Chapter 16: The Kidney Flashcards
What specialized cell types are seen in the glomerulus?
Podocytes - epithelial cells covering capillaries. Cover the outer surface of the basement membrane.
Mesangial cells: Modified smooth muscle cells that support the glomerulus
What are the three layers of the glomerular basement membrane?
Lamina densa: Central, electron rich zone
Lamina rara interna: Thin inner electron-lucent zone
Lamina rara externa: Thin outer layer
Composed of type IV collagen. GAGs, laminin, entactin, fibronectin. Charge selection-filtration (neutral, cationic), size discrim.
Where are podocytes located?
Where do their foot projections go?
What is between foot processes?
What is the major function of podocytes?
Rest on outer aspect of the GBM.
Send cytoplasmic projections, foot processes, into lamina rara externa of GBM.
Slit diaphragm between foot processes, modified adherens junction.
Barrier to protein loss in the urine - proteinuria with mutations in nephrin, podocin, alpha-actinin-4, transient receptor potential cation channel 6 (TRPC6).
What are features and functions of the mesangium?
Cellular and matrix network that supports glomerulus. Modified smooth muscle cells in center of glomerular tuft between capillary loops.
- Mechanical support of glomerulus
- Endocytosis and processing of plasma proteins (immune complexes)
- Maintenance of basement membrane/matrix elements
- Modulation of glomerular filtration by contraction of mesangial cells
- Generation of molecular mediators (prostaglandins, cytokines).
What are the features of the juxtaglomerular apparatus?
Located at hilus of glomerulus.
Macula densa: Region of TALH, packed with nuclei
Extraglomerular mesangial cells: Between macula densa and hilar arterioles
Terminal afferent arteriole and proximal efferent arteriole.
Afferent arteriole contains granular cells that synthesize renin and angiotensin.
This disease results from insufficienc amniotic fluid.
What are complications?
Potter sequence (oligohydramnios sequence). Reduced intrauterine urine production. Fetus compressed by uterus - low set ears, small receding chin, beak like nose, bent lower extremities.
Pulmonary hypoplasia - inadequate maturational stimuli, compression of chest wall.
What is renal agenesis?
Complete abscence of renal tissue. Usually stillborn with Potter sequence.
Unilateral agenesis not serious if no other abnormalities. Increased risk for progressive glomerular sclerosis (FSGS).
What defines/characterizes renal hypoplasia?
Congenital reduction in renal mass. Histologically normal with six or fewer renal lobes (medullary pyramids with overlying cortex).
What term defines enlargement of the too few glomeruli seen in renal hypoplasia?
Oligomeganephronia.
What is the term for a normal kidney in an abnormal location?
Renal ectopia. Usually in pelvis.
Simple: Ureters drain into appropriate side of bladder
Crossed: Ectopic kidney on same side as normal mate, drains into contralateral side of bladder.
What is a horseshoe kidney?
Single large midline organ, kidneys fused usually at lower poles. Increased risk for obstruction and infection (pyelonephritis) because ureters must cross over junction where organ is fused.
What characterizes renal dysplasia?
Disorder of development. Undifferentiated tubular structures lined by cuboidal or columnar epithelium surrounded by primitive mesenchyme. Cartilage? Cysts.
Genetics, obstruction of urine flow. Ureteral agenesis, ureteral atresia, uretopelvic junction obstruction, uretovesical stenosis/posterior urethral valves.
Subtypes of renal dysplasia include..
Aplastic renal dysplasia: Small misshapen dysplastic kidneys
Multicystic renal dysplasia: Unilateral, multiple cysts.
Diffuse cystic renal dysplasia: More uniformly sized cysts, preservation of kidney shape
Obstructive renal dysplasia: Intrauterine obstruction to urine flow.
What occurs in autosomal dominant polycystic kidney disease?
Kidneys are enlarged and have numerous cysts in renal parenchyma. End stage renal failure in 50%. Mutations in PKD1/2. Polycystin 1 and 2, sense extracellular environment including urine flow, regulate intracellular calcium and tubule epithelial proliferation and apoptosis.
Defects in these proteins disrupt calcium signaling from cilia that normally inhibits renal tubule growth.
**Usually fourth decade of life.
Who is generally affected by autosomal recessive polycystic kidney disease?
Infants.
Cystic transformation of collecting ducts.
Die due to pulmonary hypoplasia from Potter sequence oligohydramnios.
Mutation in PKHD1 gene - fibrocystin. Found in primary cilia of collecting ducts of kidney, biliary ducts of liver, exocrine ducts of pancreas. Diff, prolif, adhesion.
What is glomerulocystic disease?
Bowman capsule dilated in many glomeruli.
Isolated or secondary to ADPKD, nephronophthisis, medullary cystic disease complex, diffuse cystic dysplasia.
Autosomal dominant form: Mutations in hepatocyte nuclear factor -1beta.
What are two diseases causing tubulointerstitial injury and medullary cysts?
Defining features?
Nephronophthisis and medullary cystic disease.
Small kidneys, cysts at corticomedullary junction. Sclerosis and fibrosis late. Deteriorating tubular function.
What causes nephronophthisis?
Autosomal recessive, childhood, mutations in NPHP genes (nephrocystins) located in primary cilia.
What causes medullary cystic disease?
Autosomal dominant, adolescence, renal failure in adulthood with defects in MCKD1 or 2 genes.
What disease is distinguished by cysts in the papillae?
Medullary sponge kidney. Arise from collecting ducts, lined by cuboidal or columnar epithelium.
Symptomatic between 30-60. Flank pain, dysuria, hematuria, gravel in urine.
Describe simple cysts.
Acquired cysts, asymptomatic, incidental finding unless very large. Half of people over 50.
