Renal Histology Flashcards
What are the kidney functions?
- Regulate volume & composition of body fluids
- Produce ultrafiltrate of blood plasma
- Endocrine activities
What is renin made/secreted by? What does it do? What does it control?
- Synthesized and secreted by juxtaglomerular cells
- Cleaves circulating angiotensinogen to make angiotensin I
- Controls blood pressure and volume
What are the endocrine activities of the kidney?
–Erythropoietin (EPO), a glycoprotein hormone
–Renin, an acid protease
–Vitamin D3
Describe the structure of the stroma
–Thin capsule with 2 layers
•Outer: collagen fibers + fibroblasts
•Inner: myofibroblasts
–Sparse interstitial connective tissue consisting of reticular fibers
What structures pass through the hilum?
: renal pelvis (becomes ureter), nerves, vessels, lymphatics
In the parenchyma, most tissue is functional… What do the epithelial cells that are arranged to form urniferous tubules do?
Drain urine into the renal pelvis
What is the renal pelvis?
–the expansion of the proximal ureter, lies within the renal sinus, and is supported in a bed of fat
What is the renal sinus?
–(aka hilum) is the central cavity that opens medially
______________________…
–Vertical striations that appear to emanate from the medulla
–Contains straight tubules of the nephron and collecting ducts
Medullary rays
_______________:
–The regions between medullar rays that contain the renal corpuscles, convoluted tubules of the nephrons, and the collecting tubules
Cortical labyrinths
______________:
–Each nephron and its collecting tubule
•Uriniferous tubule
What is a kidney lobe?
•each medullary pyramid and one half of each adjacent renal column
_______________:
•central medullary ray and surrounding cortical material (only found in cortex)
–Made up of the collecting duct for a group of nephrons that drain into that duct
Lobule
What are the components of the renal corpuscle?
–Bowman’s capsule (double-layered epithelial cup)
–Glomerulus (10-20 capillary loops)
What are the four components of the tubule system?
–Proximal convoluted and straight tubule
–Thin descending and ascending limbs of the loop of Henle
–Distal straight (thick ascending limb) tubule
–Distal convoluted tubule
What are the two types of nephrons?
Juxtamedullary nephron
Cortical nephron
Juxtamedullary nephrons are very important in creating…
Concentrated urine
What are the cell populations of the renal corpuscle?
- squamous cells of parietal epithelium
- endothelial cells of capillaries
- mesangial cells (and matrix)
- squamous cells of visceral epithelium (podocytes)
__________________
•Double-walled epithelial structure
–Blind end of the uriniferous tubule reflected onto the capillary tuft
–Parietal epithelium – squamous outer wall; continuous with the cuboidal epithelium of the proximal convoluted tubule
–Visceral epithelium – reflected tubular epithelium
•Modified epithelial cells called podocytes
–Bowman’s space (urinary space) - between parietal and visceral layers
•Receives glomerular filtrate
Bowman’s capsule
_____________________:
•Tufts of capillaries that indents into Bowman’s capsule
–Vascular pole – where vessels enter and leave capsule
•Afferent arteriole enters and ramifies into capillaries that recombine to form efferent arteriole
–Urinary pole – where ultrafiltrate exits corpuscle
Glomerulus
How does one differentiate between distal and proximal convoluted tubules?
PC: thick walled, with a fuzzy bordered lumen that may have “stuff” in it
DC: thin walled, clean shaven lumen, not much detritus inside
Nephrin is an important structural and functional component, and mutations in the gene encoding neprhin are associated with congenital nephrotic syndrome – characterized by
massive proteinuria and edema.
_______________________:
–Possesses numerous fenestrations (70-90 nm)
–The endothelial cells possess a large number of aquaporin channels
–Endothelial cells secrete NO and prostaglandins, as well as a sialic acid-rich glycocalyx that adds negative charge to the filtration apparatus
•Endothelium of glomerular capillaries
________________:
–Thick (300-370 nm) basal lamina that is a joint product of the endothelium and podocytesEndothelium of glomerular capillaries
–
–Prominent in sections stained with the periodic acid-Schiff (PAS) procedure
–Consists of Type IV collagen, laminin, nidogen, entactin, proteoglycans, multiadhesive glycoproteins
•Glomerular basement membrane (GBM)
_____________________:
–Contains specialized cells called podocytes (visceral epithelial cells)
–These cells extend processes around the glomerular capillaries and develop numerous secondary processes called pedicels (foot processes)
•Foot processes interdigitate and create filtration slits (40 nm wide), which are covered by an ultrathin filtration slit diaphragm
•Visceral layer of Bowman’s capsule