Histology of the Urinary Tract
Lecture given:
Table of Contents
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Objectives
List the main functions of the different segments of the nephron
- nephron: production of ultrafiltrate from blood; conservation of water; removal of metabolic waste
Na/K/ATPase | H2O | Ions | Glucose, AA, protein | Uric acid, Creatinine, drugs | Diuretic | Histology | Mutation | |
---|---|---|---|---|---|---|---|---|
PCT | yes | reabs | reabs | reabs | secrete | CI | 15mm; Dark cytosol, small lumen | Fanconi's |
Thin loop (D) | little | highly reabs | little | no | no | N/A | 2-14mm; epithelial cells like sunny side up eggs | |
Thin loop (A) | yes | NO | passive reabs | no | no | N/A | ||
TAL | yes | NO | NaCl reabs, X2+ reabs | no | no | Loop | 12mm; Thicker cells, larger nucleus | Bartter's |
DCT | yes | no? | Ca2+ reabs, Cl reabs | no | no | Thiazide | 5mm; lighter cytosol, larger lumen | Gitelman's |
CD (p) | yes (aldo) | yes (ADH + Aldo) | reabs K or Cl | no | no | K sparing | 20mm; Cell divisions visible due to interdigitation | |
CD (α) | yes | no | H secretion | no | no | N/A |
describe components, location and function of the juxtaglomerular apparatus
- Located where the TAL/DCT touches the afferent arteriole
- In TAL/DCT area (macula densa) - NaCl sensor
- Juxtaglomerular cells (modified smooth muscle) senses BP through stretch receptors, and secrete renin
- Extraglomerular mesangial cells
- Renin release dependent on NaCl concentration and BP (stretch of the afferent arterial)
compare the epithelial lining of proximal tubule and distal tubule
PCT | DCT | |
---|---|---|
Cytosol | Darker (mitochondria) | Lighter |
Lumen | Narrower (hard to see)* | Wider |
Length | Longer | Shorter |
* due to brush border made of microvilli to faciliate reabsorption
describe the location and histology of the renal medulla
- Made of loops of henle, descending and ascending tubules, collecting ducts and capillaries (vasa recta) arranged in parallel
- Located deep to the cortex, but in-foldings of the cortex divides the medulla into renal pyramids
- Coalesce of CDs into papillary ducts (columnar epithelium), and open at the tips of renal papillae
explain the structure and significance of transitional epithelium
- Lines ureter and bladder
- pseudostratified with all cells attached to one basement membrane (supported by lamina propria):
- Not all cells reach the lumen, and nuclei are found at different levels. Short cells are often stem cells
- Able to rearrange to accommodate pressure
- Bladder: Protein plaques on apical plasma membrane anchored to cytoskeleton and can fold and expand as bladder fills
compare the features of ureter and urinary bladder
- Ureter
- lumen has stellate outline in transverse section due to longitudinal folds
- Thick muscularis in two layers (outer circular, inner longitudinal)
- Surrounded by adventitia
- Bladder
- thicker transitional epithelium, binucleate cells present
- surface cells contain angular vesicles, representing a reservoir of surface membrane (protein plaques)
- Mucosa normally folded in the relaxed state
- Three layers in muscularis, prominent middle layer
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page revision: 18, last edited: 15 Apr 2012 05:38