The Urinary SystemThe Urinary System

Overview Overview

The urinary system balances the The urinary system balances the water content in the blood as well as water content in the blood as well as ions of Na and K and pH.ions of Na and K and pH.

It Regulates the volume and It Regulates the volume and composition of the fluids and excrete composition of the fluids and excrete unwanted materials.unwanted materials.

Anatomy of the Urinary SystemAnatomy of the Urinary System

Internal Kidney StructureInternal Kidney Structure

Urinary Bladder AnatomyUrinary Bladder Anatomy

Trigone

Rugae- Flods of the bladder

Detrusor Muscle – smooth muscle

Urethra

Urethral Sphincter -Involuntary

Physiology of the bladder functionPhysiology of the bladder function

The bladder stretches as it fills with urine and The bladder stretches as it fills with urine and when there is 250mL you feel the need to void.when there is 250mL you feel the need to void.

Voiding begins with voluntary relaxation of the Voiding begins with voluntary relaxation of the external urethral sphincter muscle.external urethral sphincter muscle.

Once you relax the urethral sphincter the Once you relax the urethral sphincter the involuntary response of contraction takes over. involuntary response of contraction takes over. AKA micturitionAKA micturition

Inability to void because kidneys are not Inability to void because kidneys are not excreting urine is known as excreting urine is known as suppressionsuppression..

Inability to void even though urine is present in Inability to void even though urine is present in the bladder is known as the bladder is known as retention.retention.

Involuntary micturition = Involuntary micturition = IncontinanceIncontinance

UrethraUrethra

Small tube lined with mucous Small tube lined with mucous membrane leading from the floor of membrane leading from the floor of the bladder to the exterior of the body.the bladder to the exterior of the body.

In females this distance is about 3cm.In females this distance is about 3cm. In males this distance extends along a In males this distance extends along a

winding path for about 20 cm and winding path for about 20 cm and passes through the middle of the passes through the middle of the prostate gland just after leaving the prostate gland just after leaving the bladder. & is shared as part of the bladder. & is shared as part of the reproductive system.reproductive system.

Microscopic Structure of the functional Microscopic Structure of the functional unit of a kidney is the Nephron.unit of a kidney is the Nephron.

Bowman’s Capsule

Proximal convoluted tubuleLoop of HenleDistal convoluted tubuleCollecting duct

There are approximately 1.25 million nephrons Per Kidney.

Components of the Nephron

Glomeruli – Many glomerulusGlomeruli – Many glomerulus

Glomerular capillaries

Bowman’s Capsule + GlomerulusBowman’s Capsule + Glomerulus= Renal corpuscle= Renal corpuscle

The loop of Henle dips into the The loop of Henle dips into the medulla into a renal pyramid.medulla into a renal pyramid.

The collecting ducts empty into the The collecting ducts empty into the calyces which empty into the renal calyces which empty into the renal

pelvis.pelvis.

Blood vessels of the KidneysBlood vessels of the Kidneys

About 1200 ml of blood flows through About 1200 ml of blood flows through the kidneys every minutethe kidneys every minute

Which means approximately 1/5 of Which means approximately 1/5 of all the blood pumped by the heart per all the blood pumped by the heart per minute goes to the kidneys.minute goes to the kidneys.

Usual direction of blood flow isUsual direction of blood flow is

Arteries-Arterioles-Capillaries-venules-Arteries-Arterioles-Capillaries-venules-veins veins

Blood flow through Kidney tissue Blood flow through Kidney tissue follows this path…follows this path…

Renal ArteryRenal Artery Interlobular artery-penetrate the cortexInterlobular artery-penetrate the cortex Afferent arterioleAfferent arteriole GlomerulusGlomerulus Efferent arterioleEfferent arteriole Peritubular capillaries(vasa recta)Peritubular capillaries(vasa recta) VenulesVenules

Interlobular vein Interlobular vein Renal Vein Renal Vein

Function of the kidneyFunction of the kidney

KIDNEYS…KIDNEYS… Process blood plasma and excrete Process blood plasma and excrete

urine.urine. Most important organs in the body Most important organs in the body

for maintaining fluid-electrolyte and for maintaining fluid-electrolyte and acid-base balances. acid-base balances.

Excrete Nitrogenous wastes from Excrete Nitrogenous wastes from protein metabolism. (urea) protein metabolism. (urea)

Kidney Failure means homeostatic Kidney Failure means homeostatic failure and failure and

If not relieved, If not relieved,

inevitable DEATH.inevitable DEATH.

Kidneys also…Kidneys also…

Influence the rate of secretion of the Influence the rate of secretion of the hormoneshormones

ADH – Antidiuretic hormoneADH – Antidiuretic hormone

AldosteroneAldosterone

and synthesize erythropoietin –active and synthesize erythropoietin –active form of vitamin D and form of vitamin D and prostaglandins.prostaglandins.

Formation of urineFormation of urine

Urine is formed by 3 meansUrine is formed by 3 means1. 1. FiltrationFiltration – the movement of – the movement of

water and solutes from the water and solutes from the plasma in the glomerulus, across plasma in the glomerulus, across the glomerular-capsular the glomerular-capsular membrane, and into the capsular membrane, and into the capsular space of the Bowman’s capsulespace of the Bowman’s capsule

2. 2. ReabsorptionReabsorption- - movement of molecules movement of molecules out of the tubule and into out of the tubule and into the peritubular blood.the peritubular blood.

3. 3. SecretionSecretion – movement – movement of the molecules out of the of the molecules out of the peritubular blood into the peritubular blood into the tubule for excretion.tubule for excretion.

Filtration Filtration

Occurs through the glomerular capiliaries Occurs through the glomerular capiliaries to the Bowman’s Capsuleto the Bowman’s Capsule

Large substances are separated from Large substances are separated from small substances.small substances.

Blood cells and blood proteins are typically Blood cells and blood proteins are typically TOO large to filter through the glomerulus TOO large to filter through the glomerulus so as the blood leaves the glomerulus in so as the blood leaves the glomerulus in the efferent arteriole it is relatively clean the efferent arteriole it is relatively clean and has lost most of its fluid.and has lost most of its fluid.

Blood cells are too large to Blood cells are too large to filter out. filter out. So what does filter out?So what does filter out? WaterWaterSaltsSaltsBicarbonateBicarbonateH+H+UreaUreaGlucoseGlucoseAmino acidsAmino acidsSome drugsSome drugs

Returned to the blood immediately: Returned to the blood immediately: Reabsorption occurs mostly in the Reabsorption occurs mostly in the

PCT.PCT. Water and ions Water and ions Glucose and amino acidsGlucose and amino acids Passive and Active transport Passive and Active transport

mechanisms are at work in the mechanisms are at work in the tubules. tubules.

MANY Carriers are available for MANY Carriers are available for materials that need to be reclaimed.materials that need to be reclaimed.

Very few carriers for things that are Very few carriers for things that are of little or no use to the body.of little or no use to the body.

Reabsorption in Reverse: SecretionReabsorption in Reverse: Secretion

And it gets rid of substances not And it gets rid of substances not already in the filtrate such as drugs.already in the filtrate such as drugs.

H+ and K+ and creatinine move from H+ and K+ and creatinine move from the peritubular blood to the tubule.the peritubular blood to the tubule.

Urine vs. FiltrateUrine vs. Filtrate

Filtrate contains everything that Filtrate contains everything that blood plasma does (except proteins)blood plasma does (except proteins)

Most of the Water, nutrients and Most of the Water, nutrients and necessary ions are reabsorbed by the necessary ions are reabsorbed by the time it reaches the collecting ducts.time it reaches the collecting ducts.

Urine contains most of the waste and Urine contains most of the waste and unneeded substances.unneeded substances.

In 24 hoursIn 24 hours

150 to 180 liters of blood plasma filter 150 to 180 liters of blood plasma filter through the kidneys (nephrons)through the kidneys (nephrons)

Only 1 to 1.8 liters of urine are produced.Only 1 to 1.8 liters of urine are produced.

WHAT HAPPENS TO MOST OF THE FILTRATE?WHAT HAPPENS TO MOST OF THE FILTRATE?

Initial Filtrate –dilute Initial Filtrate –dilute

Final Filtrate - Final Filtrate - concentratedconcentrated

ExcretionExcretion

Urea - protein breakdownUrea - protein breakdown Uric acid – nucleic acids are Uric acid – nucleic acids are

metabolized.metabolized. Creatinine – Actively secreted into Creatinine – Actively secreted into

filtratefiltrate

associated with metabolism associated with metabolism inin

muscle tissue.muscle tissue.

Balance of Water and electrolytesBalance of Water and electrolytes

We cannot lose more water than we We cannot lose more water than we take in.take in.

Water is lost by….Water is lost by….

Respiration, Perspiration, Solid waste, Respiration, Perspiration, Solid waste, & Urine & Urine

Water is taken in Water is taken in

in Foods, beverages and metabolism.in Foods, beverages and metabolism.

Electrolyte balanceElectrolyte balance

ADH – prevents excess water loss by ADH – prevents excess water loss by causing the collecting duct cells to causing the collecting duct cells to reabsorb more water which increases reabsorb more water which increases blood volume and blood pressure.blood volume and blood pressure.

Alcohol disrupts ADH and less water Alcohol disrupts ADH and less water is reabsorbed creating more dilute is reabsorbed creating more dilute urine.urine.

If ADH is not present up to 25 If ADH is not present up to 25 liters /day could by flushed from the liters /day could by flushed from the body.= severe dehydration.body.= severe dehydration.

Aldosterone – Regulates Sodium contentAldosterone – Regulates Sodium content

Renin-angiotensin mechanism –Renin-angiotensin mechanism – When blood pressure is low the When blood pressure is low the

enzyme renin catalyzed reactions that enzyme renin catalyzed reactions that produceproduce

angiotensin II which causes angiotensin II which causes vasoconstriction of blood vessels vasoconstriction of blood vessels causing an increase in blood pressure causing an increase in blood pressure which helps filtration.which helps filtration.

Buffers Keep the balanceBuffers Keep the balance

Acidosis- When blood pH drops below Acidosis- When blood pH drops below 7.35.7.35.

Alkalosis – When blood pH rises above Alkalosis – When blood pH rises above 7.45.7.45.

Sodium Bicarbonate ions NaHCOSodium Bicarbonate ions NaHCO3-3-

Bicarbonate ion HCOBicarbonate ion HCO3-3-

AmmoniaAmmonia NHNH33

HClHCl

Renal thresholdRenal threshold

The limit for certain substances in The limit for certain substances in the blood.the blood.

Substances over the limit are forced Substances over the limit are forced out into the filtrate.out into the filtrate.

Glucose and not reabsorbed over the Glucose and not reabsorbed over the threshold limit.threshold limit.

Renal Calculi AKA Kidney stonesRenal Calculi AKA Kidney stones

Renal and Urinary disordersRenal and Urinary disorders

Hydronephrosis – Urine backs up into Hydronephrosis – Urine backs up into the kidney, causing swelling.the kidney, causing swelling.

Renal calculi – crystallized mineral Renal calculi – crystallized mineral chunks that develop in the calyces or chunks that develop in the calyces or renal pelvis(staghorn calculi) = renal renal pelvis(staghorn calculi) = renal colic(PAIN)colic(PAIN)

Renal ptosis – Kidneys may drop, Renal ptosis – Kidneys may drop, Ureters may kink and obstruct urine Ureters may kink and obstruct urine flow.flow.

Urinary tract infections Urinary tract infections UTIsUTIs

Urethritis -Bacterial infections – Urethritis -Bacterial infections – inflammation of the urethra- STDs inflammation of the urethra- STDs often cause urethritis – more often cause urethritis – more common in malescommon in males

Cystitis – inflammation of the Cystitis – inflammation of the bladder- can also accompany kidney bladder- can also accompany kidney stones and tumorsstones and tumors

Nephritis – Kidney disease – bacterial Nephritis – Kidney disease – bacterial or viral infectionsor viral infections

Kidney FailureKidney FailureAKA Renal FailureAKA Renal Failure

Acute Renal Failure – SuddenAcute Renal Failure – Sudden BUN Blood Urea Nitrogen HighBUN Blood Urea Nitrogen High 11stst stage Loss of nephrons stage Loss of nephrons 22ndnd stage Kidney can no longer adapt stage Kidney can no longer adapt

to the loss of nephrons. Remaining to the loss of nephrons. Remaining nephrons cannot handle the loadnephrons cannot handle the load

33rdrd stage Complete shutdown- Edema stage Complete shutdown- Edema and hypertension occursand hypertension occurs