AP Ch. 25 Renal System

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what does renal system produce to help regulate blood pressure: renin
what does renal sys produce to stimulate RBC production: erythropoietin
what vitamin does renal sys activate: D
what is the renal hilus: vertical cleft of the kidney where ureters, renal blood vessels, lymphatics, and nerves enter and exit
what is the renal capsule?: fibrous capsule; external tissue layer that supports the kidneys
adipose capsule; function: fatty mass that cushions the kidney and helps attach it to the body wall
renal fascia; function: outer layer of dense fibrous connective tissue that anchors the kidney
char of renal cortex: granular
char of renal medulla: cone-shaped pyramids - made up of parallel bundles of urine-collecting tubules
what are renal columns: inward extensions of cortex that separate the pyramids
what constitutes a lobe of the kidneys: medullary pyramid and its surrounding capsule
what is the renal pelvis: flattened tunnel shaped tube lateral to the hilus (where all of the connections form)
what are nephrons; general function: structural and functional units of the kidneys that form urine
what is the glomerulus; function: tuft of capillaries assoc with a renal tubule
filters substances from blood into the renal tubular filtrate
what is the proximal convoluted tubule; function: composed of cuboidal cells with many microvilli and mitochondria

reabsorbs water and solutes from filtrate
secretes additional substances into filtrate from the blood
what is the loop of Henle: hairpin shaped loop of the renal tubule
what is the distal convoluted tubule; function: distal to loop of Henle;
secretes and reabsorbs
what is the connecting tubule; function: distal portion of the DCT nearer to the collecting ducts

acid-base regulation
what are the collecting ducts; function: many nephrons empty into these

drain urine into the renal pelvis
final site of reabsorption of water and salts
two types of nephrons; explain them: cortical nephrons - most of nephrons; have very short loops of Henle

juxtamedullary nephrons - located at cortex-medulla junction; have loops of Henle that penetrate deeply into the medulle with long thin segments; required for prod of concentrated urine
the types of capillaries of nephrons; general comparison: glomerular capillaries - high pressure; for filtration (fluids and solutes pushed out of blood)
peritubular capillaries - low pressure (absorption)
glomerular capillaries (more detail): send afferent and efferent arterioles to and from glomeruli; throughout entire length of the capillary fluids and solutes are forced out of the blood (filtration)
peritubular capillaries: low-pressure, porous; arise from efferent arterioles leaving glomeruli

absorption functions; form a branched network that assoc with its renal tubules
what is vasa recta: long straight efferent arterioles assoc with juxtamedullary nephrons
what is the juxtaglomerular apparatus: where the distal tubule contacts the afferent and efferent arterioles
what are juxtaglomerular (JG) cells; contain what; actions: enlarged smooth muscle cells; form rings around afferent and efferent arterioles
contain secretory granules with renin
act as mechanoreceptors for stretch
what is the macula densa; function: part of JG apparatus?
tall closely packed distal tubule cells
lie adjacent to JC cells
function as chemoreceptors or osmoreceptors
three major processes of urine formation and adjustment of blood composition: glomerular filtration
tubular reasborption
secretion
what is the glomerular filtration membrane; layers: filter in between blood and interior of glomerular capsule

fenestrated endothelium of g. capillaries
visceral membrane of g. capsule
basement membrane
char of fenestrated endothelium; where is it: part of g. filtration membrane

porous?
char of visceral membrane; where is it: part of g. filtration membrane

made up of cells called podocytes
char of basement membrane; where is it: part of g. filtration membrane

made up of fused basal laminae of other other layers
mostly consists of glyoproteins
why does glomerulus filter more than other capillary beds: its filtration membrane is more permeable
its membrane surface area is very large
its blood pressure is higher --> higher net filtration pressure (more moving out of capillaries into filtrate in renal tubule)
what in the blood is not filtered; what does this do: plasma proteins (want water near them)
this maintains the oncotic pressure of the blood (pressure keeping water in the blood)
definition of net filtration pressure; equation: pressure responsible for filtrate formation
NFP = glomerular hydrostatic pressure - (oncotic press of glomerular blood + capsular hydrostatic pressure)

NFP = HPg - (OPg + HPc)
what is capsular hydrostatic pressure (HPc): pressure within capsule of glomerulus (contains filtrate) pushing back on capillaries preventing flow out from blood into filtrate
NFP represents pressure where: within one glomerulus
definition glomerular filtration rate; normal amount?: total amount of filtrate formed per minute by kidneys

about 125 mL/min
what affects glomerular filtration rate; what usually causes it to change most: total surface area avail for filtration
filtration membrane permeability
net filtration pressure (NFP)

normally from blood glomerular pressure (part of NFP)
effect of too high glomerular filtration rate: substances can't later be reabsorbed quickly enough (sugars, AAs, etc) and are lost in urine
effect of too low glomerular filtration rate: too much reabsorption takes place, incl wastes normally disposed of in urine
what mechanisms regulate glomerular filtration rate: renal autoregulation (intrinsic)
neural controls
hormonal mechanism (renin-angiotensin system)

i assume by changing the factors governing GFR (SA, permeability, NFP)
types of autoregulation (part of regulation of glomerular filtration rate) explain them: myogenic - responds to changes in pressure in renal blood vessels by sensing stretch

flow-dep feedback - macula densa senses changes in flow rate and composition of fluid in distal renal tubule at JG apparatus
neural control of glomerular filtration rate when sympathetic nervous sys is at rest: no symp stim to constrict renal blood vessels -- maximally dilated
autoregulation mechanisms prevail
neural control of glomerular filtration rate when system is under stress: symp sys releases NE from adrenal medulla --> afferent arterioles constrict --> filtration inhibited

(in stressful situation you don't want to filter a lot b/c then blood volume would decrease)
renin-angiotensin regulation of glomerular filtration rate -- what stimulates renin release: low BP (reduced stretch of the JG cells around afferent arteriole)
stim of JG cells by activated macula densa cells
stim of JG cells by epin/NE receptors by renal nerves
compare (generally) the two pathways for reabsorption: transcellular - substances move through the tubular epithelial cells; must cross mult membranes

paracellular - substances move passively between the tubular epithelial cells
membranes that must be crossed using transcellular pathway of reabsorption; is this active or passive?: luminal and basolateral membranes of tubule cells (renal tubule?)
endothelium of the capillaries to get back into blood

can be active or passive transport process
char of paracellular pathway of reabsorption: limited b/c of tight junctions b/w the epithelial cells --> only ions like Ca, Mg, K, and some Na are reabsorbed this way
what substances are reabsorbed using active Na+ pumping: water, aided by aquaporins

anions and fat-soluble substances by diffusion

organic nutrients by secondary active transport
location of Na-K pumps to maintain low Na+ in tubule cells: must all be on basolateral side of cells so that it pumps Na+ from tubule cells into interstitial fluid (and then it will go to capillaries) -- rather than it being pumped out of tubule cells on other side to tubule lumen! (b/c you want Na+ to LEAVE tubule lumen with organic nutrients, not ENTER it)
when does the concept of transport maximum apply; what determines transport maximum: for substances reabsorbed through transport proteins in the PCT membrane

by number of carriers in the renal tubules and their maximum velocity of transport
when is substance not fully reabsorbed: when transport proteins are saturated; this means that the substance was in excess so the excess is excreted because it stays in the filtrate
compare composition of filtrate before and after leaving PCT: composition is similar but just has decreased volume
where does reabsorption occur in kidneys: PCT
loop of Henle
DCT
collecting ducts
where is H2O not reabsorbed: in ascending loop of Henle
why does secretion occur after reabsorption; def. secretion (movement in what dir): b/c max concen of filtrate in glomerulus = concen in plasma b/c it is a nonselective process --> so if you need to remove even more, you can do so with secretion

substances move from peritubular capillaries or tubule cells into filtrate
what does secretion get rid of; other functions: substances not already in filtrate by the time reabsorption occurs
undesirable substances (urea, uric acid, drugs)
controls blood pH
definition osmolality typical osmolality of body fluids maintained by kidneys: number of solute particles per L of water

around 300 mOsm
what mechanism maintains the constant osmolality of body fluids: countercurrent multiplier mechanism
where does countercurrent multiplier mechanism act; generally involves what fluid flow: in renal medulla (juxtamedullary nephrons used)

flow of filtrate through loop of Henle and flow of blood through vasa recta blood vessels
range of solute concentration in the loop of Henle due to countercurrent multiplier mechanism: 300(toward cortex) - 1200 mOsm (in medulla)
what is countercurrent multiplier vs. exchanger: loop of Henle
vasa recta blood vessels
compare permeability of descending and ascending loops of Henle permeability in collecting ducts deep in medulla: descending -- to water
ascending - to solutes

to urea
where in loop of Henle does water leave: in descending loops
where in loop of Henle do solutes leave: in ascending loops
function of vasa recta; runs from where: maintain osmotic gradient
delivers blood to cells in the area

from efferent arterioles to veins?
if ADH is not being secreted; what happens: urine is kept dilute

collecting ducts remain impermeable to water --> no further water reabsorption
process for formation of concentrated urine: ADH increases reabsorption of water in collecting duct --> equalizes osmolality of filtrate and interstitial fluid
when does kidney not respond to ADH: if medullary osmotic gradient wasn't high
def. diuretic; char of these substances: chemicals that increase urinary volume

any substances not reabsorbed

if they exceed the ability of renal tubules to reabsorb it (ex. with high glucose levels, water is carried out of the body with the glucose)

substances that inhibit Na+ reabsorption (caffeine, things that inhibit Na+ ion channels in loop of Henle)
alcohol - inhibits rel of ADH
urine composition: nitrogenous wastes -- urea, uric acid, creatinine
Na, K, phosphate, sulfate ions
Ca, Mg, Cl ions
what are ureters: slender tubes that convey urine from the kidneys to the bladder
what causes propulsion of urine to the bladder: smooth muscle stretch in walls of ureters
diff b/w urinary bladder in Ms and Fs: Ms - surrounded by prostate gland inferiorly
Fs - it is in front of vagina and uterus
what is trigone: triangular area outlined by the openings for the ureters and the urethra - infections tend to persist in this region
layers of the bladder wall: transitional epithelial mucosa
thick muscular layer
fibrous adventitia
changes in pressure in bladder: no significant in change; as urine accumulates, the bladder expands
what is the urethra: muscular tube that drains urine from the bladder and conveys it out of body
function of urethral sphincters; which is involuntary: keep urethra closed when urine is not being passed

internal
definition micturation; process initiated by what: act of emptying bladder

distension of bladder walls initiates spinal reflexes --> these stimulate contraction of external urethral sphincter and temp inhibits detrusor muscle (bladder wall muscle) and internal urethral sphincter
effect of voiding reflexes: stimulates detrusor muscle to contract
inhibits the internal and external sphincters

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