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Chapter 25
Urinary System
116
Anatomy
Undergraduate 2
05/04/2012

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Term
How much blood do the kidneys filter daily?
Definition
200 liters
Term
What are the kidney's functions in relation to the blood?
Definition
regulate volume and chemical make up
Term
What are the kidney's functions in relation to water and salts?
Definition
maintain each in proper balance
Term
What hormone does the kidney secrete?
Definition
erythropoietin
Term
What role do the kidney's have in relation to vitamin D?
Definition
metabolizes into active form
Term
Why is the right kidney lower?
Definition
crowded by the liver
Term
What are the layers of tissue supporting the kidney?
Definition
renal capsule, perirenal capsule, renal fascia
Term
What is the renal capsule?
Definition
fibrous capsule that prevents kidney infection
Term
What is the perirenal fat (adipose) capsule?
Definition
fatty mass that cushions the kidney and helps attach it to the body wall
Term
What is the renal fascia?
Definition
outer layer of dense fibrous connective tissue that anchors the kidney
Term
What is the role of the ureters?
Definition
convey urine from the kidneys to the bladder
Term
Where do the ureters enter the bladder?
Definition
base of teh posterior wall
Term
What is advantageous of the ureters entering the base of the posterior wall?
Definition
closes their distal ends as bladder pressure increases and prevents backflow
Term
How many walls does a ureter have?
Definition
3
Term
What are the three walls of the ureter?
Definition
transitional epithelial mucosa, smooth muslce muscularis, fibrous connective tissue adventitia
Term
How do the ureters propel urine to the bladder?
Definition
Actively via response to smooth muscle stretch
Term
What happens as more urine enters the ureters?
Definition
peristalsis increases
Term
How significant is neuronal control in the ureters?
Definition
insignificant
Term
What surrounds the neck of the urinary bladder in males?
Definition
the prostate gland
Term
What are the three layers of the urinary bladder?
Definition
transitional epithelial mucosa, thick muscular (detrusor) layerr, fibrous adventitia
Term
What happens as urine accumulates in the bladder?
Definition
bladder expands superiorly
Term
What is the trigone?
Definition
triangular area outline by the openings for the ureters and the urethra
Term
Why is the trigone clinically important?
Definition
infections tend to persist in this region
Term
What is the urethra?
Definition
muscular tube that drains urine from the bladder, conveys it out of the body
Term
What sphincters keep the urethra closed when urine is not being passed?
Definition
internal urethral sphincter, external urethral sphincter
Term
What is the internal urethral sphincter?
Definition
involuntary sphincter at the bladder-urethra junction
Term
What is the external urethral sphincter?
Definition
voluntary sphincter surrounding the urethra as it passes through the urogential diaphragm
Term
What is the levator ani muscle?
Definition
voluntary urethral sphincter
Term
What is micturition?
Definition
act of emptying the bladder
Term
What do the spinal reflexes initiated by distension of bladder wall do?
Definition
stimulate contraction of the external urethral sphincter, inhibit the detrusor muscle and internal sphincter
Term
What are the voiding reflexes?
Definition
stimulate the detrusor muscle to contract, inhibit the internal and external sphincters
Term
How much cardiac output flows through the kidneys each minute?
Definition
1/4 (1200 mL)
Term
What is the structural and functional unit of the kidney that forms urine?
Definition
nephrons
Term
What is the glomerulus?
Definition
a tuft of capillaries associated with a renal tubule
Term
What it the glomerular (bowman's) capsule?
Definition
cup-shaped end of a renal tubule that completely surround the glomerulus
Term
What is the renal corpuscle?
Definition
blind end of nephron; consists of a thin capsule of epithelial tissue (Bowman's capsule) surrounding a ball of capillaries (glomerulus)
Term
Blood plasma filters from _______ _______ into ________ _______, thereby entering the renal tubule
Definition
glomerular capillaries, Bowman's capsule
Term
What is the purpose of the external parietal layer of the glomerular capsule?
Definition
structural
Term
What does the visceral layer of the glomerular capsule consist of?
Definition
modified, branching epithelial podocytes
Term
What do the extensions of the podocytes terminate in?
Definition
foot processes
Term
What are filtration slits?
Definition
openings between the foot processes that allow filtrate to pass into the capsular space
Term
What does the renal tubule consist of?
Definition
proximal convoluted tubule, loop of henle, distal convolute tubule
Term
What is the proximal convoluted tubule?
Definition
composed of cuboidal cells with numerous microvilli and mitochondria
Term
What is the role of the proximal convoluted tubule?
Definition
reasborbs water and solutes from filtrated and secretes substances into it
Term
What is the loop of henle?
Definition
a hair-pin shaped loop of teh renal tubule
Term
What is the proximal part of the loop of henle similar to?
Definition
the pCT
Term
What is the thin segment of the loop of henle composed of?
Definition
simple squamous cells
Term
What is the thick part of the loop of henle composed of?
Definition
cuboidal to columnar cells
Term
What is the distal convoluted tubule?
Definition
cuboidal cells without microvilli that function more in secretion than reabsorption
Term
What are the two important cell types found in the connecting tubules?
Definition
Intercalated cells, principal cells
Term
What are the intercalated cells?
Definition
cuboidal cells with microvilli
Term
What is the function of the intercalated cells?
Definition
maintaining the acid-base balance of the body
Term
What are the principal cells?
Definition
cuboidal cells without microvilli
Term
What are the principal cell's function?
Definition
help maintain the body's water and salt balance
Term
Where are teh majority of the nephrons located?
Definition
cortex
Term
What are teh nephrons in the cortex called?
Definition
cortical nephrons
Term
Where are teh juxtamedullar nephrons located?
Definition
cortex-medulla junction
Term
What is different about the loops of Henle of the juxtamedullar nephrons?
Definition
deeply invade the medulla, extensive thin segments
Term
What is the role of the juxtamedullary nephrons?
Definition
production of concentrated urine
Term
What are the two capillary beds of every nephron?
Definition
glomerulus, peritibular capillaries
Term
How is each glomerulus fed?
Definition
by an afferent arteriole
Term
How is each glomerulus drained?
Definition
by an efferent arteriole
Term
What are peritubular beds?
Definition
low pressure, porous capillaries adapted for absorption
Term
Where do peritubular beds arise from?
Definition
efferent arterioles
Term
Where do peritubular beds cling to?
Definition
adjacent renal tubules
Term
Where do peritubular beds empty into?
Definition
renal venous system
Term
What do cortical tubules wrap around?
Definition
PCT and DCT
Term
What do juxtamedullary tubules wrap around?
Definition
Loop of Henle (Vasa Recta)
Term
What is the vasa recta?
Definition
long, straight efferent arterioles of juxtamedullary nephrons
Term
What is the role of the JGA?
Definition
controls production of filtrate
Term
What is the JGA?
Definition
where the DCT lies against the afferent (sometimes efferent) arteriole
Term
What are JG cells?
Definition
modified pericytes
Term
What do the JG cells act as?
Definition
mechanoreceptors, pressure sensors detect BP
Term
What is the macula densa?
Definition
tall, closely packed distal tubules cells
Term
Where is the macula densa located?
Definition
adjacent to JG cells
Term
What is teh function of the macula densa?
Definition
osmoreceptors
Term
WHat sensors are present in the macula densa?
Definition
sodium sensors
Term
What do the macula densa do if Na+ is too high?
Definition
secrete vasopressive hormone that slows down afferent flow
Term
What are the mesangial cells?
Definition
phagocytic and contractile properties with lots of actin and myosin
Term
What possible role may the mesangial cells have with filtration?
Definition
contraction slows rate and influences capillary filtration
Term
What role may mesangial cells have with sending signals?
Definition
communication between macula densa and granular cells around afferent arteriole
Term
What is the filtration membrane?
Definition
site of substrate removal from blood, formation of filtrate
Term
What is the filtration membrane's role?
Definition
filter that lies between the blood and the interior of teh glomerular capsule
Term
What are the three layers of teh filtration membrane?
Definition
fenestrated endothelium, visceral membrane, basement membrane
Term
What is the basement membrane composed of?
Definition
fused basal laminae of the other layers
Term
How many times do the kidneys filter the body's entire plasma volume each day?
Definition
60
Term
What does the filtrate contain?
Definition
all plasma components except protein
Term
What are the three major processes inolved with urine formation and the adjustment of blood composition?
Definition
glomerular filtration, tubular reabsorption, secretion
Term
What is colloid osmotic pressure?
Definition
proteins in blood attract water
Term
What is capsular hydrostatic blood pressure?
Definition
fluid pressure within the capsule
Term
Why is the glomerulus more efficient than other capillary beds?
Definition
filtration membrane is more permeable, glomerular bp is higher, fenestrated capillaries
Term
What is glomerular filtration rate (GFR)?
Definition
total amount of filtrate formed per minute by the kidneys
Term
What factors govern GFR?
Definition
total SA available for filtration, filtration membrane permeability, net filtration pressure
Term
What is glomerular nephritis?
Definition
expansion of fenestrations
Term
What is GFR directly proportional to?
Definition
The net filtration pressure (NFP)
Term
What do changes in GFR normally result from?
Definition
changes in glomerular blood pressure
Term
What happens if the GFR is too high?
Definition
needed substance cannot be reabsorbed quickly enough and are lost in the urine
Term
What can cause a high GFR?
Definition
hypertension
Term
What can cause a low GFR?
Definition
hypotension
Term
What happens if the GFR is too low?
Definition
everything is reabsorbed, including wastes that are normally disposed of
Term
What is tubular reabsorption?
Definition
transepithelial process whereby most tubule contents are returned to the blood except metabolic wastes and unneeded substances
Term
What three membranes do transported substances travel through during tubular reabsorption?
Definition
luminal and basolateral membranes of tubules cells, endothelium of peritubular capillaries
Term
What ions are reabsorbed via paracellular pathways?
Definition
Ca2+, Mg2+, K+, and some Na+
Term
What happens to organic nutrients during tubular reabsorption?
Definition
all are reabsorbed
Term
How are water and ion reabsorption controlled during tubular reabsorption?
Definition
hormonally
Term
Is tubular reabsorption an active or passive process?
Definition
Can be either or
Term
What substances are not reabsorbed during tubular reabsorption?
Definition
those that lack carriers, are not lipid soluble, are too large to pass through membrane pores
Term
Which substances are the most important nonreabsorbed substances?
Definition
urea, creatinine, and uric acid
Term
What is tubular secretion?
Definition
essentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells into filtrate
Term
What kind of process is tubular secretion?
Definition
active
Term
What is tubular secretion important for?
Definition
disposing of substances not already in filtrate, eliminating undesirable subctances such as urea and uric acid, ridding the body of excess K+ ions, controlling blood pH
Term
What are some substances reabsorded in the PCT?
Definition
Sodium, all nutreints, cations, anions, water, urea, lipid-soluble solutes, small proteins
Term
What does the loop of Henle reabsorb in the descending limb?
Definition
Water, Na+, Cl-, K+
Term
What does the loop of Henle reabsorb in the ascending limb?
Definition
Ca2+, Mg2+, Na+
Term
What does the DCT absorb?
Definition
Ca2+, Na+, H+, K+, water, HCO3-, and Cl-
Term
What does the collecting duct absorb?
Definition
water and urea
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