HISTOLOGY OF URINARY SYSTEM

Histology DepartementFK USU

August 2009

Urinary SystemUrinary System: Kidney, urinary passages

Passages include:

Calyces

Renal Pelvis

Ureter

Accessory parts include:

Urinary bladder

Urethra

KidneyKidney:

Flattened, bean-shaped ~4.5 inches long

CapsuleCapsule: thin, fibrous, weakly attached (mostly collagenous fibers)

Interstitial C.T. – scant; entirely reticular tissue

Hilus: slit-like orifice – opens into expanded renal sinusrenal sinus, a flattened cavity

Renal sinus filled with: renal pelvis (expanded ureter); fat; C.T.; blood vessels; nerves

Kidney cross-section

Renal Pelvis:Renal Pelvis:

Subdivided into 2 or 3 major calyces

Major calyces (1)(1) subdivide into 7 – 10 minor calyces (2)(2)

Minor calyces fit over a renal papilla (3)(3)

11

22

33

Kidney interior: largely parenchyma

Parenchyma: many long, tortuous secretory canals (nephronsnephrons)

Excretory ducts of nephrons discharge into minor calyces

Nephron + excretory duct = uriniferous tubuleuriniferous tubule

Parenchyma divisible into CortexCortex & MedullaMedulla

Medulla (gray when fresh) composed of 10 – 15 renal renal pyramidspyramids

2 to 3 pyramids fuse: end in one papilla

i.e., 6 to 14 papillae / kidney (human)

Pyramids appear striate (tubules are straight)

Cortex ( brownish in life)

Inner border irregular

Over base of pyramid; between pyramids (Renal Renal columns of Bertincolumns of Bertin)

Nephron (Uriniferous Tubule) – Kidney is a compound gland

Uriniferous tubule composed of two parts:

Nephron & Collecting tubule

Nephron:The physiological unit of the kidney used for filtration of blood and

reabsorption and secretion of materials

Unbranched; 35 mm. long

Includes straight portions & convoluted portions

1,300,000 tubules each kidney

Collecting tubules

part of a branched, tree-like system of excretory ducts

tubules are straight

Length: 21 mm. (each)

Nephrons

Parts of the Uriniferous TubuleParts of the Uriniferous Tubule

Consecutive portions differ structurally & functionally

(proximal means near the glomerulus & distal means nearer the papilla)

The parts starting from the proximal end, taken in order:

NephronNephron

Glomerular capsule of Bowman

Proximal Convoluted Tubule (including the straight portion = thick, descending segment of Henle’s loop)

Thin segment of Henle’s loop

Thick, ascending segment of Henle’s loop

Distal Convoluted Tubule

The Excretory (= duct) PortionThe Excretory (= duct) Portion

Arched Collecting Tubule (= junctional tubule)

Straight Collecting Tubule

Papillary Duct of Bellini

Uriniferous tubule segment locations are constant (recognizable regions)

3 primary topographical regions in kidney

Cortical labyrinth

Cortical ray

Medulla

In each region, 3 different tubular segments easily recognized (marked with asterisk)

Cortical LabyrinthCortical Labyrinth

Glomerular capsule of Bowman*

Proximal Convoluted Tubule*

Thick, ascending segment of Henle’s loop

Distal Convoluted Tubule*

Arched Collecting Duct

Cortical RayCortical Ray

Straight portion of Proximal Convoluted Tubule*

Thick Ascending Segment of Henle’s Loop*

Straight Collecting Tubule*

MedullaMedulla

Straight portion of Proximal Tubule (thick, descending segment of Henle’s Loop)

Thin segment of Henle’s Loop*

Thick, ascending segment of Henle’s Loop*

Straight Collecting Tubule; Papillary Duct of Bellini*

Tubule CharacteristicsTubule Characteristics

Epithelium is specific to each segment (tubule)

Epithelium of excretory ducts is of one structural type

All rest on a basement membrane

Renal (Malpighian) CorpuscleRenal (Malpighian) Corpuscle

Spheroidal (0.2 mm. wide); Vascular glomerulus; Double-walled cup (nearly surrounds glomerulus)

GlomerulusGlomerulus

= rete mirabile

afferent arteriole enters, forms many loops (smaller bore)

efferent arteriole formed as loops unite; leaves glomerulus

afferent & efferent arterioles enter & leave together at vascular vascular polepole

Renal Corpuscle

RENAL CORPUSCLE

Endothelium thinTunica media of afferent arteriole modified near entry point

Smooth muscle cells large, pale staining, lack myofibrils= a myo-epitheliod cuff, the juxtaglomerular juxtaglomerular cellcellJuxtaglomerular cell closely associated with macula macula densadensa of ascending limb

Juxtaglomerular apparatus:•Consists of JG cell, macula densa & mesangial cell (Lacis cell or Polkissen cell)•Functions in the regulation of blood pressure •Juxtaglomerular cells – secrete renin which activates angiotensin II (a vasoconstrictor)

Juxtaglomerular Apparatus

Glomerular CapsuleGlomerular Capsule

Bowman’s Capsule – an epithelial cup

Parietal (external) & visceral (internal) layer

both are simple squamous epithelium

cell boundaries; basement membrane - clear

Layers are continuous

Layers enclose space

Parietal layer

Visceral layer

Parietal & Visceral layers continuous

Glomerulus & Sel Podosit

Renal Corpuscle and the Filtration Membrane

Neck Neck – very short segment of tubule!

Parietal layer opens into neck (urinary poleurinary pole)

Rapid epithelial change: flat capsular cells rise to cuboidal then to low columnar

Proximal Convoluted TubuleProximal Convoluted Tubule – longest (14 mm.), broadest (60 μ) tubule segment

Most of bulk of pars convoluta (cortex)

Remarkably contorted tubule!

Location: Immediate vicinity of renal corpuscle

Enters medullary (cortical) ray in ray to medulla

Straightens in ray (= straight portion of proximal tubule or thick descending segment of Henle’s loop)

Cells are low columnar

Cell limits indistinct

Nuclei: large, pale, spheroidal – 3 to 4 show in transverse section

Free surface: brush border – resorpitive function

Thin Segment of Henle’s LoopThin Segment of Henle’s Loop

Location: boundary zone of medulla

Sharp transition from thick proximal tubule: reduced to 2 to 10 mm. long & 15 μ wide

Resembles a capillary but is larger & thicker walled

Short or long and recurved

IfIf this part extends past apex of loop: makes sharp hair-pin bend

Interlocking cells – squamous with pale cytoplasm

Brush border is absent

Microvilli present (can see on EM)

Nuclei flat, bulge into lumen

Collecting Duct

Thick, descending limb

Thin Segment

Apex of Henle’s Loop:Apex of Henle’s Loop:

A very sharp bend

If loop is deep into medulla a long thin limb makes loop

If loop is high in medulla the thick ascending segment is involved

Thick Ascending Segment of Henle’s Loop:Thick Ascending Segment of Henle’s Loop:

Straight, radial tubule – 9 mm. long & 30μ wide

Abrupt transition from thin limb into cuboidal epithelium

Cells – more deeply acidophilic than those of thin limb

Resemble cells of distal convoluted tubule

= straight portion of distal tubule

Distal Convoluted Tubule

►Enters a ray – ascends passing into labyrinth

►Enclose to its glomerulus

►In contact wit juxtaglomerular cell : macula densa (cells taller, crowded, mass is elliptical)

Comparison of the tubule

Renal Pelvis – Ureter – Urinary BladderRenal Pelvis – Ureter – Urinary Bladder

Minor calyx caps each renal pyramid (7 to 10)

Calyx is double walled cup

Inner wall continuous with papillary ducts

Several minor calyces open into each major calyx

Major calyces open into renal pelvis

Ureter connects renal pelvis to urinary bladder

Mucosa of these elements: Transitional epitheliumTransitional epithelium

Calyx – 2 to 3 layers of cells

Ureter – 4 to 5 layers of cells

Urinary Bladder – 6 to 8 layers of cells

Basement membrane not obvious

Lamina PropriaLamina Propria – thin fibers, mostly collagenous

No papillae

Diffuse lymphoid tissue & occasional solitary lymph nodules

SubmucosaSubmucosa – vague or absent – deeper layers are looser, more elastic

laxity permits folding

Ureter has ~5 major and minor folds (stellate lumen)

Relaxed bladder – mucosa thrown into thick, irregular folds

MuscularisMuscularis – 2 to 3 layers loosely arranged layer (not compact)

Smooth muscle – discrete bundles

Inner layer – longitudinal

Next layer – circular

Bladder have 3rd layer (outermost) – longitudinal

Pelvis & calyces – muscle is thin, largely circular (forms sphincter around each papilla)

AdventitiaAdventitia – fibrous external tunic; blends with adjacent C.T.

Urethra – FemaleUrethra – Female

♀ ♀ Urethra = short duct, 1.5 inches long

From urinary bladder to outlet (in vestibule)

MucosaMucosa:

Epithelium Near bladder = Transitional

Middle portion (most of urethra): Pseudostratified to stratified columnar

Near outlet = stratified squamous

Nest of mucous cells can occur

Urethral glands (more numerous in males)

Basement membrane: inconspicuous

Lamina PropriaLamina Propria: no papillae; is folded longitudinally irregular lumen, crescent shaped

SubmucosaSubmucosa

Deep stratum rich in elastic fibers & veins (?)

Layer may really be part of Lamina Propria

Veins plexus of prominent, thin-walled vessels

Spongy, semi-erectile tissue

MuscularisMuscularis

Thick coat of smooth muscle

Inner layer: longitudinal

Outer layer: circular; forms internal involuntarysphincter near bladder

Skeletal muscle exterior to smooth muscle = voluntary muscle “Constrictor Urethrae”

AdventitiaAdventitia

indefinite coat (fuses to surrounding structures)

Dorsally – merges with fibrous coat of vagina

Other areas – fuses to constrictor urethrae muscle

Urethra – MaleUrethra – Male

Tube ~8 inches long; stem only homologous to female urethra

Three regional segments:

Prostatic urethraProstatic urethra: next to bladder (1.5 inches long)

elevated urethral crest (posterior wall)

prostatic utricle & paired ejaculatory duct open on crest

surrounded by prostate gland

Membranous urethraMembranous urethra: prostate to penis (0.5 inches long)

surrounded by muscles; components of urogenital diaphragm

Cavernous urethraCavernous urethra: 6 inches through penis

MucosaMucosa

Epithelium varies regionally

Transitional near bladder

Most of urethra is stratified columnar or pseudostratified

Near meatus: stratified squamous

Epithelium on thin basement membrane

Lamina Propria: resembles female L.P.

branching mucous tubules (= Urethral Glands Urethral Glands of Littrof Littréé)

ducts with intra-epithelial nest of mucous cells – open into recesses of lumen

SubmucosaSubmucosa

Not distinguishable as such

Like ♀ -- deeper layer with many veins

MuscularisMuscularis

largely confined to prostatic & membranous segments

inner layer (smooth muscle) – longitudinal

outer layer (smooth muscle) – circular

best developed at bladder neck – forms sphincter

cavernous segment lacks smooth muscle layers

longitudinal muscle – in true erectile tissue

Adventitia

No typical adventitia present

Prostatic urethra – surrounded by prostate gland

Membranous urethra – encircled by sphincter of skeletal muscle

Cavernous urethra surrounded by erectile tissue & dense outer sheath (neither belong to urethra)

Figure 26.20a

The Histology of the Organs that Collect The Histology of the Organs that Collect and Transport Urineand Transport Urine

REFERENSI

►Basic Histology : Junqueira ed.11►Human Histology ►Biology of Cell and Introduction to Pathology