Urinary SystemUrinary System

Dr. Raeesa Mohammed

Associate professor of Histology

UrinaryUrinary SystemSystem

Includes:Includes: 2 Kidneys.2 Kidneys. 2 Ureters.2 Ureters. Single Urinary Single Urinary

bladder.bladder. Single Urethera.Single Urethera.

KidneyKidney Bean-shapedBean-shaped organ organ Covered by dense Covered by dense

irregular collagenous irregular collagenous connective tissue connective tissue capsulecapsule

Has a Has a lateral convexlateral convex borderborder & a & a medial medial concaveconcave border border with with hilumhilum, where the:, where the: Arteries enterArteries enter Ureter & veins leave Ureter & veins leave

the kidneythe kidney

Kidney cont’dKidney cont’d

Each kidney is divided into:Each kidney is divided into:• OuterOuter CortexCortex• Inner Inner Medulla: Medulla: which is which is

composed of composed of 10-12 renal 10-12 renal pyramidspyramids

• The The base of pyramidbase of pyramid is is toward the cortex, and the toward the cortex, and the apex apex (renal papilla) toward (renal papilla) toward the hilumthe hilum

• Renal pyramids are Renal pyramids are separated by cortical tissue separated by cortical tissue called renal called renal columns of Bertincolumns of Bertin

P

Kidney cont’dKidney cont’d The apex of each pyramid The apex of each pyramid

is perforated by 15-20 is perforated by 15-20 large large collecting ductscollecting ducts ((papillary ducts of Bellini) papillary ducts of Bellini) that open into thethat open into the minor minor calyxcalyx

The The minor calyx,minor calyx, surrounds the surrounds the apex of apex of each pyramid each pyramid

3 or 4 minor calyces join 3 or 4 minor calyces join to form a to form a major calyx major calyx

The major calyces, 3-4 in The major calyces, 3-4 in number open into the number open into the renal pelvisrenal pelvis..

NephronNephron It is composed of :It is composed of :

• Renal corpuscleRenal corpuscle• Proximal tubuleProximal tubule• Loop of HenleLoop of Henle• Distal tubuleDistal tubule

Renal CorpuscleRenal CorpuscleComposed of:Composed of: Glomerulus:Glomerulus:

Tuft of fenestrated capillaries. Tuft of fenestrated capillaries. Afferent & efferent arterioles supply Afferent & efferent arterioles supply & drain the glomerulus at the & drain the glomerulus at the vascular polevascular pole

Bowman’s capsule:Bowman’s capsule:

Encloses the glomerulus. It has two Encloses the glomerulus. It has two layers:layers:• Parietal layerParietal layer formed by simple formed by simple

squamous epithelium.squamous epithelium.• Visceral layerVisceral layer formed by formed by

podocytespodocytes

Renal Corpuscle cont’dRenal Corpuscle cont’d Bowman’s (urinary or Bowman’s (urinary or

glomerular) spaceglomerular) space::

Space between the parietal Space between the parietal and visceral layers, drains and visceral layers, drains at the urinary pole into the at the urinary pole into the proximal convoluted proximal convoluted tubuletubule

Interstitial tissue is Interstitial tissue is composed of composed of mesengium mesengium (mesangial cells & the (mesangial cells & the extracellular matrix extracellular matrix manufactured by them)manufactured by them)

PodocytesPodocytes Are modified cells with Are modified cells with

multiple processes and multiple processes and pediclespedicles

Form the Form the visceral layervisceral layer of of Bowman’s capsuleBowman’s capsule

Their processes and pedicles Their processes and pedicles surround the glomerular surround the glomerular capillaries. capillaries.

The spaces between adjacent The spaces between adjacent pedicles, called the pedicles, called the filtration filtration slitsslits are covered by are covered by slit slit diaphragmsdiaphragms..

Form a thick Form a thick basal laminabasal lamina that is interposed between that is interposed between the podocytes and the the podocytes and the endothelial cellsendothelial cells

Glomerular Filtration BarrierGlomerular Filtration Barrier

The barrierThe barrier is formed is formed by:by: • the the podocytepodocyte layer layer

of Bowman's of Bowman's capsule capsule

• the the fenestrated fenestrated endotheliumendothelium of the of the glomerulus glomerulus

• a thick a thick basement basement membranemembrane shared shared between the two between the two cellular componentscellular components

GFB

Collecting TubuleCollecting TubuleIs composed of:Is composed of: Proximal convoluted tubuleProximal convoluted tubule: : Loop of HenleLoop of Henle: :

It has 3 regions:It has 3 regions:• Descending thin limb.Descending thin limb.• Henle’s loopHenle’s loop• Ascending thin limbAscending thin limb

Distal convoluted tubuleDistal convoluted tubule::

Proximal tubule:Proximal tubule:

It is composed of It is composed of simple cuboidal simple cuboidal epitheliumepithelium with: with:• Extensive Extensive striated striated

or brush borderor brush border

Thin limb of Henle’s Loop:Thin limb of Henle’s Loop:

It is composed of It is composed of simple simple squamous epitheliumsquamous epithelium

Distal TubuleDistal Tubule It is composed ofIt is composed of simple simple

cuboidal epithelium.cuboidal epithelium.

It has 3 components:It has 3 components:• The macula densaThe macula densa of distal tubule. of distal tubule.• Juxtaglomerular cellsJuxtaglomerular cells of glomerular of glomerular

arterioles (modified smooth muscle of arterioles (modified smooth muscle of tunica media); they secrete renin, tunica media); they secrete renin, angiotensin-converting enzyme and angiotensin-converting enzyme and angiotensin.angiotensin.

• The extraglomerular The extraglomerular mesangial cellsmesangial cells called called lacis cellslacis cells..

Juxtaglomerular ApparatusJuxtaglomerular Apparatus

Collecting DuctCollecting Duct Several distal convoluted Several distal convoluted

tubules join each tubules join each collecting collecting ductduct

Are composed of Are composed of simple simple cuboidal epithelium.cuboidal epithelium.

Renal medulla contains:Renal medulla contains:

Collecting tubules (ducts)Collecting tubules (ducts)

Henle’s loop Henle’s loop

Peritubular blood vessels (vasa recta)Peritubular blood vessels (vasa recta)

Renal interstitiumRenal interstitium

UreterUreterIs composed of:Is composed of: Mucosa:Mucosa: formed of formed of

transitional epithelium & transitional epithelium & lamina propria.lamina propria.

MuscularisMuscularis (muscular (muscular coat): is formed of 2 coat): is formed of 2 layers of smooth muscle:layers of smooth muscle:• Inner longitudinalInner longitudinal• Outer circularOuter circular

Adventitia:Adventitia: fibrous fibrous connective tissue coveringconnective tissue covering

Urinary bladderUrinary bladder It has the same structure It has the same structure

as the ureter, except: as the ureter, except:

a. Thea. The muscularis muscularis has 3 has 3 layers of smooth layers of smooth muscle, muscle, inner inner longitudinal, longitudinal, middlemiddle circular and circular and outerouter longitudinal.longitudinal.

Serosa/adventitiaSerosa/adventitia is is outer coveringouter covering

Practical SlidesPractical Slides

Kidney CortexKidney Cortex

Kidney MedullaKidney Medulla

Urinary BladderUrinary Bladder

Urinary BladderUrinary Bladder