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Urinary System

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Slide 1: Kidney cortex injected to demonstrate vascular structures. Note how the rich peritubular capillary network demonstrates the tubular elements by outlining them.  

Slide 2: Low power of a kidney showing both the cortex (to the right) and medulla. Even at this very l.p. the parallel collecting ducts and other elements of the medulla are identifiable.  

Slide 3: Human kidney, low power. Note the blood vessels at the corticomedullary junction (arculate and interlobular vessels as well as one interlobular vessel up in the cortex. It is too low power to tell if it is an artery or vein).  

Slide 4: This is a low power section of the cortex cut parallel to the surface demonstrating cross sections of medullary rays. The large lumen at the right edge of the field is possibly an obliquely sectioned arcuate artery.  

Slide 5: Kidney (infant) - corticomedullary junction region. The cortex has medullary rays in longitudinal section to the left of the field; the junction region has arcuate arteries and veins in cross section and the medulla has vasa recta (identifiable at this low magnification because they are filled with blood).  

Slide 6: Kidney cortex, PAS-H, rat (from student microscope slide #109). 4 corpuscles are shown. One is sectioned through a macula densa region and another through the urinary pole. Note that the PAS+ brush border clearly identifies proximal convoluted tubule (PCT) segments and that basement membranes (of nephron segments, peritubular capillaries, Bowman's capsule, glomerular capillaries) are all also PAS+.  

Slide 7: Plastic embedded section, toluidine blue stain. Guinea pig. One kidney corpuscle is cut near the vascular pole (lower right) and a part of another one - obliquely sectioned through the urinary pole, is also present. An empty, obliquely sectioned distal convoluted tubule (DCT) is also easily identified. The darkly staining segments filled with filtrate are also mostly DCT. Note Bowman's capsule and peritubular capillaries.  

Slide 8: Similar prep. to slide 11-7. Higher mag. showing the urinary pole, several DCT and peritubular capillaries (empty-tissue was perfused). Note the abrupt transition from Bowman's capsule to the PCT (and its brush border)and the clearly identifiable podocytes in the urinary space.  

Slide 9: Similar prep. to 11-7. Podocytes and pedicles are clear. Can you identify probable endothelial, mesangial, and parietal epithelial cell nuclei? Next to the corpuscle is a DCT.  

Slide 10: TEM. Segment of a glomerular loop with the fenestrated capillary endothelium to the left of the field and podocytes (one with both cytoplasm and nucleus) and pedicels. Note the glomerular basment membrane (GBM) between the endothelium and epithelium.  

Slide 11: TEM. This grazing section of a glomerular capillary loop shows the fenestrae of the endothelium and the interdigitating podocyte processes in the urinary space. To which cell type does the nucleus in the lower left corner belong? (Ans: endothelial cell).The section grazes the visceral epithelium of a loop. Note the interdigitating podocyte cell processes.  

Slide 12: TEM. This grazing section of a glomerular capillary loop also shows the fenestrae of the endothelium as well as pedicels and larger podocyte processes in the urinary space. The thickness of the lamina densa is exaggerated by the oblique section.  

Slide 13: TEM. A high magnification image of the filtration barrier. Identify the filtration pathway - capillary lumen (below), endothelium, lamina rara interna, lamina densa, lamina rara externa, visceral epithelium (podocytes) filtration slits, urinary space.  

Slide 14: TEM. Glomerulus of a human diabetic. Note the thickened basement membranes and abnormal looking podocyte cytoplasm(from Dr. G.Gallo). Stay tuned for next year.  

Slide 15: Plastic embedded section, toluidine blue stain. The vascular pole and juxtaglomerular apparatus (JGA). Both the artery (presumably afferent) of the vascular pole of the glomerulus and the macula densa region of the DCT are obliquely sectioned. A cell with a somewhat triangular nucleus between the two is probably a JGA (renin-secreting) cell.  

Slide 16: TEM. A modified smooth muscle (JGA cell) adjacent to Bowman's capsule. The cell with the elongated irregular nucleus is a parietal epithelial (Bowman's capsule) cell. Beneath its basement membrane are unmyelinated nerve endings and adjacent to these is the JGA cell (roundish nucleus, cytoplasmic granules). The external lamina of the JGA cell and the basal lamina of the endothelium appear as one layer. The endothelium of the afferent arteriole (identifiable only by position) is irregular, not sectioned through a nucleus and is to the left in the image. (Note the finger print in the arteriole lumen!).  

Slide 17: The kidney cortex (human) with 2 medullary rays. Definitive tubule identification is difficult at this magnification although it is important to remember that PCT's are the most abundant segments present in the pars convoluta and their irregular lumina (sometimes containing exfoliated cytoplasm) make them relatively easy to spot. What elements do you expect to find in the medullary rays? (Ans: collecting tubules, straight portions of proxminal and distal tubules, peritubular capillaries).  

Slide 18: This human kidney cortex has preservation that is typical of routinely processed paraffin embedded tissue. The large, numerous eosinophilic PCT segments with their ragged luminal surfaces are easily identified. The few DCT segments (here apparently mostly sections of the same DCT) have a somewhat smaller x.s. diameter, smaller more cuboidal cells (you see more nuclei per x.s.) with nuclei close to the apical cell surface.  

Slide 19: Plastic embedded slide (faded image), toluidine blue stain, guinea pig. PCT and DCT adjacent to a glomerulus. Note the lack of brush border of the DCT segment.  

Slide 20: Histochemical localization of alkaline phosphatase (purple-blue, the brush border) and acid phosphatase (red, the lysosomes) in PCTs. Note unstained corpuscle and DCT segment.  

Slide 21: TEM of the basal region of a PCT with infoldings and associated mitochondria. Both PCT and DCT have these but they are more extensive in the PCT. The peritubular capillary would be to the lower left corner (poorly preserved).  

Slide 22: The kidney cortex in an area with a medullary ray. Compare the straight portions of proximal tubules in the ray with PCT's in the convoluta (brush borders have been destroyed by autolysis and the debris is in the tubule lumina). Within the medullary ray the two widest lumina belong to a distal tubule (to the right) and a collecting tubule (to its immediate left).  

Slide 23: Human medulla, x.s and low power. Blood filled vasa recta are seen between areas of tubule cross sections. Large collecting ducts can be identified but the l.p. makes other identifications almost impossible.  

Slide 24: Human kidney outer medulla l.p. A cross section of a vasa recta bundle - here not containing rbc (except for 2 vessels). Also identify straight portions of proximal tubules, a collecting duct and a few probable straight portions (ascending) of distal tubules.  

Slide 25: Human outer medulla, xs. Identify collecting tubules, and straight segments (descending and ascending - distinguishing which is which is difficult in this image).  

Slide 26: Human outer medulla with rather poor preservation. Nevertheless it is possible to identify thin loops, blood vessels, straight portions and collecting tubules.  

Slide 27: Plastic embedded aection, toluidine blue stain. This is a section of guinea pig medulla. Thin limbs are distinguishable from adjacent thinner walled vasa recta (many contain plasma). The other elements are somewhat different from human straight portions - ignore them.  

Slide 28: Human medulla, x.s. Locate large collecting ducts (of Bellini). The other elements are not clearly identifiable at this magnification.  

Slide 29: Medulla. Collecting tubules and thin segments are clearly identifiable. At the center of the field a transition between a proximal straight tubule and a loop of Henle is seen.  

Slide 30: TEM. Guinea pig medulla. A thin limb and adjacent vasa recta (descending have non-fenestrated and ascending have fenestrated endothelium- see next slide). Other nephron segments are difficult to identify.  

Slide 31: TEM of guinea pig medulla, higher power than slide 30. A thin loop and adjacent ascending vasa recta (endothelium has a nucleus in the section, note the fenestrae) containing plasma (and some NY dirt!). Each has its own basal lamina.  

Slide 32: Human. Interlobar vein (bottom right corner) branching into an arcuate vein and an accompanying arcuate artery. Which direction is the cortex? (Ans: to the left- note the glomerulus).  

Slide 33: The blood vessels of this kidney were filled with a red dye (mostly the arterial side as far as peritbular capillaries). Locate interlobular arteries, afferent arterioles (and a few efferent that are sure), peritubular capillary network and straight vessels (vasa recta) which carry blood to the medulla.  

Slide 34: This thick, slightly overstained section has an interlobular artery and vein (in different parts of the field) Hint: the artery is to the lower left corner of the field. Review the elements of the pars convoluta.  

Slide 35: Human embryonic kidney, low power. Note the developing cortex and medulla of several lobes and the apparent origin of the cortical columns (of Bertin for classicists!).  

Slide 36: This a human kidney papilla obliquely sectioned showing the simple columnar epithelium of the papillary surface obliquely sectioned. Also note the ducts of Bellini with simple columnar epithelium and thin limbs.  

Slide 37: Human kidney deep medulla. Ducts of Bellini appear pseudostratified. Here there are also some loops of Henle that are identifiable.  

Slide 38: This ureter of a small animal has desquamated epithelium (artifact) in its lumen. Note the fat and covering mesothelium.  

Slide 39: Higher power of the transitional epithelium of ureter shown in the previous slide.  

Slide 40: The bladder of a small animal. The lumen is to the ? (Ans: left).  

Slide 41: Bladder, higher power of the lining and lamina propria of the previous slide.  

Slide 42: Bladder, transitional epithelium.  

Slide 43: SEM and TEM of transitional epithelium (urothelium). The luminal surface has flat and plaque-like areas of thickened membrane and the apical cytoplasm contains vesicles with similar membrane. These may allow insertion and retrieval of membrane as function demands. (From Fawcett, 82 p.27).  

Slide 44: Transitional epithelium, Plastic embedded section. H&E. The basal aspect of the epithelium is not in the field. Note the domed surface cells and binucleate cells.  

Slide 45: The transitional epithelium of the human female urethra. The male urethra will be considered with the male reproductive tract.

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