Histology of Histology of Kidney,Ureter and Kidney,Ureter and Urinary BladderUrinary Bladder

ObjectivesObjectives

At the end of the session the student should be able toAt the end of the session the student should be able to Describe the parts of the nephronDescribe the parts of the nephron Describe and identify the renal corpuscle and its Describe and identify the renal corpuscle and its

components i e ; glomerulus and cells,Bowman’s components i e ; glomerulus and cells,Bowman’s capsule,etc.capsule,etc.

Identify and list the structures that form filtration Identify and list the structures that form filtration membranemembrane

Describe and identify the juxtaglomerular apparatus Describe and identify the juxtaglomerular apparatus and its components i e; JG cells,Macula densa,Lacis and its components i e; JG cells,Macula densa,Lacis cellscells

Identify the parts of the renal tubule i e;proximal and Identify the parts of the renal tubule i e;proximal and distal collecting tubules, loop of Henle and collecting distal collecting tubules, loop of Henle and collecting tubules tubules

Correlate the structure and function of different parts Correlate the structure and function of different parts of nephron and JG apparatusof nephron and JG apparatus

Section of Right KidneySection of Right Kidney

Structure/OrganizationStructure/Organization CortexCortex-paler outer region (Gross -paler outer region (Gross

app)app) MedullaMedulla-darker inner region-darker inner region Renal pyramidsRenal pyramids 8-18 conical 8-18 conical

masses in the medulla; masses in the medulla; base of pyramids are at the base of pyramids are at the

corticomedullary junction and the corticomedullary junction and the apex points towards the apex points towards the pelvis pelvis forms the forms the papillapapilla

Small outlets in the papillae urine Small outlets in the papillae urine drains into the expanded cup-drains into the expanded cup-shaped out pouchings of the shaped out pouchings of the pelvis called pelvis called minor calycesminor calyces and and then into then into 1-2 major calyces1-2 major calyces

NEPHRONNEPHRON NephronNephron is the functional unit is the functional unit

of the Kidney(.3-1 of the Kidney(.3-1 million/kidney)million/kidney)

Avg length-4cm; total length Avg length-4cm; total length for both kid 50km/30milesfor both kid 50km/30miles

2 components2 components (i)(i)Renal corpuscleRenal corpuscle ( for ( for

filtration of plasma)filtration of plasma)– Bowman’s capsuleBowman’s capsule– Glomerulus-Glomerulus-

(ii)(ii)Renal tubuleRenal tubule- uriniferous - uriniferous tubules(for selective tubules(for selective reabsorption of water, reabsorption of water, inorganic ions, other inorganic ions, other molecules from the molecules from the glomerular filtrate)glomerular filtrate)– Proximal convoluted Proximal convoluted

tubule (PCT)tubule (PCT)– Loop of Henle Loop of Henle

(descending&ascending (descending&ascending limbs)limbs)

– Distal convoluted tubule Distal convoluted tubule (DCT)(DCT)

– Collecting tubuleCollecting tubule

Histological Histological Section of Section of

KidneyKidneyCortex composed of most of the origins of the nephron.The medullary rays actually in the cortex contains the straight parts of the proximal and distal convoluted tubules and the collecting ducts which extend into the medulla

Renal CortexRenal Cortex Renal corpuscles Renal corpuscles

appear as dense appear as dense rounded structures rounded structures surrounded by a surrounded by a narrow Bowman’s narrow Bowman’s space (red arrows)space (red arrows)

In between the In between the corpuscles are mainly corpuscles are mainly proximal convoluted proximal convoluted tubules and a small tubules and a small number of distal number of distal convoluted tubules & convoluted tubules & collecting ducts(yellow collecting ducts(yellow arrows)arrows)

Renal Renal CorpuscleCorpuscle I.Bowman’s capsule I.Bowman’s capsule

– single layer of flattened single layer of flattened cells resting on basement cells resting on basement membrane (parietal layer)membrane (parietal layer)

– forms a distended,blind forms a distended,blind end of the renal tubuleend of the renal tubule

II.GlomerulusII.Glomerulus– Network of anastamosing Network of anastamosing

capillaries invaginating capillaries invaginating the Bowman’s Capsulethe Bowman’s Capsule

– Invested by a layer of Invested by a layer of epithelial cells called epithelial cells called podocytes= visceral layer podocytes= visceral layer of Bowman’s capsuleof Bowman’s capsule

– Bowman’s space-Bowman’s space-continuous with the renal continuous with the renal tubuletubule

Type of cells in Type of cells in GlomerulusGlomerulus

Cells of the glomerulusCells of the glomerulus– 1.Endothelial cell (red arrow)1.Endothelial cell (red arrow)– 2.Podocytes /visceral layer 2.Podocytes /visceral layer

(yellow arrow)(yellow arrow)– 3.Mesangial cells (blue 3.Mesangial cells (blue

arrow)-are specialise smooth arrow)-are specialise smooth muscle cells,that have muscle cells,that have contractile property and can contractile property and can control the blood flow control the blood flow through the glomerulusthrough the glomerulus

– Produces some cytokines Produces some cytokines when stimulated and are when stimulated and are capable of phagocytosiscapable of phagocytosis

Cells of parietal layer of Cells of parietal layer of Bowman’s capsule (green)Bowman’s capsule (green)

Glomerular Filter/Filtration Glomerular Filter/Filtration membranemembrane

Blood passes through the glomeruli to Blood passes through the glomeruli to be filtered:( glomerular filtrate) passes be filtered:( glomerular filtrate) passes through 3 layers-selective filtration through 3 layers-selective filtration process to enter the tubular systemprocess to enter the tubular system

Capillary endotheliumCapillary endothelium with large fenestrations- luminal with large fenestrations- luminal cell coat-negative electric chargecell coat-negative electric charge

Glomerular basement Glomerular basement membranemembrane (type IV collagen , (type IV collagen , glycoprotein, proteoglycan )-glycoprotein, proteoglycan )-thick-3 layersthick-3 layers

PodocytesPodocytes--cytoplasmic cytoplasmic extensions-primary & secondary extensions-primary & secondary processes-processes-filtration slitsfiltration slits between between secondary processes secondary processes

EM picture of GM cells & EM picture of GM cells & basement membranebasement membrane

Filtration Membrane

Blood Supply of KidneyBlood Supply of Kidney

Renal arteryRenal artery—branch of —branch of Abdominal aorta divides Abdominal aorta divides at the hilum into at the hilum into segmental branchessegmental branches

Lobar arteriesLobar arteriesInterlobar arteriesInterlobar arteries

ascend to ascend to corticomedullary junctioncorticomedullary junction

Arcuate arteriesArcuate arteries Interlobular arteriesInterlobular arteries

(cortical radial) arise (cortical radial) arise from arcuate arteries from arcuate arteries

Afferent and Efferent Afferent and Efferent arteriolesarterioles

Afferent arteriolesAfferent arterioles of the of the glomerulus are branches of glomerulus are branches of interlobular arteries—give rise interlobular arteries—give rise to to Capillaries of glomeruli…Capillaries of glomeruli…

Efferent arteriolesEfferent arterioles---- form ---- form peritubular capillary bed peritubular capillary bed ….vasa recta….vasa recta microcirculation microcirculation of medulla & cortexof medulla & cortex

——arcuate & interlobular veins----arcuate & interlobular veins----renal vein-inferior vena cava—renal vein-inferior vena cava—right atrium of heartright atrium of heart

Microcirculation of the Microcirculation of the KidneysKidneys

Blood supply of KidneysBlood supply of Kidneys

Diameter (lumen) of afferent arteriole is larger than efferent arteriole

An arrangement which maintains

pressure within glomerular capillaries

necessary for the

blood plasma to be filtered

into Bowman’s space 

 

Juxtaglomerular Juxtaglomerular ApparatusApparatus

3 Components3 Components

Macula densa (DCT)Macula densa (DCT)Juxtaglomerular Juxtaglomerular

cellscells (smooth muscle (smooth muscle fibers from afferent fibers from afferent arteriole) +arteriole) +

Lacis cellsLacis cells (extraglomerular (extraglomerular mesangial cells)mesangial cells)

= = Juxtaglomerular Juxtaglomerular Apparatus (JGA)Apparatus (JGA)

JUXTAGLOMERULAR JUXTAGLOMERULAR APPARATUSAPPARATUS

(1) (1) The juxtaglomerular cells are The juxtaglomerular cells are specialised specialised smooth muscle cells of the wall of afferent smooth muscle cells of the wall of afferent arterioles arterioles produces Renin produces Renin ((Regulation of Blood Regulation of Blood Pressure via Renin-angiotensin-aldosterone Pressure via Renin-angiotensin-aldosterone mechanismmechanism ) )

(2) a group of extraglomerular mesangial cells (2) a group of extraglomerular mesangial cells ,between the efferent and afferent ,between the efferent and afferent arterioles at the vascular pole of the renal arterioles at the vascular pole of the renal corpuscle,corpuscle, (Lacis)cells (Lacis)cells produces erythropoitein produces erythropoitein stimulates red cell productionstimulates red cell production

(3) the macula densa of the distal convoluted (3) the macula densa of the distal convoluted tubuletubule.. small& tall with prominent nuclei, thin small& tall with prominent nuclei, thin basement membrane sensitive to concentration of basement membrane sensitive to concentration of sodium (osmoreceptor) sodium (osmoreceptor) in the fluid in the distal in the fluid in the distal convoluted tubules convoluted tubules

Juxtaglomerular ApparatusJuxtaglomerular Apparatus

Histology of JG ApparatusHistology of JG Apparatus

Macula densa

Glomerulus & Nephron Glomerulus & Nephron DCT,PCT( H&E)DCT,PCT( H&E)

PCT

DCT

Proximal and Distal Proximal and Distal convoluted tubulesconvoluted tubules

PCT-longest part –numerous in PCT-longest part –numerous in CortexCortex– Lined by simple tall cuboidal Lined by simple tall cuboidal

epith,with tall microvilli forming epith,with tall microvilli forming brush border almost fills the brush border almost fills the lumenlumen

– Prominent basement membraneProminent basement membrane– Stains intensely –d/t organellesStains intensely –d/t organelles

DCT-less numerousDCT-less numerous– absence of brush borderabsence of brush border– Larger & distinct lumenLarger & distinct lumen– More nuclei /c.s cells are smallerMore nuclei /c.s cells are smaller– Less affinity for cytoplasmic stainsLess affinity for cytoplasmic stains

Glomerulus ,PCT&DCT (X Glomerulus ,PCT&DCT (X 40)40)

Urinary SystemUrinary System

URETER URETER (H&E)(H&E)

Star-shaped lumen

Lined by transitional epithelium with thick lamina propria many elastic fibers

2 layers of thick smooth muscle wall;inner longitudinal outer circular

May have 3 layers at distal end

Adventitia-loose connective tissue

UROEPITHELIUMUROEPITHELIUMStretchable and urine resistant 5-6 layersUpper layer of cells-umbrella/dome shapedMiddle layer –polygonalBasal layer-cuboidal

Urinary bladder H & EUrinary bladder H & E

3 layers of smooth muscle wall-detrusor muscles

Thank You!Thank You!Please study the slides Please study the slides under the microscopeunder the microscope