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123 Cards in this Set

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  • Back
3 functions of the kidneys:
1. Excretory
2. Homeostatic
3. Endocrine
How much urine do the kidneys produce daily?
1500 ml
What does the kidney excrete?
-Excess water/ions
-Drugs/toxins/toxin byproducts
-Urea/Creatinine
What are the 2 main homeostatic functions of the kidney?
1. Regulate/maintain the ECF
2. Maintain Acid/base balance
3 Endocrine functions of the kidney:
1. Erythropoeitin
2. Renin
3. Vit D activation
What is the general macroscopic structure of the kidney like?
-Solid organ
-Mostly parenchyma
-Little stroma
-2 subdivisions (medulla/cortex)
What is the appearance and consistency of the cortex?
-Granular
-Homogenous
Medullary Rays:
Extensions of the medulla into cortex.
What is the appearance of the medulla?
Striated
What makes up the medulla?
6-18 Renal pyramids
What is the apex of each pyramid called?
Renal papilla
What is a Kidney Lobe?
A macroscopic subdivision of the kidney - consists of:
-Renal pyramid
-Its surrounding cortex
What is a Kidney Lobule?
A microscopic subdivision - consists of:
-Medullary ray
-Cortical tissue on either side
How are cortical nephrons connected to the medulla?
Via collecting ducts
What surrounds the kidney?
A capsule consisting of mainly fibrous connective tissue
How much of CO does the kidney recieve?
20-25%
How much of the total body weight are the kidneys together?
0.5%
How much blood volume passes thru the kidneys every 4/5 minutes?
All of it
How much of the blood flowing through the kidney is extracted each minute? (filtered)
125 mL
How much of that 125 ml is reabsorbed and excreted?
Reabsorbed: 124 ml
Excreted: 1 ml
6 Levels in the Arterial Supply hierarchy of the kidney:
1. Renal artery
2. Lobar artery
3. Interlobar artery
4. Arcuate artery
5. Interlobular artery
6. Afferent arteriole / Subcapsular artery
Pneumonic for the vascular supply:
RL IAIA S
What are the 2 capillary plexes associated with each nephron?
-Glomerulus
-Tubular Capillary Plexus
What supplies the glomerular capillary plexus?
The afferent arteriole
What drains the glomerulus?
The efferent arteriole
What supplies the tubular capillary plexus?
The efferent arteriole
What are the Vasa Recta part of? What are they?
Part of the tubular plexus - long capillary loops.
What type of nephrons are the vasa recta part of?
Juxtamedullary nephrons
Where are juxtamedullary nephrons located?
Near the cortex-medulla border
What percentage of all nephrons are juxtamedullary?
15%
What is the veinous drainage of the kidney like?
Follows the arterial pattern.
What is a nephron from a developmental perspective?
-Renal corpuscle
-Proximal/intermed/distal tubules
What is a nephron from a functional perspective?
-Renal corpuscle
-All tubules
-Collecting duct
Collecting ducts are aka:
Uriniferous tubules
What is the Renal Corpuscle?
A spherical double-layered sac that surrounds a network of capillaries.
What is the double-layered sac called?
Renal capsule
What are the 2 poles of the renal corpuscle?
-Vascular pole (where arterioles enter and exit)
-Urinary pole (continuous with the proximal tubule)
Where can renal corpuscles be found?
Only in the cortex!
2 Components of the renal corpuscle:
-Glomerulus
-Renal Capsule (Bowman's)
What is the role of the Afferent and Efferent arterioles in supplying/draining the glomerulus?
The maintain the filtration pressure.
What exactly is Bowman's capsule?
A double layered epithelial sac surrounding the glomerulus.
What type of epithelium is the outer (Parietal) layer of bowman's capsule?
Simple squamous
What is the visceral layer of Bowman's capsule?
Simple epithelium, but cells are specialized Podocytes
What are podocytes?
Specialized cells with primary processes + 2ndry foot processes
What are the 2ndry foot processes in podocytes called?
Pedicles
What are the pedicles of podocytes aligned along?
The glomerular capillary basement membrane.
What is the space between the visceral and parietal layers of the renal capsule called? What is it continuous with?
The urinary space - continuous with the proximal tubule.
Why is the urinary space important?
Because that's where filtrate from bowman's tuft flows into.
What is the Glomerular Filtration Barrier, and what are its 3 components?
The kidney's filtration membrane:
1. Capillary endothelium
2. Basement membrane
3. Visceral layer of bowman's capsule
What type of endothelium is the glomerular capillary endothelium (GCE)?
Discontinuous
How big are the pores in the Gcap endothelium?
70-90 nm
What is the GCE permeable to?
-Freely permeable to water
-Freely permeable to solutes <6-8 kD
-Semipermeable to solutes 8-16kD
What is Podocalyxin?
A coating on the luminal surface of the GCE that gives it a net negative charge.
What is unique about the thickness of the Glomerular Basement Membrane (GBM)?
it is 2-3X thicker than the normal basement membrane.
What is the function of the GBM's thickness?
Prevents protein from entering the filtrate.
What are 2 ways in which the glomerular basement membrane is a barrier to proteins?
-Physical barrier to proteins >70 kD
-Charge barrier to proteins <70kD
3 layers of the basement membrane seen on EM:
-Internal Lucent layer
-Dense layer
-External lucent layer
Why are the internal and external layers of GBM lucent?
Because they are rich in polyanions
Why is the middle layer dense?
Because it has Type IV collagen.
5 components that make up GBM:
1. Type IV collagen
2. Sialoglycoprotiens
3. Non-collagenous glycoproteins
4. Proteoglycans
5. Glycosaminoglycans
What is the Visceral layer of bowman's capsule made up of?
Podocytes - epithelial cells
How is the visceral layer of podocytes related to the GBM?
Pedicles interdigitate along it.
What are pedicles again?
2ndary foot processes on podocytes.
And podocytes are?
Specialized epithelial cells with Primary and 2ndry foot processes.
What are the spaces between pedicles called?
Filtration slits
How wide are filtration slits? Are they just open?
25 nm wide - bridged by an electron dense diaphragm.
What covers the urinary surface of podocytes and filtration slits?
Another layer of Podocalyxin
What is the Mesangium?
A layer of cells and ECM that abut the inner side of the GBM (glom basmnt memb).
What are the cells in the mesangium?
Modified pericyte/smooth muscle cells w/ receptors for ANP and ANG ii
What does the mesangium ECM contain?
Fibronectin
3 Functions of the Mesangium:
-Physical support of glomerulus
-Regulation of glomerular bflow
-Maintain endothelial side of GBMemb via phagocytic activity
What results when one or more components of the glomerular filtration barrier, or the mesangium, becomes damaged?
Glomerulonephritis
What clinical problems are seen with glomerulonephritis?
-Increased permeability of filtration membrane
-Proteinuria
-Sometimes hypertension
What is the beginning of the Proximal Tubule? Where is it?
The convoluted portion beginning at the urinary pole - in the cortex.
What type of epithelial cells line the convoluted prox tubule?
Cuboidal to columnar.
What is at the apex (lumenal side) of each epithelial cell lining the tubule?
A brush border coated w/ glycocalyx.
What are Apical Canaliculi?
Infoldings of the apical cell membrane that provide additional surface for endocytosis.
What section of the proximal tubule comes after the convoluted segment?
Straight portion
What makes the straight portion different from convoluted?
Less absorption, and extends from cortex into medulla.
What is the intermediate tubule?
The loop of henle
4 parts of the Loop of Henle:
1. Straight portion of proximal tubule
2. Thin descending loop
3. Thin ascending loop
4. Straight portion of distal tubule
Where are the components of Henle's loop found primarily?
In the medulla
What kind of henle's loop do Cortical nephrons have?
Only a descending thin limb
What kind of Henle's loop do Juxtamedullary nephrons have?
Ascending AND desc. thin limbs
What type of epithelial cells line the loops of Henle at their
-Thin segments
-Thick segments
Thin = simple squamous
Thick = cuboidal
Are the ascending limbs permeable to water? Why/why not?
No - because lateral borders of cells are highly interdigitated and thus water impermeable.
What is the nature of the fluid in the:
-Descending limb?
-Ascending limb?
Descending = hypotonic
Ascending = isotonic
2 components of the distal tubule:
-Straight portion
-Convoluted portion
What is the Straight portion of the distal tubule really?
The thick portion of the ascending limb of Henle's loop.
What marks the border between the end of the straight portion and start of convoluted?
When the ascending tubule touches its contributing renal corpuscle at the Macula Densa
What is the macula densa?
Specialized distal tubule epithelial cells at the arterial pole of the corpuscle
What type of epithelium lines the straight and convoluted ascending tubules?
Simple cuboidal w/ fewer microvilli and lots of basal mitochondria.
What exactly are collecting tubules?
Transition segments between the nephron and collecting duct.
What is the distinct feature of the epithelial cells lining the collecting ducts?
They have ADH sensitive AQP-2 water channels.
What happens in collecting ducts when ADH is present?
Urea and water diffuse out of the collecting duct into renal interstitium. Urine tonicity increases.
What happens when ADH is absent?
Water is excreted, leading to Polyuria and Hypotonic urine
What type of diabetes is associated with polyuria and hypotonic urine?
Diabetes insipidus
What 2 pathological deposits can be left in the collecting duct?
-Gout urate crystals
-Calcium deposits
What is the main problem that results from tubular disease?
Acidosis due to inability to excrete acid.
Where is the Renal Interstitium?
Meulla
What does the Renal Interstitium do?
Its fibroblasts secrete the interstitial connective tissue
What type of cells are in the interstitium? What do they secrete?
Stellate cells - secrete Medullipin I.
What happens to medullipin I?
It is converted in the liver to Medullipin II
What does Medullipin II do?
suppresses symp activity - counteracts RAS functions.
What is the Countercurrent Multiplier Effect?
Interaction between collecting ducts, portions of henle's loops, and vasa recta for modifying/concentrating urine.
What does the Countercurrent Multiplier Effect yield?
Hypotonic fluid in the distal tubule
2 reasons why distal tubule fluid is hypotonic:
1. Asc limb of henle's loop is impermeable to water
2. Desc limb of henle's loop is somewhat water permeable.
What is the function of the Countercurrent Exchanger?
To maintain the ionic gradient established by the countercurrent multiplier effect.
4 Endocrine secretions of the kidney:
1. Medullipin
2. Renin
3. EPO
4. Activated Vit D
3 components of the juxtaglomerular apparatus:
1. Renin producing JG cells
2. Extraglomerular Mesangial cells
3. Macula densa
What do the Macula densa cells do?
Detect Cl and Na concentration in filtrate and alter the filtration rate and blood vol autoregulation in response.
What does the Acute Renal Failure clinical picture include? Chronic?
Azotemia and high toxins in blood - oliguria/ischemia.

Chronic is irreversible; uremia and hematuria are features.
What are the Excretory passageways of the urinary system?
1. Calyces/Pelvis/Ureters
2. Urinary bladder
3. Urethra
What type of epithelium lines the mucosa of the excretory passageways?
Transitional epithelium
What does the middle layer of the walls of the ureters contain?
Smooth muscle - the Muscularis
What is the Adventitia made of?
Fibrous connective tissue.
What covers the urinary bladder?
More transitional epithelium
How many layers are in the bladder muscularis?
3
How long is the urethra in:
-Males
-Females
Males = 15-20 cm
Females = 3-5 cm
3 subdivisions of the male urethra:
What type of epithelium lines each part?
-Prostatic - Transitional
-Membranous
-Penile
(Last 2 lined w/ Stratified to Pseudostratified columnar epith)
What type of epithelium lines the navicular fossa at the distal tip of the penile urethra?
Stratified squamous
What lines the female urethra?
-Initially transitional epithel
-Then stratified squamous
3 common clinical problems that obstruct excretory passages:
1. Nodular hyperplasia (benign prostatic hypertrophy)
2. Renal calculi (kidney stones)
3. Bladder cancer