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Flashcards in 1 Renal Anatomy & Histology Deck (34):
1

General functions of the kidney

  • Most important
  • Excretion
    • Responsibilities
    • Filtration
    • Reabsorption
    • Secretion
  • Endocrine
  • Metabolic

  • Most important
    • Maintain salt & water balance (aqueous homeostasis)
  • Excretion
    • Responsibilities
      • Form urine
      • Remove metabolic wastes
      • Balance internal ion concentrations
      • Eliminate exogenous substances (drugs, pesticides, & other chemicals)
    • Filtration
      • Passive process based on size & charge of plasma components
      • Removal of breakdown products of protein metabolism
      • Occurs in glomeruli
    • Reabsorption
      • Retention of essential substances (water, glucose, amino acids, sodium, bicarbonate) from the filtrate back into the blood
      • Occurs in the tubules
    • Secretion
      • Cellular transport into the tubular lumen of substances/drugs too large or charged to enter the filtrate of the glomerulus
        • Ex. penicillin, contrast dyes
      • ATP binding cassette (ABC) trasnporters shuttle lipophilic substances across tubular membranes
  • Endocrine
    • Kidney releases secretions into circulation
    • --> systemic effects
      • Renin --> retain Na & water
      • Erythropoietin --> RBC maturation
    • --> local effects
      • Prostaglandins & kinins affect local blood flow through the kidney
  • Metabolic
    • Peptide hormone degradation (PTH, insulin)
    • Vitamin D --> 1,25 dihydroxyvitamin D3 (active form)
    • Hypoglycemia --> gluconeogenesis
    • Citrulline --> arginine as urea cycle processes NH4
      • All components of the uric cycle except the last step (arginase enzyme) so citriulline --> arginine
      • Severe kidney disease: arginine --> essential amino acid

2

Light microscopy

  • H&E
  • PAS
  • Mallory's trichrome stain
  • Silver stain

  • H&E
    • Highlights overall kidney morphology (rare)
  • PAS
    • Highlights thickness of basement membrane & ECM
    • Bright pink = proteoglycans / carbohydrates
  • Mallory's trichrome stain
    • Highlights degree of collagen deposits in interstitial matrix
    • Blue = collagen I (& II & III)
  • Silver stain
    • Highlights fine collagen III in the matrix
    • Black = collagen III (reticulin fibers)

3

Electron & immunofluorescence microscopy

  • EM
    • Ultrasound that looks at the glomerular filtration membrane
    • For diagnosis (esp glomerular disorders)
  • IM
    • Antibodies labeled w/ fluorescein bind to immunoglobulins (ex. IgG, IgA), C3, or C4 which may accumulate in certain renal pathologies
    • IM visualizes the locaiton of these molecules

4

Renal biopsy

  • 4 phsycial elements / histological areas examined for involvement in disease processes
    • GLomeruli
    • Tubules
    • Interstitium
    • Blood vessels
  • Visible interstitium --> too much (normally souldn't see)
  • Enlarged blood vessels --> renal vascular disease

5

Gross histology (A-Q)

  • A: Capsule
    • Thick, strong, w/ capsular veins
  • B: Hilus
    • Blood vessel entrance/exit
    • Ureter exit
  • C: Renal artery & vein
  • D: Cortex (outer)
    • W/ glomeruli & tubules
    • Darker reddish brown due to richer blood supply
  • E: Medulla (inner)
    • W/ straight tubules
    • Shaded zones due to thickness of tubules
  • F: Medullary rays
    • Bundles of straight tubules in cortex which travel to & from the medulla (not part of the medulla)
  • G: Medullary pyramids
    • Conical shaped w/ their apex toward the renal hilus
    • Lighter & striated appearance
  • H: Renal papilla
    • Apex of the renal pyramid
  • I: Renal lobes
    • Medullary pyramid + cap of cortex (8-14 in humans)
    • Interlobar arteries
  • J: Renal lobules
    • Medullary ray + associated nephrons
    • Interolobular arteries
  • K: Minor calyx (8-14)
    • Receives tips of each medullary lobe
  • L: Major calyx (3-4)
    • Receives tips of minor calyces
    • Empties into the renal pelvis
  • M: Renal pelvis
    • Continuous w/ ureter
    • Once urine gets here, we lose the capacity to make alterations to the urine
  • N: Nephron
  • O: Interlobular artery
  • P: Arcuate artery
  • Q: Ureter

6

Nephron

  • Bowman's capsule
  • Proximal tubule
  • Thin limbs of the loop of henle (descending & ascending)
  • Thick ascending limb of the loop of henle
  • Distal convoluted tubule
  • Collecting duct
  • Number of nephrons
  • Classification

  • Bowman's capsule
    • ​Associated w/ the glomerulus (a tuft of capillaries) --> filtration
  • Proximal tubule
    • Integrated w/ peritubular capillaries --> reabsorption & secretion
  • Thin descending, thin ascending & thick ascending limbs of the loop of henle
    • Interaction w/ surrounding vasa recta --> hypertonic interstitium for altering the tonicity of excreted urine
  • Distal convoluted tubule
    • Integrated w/ peritubular capillaries for reabsorption & secretion
  • Collecting duct
    • Close association w/ the vasa recta --> final assimilation of water & ions from the urine back to the blood
  • Number of nephrons
    • ~1 million per kidney
  • Classification
    • Based on the location of the glomerulus (filtration unit)
      • Superficial: outside
      • Juxtamedullary: inside (near the medulla)
      • Midcortical: in between
    • Based on the length of the loop of henle
      • Short loop: superficial
      • Long loop: juxtamedullary

7

Glomerulus

  • Function
  • Location
  • Components
  • Vascular pole
  • Urinary pole
  • CO, filtrate, & excreted urine

  • Function
    • Filtration unit of the kidney
    • aka renal corpuscle
  • Location
    • Cortex
    • Surrounded by coiled tubules
    • B/n medullary rays
  • Components
    • Blood vessels (glomerular capillaries)
    • Epithelium of the nephron tube (bowman's capsule)
    • Intervening basement membrane b/n the endothelial layer of capillary & bowman's capsule
    • Stalk of intraglomerular support cells (mesangial cells)
  • Vascular pole
    • Entering afferent arteirole & exiting efferent arteriole cluster here
  • Urinary pole
    • Continuation of the nephron tubule exits the glomerulus here
  • CO, filtrate, & excreted urine
    • ~20% of blood volume leaving the heart (CO) is filtered through the kidney (1 L/min of the total CO of 5 L/min)
    • Kidneys produce 180 L of filtrate / day but only excrete 1-2 L urine / day

8

Glomerulus: blood vessels

  • Afferent arteriole
  • Capillary endothelium
  • Efferent arteriole
  • Both arterioles
  • Portal system

  • Afferent arteriole
    • Incoming, larger
    • Branches to form a tuft of glomerular capillaries where filtration ocurs
  • Capillary endothelium
    • Fenestrated w/ no diaphragms spanning the pores
      • Capillaries are riddled w/ holes in endothelial cells
      • Gaps keep cellular elements out but can let large proteins in based on damage
    • Patent capillary loops: histological landmark where filtration occurs
  • Efferent arteriole
    • Outgoing, smaller
    • Formed from merged glomerular capillaries
  • Both arterioles
    • Surrounded by smooth muscle that contracts & relaxes to affect filtration pressure in the glomerular capillaries
  • Portal system
    • 2 capillary beds + 1 loop of circulation
    • Occurs in the liver, kidney, & pituitary

9

Glomerulus: bowman's capsule

  • General
  • Parietal epithelium
  • Visceral epithelium
  • Vascular pole
  • Urinary pole

  • General
    • Blind beginning of tne nephron tube
    • Bulbous expansion
  • Parietal epithelium (outermost)
    • Simple squamous epithelium
    • Forms the outer wall of the urinray space
    • Where provisional urine accumulates
  • Visceral epithelium (innermost)
    • Reflects over the glomerular tuft of capillaries
    • Coats capillaries
  • Vascular pole
    • Parietal epithelium is continuous w/ the visceral epithelium
    • Where incoming afferent arterioles, capillaries, & efferent arterioles exist
  • Urinary pole
    • Parietal epithelium is continuous w/ the proximal tubule
    • Where extra filtrate exits

10

Glomerulus: podocytes

  • General
  • Foot processes (pedicels)
  • Filtration slit diaphragm
  • Nephrin
  • Intracellular linkage molecules
  • Minimal change disease

  • General
    • Specialized cells that form the visceral epithelium of bowman's capsule that covers glomerular capillaries
    • 2 podocyte cells coat capillaries
  • Foot processes (pedicels)
    • Formed by podocyte processes or trabeculae interdigitating w/ processes from neighboring podocytes
    • Coated w/ podocalyxin (a glycoprotein rich in negatively charged sialic acid)
      • Provides repulsion b/n adjacent podocytes
    • Spacing is essential for proper glomreular filtration
      • Fusion of adjacent pedicles only occurs in pathologcial states
  • Filtration slit diaphragm
    • Specialized juncitonal complex that spans spaces b/n foot processes
  • Nehprin
    • Transmembrane protein of the immunoglobulin superfamily (ex. cadherins)
    • Forms homodimers to link neighboring foot processes
    • Maintains podocyte integrity to regulate filtration
    • Ca depending binding
    • Actin: fibers that nephrins connect to
  • Intracellular linkage molecules
    • Interface b/n nephrin & actin cytoskeleton
    • Ex. ZO-1, alpha-actinin4, podocin
  • Minimal change disease
    • 3 hallmarks: diffuse loss podocyte foot processes, vacuoles, microvilli
    • Foot process fusion

11

Glomerulus: basement membrane

  • General
  • 3 layers
  • Interna & externa
  • Diabetes

  • General
    • 320-33 nm thick
    • Lies b/n the glomerular capillary endothelium & the podocyte foot processes
  • 3 layers
    • Lamina rara externa: contacts glomerular podocytes
    • Lamina densa: central dense layer
      • Collagen IV limits porosity of the BM to small substances
      • Some albumin can get through (anything smaller: yes, anything larger: no)
    • Lamina rara interna: contacts capillayr endothelium
  • Interna & externa
    • Contain anchoring proteins laminin & fibronectin + heparan sulfate-rich anionic proteoglycans
      • Laminin: linker molecule b/n collagen, proteoglycans, & integrins found in all layers except right underneath filtration slit membranes
    • Repel negativley charged plasma proteins (anions)
    • Allow positivley charged proteins (cations) to pass through more easily
  • Diabetes
    • Decrease in BM heparan --> proteinuria

12

Glomerulus: filtration barrier

  • 3 layers that comprise the glomerular filtration barrier
  • Factors that determine glomerular filtration rate (GFR) through these layers
  • Histological structures that fine tune GFR

  • 3 layers that comprise the glomerular filtration barrier
    • Fenestrated endothelium
    • Glomerular basement membrane
    • Foot processes w/ filtration-slit diaphragm
  • Factors that determine glomerular filtration rate (GFR) through these layers
    • Hydrostatic pressure: BP within the glomerular capillaries
    • Oncotic pressure: created by plasma proteins
  • Histological structures that fine tune GFR
    • Smooth muscle in the media of afferent & efferent arterioles
    • Contractile intraglomerular mesangial cells

13

Glomerulus: intraglomerular mesangial cells

  • General
  • Smooth muscle-like mesangial cells
  • Bone marrow-derived macrophages
  • Glomerular sclerosis

  • General
    • Connective tissue cells that support the tuft of capillaries
  • Smooth muscle-like mesangial cells
    • Contractile (express alpha-actin) --> decreaes surface area for filtration
    • Sensitive to AII --> constrict cells --> limit area for filtration
    • Synthesize & degrade extracellular matrix components
      • Collagen: mainly IV & V, more I & III when activated by cytokines
      • Fibrinonectin, thrombospondin, laminin, vitronectin, proteoglycans
    • Synthesize enzymes for turnover of ECM
      • Metalloproteinases, serine-proteinases
    • Secrete prostaglandins --> vasodilate glomerular arterioles --> counteract AII
    • Secrete & sensitive to hormones, cytokines, growth factors, & paracrine agents
  • Bone marrow-derived macrophages
    • Phagocytose apoptotic cells in the basement membrane
      • Utilize C3b or Fc receptors to bind opsonized particles
    • Express MHC class II antigens --> act as antigen presenting cells
  • Glomerular sclerosis
    • Normal glomeruli: minimal intraglomerular mesangial CT
    • Glomerular sclerosis: increased mesangial expansion at the expsne of open capillary loops

14

Proximal tubule

  • General
  • Osmoticity of absorption
  • Physiological segments
  • Anatomical segments

  • General
    • First portion after leaving bowman's capsule
    • Reabsorptive workhorse
    • Reabsorbs...
      • All gluocse, amino acids, citrate, & small peptides
      • Most water, Na, K, bicarbonate, Ca, & PO4
  • Osmoticity of absorption
    • Isomotic: absorptoin of solutes is proportional to that of water
    • For any solute that is reclaimed, water can come w/ it
  • Physiological segments
    • Based on the distribution of transporters: S1, S2, & S3
  • Anatomical segments
    • Proximal convoluted tubules: coil & occupy most of hte cortex around glomeruli
    • Proximal straight tubules
      • In the cortex: in a medullary ray
      • In the medulla: by itself

15

Proximal tubule: histology

  • Lining
  • Lumen
  • Peritubular capillaries

  • Lining
    • Simple cuboidal epithelium w/ a large, central, prominent nucleus
  • Lumen
    • Collapsed & star-shaped w/ fuzzy edges
  • Peritubular capillaries
    • Carmmed into spaces b/n tubules

16

Proximal tubule: apical plasma membrane

  • Brush border
  • Apical tight junctions & desmosomes
  • Junctional complexes
  • Claudins
  • Aquaporins
  • Megalin

  • Brush border
    • Tall, regular microvili that increase surface area
    • Carriers are inserted for secondary active transport of reabsorbed amino acids, glucose, citrate, & bicarbonate
    • Molecules are coupled w/ Na in positively charged carrier complexes
  • Apical tight junctions & desmosomes
    • Tight junctions aka zonula occludens
    • Less frequent & thinner than in other tissues
  • Junctional complexes
    • Provide large pores for water to go through freely
  • Claudins
    • Create leaky epithelium in tight junctions to permit paracellular movement of water & Ca from the lumen to the interstitial space below the epithelium
  • Aquaporins
    • Water channels for water to move through the apical membrane
  • Megalin
    • Wedge of small vesicles w/ different shapes & sizes
    • Clathrin-mediated receptor anaglogous to the LDL receptor
    • Binds to amino acids & small peptides to clear small peptides

17

Proximal tubule: apical cytoplasm

  • Endocytic apparatus
  • Megalin
  • Inhibition

  • Endocytic apparatus
    • Consists of vesicular invaginations b/n the bases of microvilli, clathrin coated vesicles, large vacuoles, lysosomes, & condensing vacuoles
    • Here, peptides from teh filtrate are endocytosed & degraded before release outside the basolateral aspect of the cells
  • Megalin
    • Specific endocytosis receptor for albumin & small proteins recovered in the proximal tubule
      • Clathrin-mediated receptor analogous to the LDL receptor
    • Wedge of small vesicles w/ different shapes & sizes
    • Binds to amino acids & small peptides to clear small peptides
  • Inhibition
    • TGF-beta downregulates meglain during inflammatory conditions contributing to proteinuria
    • Inhibitors of 3-hydroxy-3 methylglutary-CoA (statins) also inhibit this & endocytosis & can contribue to proteinuria

18

Proximal tubule: basolateral plasma membrane

  • Na/K ATPase
  • Mitochrondia

  • Na/K ATPase
    • Extensive folding provides surface area for Na/K ATPase transporters
    • Na/K ATPase pumps Na out of the cell & into the basolateral extracellular space
    • Na electrochemical gradient powers secondary active transport at the apical border
  • Cytoplasmic mitochondria
    • Occupy folds b/n basolateral invaginations providing ATP for the energy demands of active transport

19

Loop of henle

  • 4 portions
  • Length
  • Interstitium tonicity

  • 4 portions
    • Thin descending limb
    • Thin ascending limb
    • Medullary thick ascending limb
    • Cortical thick ascending limb
  • Length
    • Varies w/ location
    • Short loops: superficial glomeruli
    • Long loops: juxtamedullary glomeruli
      • Extend to the tips of the medullary papillae
  • Interstitium tonicity
    • long LOHs establish a hypertonic interstitium in the medulla to produce hypertonic urine
    • Countercurrent exchange b/n the tubules & vasa recta establishes & maintains the hypertonic interstitium
    • 13% of nephrons contain long LOHs to produce hypertonic urine

20

Loop of henle: thin descending limb

  • General
  • Permeability
  • Water movement
  • Tubular fluid

  • General
    • Simple squamous epithelium
    • Variations in the # of interdigitations & mitochondria
  • Permeability
    • Permeable to water & urea (passive process)
    • Impermeable to Na & Cl
  • Water movement
    • Water & urea passively move from the tubular fluid into the interstitium as the thin limb descends into the hypertonic interstitium of the medulla
    • Water moves paracellular through shallow tight junctions & intracellularly through aquaporin channels
  • Tubular fluid
    • In equilibrium w/ interstitial mileu throughout its descent

21

Loop of henle: thin ascending limb

  • Main function
  • Permeability
  • Salt movement
  • Water movement
  • Active transport of Na or Cl

  • Main function
    • maintain & stabilize the hyperotnic gradient of the medullary interstitium
  • Permeability
    • Permeable to Na & Cl (passive process)
    • Impermeable to water
  • Salt movement
    • Salt exits the tubule as flow ascends into less hypertonic regions of the medulla
  • Water movement
    • Water movement is prevented by more extensive tight junctions w/ claudins that seal & the lack of aquaporins
  • Active transport of Na or Cl
    • No active transport of Na or Cl anywhere laong the thin limb of the LOH

22

Loop of henle: thick ascending loop (TAL)

  • Location
  • Tonicity
  • Basolateral plasma membrane
  • Mitochondria
  • Apical plasma membrane
  • Net result
  • Inhibition

  • Location
    • Near the hairpin turn in short looped nephrons
    • At the transition from the outer to inner medullayr zones in long looped nephrons
  • Tonicity
    • TAL aka diluting segment b/c the lumenal contents are hypotonic when they exit
  • Basolateral plasma membrane
    • Simple cuboidal epithelium displays numerous invaginations
    • Folds extend almost to the apical end of TAL cells
    • Site of Na/K ATPase active transport pumps
  • Mitochondria
    • Contained within cytoplasm b/n the folds
    • More round than the elongated ones of the proximal tubule
  • Apical plasma membrane
    • Slightly irregular
    • Contains a Na/K/2Cl symporter
    • Extensive tight junctions block the paracellular movement of water
    • No aquaporin channels --> impermeable to water
    • Claudins permid passage of Mg, Ca, & Na
  • Net result
    • Movement of Na & Cl from the lumen into the interstitium
    • Ion pumping produces the hypertonic medulary interstitium & delivers hypotonic, dilute tubular fluid to the distal convoluted tubule
  • Inhibition
    • Loop diuretics (ex. furosemide) inhibit the apical co-transporter

23

Loop of henle: macula densa

  • Last segment of the cortical TAL
  • Each macula densa returns to its glomerulus of origin
  • Component of the juxtaglomerular apparatus that's responsible for renin secretion

24

Distal convoluted tubule

  • Location
  • Length, lining, coiling, & tight junctions vs. proximal tubules
  • Apical surface
  • Basolateral surface
  • Response to aldosterone & parathyroid hormone (PTH)

  • Location
    • In the cortex intermingled w/ the proximal convoluted tubules
  • Length, lining, coiling, & tight junctions vs. proximal tubules
    • Length: shorter w/ fewer sections per area
    • Lining: lower cuboidal epithelium
    • Coiling: not as much b/c doesn't do as much work
    • Tight junctions: broader w/ sealing claudins to prevent paracellular water movement
  • Apical surface
    • Devoid of microvilli --> smooth lumen
  • Basolateral surface
    • Highly folded w/ Na/K ATPase pumps & mitochondria
    • Pumps drive reabsorption of Na & Cl
  • Response to aldosterone & parathyroid hormone (PTH)
    • Aldosterone: reabsorb Na
    • PTH: reabsorb Ca

25

Collecting duct

  • 3 segments
  • Function
  • Under the control of...
  • Lining
  • Principal (light) cells
  • Intercalated (dark) cells

  • 3 segments
    • Connecting segment
    • Cortical collecting duct
    • Medullary collecting duct
  • Function
    • Final adjustments to volume & tonicity of excreted urine
  • Under the control of...
    • Vasopressin (antidiuretic hormone, ADH)
    • Aldosterone
  • Lining
    • Initially: simple cuboidal epithelium
    • Toward the medullary papilla: tall, columnar, & pseudostratified at the exiting papillary ducts
    • Full length: distinct lateral cell borders
  • Principal (light) cells
    • Pale cytoplasm, small random mitochondria, few basal infoldings, few microvilli, & a single cilium
    • Cilium: flow sensor linked to a Ca channel
    • Response to aldosterone: reabsorb Na & secrete K
    • Response to ADH: increase luminal permeability to wtaer
  • Intercalated (dark) cells
    • More electron dense
    • Secrete H for acid/base balance & urine acidification

26

Juxtaglomerular apparatus

  • Where it fits in w/ the other parts of the nephron
  • Function
  • Structures
  • Sensors

  • Where it fits in w/ the other parts of the nephron
    • Proximally: reabsorb filtrate
    • Distally: fine-tuning
    • In b/n: juxtaglomerular apparatus provides feedback about what the nephron is doing
  • Function
    • Control GFR to not flood out the capacity of the distal nephron
    • Prevents excessive salt & water loss
    • Adjusts renal hemodynamics during increased or decreased perfusion
    • Activates renin, AII, & aldosterone
  • Structures
    • Afferent arteriole
    • Efferent arteriole
    • Macula densa
    • Extraglomerular mesangial cells
  • Sensors
    • Afferent arteriole stretch receptors
    • Macula densa Cl/osmolality receptors

27

Juxtaglomerular apparatus: juxtaglomerular (JG) cells in the afferent arteriole

  • Specialized cells that comprise smooth muscle in the media
  • Contain intracellular actin, myosin, dense bodies, RER, golgi, & secretory vesicles
  • Decrease BP --> decrease arteriorlar stretch --> JG cells secrete renin
  • Increase BP --> JG cells vasoconstrict the AffA

28

Juxtaglomerular apparatus: macula densa

  • Location
  • Base
  • Nuclei
  • Response to flow related alterations in levels of Cl (osmolality) in the fluid being delivered from the thick ascending limb

  • Location
    • Where the cortical thick ascending limb returns to its glomerulus of origin
  • Base
    • Interdigitate w/ underlying extraglomerular mesangial cells & JG cells
  • Nuclei
    • Forced apically toward the luemn
  • Response to flow related alterations in levels of Cl (osmolality) in the fluid being delivered from the thick ascending limb
    • High Cl flow rates --> high glomerular perfusion rate --> macula densa releases adenosine & NO (directly) & AII & thromboxane (indirectly) --> blocks JG cell renin release

29

Juxtaglomerular apparatus: extraglomerular mesangial cells

  • Lie b/n the AffA & EffA, macula densa, & glomerulus
  • Interact w/ macula densa & JG cells
  • Regulate renin secretion & vasoconstriction

30

Juxtaglomerular apparatus: efferent arteriole

  • EffA smooth muscle contraction increases hydrostatic pressure within the glomerulus
  • Low pressure/flow: AII--> EffA constriction --> preserve GFR
  • High pressure/flow: local synthesis of prostaglandins --> EffA vasodilation --> preserve blood flow to medulla

31

Renal interstitium

  • General
  • Cortex
  • Medulla
    • Type I
    • Type II
    • Type III

  • General
    • Minor component of connective tissue cells b/n tubular & vascular elements of the kidney
  • Cortex
    • Fibroblast-like interstitial cells
      • Secrete ECM & contain contractile filaments
      • May secrete erythropoietin
    • Phagocytic interstitial cells
      • Derived from monocytes
  • Medulla
    • Type I interstitial cells
      • Fbroblast-like w/ lipid droplets, SER, & mitochondria w/ vesicular cristae
      • Site of prostaglandin synthesis to maintain blood flow in the medulla
    • Type II interstitial cells
      • Rounded cells w/ free ribosomes & lysosomes but no lipid droplets
    • Type III interstitial cells
      • Similar to pericytes, found in the BM of the vasa recta
      • Source of regenerative cells to support the wall when secreting new endothelial cells

32

Renal circulation

  • Distribution of blood flow
  • Ischemia
  • Hypovolemic states

  • Asymmetrical distribution of blood flow
    • 80% --> outer cortex (where 85% of glomeruli are located)
    • 10-15% --> inner cortex (where 15% of glomeruli & juxtamedullary nephrons are located)
    • 5-10% --> medulla
  • Ischemia
    • Greater risk to low flow areas
  • Hypovolemic states
    • Blood flow from the outer cortex is diverted to the inner cortex

33

Renal circulation pathway

  1. Renal artery
  2. Interlobar artery
    • Located b/n renal lobes
    • Branch from renal arteries at the base of the medullary pyramids
    • Penetrate the medulla b/n renal lobes
  3. Arcuate arteries
    • Flow along the junction b/n cortex & medulla
    • Don't anastomose (each is responsible for supplying a specific portion of cortex)
  4. Interlobular arteries
    • Located b/n lobules
    • Arise from the arcuate & penetrate the cortex b/n medullary rays
    • Give rise to AffAs directly or to short intralobular arteries first
  5. Intralobular arteries (sometimes)
  6. Afferent arterioles
    • Come off intralobulra arteries & go to glomeruli
  7. Glomerular capillaries (capillary tufts)
    • Superficial glomeruli --> peritubular capillary plexus to assimilate reabsorbed materials
    • Juxtamedullary glomeruli --> vasa recta --> medulla to accompany LOH to the papillary tips
  8. Efferent arterioles
  9. 2nd capillary bed
    • Follows its nephron of origin
    • Superficial nephron --> short LOH --> peritubular capillaries
    • Juxtamedullary nephron --> long LOH --> vasa recta
  10. Arcuate veins
  11. Interlobar veins (sometimes)
  12. Renal vein
    • Exits renal pelvis

34

Summary

  • Bowman's capsule
  • Proximal tubule
  • LOH
  • Distal convoluted tubule
  • Collecting duct
  • Internal regulation/feedback

  • Bowman's capsule
    • Glomerular capillaries
  • Proximal tubule
    • Peritubular capillaries b/n proximal tubules
  • LOH
    • Vasa recta
  • Distal convoluted tubule
    • Peritubular capillaries
  • Collecting duct
    • Vasa recta in the inner medulla
  • Internal regulation/feedback
    • Afferent arteriole
    • Macula densa