidney disease, marked by the presence of protein (albumin) in the urine
CP: capsular pressure, results from high rate of filtration and continual accumulation of fluid in capsule
how to calculate
BHP
- COP
- CP
= NFP net filtration pressure
~20% fluid filtration
~ 80% goes to peritubular capillaires
~ 99 % reabsorbed after filtering
entire blood supply filtered 60x/day
explain net filtration pressures's relationship to glomerular filtration rate:
GFR: the amount of filtrate formed per minute by the two kidneys combinded
adjusted by the changing pressure of the glomerular capillaires - vasoconstriction/dilation of afferent/efferent arterioles
an increase in PGC > increases NFP > increase GFR, too rapid to reabsorb the usual amout of water/solutes, output rise, dehydration and electrolyte loss
decreased GFR > reaborbs wastes that should be eliminated
explain how GFR is regulated by renal autoregulation:
the ability of the nephrons to adjust their own blood flow and GFR with external (nervous/hormonal) control, enables them to maintain stable GFR despite changes in BP
myogenic mechanism: based on the tendency of smooth muscle to contract when stretched, when BP rises it strectchs afferent arteriole, mechansim constricts arteriole to prevent blood flow and changing GFR
tubolomerular feedback: glomerulus recvs feedback on the status of downstream tubular fluid, adjusts filtration to reg is compsition, nephron preformance, compensate flucutaions in BP, if GFR rises> increase flow tubular fluid + rate of Na+ reabsorption by the PCT > macula densa senses variation > secrete paracrine > JG cells contract afferent arteriole > reduces GFR
explain how GFR is regulated by Sympathetic control:
sympatheitc stimulation and adrenal epinephrine constrict the afferent arterioles, this reduces GFR, redirecting blood from kidneys to the heart, brain, skeletal muscles where is its needed
describe the structure and fxn of the juxtaglomerular apparatus:
found at the end of the nephron loop where it comes into contact with afferent and efferent arterioles of renal copruscle
macula densa: epithelial cells on the side facing the aterioles
justaglomerular cells: smooth muscle cells, in afferent afteriles, when stimulated by macula they dilate or constrict afterioles, contain granules of renin, which are secreted in response to drop in blood pressure
mesangial cells: contstrict or relax glomerulus capillaries to regulate blood flow and GFR and phagocytize tissue debris
explain how GFR is regulated by the renin- angiotensin - aldosterone mechanism:
decreased BP> decreased baroreceptor firing > increased SNS to JG cells to secrete renin
renin: acts on angiotensionogen, a protein in blood plasma, into peptid called angiotensin I
angiotensin-converting enzyme (ACE): converts angiotensin I into angiotensin II
angiotensin II: vasoconstrictor - (widespread), constrict efferent arterioles, enhances reabsorption of NaCl and water from nephron; stimulates aldosterone - promotes Na+ and water reabsorption; stimulates hypothalmus to secrete anitdiuretic hormone - promotes water reabsorption (thru thirst)
explain the role of tubular reabsorption:
the process of reclaiming water and solutes from teh tubular fluid and returing them to the blood, PCT
Put the following vessels in order according to blood flow through the kidney:
Using the following information, calculate the net filtration pressure: blood hydrostatic pressure = 73 mm Hg, colloid osmotic pressure = 30 mm Hg, capsular pressure = 21 mm Hg.
64 mmHg
124 mmHg
16 mmHg
22 mmHg
82 mmHg
22 mmHg
Which of the following leads to increased secretion of aldosterone? Choose ALL that apply.
drop in K+ concentration
drop in blood pressure
drop in Na+ concentration
calcium deficiency
drop in blood pressure
drop in Na+ concentration
Which of the following is not expected in a healthy person’s urine?
Which of the following mechanisms is important for maintaining osmolarity in the renal medulla?
renal autoregulation
micturition reflex
excretion
countercurrent exchange system
juxtaglomerular apparatus
juxtaglomerular apparatus
The ______________ secrete(s) renin in response to _______________.
juxtaglomerular cells; a drop in blood pressure
macula densa; a drop in blood volume
mesangial cells; a rise in blood pressure
myogenic mechanism; increased Na+
hypothalamus; a drop in renin
juxtaglomerular cells; a drop in blood volume
Tubular secretion moves substances from the _______ into the _________.
Homer has been chasing a space coyote through the desert and has become severely dehydrated. As a result, his daily urine volume is only 50 mL. What condition does Homer have?
anuria
oliguria
hypouria
metauria
polyuria
anuria
differentiate between paracellular and transcellular reabsorption:
paracellular: substances pass thur gaps between the cells, "next to", pass between tight junctions
molecules that can pass thru paracellular: H2O, urea, uric acid, Na+, K+, Cl-, Mg2+, Ca2+, P
transcellular: substances pass thru the cytoplasm and out of the base of the epithlial cells, "across"
types of transcellular reabsorption: symports, anitports, aquaporins
Explain the mechanisms and sites of reabsorption of Na+:
symports: simultaneously bind Na+ and another solute such as glucose, amnio acids, or lactate to be transported thru the cell, diffusion
antiports: pulls Na+ into the cell while pumping H+ out of the cell into the tubular fluid, activated by angiotensin II, active transport
summarize the mechanisms and sites of reabsorption of Cl-:
follow Na+ because they are electrically attracted to it
antiports: cell membrane absorbs Cl- in exchange for other anions that they eject into the tubular fluid, active transport
symports: Cl- and K+, diffusion
paracellular route
summarize the mechanisms and sites of reabsorption of K+:
paracellular: diffusion, along with water
summmarize the mechanisms and sites of reabsorption of H2O:
reabsorbed by the PCT
paracellular: follows solutes by osomsis, diffusion
transcellular: water channels called aquaporins, enables water to enter at the apical sufrace, and leave to return to the blood at the basolateral surface
summarzie the mechanisms and sites of reabsorption of glucose:
sodium - glucose transporters (SGLTs): symports in which glucose is cotransported with Na+, removed from basolateral surface by facilitated diffusion
summarzie the mechansims and site of absorption of urea:
paracellular: passes with water, diffusion, solvent drag
define glycosuria and explain its relationship to the concept of transport maximum:
there is a limit to the amount of solute that the renal tubule can reabsorb because there are limited # of transport proteins in the plasma membranes
transport maximum (TM): transporters are saturated
each solute reabsorbed has its own TM
Glucose: when blood glucose levels rise, glucose is filtered faster than the renal tubules can reabsorb it, excess passes thru the urine
glycosuria: excess glucose in the urine, diabetes mellitus
if all thransporters are occupied, then no reabsorption, flows into urine
explain the role of tubular secretion and summarize the sites of secretion of K+, H+, urea, and drugs toxins:
a process in which the renal tubules extracts chemicals form teh capillary blood and secretes them into the tubular fluid
waste removed: urea, uric acid, bile acids, ammonia and creatinine secreted into tubules
drugs/toxins: secretion of pollutants, morphoine, penicillin, aspirin,
H+: secretino regulates the pH of body fluids
describe the fxn, mechanism of action, site of action, and effects of hormones that regulate Na+ and water reabsorption (aldosterone):
Na+: aldosterone: "salt retaining" hormone, secreted when blood Na+ concentration falls, increases salt reabsorption
K+ secretion: aldosterone: secreted when blood K+ concentration rises
net affect of aldoseterone: body retains NaCl and water, urine volume is reduced, and the urine has an elevated K+ concentration
renal targets: nephron loop, DCT, and CD
describe the fxn, mechanism of action, site of action, and effects of hormones that regulate Na+ and water reabsorption (ANP):
ANP: artrial natriuretic peptides, secreted by the heart in response to high blood pressure, stimulated by stretch of right atrium
result: excretion of more salt and water in the urine, reducing blood volume/pressure
a. dilate afferent arteriole and constrict efferent arteriole, increase GFR
b. inhibit renin adn aldosterone secretion
c. inhibit ADH and its action on the kidney
d. inhibit NaCl reabsorption by collecting duct
renal targets: afferent and efferent arterioles, CD
describe the fxn, mechanism of action, site of action, and effects of hormones that regulate Na+ and water reabsorption (autidiuretic hormone):
ADH: secreted by hypothalmus in response to dehydration, and rising blood osmolarity
result: makes collecting duct more peremable to water, reduces urine volume, increases concentration
renal targets: collecting duct
summarize how ANP aids regulation of Na+ and H2O reabsorption affects blood volume and blood pressure:
describe how the counter current multiplier system works and explains its role in urine formation:
the ablility of the CD to concentrate urine depends on the osmotic gradient of the renal medulla
countercurrent multiplier: contiunally recaptures salt and returns it toe the deep medually tissue, based on fluid flowing in two opposite directoins in two adjacent tubules
1. more salt is continually added by the PCT
2. the higher the osmolarity of the ECF, the more water leaves the descending limb by osmosis
3. the more water that leaves the descending limb, the saltier the fluid is that remains in the tubule
4. the saltier the fluid in the ascending limb, the more salt the tubule pumps into the ECF
5. the more salt that is pumped out of the ascending limb, the saltier the ECF is in the renal medulla
**Negative feedback
describe the typical physical and chemical characteristics of urine:
appearance: colorless to amber, yellow due to the breakdown of hemoglobin, clear, cloudy suggests infection, contaminatin, or too many crystals
odor: distincitve, can be altered by food or infection
specific gravity: 1.001 when it is very diluted, 1.028 when it is very concentrated
osmolarity : 50 mOsm/L if person is hydrated, to 1,200 mOsm/L if person is dehydrated
recognize abnormal phyusical and chemical characteristics of urinalysis:
glucose, free hemoglobin, albumin, ketones, or bile pigments, WBC, RBC, protein
define diuretic and explain the mechansim by which diruetics like caffeine and alcohol affect urine output:
diuretic: any chemical that increases urine volume
caffine: act by increaseing glomerular filtration by which dilates the afferent arteriole
alcohol: reduces tubular reabsorption of water, inhibits ADH secretion, reduces reabsorption in collecting ducts
explain the difference between diabetes mellitus and diabetes insipidus in terms of the mechanism by which they cause diuresis/polyuria:
polyuria: results from a high concentration fo glucose in the renal tubule
diabetes mellitus: osmotic diuresis - waters passes in the urine, "passes thru", test for sweetness, failure to reabsorb all glucose, not enough symport channels, increase glucose for increse water from plasma to tublues - more water excreted by osmosis
diabetes insipidus: ADH hyposecreteion, collecting duct does not reabsorb much water, so more water passes thru urine, passing thru tasteless, the urine contains no glucose
define/calculate renal clearnace and understand how renal clearance is used to assess renal fxn:
renal clearance: the volume of blood plasma from which a particular waste is completely removed in 1 min, measures elimiation efficiency
RPC = U(urea concentration in urine)x V (rate of urine output) / P (urea concentation in plasma)
If RPC < less than GFR = substance reabsorbed
if RPC > greater than GFR = substance secreted
normal: 60ml of blood plasma cleared of urea/min, if normal GFR of 125 ml/min then
60/125 = 48% of urea clearance, suficient to maintain safe levels of urea in blood
explain how inulin and creatinine cleareance are used in determining GFR:
to measure GFR ideally requires a substance that is not secreted or reabsorbed at all, so that all of it in the urine gets there by glomerular filtration:
inulin: filtered by glomerulus, remains in renal tubules and apprears in the urine, not reabsorbed or secreted, must be injected
creatinine: small but acceptable error of measurement, easier than injection, slightly secreted
describe the anatomy of urine sotrage and elimination:
internal urethral sphincter: - compresses the urethra and retains urine in the bladder, smooth muscle
external uretheral sphincter: skeletal muscle, voluntary control over voiding urine
compare and contrast the structure and fxn of the male and female urethra:
male urethera: 18 cm long, prostate gland
female urethra: 3 to 4 cm long
describe the events in the mactrurition reflex including neural control:
involuntary micturition reflex1. stretch receptors detect filling of bladder, transmit affernt signals to spinal cord
2. singnals return to the bladder from spinal cord segments S2 and S3 via parasympathetic fibers in the pelvic nerve
3. efferent signals excite detrusor muscle
4. efferent signals relax internal urethral sphincter. Urine in involunatarily voided if not inhibited by brain
voluntary control1. micturition center in pons recives signals from stretch receptors
2. if it is timely to urinate, pons returns signals to spinal interneurons that excite detrusor and relax internal sphincter. urine is voided
3. if it is timely to urinate, singals to pons cease and external urethra sphincer relaxes. urine is voided
describe the muscles used in micturition and describe its innervation:
detrusor (smooth muscle)
type: parasympathetic (causes contration)
during filling: inhibited
during micturition: stimulated
internal urethral sphincter smooth muscle
type: sympathetic (causes contraction)
during filling: stimulated
during micturition: inhibited
external urethral sphincter
skeletal muscle
type: somatic motor (causes contraction)
during filling: stimulated
during micturition: inhibited
which of the following is NOT a fxn of the urinary system?
D. regulation of blood glucose concentration
the movement of fluid and solutes from the nephron tubules into the peritubular capillairies is :
C. reabsorption
if blood hydrostatic pressure is 70 mmHg, capsular hydrostatic presure is 30 mmHg, and colloid osmotic pressure of the blood is 10 mmHg, then net filtration pressure is:
D. 30 mmHg
constriction of the afferent arteriole directly causes a/an:
A. decrease in the glomerular filtration rate
most nephrons in the kidney are:
B. cortical nephrons, which have short nephron loops
the retention of H2o occurs in which part of the nephron?
A. nephron loop
tubuloglomerular feedback is best described as vasoconstriction of the afferent arteriole in response to:
A. increased fluid flow in the DCT
glucose is reabsorbed via:
C. transporters
which of the following substances is secreted?
D. H+
if blood volume drops, which of the following will occur to restore blood volume back to normal?
B. the concentration of aldosterone in the blood will increase
the osmolarity gradient inside the renal medulla exists because the ascending limb of the nephron loop is permeable to _____; and the descending limb is permeable to ______:
B. NaCl, H2o
antidiuretic hormone (ADH):
B. stimulates the increase of acquporins in the collecting ducts
which of the following characteristics is NOT normal for human urine?
A. osmolarity ~ 1900 mOsm/L
the renal plasma clearance of inulin can be used to measure GFR because inulin is filtered:
a. but not secreted nor reabsorbed
b. and reabsorbed but not secreted
c. and secreted but not reabsorbed
d. and secreted and reabsorbed
a. but not secreted nor reabsorbed
the micturition relfex requires changes in input from the PSNS, SNS, and somatic nervous system to the organs of the urinary system. Neurons from the sympathetic nervous system (SNS) innervate which of the following?
B. internal urethra sphincter
aldosterone causes:
D. increased Na+ rebsorption and increased K+ secretion
