Chapter 14: Urinary System Flashcards
the kidneys are primarily responsible for
- maintaining the stability of the ECF volume
- water and electrolyte composition
- blood pressure
- osmolarity
kidneys are the main route for
- eliminating potentially harmful substances
- metabolic wastes
- foreign compounds in the body
the outer surface of the kidney is called
the renal cortex
the inner surface of the kidney is called
renal medulla
function of the ureters
carry urine from the kidneys to the urinary bladder
function of the urinary bladder
- temporarily stores urine
- excretion
urethra function
- provides route for eliminating urine from the bladder
- provides a route for semen in males
in which gender is the urethra longer
males
how many nephrons are there in a kidney
1 million
the renal medulla is made up of
striated triangles called renal pyramids
what structures are apart of the vascular component
- afferent arteriole
- glomerulus
- efferent arteriole
- peritubular cappilaries
afferent arteriole
carries blood to the glomerolus
glomerulus
a tuft of capillaries that filters a protein free plasma into the tubular component
efferent arteriole
carries filtered blood from the glomerulus
peritubular capillaries
supply the renal tissue; involved in exchange within the fluid in the tubular lumen
what structures are apart of the tubular component
- bowmans capsule
- proximal tubule
- loop of henle
- distal tubule and collecting duct
bowmans capsule
- collects the glomerolar filtrate
proximal tubule
uncontrolled reabsortion and secretion of selected substances occur here
loop of henle
establishes an osmotic gradient in the renal medulla that is important in the kidneys ability to produce urine of varying concentrations
distal tubule and collecting duct
- variable, controlled reabsorption of sodium and water, and secretion of potassium and hydrogen occur here
- fluid leaving thr collecting duct is urine which enters the renal pelvis
what structure is apart of the combined tubular/vascular component
- Juxtaglomerular apparatus
Juxaglomerular apperatus
produces substances involved in the control of kidney function
cortical nephrons
- lie in the outer layer of the cortex
what percentage of nephrons are cortical
80
juxtamedullary nephrons
- lie in the inner layer of the cortex
- performs most urine concentrations
glomerular filtration
filtrate protein free plasma
what structures are involved in glomerular filtration
- glomerulus
- bowmans capsule
tubular reabsorption
- absorbs nutrients, ions, and electrolyte
what structures are involved in tubular secretion
- kidney tubules
- peritubular capillaries
tubular secretion
- movement of non filtered substances
structures involved in tubular secretion
- peritubular capillaries
- kidney tubules
glomerular capillary wall
- a single layer of endothelial cells
- more permeable to water and solutes than capillaries elsewhere in the body
- filtration
basement membrane
- acellular gelatinous layer
- composed of collagen and glycoproteins (discourage filtration of small proteins)
- do not filter plasma proteins
inner layer of the bowmans capsule is made up of
podocytes foot processes that encircle the glomerolar tuft
- connective tissue
what are the barriers to the substances that are filtered
- endothelial cells
- basement membrane
- podocyte foot proceeses with filtration slips
what do podocytes contain
filtration slips
which structure within the glomerolus discourages that plasma protein filtration
basement membrane
pressure excreted by the blood within the glomerular capillaries depends on (3 things)
- contration of the heart
- resistance to blood flow offered by afferent and efferent arterioles
- the smaller diameter of the efferent arteriole
what is the major force producing glomerular filtration
Glomerular capillary blood pressure
Glomerular capillary blood pressure effect
favours filtration
Glomerular capillary blood pressure magnitude
55
Plasma colloid osmotic pressure is caused by
the unequal distribution of plasma proteins across the glomerular membrane (by osmosis)
Plasma colloid osmotic pressure effect
opposes filtration
Plasma colloid osmotic pressure magnitude
30
the pressure excreted by fluid in the initial part of the tubule
Bowmans Capsule Hydrostatic pressure
Bowmans Capsule Hydrostatic pressure effect
opposes filtration
Bowmans Capsule Hydrostatic pressure magnitude
15
Differnece between force favouring filtration and forces opposing filtration
Net filtration pressure
Net filtration pressure effect
favours filtration
Net filtration pressure magnitude
10
How to calculate glomerular filtration rate
Glomerular capillary blood pressure - (plasma colloid pressure + bowmans capsule hydrostatic pressure)
Glomerular filtration rate depends on (3 things)
- net filtration pressure
- glomerular surface area avaliable for penetration
- permeable golmerolar membrane
GFR in males
125ml/min
GFR females
115ml/min
When the plasma colloid pressure and Bowmans Capsule hydrostatic pressure is constant, the glomerular capillary goes up, and the net filtration pressure increases what is the effect of the GFR
increases
effect of increasing the arterial blood pressure on GFR
increases GFR
what are the two mechanisms that control GFR
- auto regulation
- Extrinsic sympathetic NS
autoregulation
prevents spontaneous changes in GFR
- myogenic mechanism (effects smooth muscles)
- tubuloglomerular feedback (TGF)
Extrinsic sympathetic control
- regulates long term blood pressure regulation
- mediated by the sympathetic nervous system input to the afferent arterioles
- baroreceptor reflex
mechanisms effect on GFR
- regulates caliber / diameter
- resistance in the afferent arterioles
vasoconstriction in the afferent arterioles effect on GFR
decreases GFR
vasodilation in the afferent arterioles effect on the GFR
increase GFR
smooth muscle cells within the wall of the afferent arteriole contains
granular cells
specialized tubular cells in the juxtaglomerular region contains
macula densa cells
function of the macula densa cells
converts ATP to adenosine
effect of adenosine on the afferent arterioles
vasodilates them, increasing the GFR
extrinsic control of the GFR is perpetrated by
- sympathetic nervous system
- baroreceptors
- filtration coefficent
paprasympathic effect on kidneys
there is no parasympathetic effect on the kidneys
which mechanisms is stronger
extrinsic controls can override the auto regulatory responses
where are the barorecpetors located
- aprtic arch
- carotid sinus
decreased GFR effect on urine production
decreases urine production
reduced urine output effect on GFR
decreases
the rate of glomerular filtration depends on,
- filtration coefficent
- net filtration pressure
the KF depends on
- surface area
- the permeability of the glomerular membrane
what determines the permeability of the glomerular membrane
- the number of flitration slips in the podocytes open
purpose of tubular reabsorption
maintain the proper composition & volume of the ECF
the tubules have a ____ _______ ______. for substances needed by the body
high absorpative capacity
excess amounts of essential electrolytes are
excreted in the urine
the rate at which substances are reabsorbed depends upon
- deficency
- absorbative capacity
tubular reabsorption involves ________ transport
transepithelial
what is the sequence of transepithelial transport in tubular reabsorption
- luminal cell membrane
- the cytosol
- the basolateral cell membrane
- the interstitial fluid
- the peritubular capillary wall
what is the sequence of transepithelial transport in tubular secretion
- the peritubular capillary wall
- the interstitial fluid
- the basolateral cell membrane
- the cytosol
- the luminal cell membrane
ways of transport
- active
- passive
passive transport
- no energy required
- substances move down the electrochemical and osmotic gradients
active transport
- requires ATP use
- substances move against the electrochemical gradient
examples of active transport
- glucose
- Na / K
- Cl
- electrolytes
- PO4/3
average percentage of filtered water reabsorbed
99
average percentage of sodium reabsorbed
99.5
average percentage of glucose reabsorbed
100
average percentage of urea reabsorbed
50
average percentage of phenol reabsorbed
0
average percentage of filtered water excreted
1
average percentage of filtered sodium excreted
0.5
average percentage of glucose excreted
0
avergae percentage of filtered urea excreted
50
average percentage of filtered phenol excreted
100
phenol is a _____
toxin
what percentage of Na si reabsorbed in the proximal tubule
67
proximal tubule plays a role in reabsorbing
- glucose
- amino acids
- h2o
- cl
- urea
percentage of Na reabsorbed in the ascending limb of the loop of henle
25
the ascending loop of henle plays a critical role in the kidneys ability to
produce urine of varying concentration
percentage of Na reabsorbed in the distal and collecting tubules
8
what part of the kidney is effected by ADH during dehydration
distal and collecting tubules
of the total energy spent by the kidneys what percentage is used for Na transportation
80
glucose and amino acids are reabsorbed by which part of the nephron
proximal tubules
how are amino acids and glucose reabsorbed
co-transport carrier molecules
filtered load of glucose
quantity of any substance filtered per minute
what is the normal plasma concentration of glucose
100mg/100ml
formula for filtered load
plamsa concentration x GFR
at constant GFR, the filtered load of glucose is __________ proportional to the plasma glucose concentration
directly
what is the tubular maximum for glucose
375mg/min
what happens if the glucose level is above the TM
- TM will exceed 375
- plasma glucose concetration must not exceed more than 375
- spill into the urine
TM
- when the moximum reabsorption rate is reached, and when all carriers specific for a particular substance is fully occupied, they cannot handle any additional glucose at this time, this is TM
what is one of the first characteristics identified in a patient with sever renal failure
elevated urea
TS provides
a socond route of entery to the tubule for selected substance
tubular secretion includes
- h
- k
- organic ions and cation
H
important in regulating the acid base balance
- secreted in the proximal, distal, and collecting tubules
k
- keeps the plasma concentration at an approprite level to maintain the normal membrane excitability in the muscles and nerves
- secreted only in the distal and collecting tubules under the control of aldosterone
organic ions
- accomplish more efficent elimination of foreign organic compounds from the body
- secreted only in the proximal tubule
h is secreted in
- proximal, distal and collectign tubules
k is secreted in
the distal and collecting tubules under the control of aldosterone
organic ions is secreted in
the proximal tubule
decrease in na / ECF volume / decreased arterial blood pressure
Activates RAAS
casues an increase in renin –> increased angiotension I –> concerts to angiotension II –>stimulates aldosterone
effect of aldosterone
- increases tubular k secretion (increased urinary k excretion)
- increased tubular Na reabsorption (decreased urinary Na excretion)
plasma clearance
the volume of plasma cleared of a particular substance / min
OR
the plasma volume completetely cleared of the substance ny kidney/min
plasma clearance ecpresses
the kidneys effectiveness in removing substances from the internal fluid enviorment
what percentage of insulin is excreted
100
what percentage of of urea is excreted
50
what percentage of glucose is excreted
0
what percentage of h are excreted
100
plasma clearance formula
urine concentration x urine flow rate
what are three diuretic substances
- ANP
- Alcohol
- coffee
Atrial natriuretic peptide
where is it secreted?
when is it secreted?
- hormone secreted by the atria
- secreted is responce to increased salt, increased volume, or increased artrial pressure
Atrial natriuretic peptide effects
- decreased sodium reabsorption by the kidney tubules (increased sodium and water excretion in the urine)
- decreased salt conserving renin-angiotensin-aldosterone system (increased sodium and water excretion in the urine)
- smooth muscle of afferent arterioles vasodilation (increases GFR)
- sympathetic nervous system, decreases CO and TPR (decreases arterial blood pressure)
Isotonic
solute concentration is equal to the water concentration
hypotonic
if too much water is present than the solute load, the body fluid is said to be hypotonic / diluted
hypertonic
if less water is present than the solute load, the body fluid is too concentrated
what part of the nephron is involved in the formation of concentrated or diluted urine
loop of henle
decending loop of henle is only permeable to ______
water
what is the result of the filtrate once it is filtered through the descending loop of henle
- highly concentrated urine
- hypertonic solution
ascending loop of henle is only permeable to ______
salt
- impermeable to water
vasopressin is present during
dehydration
the countercurrent multiplication mechanism is established by the
medullary vertical osmotic gradient
countercurrent multiplication
the passive exchange of solutes and water between the two limbs of the loop of henle
obligatory is located in the
proximal tubule
secretion of vasopressin ______ cells permeability to water
increases
vasopressin runs on a _______ feedback loop
negative
what are the four functions of the renin-angiotensin-aldosterone system
- aldosterone increases reabsorption in the distal and collecting tubules
- promotes salt retention and resultant water retention and elevation of arterial blood pressure
- angiotension -II is a potent constrictor of the systemic arterioles, thus increasing blood pressure and peripheral resistance
- stimulates thirst and vasopressin release
angiotensinogen is secreted by the
liver
renin is secreted by the
kidneys
angitotensin-I converts to angiotension-II through what enzyme
angiotension converting enzyme
angiotension converting enzyme is secreted by the
lungs
the adrenal cortex is responsible for
- aldosterone
- thirst
angiotensin II causes the secretion of ______ form the _______
vasopressin / ADH
posterior pituitary
ADH is produced by the
hypothalmus
functions of angiotensin II
- cause the release of vasopressin
- stimulates thirst
- responsible for arteriolar vasoconstriction
the bladder is guarded by
two sphincters
- internal
- external
micturition 2 types of control
- reflex control
- voluntary control
external urethral spinchter opens when
motor neuron in INHIBITED
external urethral sphincter closes when
motor neuron is STIMULATED
