Chapter 14 Flashcards
job of the kidney
filtration, reabsorption, and secretion
what would kill you first if there were no kidneys?
the lack of potassium secretion causing an increase in ECF which would cause convulsions and make the gradients less steep so AP are easier to fire
renal blood supply is what percentage of cardiac output
20-22%
cortex of the kidney is seen where?
outside
medulla of the kidney is located where?
inside
what is the functional unit of the kidney
nephron
two types of the nephron
cortical (80%) and juxtamedullary (20%)
cortical region of the nephron loop of henle
hairpin loop
juxtamedullary region of the nephron contains
the vasa recta
where is the juxtamedullary region found
deep in the medulla
what does the juxtamedullary region do
establish concentration gradient and affects concentrations of urine
what would happen if you did not have a juxtamedullary region?
you would pee to death
vascular component of the nephron
- afferent arteriole
- glomerulus
- efferent arteriole
what is the glomerulus
group of capillaries that filters into bowman’s capsule
efferent arteriole
unfiltered blood leaving the glomerulus
parts of the efferent arteriole
peritubular capillaries and vasa recta
peritubular capillaries
supply renal tissues with blood and exchanges between tubular system and blood during conversion of filtrate to urine
bowman’s capsule
collects glomerular filtrate
proximal tubule
uncontrolled reabsorption and secretion of selected substances occur here
loop of henle of nephron
establish osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentration
distal tubule and collecting duct (distal nephron)
variable, controlled reabsorption of sodium and water and secretion of potassium and hydrogen occur here; fluid leaving the collecting duct is urine which enters the renal pelvis
juxtaglomerular apparatus
produces substances involved in the control of kidney function
descending loop of henle
thin portion- squamous epithelium
ascending loop of henle
thick portion- cuboidal epithelium
what is the only controlled portion of the nephron
distal tubule and collecting duct
t/f: juxtamedullary nephron is long-looped and is important for establishing the osmotic gradient
true
what is the most abundant type of nephron
cortical nephron
glomerular filtration anatomy
- huge fenestrated endothelium
- basement membrane
- podocytes with filtration slits
- 100x more permeable
t/f: capillaries don’t have pores
false
what are the filtration slits in podocytes similar to (IRL example)
interlocking fingers and still have gaps for things to squeeze between
where is filtrate found
in the nephron
what is secretion
actively putting something into the nephron (skip filtration via glomerulus)
t/f: plasma proteins and RBC are filtered by the glomerular capillary
false
what substances can fit in the pores between the glomerular capillary and bowman’s capsule
glucose and ions
albumin
smallest plasma protein that can fit through pores but is repelled by the negatively charged glycoproteins
lupus
protein in urine
glomerular capillary blood pressure
55 mmHg
how much of plasma that enters the glomerulus is filtered
20%
Glomerular filtration rate
125 mL/min
how often do the kidneys filer plasma volume?
65 times per day
blood capillary blood pressure
37 mmHg
hypertensive affect on glomerular filtration
increase hydrostatic pressure which causes you to filter more than you should
inward pressures of glomerular filtration
plasma colloid osmotic pressure and Bowman’s capsule hydrostatic pressure
outward pressure of glomerular filtration
glomerular capillary blood pressure
net filtration
outward pressures - inward pressures
how much urine is produced per minute
1 mL/min
GFR equation
Kf * NFP
importance of glomerulus
filtration and reabsorption
what happens to GFR when MAP increases and why
increases; increased MAP causing increased glomerular capillary blood pressure (outward) which increase net filtration pressure(NFP) which increases GFR
what does vasoconstriction do to GFR and why
decrease GFR; less blood flow to glomerulus
what does vasodilation do to GFR
increase GFR; more blood flow to glomerulus
autoregulation mechanisms of GFR
myogenic mechanism and tubuloglomerular feedback mechanism
tubuloglomerular feedback mechanism
macula densa
- release vasodilator if flow is too slow
- release vasoconstrictor if flow is too fast
what is adenosine?
vasoconstrictor
t/f: adenosine is potentially potent
true
sympathetic stimulation of kidneys affects GFR how
constricts arterioles
mesangial cells
hold glomerular capillary in position and control the size of the filtration pore
transepithelial transport
places substances back into the peritubular capillaries
barriers of tubular reabsorption
- membrane of tubular cells
- cytosol of tubular cell
- membrane at lateral space
- interstitial fluid
- capillary wall
active tubular reabsorption
at least one step requires energy - goes against electrochemical gradient
passive tubular reabsorption
no steps require energy - with/down concentration gradient
t/f: majority of the filtrate is reabsorbed per day
true
how much glucose is reabsorbed (%)
100%
how much water is reabsorbed? (%)
99%- almost all
how much sodium is reabsorbed? (%)
99.5%- not all of the salt from the diet is reabsorbed
how much energy does sodium require?
80% of all energy used by kidneys
how much sodium is reabsorbed in the proximal tubule?
67%
the proximal tubule plays a pivotal role in reabsorbing what substances?
glucose, amino acids, water, chloride, and urea
how much sodium is reabsorbed in the loop of henle?
25%
what does the sodium reabsorption in the loop of henle create?
osmotic gradient
what does the loop of henle affect?
chloride reabsorption, water conservation, urine variations in concentration and volume
how much sodium is reabsorbed in the distal and collecting tubules?
8%
what does the distal and collecting ducts affect?
regulate ECF volume linked to potassium secretion
how is the distal nephron controlled?
hormones
How is sodium brought from the lumen into the tubular cell?
with glucose through the SGLT2 carrier
t/f: sodium potassium pumps are required to exchange sodium and potassium from the ISF and tubular cell
true
hormonal influences on distal nephron
- RAAS
- decrease in salt and BP cause granular cells to release renin
- renin converts angiotensin to angiotensin 1
- ACE converts angiotensin 1 to angiotensin 2 (LUNGS)
What does the RAAS system respond to
decrease in NaCl, ECF volume, and arterial BP
macula densa
contains sensor for sodium to release renin when too much sodium is passing by
how does arterial BP increase renin secretion?
baroreceptors activate sympathetic activity which stimulates the granular cells to secrete more renin (juxtamedullary apparatus cells)
what does an increase in arterial BP do to plasma volume
increase
how is plasma volume restored
osmotically inducing water retention
where is ACE found
high in the pulmonary capillaries- high in lungs because 100% of cardiac output goes through the lungs and is the easiest way to disperse
treatments for hypertension and congestive heart failure
ACE inhibitors and aldosterone receptor blockers
Angiotensin 2
Arteriolar constriction
- stimulate thirst
- release ADH
- release aldosterone from adrenal cortex
aldosterone
increase sodium reabsorption at distal tubules via PRINCIPAL CELLS
- increase sodium leaky channels in luminal membrane and increase Na+K+ pumps in the basolateral membranes
what happens when sodium load, ECF and plasma volume, and arterial pressure are above normal?
- renin is inhibited
- no aldosterone
- sodium excreted in urine (large loss of sodium after multiple days)
natriuretic peptide (ANP)
inhibits sodium reabsorption (excrete more sodium)
inhibits RAAS
when is ANP released?
when heart muscle cells are mechanically stretched by an expansion of circulating plasma volume when ECF volume increases which is caused by sodium and water retention that increases BP
inhibiting RAAS does what to sodium reabsorption
inhibit sodium reabsorption and increase excretion (along with H2O)
t/f: inhibiting RAAS will inhibit actions of vasopressin (ADH)
true
what is the problem with using natriuretic peptide? how is the problem solved?
more sodium is passing the macula densa (more sodium being excreted) along with water which decreases blood volume
- ACE inhibitor used to combat this
transport maximum of glucose
375 mg/min
t/f: kidneys don’t regulate chloride
true
GLUT transporter
facilitate glucose and amino acids across basolateral membrane
t/f: phosphate and calcium reabsorption can be regulated by parathyroid hormones
true
what does ADH do for water reabsorption?
increase aquaporin channels (AQP2) to increase water reabsorption
how much urea is excreted? how much is reabsorbed?
50%, 50%
t/f: tubular secretion is controlled by systemic pH
true
What does aldosterone do to K+ secretion?
reabsorb more K+ than we secrete
what do secretion of drugs, metabolites, and pollutants do to the excretion of them?
increase elimination
what ions are secreted?
hydrogen and potassium
aldosterone up-regulate mechanisms
- add more Na+K+ pump
- add more K+ carriers (K+ back into lumen)
- add more sodium channels (Na+ into distal nephron)
short term regulation of secretion
insulin- push K+ into the cell, keep ECF levels regulated
t/f: reabsorption is controlled in the proximal tubule
false
plasma clearance
volume of plasma cleared of specific substance per minute
t/f: plasma clearance depends on the concentrations that are cleared out
false
plasma clearance formula
PC = (Xurine * UFR)/ (Xplasma)
What does it mean when PC= GFR?
Excretion ONLY– no reabsorption or secretion
- measures arteriolar and glomerular health
two substances that have a PC=GFR
inulin and creatine
What does it mean when PC < GFR?
REABSORPTION– not secreted
substance that has a lower PC than GFR
urea
What does it mean when PC > GFR?
secreted but not reabsorbed
- determine health of nephron
substances that have PC greater than GFR?
Hydrogen and PAH
isotonic urine: _______ BP
normal
hypotonic urine: _______ BP/BV
decrease (hypertensive)
hypertonic urine: _______ BP/BV
increase in response to hypotension
t/f: hypotonic urine releases more water
false
t/f: hypertonic urine releases more water
true
Descending loop of henle: iso, hypo, or hyper tonic
hypertonic
Ascending loop of henle: iso, hypo, or hyper tonic
hypotonic
ISF: iso, hypo, or hyper tonic
isotonic
ADH
produced by hypothalamus
acts at basolateral membrane in distal nephron
- opens AQP2
- concentrates the urine
What kind of urine is produced without ADH
hypotonic
What kind of urine is produced with low levels of ADH
isotonic
t/f: ADH os water soluble
true
how do arterioles balance osmolarity
pick up salt and lose water at first, then before leaving to the veins, pick up water and lose salt
micturition
spinal reflex
Parasympathetic activity of micturition
initiates contraction of smooth muscle- detrussor muscle
initiates relaxation of smooth muscke- Internal urethral sphincter
Somatic control of micturition
relaxation of urethral sphincter (skeletal muscle)
t/f: somatic control of micturition can override the parasympathetic contraction by the detrussor muscle
true
t/f: in micturition, parasympathetic will always win
true
