L2. Renal Histology Flashcards
What are the functions of the kidney
- filter the blood to remove waste as urine
- regulate water, salt, acid-base balance
- regulate bp
- produce hormones/enzyme: epo, renin, vit D.
What portions of the nephron are in the lobe of kidney
Nephrons lie from deep to outer locations
Renal capsule, Cortex: renal corpuscle, portions of the proximal and distal tubule,
Medulla: 1 collecting duct for multiple nephrons, and loops of henle
Collecting ducts fuse to form large ducts that open at the renal papillae.
What are the parts of the Nephron in order, their function and which are the loop of henle
- Renal corpuscle: blood filtration
- Proximal convoluted tubule:
- Proximal straight tube
Bulk reabsorption of 65% blood filtration (water, glucose, amino acid) secretion of drugs - Thin descending limb
- Thin ascending limb
- Thick ascending limb
Urine concentration: reabsorbing water (and NaCl) - Distal convoluted tubule
- Connecting tubule
Fine tuning of salts and pH - Collecting tube: reabsorption of water
Loop of Henle = 3-6
Describe the cells involved and microscopic structure of renal corpuscle
Capillary tuft : loops of capillary bv- known as the glomerulus which are surrounded by podocytes. Parietal (squamous) epithelial cells line inner wall of the corpuscle.
At the vascular pole, podocytes and parietal epithelial cells are continuous.
What are the 3 components of the glomerular filtration barrier from inside capillary to the urinary space outside and what does it filter
- Fenestrated glomerular capillary
Permeable to small molecules, has a - charged glycocalyx coat for repelling most plasma proteins - Glomerular basement membrane: Thick Made of collagen and negatively charged proteoglycans with a dense core and 2 negatively charged lighter layers.
Physical and charge barrier - Podocyte slit membrane: made from interdigitating 1’ and 2’ processes linked by a protein bridge. Covered in - charged glycocalyx coat. Fine filter with charge barrier.
Therefore restricts cells, albumin and other large proteins
What does podocyte effacement mean and what does it indicate
Podocyte effacement is loss of interdigitation foot processes- flat, after damage or a leaky glomerulus which is a sign of glomerular disease caused by defect in any of the 3 layer. This leads to proteinuria
What are mesangial cells function and where are they.
modified Smooth muscle cells packed internal to the capillary tuft important for maintaining the structure of loops within the capsule - using contractility.
They also produce extracellular matrix and are involved in glomerulosclerosis (glomerular scarring)
What are the two ways you can get scarring in the renal corpuscle
When there is damaged glomerulus or podocytes, these are replaced by mesangial cell proliferation and ECM deposition which can block blood flow as they make a scar
- Also with loss of podocytes, the parietal cells can proliferate to plug up the gap between wall and glomerulus
What are the cells included in the juxtaglomerular (JG) apparatus and the main role of the apparatus - tubular glomerular feedback
JG cells which are modified SM cells which secrete renin-> angiotensin 2-> raise bp, salt retention
- Macula densa cells which are in the wall of the ThickAL which sense salt conc in the TAL after water reabsorption.
- More NaCl = more filtering. Signal sent to afferent arteriole for vasoconstriction
- Less NaCl= less filtering. Signal sent to JG cells to release renin.
- Extraglomeral mesangial cells.
What are the cells in the proximal tubule and their features
- bulk reabsorption, highly metabolic
Cuboidal epithelium:
- Prominent brush border on apical surface to increase SA for transporters
- Pinocytosis (uptake of droplets with macromolecules)
- Lateral processes and basolateral projections (interdigitation) to increase SA on that side
What are the cells in the thin limb and their features
reabsorb water
Thin squamous epithelium which reabsorb water in the loop of Henle. Have nuclei that bulge into the lumen
What are the cells in the Distal tubule cells (also distal convoluted) and their features/ functions
Fine tuning salt, pH, and concentrating urine
Cuboidal cells with interdigitating lateral processes and basolateral projections. There is no brush border but have short microvilli). No pinocytosis.
What are the cells in the Collecting duct and their features/ functions
Final modifier of water, salt, pH of urine
They go from cortex to medulla and have cuboidal to columnar epithelium
What are the medullary rays and what are they part of
Straight bundles of tissue containing a collecting duct and proximal and distal tubules going to and from the medulla.
This defines the centre of a lobule which is a portion of the cortex. The tissue between the medullary ray and the renal corpuscles is the cortical labyrinth
What is the vessels of the arterial blood until capillary tuft and then how do they come back to the renal vein - 2 ways
- Renal artery
- interlobar artery 3. arcuate artery
- interlobular artery 5. afferent arteriole
- capillary tuft.
Outer renal corpuscle
- efferent arteriole forms peritubular capillary bed
- venous capillary
- interlobular vein
- arcuate vein
- Interlobar vein -> renal vein
Deep renal corpuscle juxtamedullary nephron
- efferent arteriole goes to arterial vasa recta: long straight vessels bundled with collecting duct and loops of henle in the medulla.
- Branch to capillary beds around the loops.
- Venous return via venous vasa recta (also bundled) which join to arcuate vein or interlobular vein
