1st lecture on the histology of urinary system by dr roomi
TRANSCRIPT
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HISTOLOGY
OF URINARY SYSTEM
By
Dr. Mudassar Ali Roomi (MBBS, M.Phil)
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Urinary system
It comprises ofkidneys, ureters,urinary bladder and
urethra.
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Overview
Large, bean-shaped organwith thin C.T capsule.
Retroperitoneal organ.
The concave, medial borderof the kidney is the hilum,which contains three largestructures.
renal artery
renal vein
funnel-shaped renal pelvis
(expanded upper end of theureter)
Pelvis of kidney is subdividedinto large and small cupsreferred to as major andminor calyces.
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Inspection of Verticalhemisection ofkidney
Darker, granular outer zonecortex
lighter, striated inner zonemedulla
A portion of the cortex alsoextends on each side of therenal pyramids to form therenal columns(of Bertin).
Medullary material continuesinto the cortex as medullaryrays.
Medulla consists of numerous(8-18) cone-shaped renalpyramids.
The round apex of eachpyramid extends downward tothe renal pelvis to form therenal papilla.
Pyramid+ associated cortex= alobe of kidney
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Inspection of Vertical hemisection ofkidney
Each renal papilla issurrounded by a funnel-shaped minor calyx,which collects urine from
the papilla.
The minor calyces join inthe renal sinus to form amajor calyx.
Major calyces, in turn,join to form the largerfunnel-shaped renalpelvis
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Parenchyma of kidneys
Parenchyma of kidneyconsists of uriniferoustubules
Uriniferous tubule=nephron + collecting
tubule. Nephron: 30-40 mm long,
responsible for productionof urine. It is derived frommetanephric blastema
Collecting tubule: about20 mm long, conveys urineto the renal pelvis. Derivedfrom ureteric bud.
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Nephrons
2 Million nephrons are present in eachkidney.
Two types of nephrons:
1. Cortical nephron: their renalcorpuscle is located in the cortex ofkidney.
2. Juxtamedullary nephron: theirrenal corpuscle is situated near the
junction of the cortex and medulla.
Possess longer loops ofHenle
Produce a hypertonic
environment in theinterstitium of the kidneymedulla that results in theproduction of concentrated(hypertonic) urine.
Consists of approx 1/7th oftotal nephron population.
Each nephron, in turn, is subdivided intotwo components, a renal corpuscle andrenal tubules.
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Two types of nephrons9
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Parts of nephron
Bowmans capsule
Renal corpuscle=Bowmans capsule+glomerulus
Proximal tubule =PCT+ PST
Intermediate tubule =thin segment
Distal tubule = DST +DCT
Loop of Henle=PST+DST+Thinsegment
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Renal Corpuscle
Renal corpuscle is the Initial segmentof each nephron
150-205 um in diameter
It has a vascular pole and a urinarypole.
It Consists of a tuft of capillaries,called the glomerulus, surrounded bya double layer of epithelial cells,called the glomerular (Bowmans)capsule.
The inner or visceral layer of thecapsule consists of unique and highlymodified branching epithelial cells,
called podocytes. The podocytes are adjacent to and
completely invest the glomerularcapillaries.
The outer or parietal layer of theglomerular capsule consists of simplesquamous epithelium.
Urinary or capsular space ispresent b/w two layers of theBowmans capsule.
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Podocytes
Star shaped highlymodified epithelial cells
Share a common basallamina with endothelial
cells Primary processes
Secondary processes orfoot processes or footpedicles
filtration slits = 5nm thick.These are elongatedspaces b/w the adjacentpedicles.
Slit diaphragm havingpores (each having an
average diameter of 6nm)
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Renal filtration barrier
Structure:
It is composed offenestrated endothelium ofthe glomerular capillaries,
the basal lamina,
and the filtration slits withthe diaphragm betweenpedicles of the podocytes.
Function: formation ofultrafiltrate of blood plasma
in the Bowmans spacewhich contains water, ionsand small molecules butnot the protein moleculesand other large negativelycharged molecules.
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