Histology for Pathologist Flashcards
(33 cards)
What are the three embryologic kidney progenitors? WHen do they form?
Pronephros (3rd week of gestation)
Mesonephros (4th week of gestation)
Metanephros (5th week of gestation)
What does the mesonephros form in men and women?
Men: Epididymis
Women: Epoophoron, paraoophoron, Gartner duct
What is blastema?
Metanephric mesenchyme, which becomes the mature kidney parenchyma due to interaction with the mesonephric duct.
When do fetal lobations form and regress?
Form at 6-7 weeks, regress starting at 28 weeks (but may persist)
Recite the layers of the renal cortex.
Inner (juxtamedullary) and outer (superficial).
“Cortex corticis” is a glomerulus-free area just under the renal capsule.
What are medullary rays of Farrein?
Groups of tubules that extend to the cortical surface, dividing the kidney into lobules.
What is the normal glomerular basement membrane thickness? What is it composed of?
Around 310-380nm, thicker in men and older patients. Composed of type IV collagen, laminins, and glycosaminoglycans.
How many nephrons are in a typical kidney? When do they form?
Usually between 600,000 and 1.2 million. All develop in utero, though maturation continues into childhood.
What are ectopic glomeruli?
Glomeruli found usually in the renal sinus which regress in infancy.
What is a typical kidney weight? Are they the same size?
Around 140g (men > women).
The left kidney is usually slightly larger.
How many pyramids are found in the typical kidney? What separates them?
8-18, separated by the septa of Bertin.
Why do Wilm’s tumors usually invade through the renal sinus?
There, the capsule does not enclose the renal parenchyma.
What are the normal components of the glomerulus?
Mesangium (mesangial cells)
Capillaries with endothelial cells
Podocytes, parietal and visceral epithelium
Basement membrane
How large is the normal glomerulus?
Normally around 200 microns, can be larger in hypertrophy.
How can normal age-related global glomerulosclerosis be calculated?
(age/2) - 10 %
Describe the appearance and functions of glomerular endothelial cells.
Oval nuclei within the capillary lumina.
Expresses polyanionic glycoproteins (Podocalyxin), has fenestrations (induced by VEGF), and synthesizes NO and endothelin.
Describe the appearance and functions of glomerular mesangial cells
PAS/GMS+ structural support cells that also express actin and myosin to confer contractile function. Also reparative.
What are the layers of the glomerular basement membrane?
Lamina rara externa
Lamina densa
Lamina rara interna
Describe the appearance and functions of podocytes.
Large hobnailed cells. Synthesize GBM, provides filtration via foot processes & filtration slits. WT1+, desmin-.
What are the three components of the glomerular filtration barrier? What size of filtration do they confer?
Fenestrated endothelium (70-100nm)
Glomerular basement membrane
Filtration slit (30-40nm)
Describe the appearance and functions of parietal epithelial cells.
Hobnailed cells lining the outsides of glomeruli. Synthesizes type IV collagen. Expresses CK8, Pax2, and cadherens.
Describe the structure and function of the juxtaglomerular apparatus.
A region in the vascular pole which regulates the RAAS axis. Composed of granular cells especially in the afferent arteriole, and extraglomerular mesangium (Goormaghtigh cells).
Describe the structure and function of the macula densa.
Specialized cells in the distal convoluted tubule which detect NaCl concentration to regulate afferent arteriolar flow and regulate renin release.
Describe the morphology of proximal tubule epithelium.
Cuboidal to low-columnar cells with eosinophilic granular cytoplasm with round, usually basally-located nuclei. Luminal PAS+ brush border of microvilli.
