Lecture 15: Urinary System Flashcards
Kidney structure
Several lobes w/ cortex + medulla. Each lobe = multiple lobules
Hilum
Aka hilar region/hilus. Region where renal artery, vein, and ureter enter the kidney.
Renal sinus
CT space between lobes continuous with the hilus. Contains first major vessel branches and distal ureter branches (aka major/minor calyces)
Medullary pyramid
Structure shaped by epithelia-lined minor calyces. Separates renal sinus from medullae of lobes
Collecting ducts
Series of tubes extending into medulla; extension of calyx lumen. Each drains several nephrons via short tangential collecting tubules.
Ducts of Bellini
Area of collecting ducts opening up to minor calyx.
Medullary ray
Collection of collecting ducts in medulla, defines center of corticle lobule
Nephron
Basic functional unit of kidney. Contains 1 highly folded tubule and a capillary bed.
Glomerulus
Encapsulated capillary bed at distal end of nephron. Located in cortex; tube descends and returns through the medulla.
Juxtaglomerular apparatus (JGA)
Returning DCT comes in close approximation to the originating glomerulus. Set of structures for signaling filtration efficiency
JGA structures
- Macula densa
- Extraglomerular mesangial cells (lacis cells)
- Juxtaglomerular cells
Macula densa (JGA)
Concentrated nuclei of JGA on side of glomerulus. Senses filtrate salt balance at apical surface. Communicates with other JGA cells via paracrine signals.
Extraglomerular mesangial cells
Aka lacis cells. Nearby CT cells sitting between the other structures. Forms cap over glomerulus vascular pole.
Juxtaglomerular cells
First and last sm. muscle cells in a/efferent arterioles to/from glomerular capillaries. Controls GFR by vessel diameter and renin secretion.
Nephric tubule
From distal to prox (rel. to kidney): PCT -> prox. straight -> thick descend. -> thin descend./ascend. -> thick ascend. -> dist. straight -> DCT
Prox./dist. in terms is relative to glomerulus
Nephric tubule morphologies
PCT + thick descend. = large cells w/ apical brush border + basal enfoldings (ion pumps/pore proteins)
Thin tubule = near-squamous
Thick ascend. + DCT = basal strations, smaller cells vs PCT
Collecting duct = (major.) principal cells + (minor.) intercalated cells (more mito.)
Bowman’s capsule
Epithelial-lined space by which nephric tubule encapsulates its associated glomerulus. Has inner visceral and outer parietal epithelia.
Inner visceral epithelium of Bowman’s capsule
Part of glomerulus; podocytes w/ interdigitating pedicels.
Podocytes
Form filtration slits through interdigitating pedicels, spanned by filtration diaphragm
Filtration diaphragm
Spans filtration slits between pedicels, made of transmembrane nephrin
Outer parietal epithelium of Bowman’s capsule
Simple squamous cells
Bowman’s space
Aka urinary space. Space between inner/outer visceral/parietal epithelia of Bowman’s capsule. Filtrate drains into here toward urinary pole.
Intraglomerular mesangial cells
Major element of glomerulus CT space, between podocytes and endothelium. Similar to JGA lacis cells. Phagocytic, contractile, CT matrix production, growth factor release.
Glomerulus
Highly convoluted capillary bed under visceral epithelium and basal CTs (minimal CT space). Forms arterial portal system between afferent/efferent arterioles.
Minimum kidney filtration barrier
- Fenestrated endothelium + basement
- Podocyte basement + filtration slit
Selects substances by size + charge.
Renal corpuscle
Glomerulus + encapsulating nephric tubule (parietal Bowman’s capsule layer)
Vascular pole of renal corpuscle
Afferent/efferent arteriole regions
Urinary pole of renal corpuscle
Origin of PCT
Renal artery branching (afferent)
Enters at hilum -> 5 branches in renal sinus -> segmental -> interlobar -> arcuate (entering lobe, cortico-medullary) -> interlobular -> afferent arterioles
Renal vein branching (efferent and out)
Efferent arterioles -> 2nd cap. bed of portal system (peritubular cap. plexus/vasa recta) -> interlobular veins -> arcuate -> interlobar -> renal vein
All run parallel to homonymous arteries
Peritubular capillary plexus
Capillary blood supply for cortical layers
Vasa recta
Capillary blood supply for medullary layers
Erythropoietin production
Produced by cortical interstitum, controls marrow RBC production. Secretion triggered by low kidney O2
Prostaglandin production
Producing cells found in medullary interstitum
Kidney functional compartments
- Superficial renal cortex
- Medulla
Columns of Bertin
Cortical tissue separating renal pyramids (medullary tissue)
Filtrate path
Cortex -> through pyramids -> renal papilla -> minor calyx -> major calyx -> renal pelvis -> ureter
Blood path
Renal artery -> hilus -> renal pelvis, calyces, sinus -> cortical branching -> renal vein draining
Nephron types
- Cortical (shorter tubule, higher in cortex)
- Juxtamedullary (much longer loop of Henle, important for urine concentration)
Loop of Henle
Thick/thin descending/ascending tubules
Relative tubule permeability
PCT: glucose, ions, H2O, AAs
Thick/thin descend.: H2O
Thick/thin ascend.: Na+, Cl-
DCT: Ca++, Na+, Cl-
Collecting duct: H2O, Ca++, Na+, Cl-
Hormonal system control of tubules
Nephron/collect. duct system has different localized aquaporin channels. Hormones like ADH control aquaporin activation and H2O resorption
Medullary osmolarity
Deeper into the medulla osmolarity increases, up to 1200 mOsm near the renal papilla. Allows more efficient H2O resorption.
Nephric tubule functional roles
PCT: Active H2O/Na+ adjustment, large molecule/nutrient resorption
Thin descend. loop of Henle: Passive H2O diffusion only
Thick ascend./DCT: active ion transport, H2O impermeable
Collecting duct: H2O, Na+ resorption; active HCO3-/H+ acid/base transport by intercalated A+B cells.
Prostaglandins + angiotensin II
Both increase GFR. Prostaglandins increase afferent arteriole diameter, angiotensin increase efferent arteriole diameter
RAAS activation by JGA
- Macula densa cells sense low Na+ in DCT indicating low GFR
- Macula densa signals JG cells to release renin
- Renin increases angiotensin II which increases Na+ resorption
COX-1/-2
Macula densa signals for prostaglandin increase via COX1/2