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124 Cards in this Set
- Front
- Back
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what are the extreme of Na+ intake in which the normal kidney can maintain sodium homeostatis
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1500 mEq/day down to 10 mEq/day (>10 times and <1/10 normal)
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What other ions fluxuation are the kidneys able to handle (like Na+)
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Cl-, K+, Ca2+, H+, Mg+, phosphate ions
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long term regulation of arterial P by kidneys
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excretion of vaiable amounts of Na+ and water
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short term regulation of arterial P by kidneys
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vasoactive factors like renin
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what acids are the kidneys the only source of elimination
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sulfuric and phosphoric acids; generated by the metabolism of proteins
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how are kidneys involved with vit D
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produce the active form 1, 25-dihydroxyvitamin D3 (calcitriol)
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what is calcitrol vital for
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normal Ca2+ deposition in bone and calcium reabsorption by GI tract; role in phosphate and calcium regulation
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when do kidneys synthesize glucose from aas
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during prolonged fasting; rivals that of liver
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with complete renal failure, what occurs
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K+, acids, fluid, and other substances accumulate in the body and can cause death within a few days if not treated
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location of kidneys
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posterior wall of abdomen outside peritoneal cavity
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what is located in the hilum
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vein, lymphatics, nerve supply, ureter, artery
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outside of kidney
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surrounded by tough fibrous capsule
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what is the medulla divided into
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cone-shaped masses called renal pyraminds
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what percent of CO is blood to the kidneys
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22% or 1100 ml/min
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branches of renal artery
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interlobular ateries, arcuate arteries, interlobular arteries (radial arteries), afferent arterioles, glomerular capillaries
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where do the distal ends of the capillaries in each glomerulous lead
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coalece to form efferent arteriole then into a second capillary network-peritubular capillaries that surround the renal tubules
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how are the glomerular and peritubular capillary beds arranged
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in series
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what is the job of the efferent arterioles btwn the two capillary beds
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regulate hydrostatic P in both sets of capillaries
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what is generally the range of hydrostatic P in the capillary beds of the kidney
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60 mmHg for high P (rapid fluid filtration) and low 13 mmHg for low P (more fluid reabsorption)
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venous system from peritubular capillaries
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interlobular veins, arcuate veins, interlobar veins, renal vein
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what occurs to nephron number after 40 years of age
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number of functioning nephrons decreases about 10% every 10 years
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why isn't the decrease in functioning nephrons a huge concern
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adaptive changes allow proper amounts of water, electrolytes, and waste product excretion
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what does Bowman's capsule house
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glomerulous
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where does fluid filtered into Bowman's capsule from the glomerular capillaries go
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proximal tubule in the cortex of the kidney, then into loop of Henle
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what does each loop of Henle contain
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descending and ascending limb
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what is at the end of the thick ascending limb
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macula densa
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how many large collecting ducts are in each kidney
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250, each collecting urine from 4000 nephrons
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cortical nephrons
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glomeruli located in the outer cortex and have short loops of henle that only penetrate a short distance into the medulla
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juxtamedullary nephrons
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20-30% of nephrons; glomeruli deep in renal cortex near medulla; long loops of henle
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vascular structures supplying juxtamedullary nephrons
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long efferent arterioles extend from glomeruli down into the outer medulla and then divide into peritubular capillaries; called vasa recta
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vascular structures supplying cortical nephrons
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entire tubular system surrounded by extensive peritubular network of capillaries
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two steps of micturition
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1) bladder fills progressively until tension in walss raise to threshold level 2) micturition reflex
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where does the micturition reflex signal come from
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autonomic spinal cord reflex; can be inhibited or facilitated by centers in cerebral cortex or brain stem
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two main parts of the bladder
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1) body 2) neck
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detrusor muscle
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smooth muscle of the bladder
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how much can contracting the detrusor muscle increase P
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40-60 mmHg
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trigone location
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posterior wall of bladder immediately above neck
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lowermost part of trigone
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neck opens into posterior urethra
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uppermost portion of trigone
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ureters enter bladder
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what is different about trigone mucosa
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smooth, whereas the rest of the bladder contains rugae
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how long is the bladder neck (posterior urethra)
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2-3 cm
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what is contained in the bladder neck
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large amout of elastic tissue; internal sphincter
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where does urethra pass
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through urogenital diaphragm which contains the external spincter (voluntary muscle)
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nerve supply of bladder
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pelvic nerve via sacral plexus (mainly S2 and 3)
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what do sensory fibers in bladder detect
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stretch
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motor nerves of bladder
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parasympathetic fibers
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what innervates skeletal muscle fibers involved in bladder fxn
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pudendal nerve (external sphincter)
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where does bladder receive sympathetic innervation
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via hypogastric nerves (especially L2)
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fxn of sympathetic innervation in bladder
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stimulate mainly blood vessels and have little to do with bladder conraction
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what are ureters innervated by
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sympathetic, parasympathetic, and intramural plexus of neurons
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peristaltic contrations of the ureter are enhanced by
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parasympathetic stimulation
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what pervents backflow of urine into ureters from bladder
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normal tone of detrusor muscle
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how can urine enter bladder if detrusor's natural tone prevents urine movement
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peristaltic waves increases P in ureter so bladder wall opens and allows urine flow
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vesicoureteral reflux
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backflow of urine into ureters during micurition
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what can vesicoureteral reflux cause
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enlargement of ureters, if severe, increase P in renal calyces and structures of renal medulla causing damage
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ureterorenal reflex
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when ureter blocked (stone), sympathetic reflex causes kidney to constrict renal arterioles
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when does intravesicular P in bladder rise rapidly
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beyond 300-400 ml of urine collection
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micturition waves
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periodic acute increases in P from a few cm of water to over 100
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what area is most sensitive to bladder filling
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receptors in posterior urethra
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common cause of atonic bladder
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crush injury to sacral region of spinal cord
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overflow incontinence
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bladder fills to capacity and overflows a few drops at a time via uretha
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tabes dorsalis
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syphilis can cause constructive fibrosis around the dorsal root nerve fibers; results in tabetic bladder
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injury of spinal cord above sacral region
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micturition can still occur, but no longer controlled by brain
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urinary excretion rate formula
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filtration rate-reabsorption rate+secretion rate
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when is filtration rate the same as excretion rate
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when substance is not reabsorbed or secreted; creatinine
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when is filtration rate more than excretion rate
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when substance reabsorbed from tubules back into blood; most electrolytes
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when does filtration occur, but there is no excretion
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all substance reabsorbed; aas and glucose
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when is excretion rate greater than filtration rate
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additional quantities secreted from peritubular capillaries into renal tubules; organic acids and baases
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advantage of high GFR
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rapidly remove waste products, allows all body fluids to be processes many times each day (control V and composition precisely)
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glomerular filtrate
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protein free and devoid of cellular elements; most concentrations equal to plasma concentrations
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examples of low MW substances not freely filtered
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Ca2+, fatty acids since partially bound to plasma proteins
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GFR is what percent of renal plasma flow
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about 20%
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what determines GFR
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1) balance of hydrostatic and osmotic forces 2) capillary filtration coefficient
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what is the capillary filtration coefficient
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product of permeability and filtering SA of capillaries
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glomerular capillary filtration
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high; high hydrostatic P and large Kf
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GFR in average adult human
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125 ml/min or 180 L/day
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3 major layers of glomerular capillary membrane
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1) endothelium of capillary 2) basement membrane 3) layer of epithelial cells (podocytes)
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fenestrae of kidney
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relatively large and endothelial cells have fixed negative charges that hinder plama protein passage
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basement membrane is made up of
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meshwork of collagen and proteoglycan fibrillae that have large spaces through which large amount of water ans small solutes can filter
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what in the basement membrane prevents protein passage
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strong negative charges associated with proteoglycans
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slit pores in kidney
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produced by gaps in foot processes of podocytes; also have negative charges
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molecular size of albumin vs pores in kidney
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6 nm vs 8 nm; negative charge prevents filtration
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minimal change nephopathy
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negative charges on basement membrane lost even before noticeable changes in kidney histology
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net filtration P
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sum of hydrostatic and colloid osmotic P
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under normal conditions, wht can be said about bowman's capsule colloid osmotic P
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0 since protein in filtrate so low
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average net filtration P
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10 mmHg
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how is Kf estimated experimentally
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GFR/Net filtration P
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Are Kf changes a primary mechanism for day to day GFR regulation
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no; although may be in disease states
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estimate for hydrostatic P in bowman's capsule
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18 mmHg; not a primary means of regulating GFR
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what pathologic states affect Bowman's capsule hydrostatic P
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obstruction of urinary tract
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how much does plasma protein content increase in efferent arterioles once leaving glomerulous
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about 20%
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how does increased protein content change colloid osmotic P
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from 28 mmHg to 35 mmHg (about 32 mmHg in glomerulous)
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what influences glomerular capillary colloid osmotic P
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arterial plasma colloid osmotic P and fraction of plasma filtered by glomerular capillaries
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glomerular hydrostatic P is determined by
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1) arterial P 2) afferent arteriolar resistance 3) efferent arteriolar resistance
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dilation of afferent arterioles causes
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increases in glomerular hydrostatic P and GFR
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constriction of efferent arterioles causes
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raises glomerular hydrostatic P and if renal blood flow isn't reduced too much, causes slight GFR increase
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biphasic effect of efferent arteriole constriction on GFR
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moderate constriction slight increase, severe there is decrease
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Donnan effect
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higher the protein concentration, the more rapidly the colloid osmostic P rises; due to ions bound to proteins
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what does renal oxygen consumption vary with
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in proportion to renal tubular sodium reabsorption
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what is renal O2 requirement if sodium reabsorption is ceased
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decreased to about 1/4 normal
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Renal blood flow equation
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(renal artery P-renal vein P)/(total vascular resistance)
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average renal vein P
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3-4 mmHg in most conditions
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where is most of the renal vascular resistance
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interlobular arteries, afferent arterioles, efferent arterioles
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what is resistance of these vessels controlled by
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sympathetic nervous system, various hormones, local internal renal control mechanisms
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what range can kidneys maintain relavitively constant GFR
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80 mmHg to 170 mmHg arterial P
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what percent of renal blood flow is in renal medulla
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1-2 %; vasa recta
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most variable determinants of GFR
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glomerular hydrostatic P and glomerular osmotic P
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when are renal sympathetic nerves most important
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severe, acute disturbances lasting a few minutes/hours; otherwise little influence on renal blood flow
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hormones that constrict afferent and efferent arterioles causing reductions in GFR and renal blood flow
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norepinephrine and apinephrine from adrenal medulla; only in extreme conditions
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endothelin
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peptide released by damaged vascular endothelial cells of kidney; vasoconstrictor
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angiotensin II
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constricts efferent arterioles; helps prevent decreases in glomerular hydrostatic P and GFR
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role of prostaglandins and bradykinin in increaseing GFR
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oppose vasoconstriction of afferent arterioles
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major fxn of autoregulation in kidneys
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maintain relatively constant GFR to allow precise control of renal excretion of water and solutes
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glomerulotubular balance
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increase reabsorption rate when GFR increases
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pressure diuresis/natriuresis
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renal excretion of sodium and water are significantly changed due to arterial P
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autoregulation feedback mechanism in kidneys
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link changes in NaCl concentration at the macula densa with control of renal arteriolar resistance
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where are juxtaglomerular cells located
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in walls of afferent and efferent arterioles
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2 affects of low NaCl on macula densa
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1) decreases resistance to blood flow in afferent arterioles 2) renin secretion which constricts efferent arterioles
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effect of angiotensin blockers on renal fxn
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greater reduction in GFR than usual when arterial P falls below normal
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contraindication for ACE inhibitors
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renal artery stenosis
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myogenic mechanism
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ability of individual vessels to resist stretching during increased arterial P
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effect of high protein intake on GFR
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increase renal blood flow and GFR
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cause of increased GFR after high protein meal
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aas and Na+ cotransported causing macula to sense low Na+ and increase GFR
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what can damage proximal tubules
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heavy metal poisoning
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