Introduction to Renal Histology
Part 2 of 2
Anjali Satoskar MD PhD
Department of Pathology
anjali.satoskar@osumc.edu
Tubules
Tubules - Proximal tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting tubule
- Collecting duct
Tubules – Modify the glomerular filtrate by
reabsorption and secretion (180 liters to 1.5 liters)
95% of the renal cortex is occupied by tubules
(proximal tubules)
Renal medulla contains only tubules, no glomeruli
Tubules
- Proximal tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting tubule
- Collecting duct
PROXIMAL TUBULE
Reabsorption
• S1 and S2 segments
– Reabsorb most of NA+, Cl-, K+, H2O and most of
HC03- as well as glucose, amino acids.
– Luminal brush border and basolateral membrane
infoldings, many mitochondria.
• S3 segment (or pars recta)
– Secretion of various ions, drugs, toxins
Susceptible to toxic injury.
– Less prominent brush border, less mitochondria,
little basolateral infoldings.
Proximal tubule
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Metabolically active cells.
Tall, lots of cytoplasm.
Mitochondria at the base.
Brush border at the luminal surface, to increase surface
area of absorption.
Proximal convoluted tubule – Brush border and
basolateral infoldings
Histology of proximal tubules, prominent brush
border
Proximal tubules - Basolateral folds with mitochondria
Ultrastructural appearance of proximal tubule
Loop of
Henle
Small flattened
cells
LOOP OF HENLE
Urine concentration
(Medullary concentration gradient countercurrent
multipliers)
• Thin descending limb
– Simple thin cells, few organelles
– Water permeable
• Thin ascending limb
– Simple thin cells, few organelles
– Water impermeable
• Thick ascending limb of Henle (TALH)
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Cuboidal cells, basolateral infoldings, mitochondria
Relatively water impermeable
Produces Tamm-Horsfall protein
No brush border
Loop of Henle – Maintenance of Medullary concentration gradient
Thin limbs of Loop of Henle
Thin loop of Henle
Thick ascending loop of Henle (secrete Tamm-Horsfall protein)
Juxta-glomerular apparatus
Tubulo-glomerular feedback
Location of the Juxtaglomerular apparatus
Juxta-Glomerular Apparatus (JGA)
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3 major components:Juxta-glomerular cells - arterioles
Macula densa – distal tubule
Lacis cells – mesangial cells
Juxta-Glomerular Apparatus (JGA)
Juxta-Glomerular Apparatus (JGA)
Function of Juxtaglomerular apparatus
Tubuloglomerular feedback
• Autoregulation – Adjust renal blood
flow and the GFR
• Long term blood pressure control
JG apparatus seen in a histologic section
Renin granules (electron microscopy)
Questions to Review
1. Where is the JGA apparatus located?
2. Renin is secreted by which cells?
3.Proximal tubule brush border serves what
purpose?
4. Where does the proximal tubule arise
from?
Distal
tubule
DISTAL CONVOLUTED TUBULE
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Absence of brush border
Basolateral infoldings.
Similar to TALH
Higher N/C ratio than proximal tubular
epithelial cells
• Connecting segment is between the distal
convoluted tubule and the cortical
collecting duct.
Distal convoluted tubules (arrows)
Distal convoluted tubule
Collecting
tubule
COLLECTING DUCT
• Principal cells (2/3 of cells)
– Light cells with few organelles
– ADH sensitive and role in K+
secretion
• Intercalated cells (1/3 of cells)
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Dark cells
Acid base regulation
Type A: H+ secretion
Type B: HCO3- secretion
Type A
Type B
COLLECTING DUCT
Medullary collecting ducts
COLLECTING DUCT
RENAL INTERSTITIUM
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Extracellular space
Peritubular capillaries
RELATIVE INTERSTITIAL VOLUME
7% in cortex
10-15% medulla
30-40% deep medulla - papilla
Cortex with little interstitium
Outer renal medulla with interstitial space between
collecting ducts
Deep renal medulla with more interstitial space
between collecting ducts and loops of Henle
FUNCTIONS OF RENAL INTERSTITIUM
• Tubular oxygen supply
• Osmoregulation (together with distal
tubules)
• Immune function (interstitial dendritic
cells)
• Some endocrine function (interstitial cells)
Renal vasculature
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Renal artery
Segmental arteries
Interlobar arteries
Arcuate arteries
Interlobular arteries
Afferent arterioles
Glomeruli
Efferent arterioles
Peritubular capillaries
Venules-veins
Nephron and the surrounding vascular framework
Cross-section of the intra-renal arteries
Arteriole
Renal oxygen supply is provided
by the postglomerular capillaries
(peritubular capillaries in the
cortex, vasa recta in the
medulla)
Quiz for revision
1. In which segment of the tubules, does
the majority of reabsorption of solutes
take place?
2. Aldosterone influences potassium
excretion in which segment of the
tubules?
3. Where is the renal papilla situated?
4. Where are the slit diaphragms situated?
Summary
• Kidney
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Pair of bean-shaped organs, retroperitoneal.
Capsule, cortex, medullary pyramids, calyces, pelvis,
ureter.
Functional unit - Nephron
• Glomerulus
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Glomerular basement membrane structure.
Podocytes foot processes, slit diaphragm.
Fenestrated endothelium.
Glomerular filtration barrier.
• Tubules
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Proximal, distal, loop of Henle, collecting ducts.
Juxta-glomerular apparatus – Autoregulation
• Vasculature
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Renal arteries directly branch from aorta.
Elaborate branching pattern in the kidney
• Interstitium
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Surrounds the nephrons and vasculature
Less in cortex, more in the medulla.
Important in maintenance of osmotic gradient around
the loops of Henle.
Oxygen supply of tubules – peritubular capillaries
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Thank you, Any questions?
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Contact me at:
anjali.satoskar@osumc.edu
Department of Pathology
Division of Renal and Transplant pathology
References
• Basic Histology Lange medical text book
• Pathologic Basis of Disease Robbins and
Cottran
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