General Anatomy of General Anatomy of Urinary SystemUrinary System

URINARY SYSTEM ORGANSURINARY SYSTEM ORGANS

Kidneys (2)Kidneys (2) Ureters (2)Ureters (2) Urinary bladderUrinary bladder UrethraUrethra

KIDNEY FUNCTIONSKIDNEY FUNCTIONS

Control blood volume and compositionControl blood volume and composition

KIDNEY FUNCTIONSKIDNEY FUNCTIONS

Filter blood plasma, eliminate wastesFilter blood plasma, eliminate wastes Regulate blood volume, pressureRegulate blood volume, pressure Regulate fluid osmolarityRegulate fluid osmolarity Secrete reninSecrete renin Secrete erythropoietin (EPO)Secrete erythropoietin (EPO) Regulate PRegulate PCOCO22, Acid-Base balance, Acid-Base balance Synthesize calcitriol (Vitamin D)Synthesize calcitriol (Vitamin D) Detoxify free radicals, drugsDetoxify free radicals, drugs GluconeogenesisGluconeogenesis

EXCRETIONEXCRETION

Removal of wastesRemoval of wastes Respiratory systemRespiratory system

COCO22, water, water Integumentary systemIntegumentary system

Water, salts, lactic acid, ureaWater, salts, lactic acid, urea Digestive systemDigestive system

Water, salts, COWater, salts, CO22, lipids, bile pigments, cholesterol, , lipids, bile pigments, cholesterol, etc.etc.

Urinary systemUrinary system Metabolic wastes, toxins, drugs, hormones, salts, HMetabolic wastes, toxins, drugs, hormones, salts, H++, ,

waterwater

KIDNEY ANATOMYKIDNEY ANATOMY

Protected by three connective tissue Protected by three connective tissue layerslayers

Renal fasciaRenal fascia Attaches to abdominal wallAttaches to abdominal wall

Adipose capsuleAdipose capsule Fat cushioning kidneyFat cushioning kidney

Renal capsuleRenal capsule Fibrous sacFibrous sac Protects from trauma and infectionProtects from trauma and infection

KIDNEY ANATOMYKIDNEY ANATOMY

Gross anatomyGross anatomy Renal sinusRenal sinus Renal parenchymaRenal parenchyma

KIDNEY ANATOMYKIDNEY ANATOMY

Renal sinusRenal sinus Surrounded by renal parenchymaSurrounded by renal parenchyma Contains blood & lymph vessels, nerves, Contains blood & lymph vessels, nerves,

urine-collecting structuresurine-collecting structures

KIDNEY ANATOMYKIDNEY ANATOMY

Renal parenchymaRenal parenchyma Glandular tissueGlandular tissue Forms urineForms urine Two zonesTwo zones

Outer cortexOuter cortex Inner medullaInner medulla

KIDNEY ANATOMYKIDNEY ANATOMY

Renal parenchymaRenal parenchyma Renal pyramidsRenal pyramids

Extensions of cortex (renal columns) divide medulla Extensions of cortex (renal columns) divide medulla into 6 – 10 into 6 – 10 renal pyramidsrenal pyramids

Pyramid + overlying cortex = LobePyramid + overlying cortex = Lobe Point of pyramid = Papilla Point of pyramid = Papilla Papilla nested in cup (minor calyx)Papilla nested in cup (minor calyx) 2 – 3 minor calices 2 – 3 minor calices Major calyx Major calyx 2 – 3 major calices 2 – 3 major calices Renal pelvis Renal pelvis Renal pelvis Renal pelvis Ureter Ureter

KIDNEY ANATOMY: NEPHRONSKIDNEY ANATOMY: NEPHRONS

NephronsNephrons Functional units of kidneyFunctional units of kidney ~1.2 million per kidney~1.2 million per kidney Three main partsThree main parts

Blood vesselsBlood vessels Renal corpuscleRenal corpuscle Renal tubuleRenal tubule

NEPHRONSNEPHRONS

Blood vessels servicing kidneyBlood vessels servicing kidney Supplied by renal arterySupplied by renal artery

~21% or cardiac output~21% or cardiac output (Mass in only ~ 0.4%)(Mass in only ~ 0.4%) Afferent arteriolesAfferent arterioles Capillary cluster (glomerulus)Capillary cluster (glomerulus)

NEPHRONSNEPHRONS

Blood vessels servicing kidneyBlood vessels servicing kidney GlomerulusGlomerulus

Fenestrated capillariesFenestrated capillaries Capillary filtration in glomerulus initiates urine Capillary filtration in glomerulus initiates urine

productionproduction Filtrate lacks cells & proteinsFiltrate lacks cells & proteins Drained by efferent arterioleDrained by efferent arteriole Peritubular capillariesPeritubular capillaries Renal veinRenal vein

NEPHRONSNEPHRONS

Renal corpuscleRenal corpuscle Glomerulus plus capsuleGlomerulus plus capsule Glomerulus enclosed in two-layered glomerular Glomerulus enclosed in two-layered glomerular

capsulecapsule ““Bowman’s capsule”Bowman’s capsule”

Fluid filters from glomerular capillariesFluid filters from glomerular capillaries ““Glomerular filtrate”Glomerular filtrate”

Fluid collects in capsular spaceFluid collects in capsular space Fluid flows into renal tubuleFluid flows into renal tubule

NEPHRONSNEPHRONS

Renal tubuleRenal tubule Leads from glomerular capsuleLeads from glomerular capsule Ends at tip of medullary pyramidEnds at tip of medullary pyramid ~3 cm long~3 cm long Four major regionsFour major regions

Proximal convoluted tubuleProximal convoluted tubule Nephron loopNephron loop Distal convoluted tubuleDistal convoluted tubule Collecting ductCollecting duct

NEPHRONSNEPHRONS

Renal tubuleRenal tubule Proximal convoluted tubule (PCT)Proximal convoluted tubule (PCT) Arises from glomerular capsuleArises from glomerular capsule Longest, most coiled regionLongest, most coiled region Prominent microvilliProminent microvilli

Function in absorptionFunction in absorption Much contact with peritubular capillariesMuch contact with peritubular capillaries

NEPHRONSNEPHRONS

Renal tubuleRenal tubule Nephron loop (“Loop of Henle”)Nephron loop (“Loop of Henle”) ““U” – shaped, distal to PCTU” – shaped, distal to PCT Descending and ascending limbsDescending and ascending limbs Thick segmentsThick segments

Active transport of saltsActive transport of salts High metabolism, many mitochondriaHigh metabolism, many mitochondria

Thin segmentsThin segments Permeable to waterPermeable to water Low metabolism Low metabolism

NEPHRONSNEPHRONS

Renal tubuleRenal tubule Distal convoluted tubule (DCT)Distal convoluted tubule (DCT) Coiled, distal to nephron loopCoiled, distal to nephron loop Shorter than PCTShorter than PCT Less coiled than PCTLess coiled than PCT Very few microvilliVery few microvilli Contacts afferent and efferent arterioles Contacts afferent and efferent arterioles

(regulation imparted)(regulation imparted) Contact with peritubular capillariesContact with peritubular capillaries

NEPHRONSNEPHRONS

Renal tubulesRenal tubules Collecting ductCollecting duct DCTs of several nephrons empty into a DCTs of several nephrons empty into a

collecting ductcollecting duct Passes into medullaPasses into medulla Several merge into papillary duct (~30 per Several merge into papillary duct (~30 per

papilla)papilla) Drain into minor calyxDrain into minor calyx

URINE FORMATIONURINE FORMATION

OverviewOverview Blood plasma Blood plasma Urine Urine Four stepsFour steps

Glomerular filtrationGlomerular filtration Tubular reabsorptionTubular reabsorption Tubular secretionTubular secretion Water conservationWater conservation

URINE STORAGEURINE STORAGE

UretersUreters Carry urine from kidneys to urinary bladder Carry urine from kidneys to urinary bladder

via peristalsisvia peristalsis Rhythmic contraction of smooth muscleRhythmic contraction of smooth muscle

Enter bladder from belowEnter bladder from below Pressure from full bladder compresses Pressure from full bladder compresses

ureters and prevents backflowureters and prevents backflow

URINE STORAGEURINE STORAGE

UretersUreters Small diameterSmall diameter Easily obstructed or injured by kidney Easily obstructed or injured by kidney

stones (renal calculi)stones (renal calculi)

URINE STORAGEURINE STORAGE

Urinary bladderUrinary bladder Muscular sacMuscular sac Wrinkles termed rugaeWrinkles termed rugae Openings of ureters common site for Openings of ureters common site for

bladder infectionbladder infection

URINE ELIMINATIONURINE ELIMINATION

UrethraUrethra Conveys urine from bodyConveys urine from body Internal urethral sphincterInternal urethral sphincter

Retains urine in bladderRetains urine in bladder Smooth muscle, involuntarySmooth muscle, involuntary

External urethral sphincterExternal urethral sphincter Provides voluntary control over voiding of urineProvides voluntary control over voiding of urine

URINE ELIMINATIONURINE ELIMINATION

UrethraUrethra 3 – 4 cm long in females3 – 4 cm long in females

Bound by connective tissue to anterior wall of Bound by connective tissue to anterior wall of vaginavagina

Urethral orifice exits body between vaginal Urethral orifice exits body between vaginal orifice and clitorisorifice and clitoris

URINE ELIMINATIONURINE ELIMINATION

UrethraUrethra ~18 cm long in males~18 cm long in males

Prostatic urethraProstatic urethra• ~2.5 cm long, urinary bladder ~2.5 cm long, urinary bladder prostate prostate

Membranous urethraMembranous urethra• ~0.5 cm, passes through floor of pelvic cavity~0.5 cm, passes through floor of pelvic cavity

Penile urethraPenile urethra• ~15 cm long, passes through penis~15 cm long, passes through penis

URINE ELIMINATIONURINE ELIMINATION

Urination (micturition)Urination (micturition) ~200 ml of urine held~200 ml of urine held Distension initiates desire to voidDistension initiates desire to void Internal sphincter relaxes involuntarilyInternal sphincter relaxes involuntarily

Smooth muscleSmooth muscle External sphincter voluntarily relaxesExternal sphincter voluntarily relaxes

Skeletal muscleSkeletal muscle Poor control in infantsPoor control in infants

Bladder muscle contractsBladder muscle contracts Urine forces through urethraUrine forces through urethra