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Introduction to Renal Histology
Part 2 of 2
Anjali Satoskar MD PhD Department of Pathology
Tubules - - Proximal tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting tubule
- Collecting duct
Tubules
- Proximal tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting tubule
- Collecting duct
Tubules
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• Metabolically active cells.• Tall, lots of cytoplasm.• Mitochondria at the base.• Brush border at the luminal surface, to increase surface
area of absorption.
LOOP OF HENLEUrine 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)– Cuboidal cells, basolateral infoldings, mitochondria– Relatively water impermeable– Produces Tamm-Horsfall protein– No brush border
Juxta-Glomerular Apparatus (JGA)
• 3 major components:-• Juxta-glomerular cells - arterioles • Macula densa – distal tubule • Lacis cells – mesangial cells
Function of Juxtaglomerular apparatusTubuloglomerular feedback
• Autoregulation – Adjust renal blood flow and the GFR
• Long term blood pressure control
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 CONVOLUTED TUBULE
• 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.
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)
– Dark cells– Acid base regulation– Type A: H+ secretion– Type B: HCO3- secretion
RENAL INTERSTITIUM• Extracellular space • Peritubular capillaries• RELATIVE INTERSTITIAL VOLUME• 7% in cortex• 10-15% medulla• 30-40% deep medulla - papilla
FUNCTIONS OF RENAL INTERSTITIUM
• Tubular oxygen supply• Osmoregulation (together with distal
tubules)• Immune function (interstitial dendritic
cells)• Some endocrine function (interstitial cells)
Renal vasculature
• Renal artery• Segmental arteries• Interlobar arteries• Arcuate arteries• Interlobular arteries• Afferent arterioles• Glomeruli• Efferent arterioles• Peritubular capillaries• Venules-veins
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
• Glomerulus
• Tubules
• Vasculature
• Interstitium
• Pair of bean-shaped organs, retroperitoneal.• Capsule, cortex, medullary pyramids, calyces, pelvis,
ureter.• Functional unit - Nephron
• Glomerular basement membrane structure.• Podocytes foot processes, slit diaphragm.• Fenestrated endothelium.• Glomerular filtration barrier.
• Proximal, distal, loop of Henle, collecting ducts.• Juxta-glomerular apparatus – Autoregulation
• Renal arteries directly branch from aorta.• Elaborate branching pattern in the kidney
• 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
Thank you, Any questions?
• Contact me at:• [email protected]• 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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