The Urinary SystemThe Urinary System

FunctionsFunctions

• Excretion of aqueous wastesExcretion of aqueous wastes

• Monitor and regulate:Monitor and regulate:– Fluid balanceFluid balance– Blood volumeBlood volume– Blood pressureBlood pressure– Red blood cell levelsRed blood cell levels– Blood chemistryBlood chemistry

• Vitamin D synthesisVitamin D synthesis

Four Organs of Urinary Four Organs of Urinary SystemSystem

Placement of KidneysPlacement of Kidneys

• Kidneys are retroperitonealKidneys are retroperitoneal

Internal Anatomy of the Internal Anatomy of the KidneyKidney

• Filtration occurs in the cortexFiltration occurs in the cortex• Medulla fine-tunes filtrate into urineMedulla fine-tunes filtrate into urine

Kidney Kidney Blood Blood FlowFlow

Kidney Kidney Blood Blood FlowFlow

• Your body takes nutrients from food and uses Your body takes nutrients from food and uses them to maintain all bodily functions including them to maintain all bodily functions including energy and self-repair. After your body has taken energy and self-repair. After your body has taken what it needs from the food, waste products are what it needs from the food, waste products are left behind in the blood and in the bowel. The left behind in the blood and in the bowel. The urinary system works with the lungs, skin, and urinary system works with the lungs, skin, and intestines—all of which also excrete wastes—to intestines—all of which also excrete wastes—to keep the chemicals and water in your body keep the chemicals and water in your body balanced. balanced.

• Adults eliminate about a quart and a Adults eliminate about a quart and a half of urine each day. The amount half of urine each day. The amount depends on many factors, especially depends on many factors, especially the amounts of fluid and food a person the amounts of fluid and food a person consumes and how much fluid is lost consumes and how much fluid is lost through sweat and breathing. Certain through sweat and breathing. Certain types of medications can also affect types of medications can also affect the amount of urine eliminated.the amount of urine eliminated.

KidneysKidneys

• The kidneys remove urea from the blood The kidneys remove urea from the blood through tiny filtering units called nephrons. through tiny filtering units called nephrons.

• Each nephron consists of a ball formed of Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, small blood capillaries, called a glomerulus, and a small tube called a renal tubule. and a small tube called a renal tubule.

• Urea, together with water and other waste Urea, together with water and other waste substances, forms the urine as it passes substances, forms the urine as it passes through the nephrons and down the renal through the nephrons and down the renal tubules of the kidney.tubules of the kidney.

UretersUreters

• From the kidneys, urine travels down two thin From the kidneys, urine travels down two thin tubes called ureters to the bladder. tubes called ureters to the bladder.

• The ureters are about 8 to 10 inches long. The ureters are about 8 to 10 inches long. Muscles in the ureter walls constantly tighten and Muscles in the ureter walls constantly tighten and relax to force urine downward away from the relax to force urine downward away from the kidneys. kidneys.

• If urine is allowed to stand still, or back up, a If urine is allowed to stand still, or back up, a kidney infection can develop. Small amounts of kidney infection can develop. Small amounts of urine are emptied into the bladder from the urine are emptied into the bladder from the ureters about every 10 to 15 seconds.ureters about every 10 to 15 seconds.

BladderBladder

• The bladder is a hollow muscular organ The bladder is a hollow muscular organ shaped like a balloon. It sits in your shaped like a balloon. It sits in your pelvis and is held in place by ligaments pelvis and is held in place by ligaments attached to other organs and the pelvic attached to other organs and the pelvic bones. The bladder stores urine until bones. The bladder stores urine until you are ready to go to the bathroom to you are ready to go to the bathroom to empty it. It swells into a round shape empty it. It swells into a round shape when it is full and gets smaller when when it is full and gets smaller when empty.empty.

SphincterSphincter

• Circular muscles called sphincters Circular muscles called sphincters help keep urine from leaking. The help keep urine from leaking. The sphincter muscles close tightly like a sphincter muscles close tightly like a rubber band around the opening of rubber band around the opening of the bladder into the urethra, the tube the bladder into the urethra, the tube that allows urine to pass outside the that allows urine to pass outside the body.body.

Nerves in the bladderNerves in the bladder

• Nerves in the bladder tell you when it is time to Nerves in the bladder tell you when it is time to urinate, or empty your bladder. urinate, or empty your bladder.

• As the bladder first fills with urine, you may As the bladder first fills with urine, you may notice a feeling that you need to urinate. notice a feeling that you need to urinate.

• The sensation to urinate becomes stronger as the The sensation to urinate becomes stronger as the bladder continues to fill and reaches its limit.bladder continues to fill and reaches its limit.

• At that point, nerves from the bladder send a At that point, nerves from the bladder send a message to the brain that the bladder is full, and message to the brain that the bladder is full, and your urge to empty your bladder intensifies.your urge to empty your bladder intensifies.

Nephron AnatomyNephron Anatomy

• Millions of these units accomplish the filtering of bloodMillions of these units accomplish the filtering of blood

Glomerular PressureGlomerular Pressure

• What consequences would a drop in blood pressure What consequences would a drop in blood pressure produce here?produce here?

Renal Corpuscle HistologyRenal Corpuscle Histology

• Filtration occurs here through fenestrationsFiltration occurs here through fenestrations

• Formed elements and plasma proteins remainFormed elements and plasma proteins remain

Proximal Convoluted TubuleProximal Convoluted Tubule

• What feature facilitates the reabsorption of What feature facilitates the reabsorption of important solutes?important solutes?

Distal Distal Convoluted Convoluted TubuleTubule

• Secretion of larger unwanted substancesSecretion of larger unwanted substances• Final fine-tuning of blood in peritubular capillariesFinal fine-tuning of blood in peritubular capillaries

NephroNephron Loopn Loop

• Countercurrent multiplication produces a very salty medullaCountercurrent multiplication produces a very salty medulla• Descending limb permeable to water, ascending limb is notDescending limb permeable to water, ascending limb is not

Urine Formation SummaryUrine Formation Summary

UretersUreters

• Carry urine from renal pelvis to urinary bladderCarry urine from renal pelvis to urinary bladder

Urinary BladderUrinary Bladder

• Transitional epithelium allows this organ to stretchTransitional epithelium allows this organ to stretch

• Mucus protects lining from toxic substances in urineMucus protects lining from toxic substances in urine

UrethraUrethra

• Compare the male and female urethra.Compare the male and female urethra.

UrethraUrethra

• Compare the male and female urethra.Compare the male and female urethra.

Dilute Urine Dilute Urine FormationFormation

• Brown and blue line indicate impermeability Brown and blue line indicate impermeability to water in specific regionsto water in specific regions

Concentrated Urine FormationConcentrated Urine Formation

• Salty medulla and ADH create the conditions for Salty medulla and ADH create the conditions for producing concentrated urineproducing concentrated urine

Antidiuretic Antidiuretic Hormone and Hormone and HomeostasisHomeostasis

• Acts to preserve volume of water in Acts to preserve volume of water in body at healthy levelbody at healthy level

• Increases permeability to water at Increases permeability to water at end of nephronend of nephron

Other FactorsOther Factors

• AldosteroneAldosterone– Excretion of KExcretion of K++ and reabsorption of Na and reabsorption of Na++

• Atrial natriuretic peptide, brain Atrial natriuretic peptide, brain natriuretic peptidenatriuretic peptide– Oppose ADHOppose ADH

• Caffeine and alcoholCaffeine and alcohol– Decreases ADH productionDecreases ADH production

Bicarbonate Buffer SystemBicarbonate Buffer System

HH++ + HCO + HCO33-- H H22COCO33 H H22O + COO + CO22

• As indicated by the arrows, this chemical As indicated by the arrows, this chemical reaction can proceed in either directionreaction can proceed in either direction

• For example, increasing COFor example, increasing CO22 will drive will drive the reaction to the leftthe reaction to the left– Increases acidityIncreases acidity

Respiratory Respiratory Regulation of Regulation of Blood pHBlood pH

Urinary Regulation of Blood Urinary Regulation of Blood pHpH

• Kidneys can adjust excretion of HKidneys can adjust excretion of H++ and HCO and HCO33--

according to the needaccording to the need

Urinary Regulation of Blood Urinary Regulation of Blood pHpH

• Kidneys can adjust excretion of HKidneys can adjust excretion of H++ and HCO and HCO33--

according to the needaccording to the need

UrinalysisUrinalysis

UrinalysisUrinalysis

Urinary DisordersUrinary Disorders

• Benign prostatic hyperplasia (BPH)Benign prostatic hyperplasia (BPH) is a is a condition in men that affects the prostate gland, condition in men that affects the prostate gland, which is part of the male reproductive system. which is part of the male reproductive system. BPH is an enlargement of the prostate gland that BPH is an enlargement of the prostate gland that can interfere with urinary function in older men. can interfere with urinary function in older men.

• It causes blockage by squeezing the urethra, It causes blockage by squeezing the urethra, which can make it difficult to urinate. Most men which can make it difficult to urinate. Most men over age 60 have some BPH, but not all have over age 60 have some BPH, but not all have problems with blockage. There are many different problems with blockage. There are many different treatment options for BPH.treatment options for BPH.

Urinary DisordersUrinary Disorders

• Kidney stonesKidney stones is the term commonly used to is the term commonly used to refer to stones, or calculi, in the urinary system. refer to stones, or calculi, in the urinary system. Stones form in the kidneys and may be found Stones form in the kidneys and may be found anywhere in the urinary system. They vary in anywhere in the urinary system. They vary in size. Some stones cause great pain while others size. Some stones cause great pain while others cause very little. The aim of treatment is to cause very little. The aim of treatment is to remove the stones, prevent infection, and remove the stones, prevent infection, and prevent recurrence. Both nonsurgical and prevent recurrence. Both nonsurgical and surgical treatments are used. Kidney stones surgical treatments are used. Kidney stones affect men more often than women.affect men more often than women.

Kidney StonesKidney Stones

• As water is As water is absorbed, absorbed, stones can formstones can form

• Jagged edges Jagged edges are painfulare painful

• Larger stones Larger stones can be broken can be broken by ultrasoundby ultrasound

Kidney DiseasesKidney Diseases

• Failing kidneys require helpFailing kidneys require help

• Dialysis artificially mimics the kidneys by diffusion Dialysis artificially mimics the kidneys by diffusion across a membraneacross a membrane– HemodialysisHemodialysis

• Blood is withdrawn and passed across a dialysis membraneBlood is withdrawn and passed across a dialysis membrane

• A carefully prepared solution will prevent necessary A carefully prepared solution will prevent necessary components from being lost and force the diffusion of components from being lost and force the diffusion of wasteswastes

– Peritoneal dialysisPeritoneal dialysis• Dialysis fluid is put directly into abdominal cavity and left Dialysis fluid is put directly into abdominal cavity and left

to diffuseto diffuse

Urinary DisordersUrinary Disorders

• Renal (kidney) failureRenal (kidney) failure results when the kidneys results when the kidneys are not able to regulate water and chemicals in are not able to regulate water and chemicals in the body or remove waste products from your the body or remove waste products from your blood. Acute renal failure (ARF) is the sudden blood. Acute renal failure (ARF) is the sudden onset of kidney failure. This condition can be onset of kidney failure. This condition can be caused by an accident that injures the kidneys, caused by an accident that injures the kidneys, loss of a lot of blood, or some drugs or poisons. loss of a lot of blood, or some drugs or poisons.

• Can be saved if caught in timeCan be saved if caught in time

Urinary DisordersUrinary Disorders

• Urinary tract infections (UTIs)Urinary tract infections (UTIs) are caused by are caused by bacteria in the urinary tract. Women get UTIs bacteria in the urinary tract. Women get UTIs more often than men. UTIs are treated with more often than men. UTIs are treated with antibiotics. Drinking lots of fluids also helps by antibiotics. Drinking lots of fluids also helps by flushing out the bacteria.flushing out the bacteria.

• The name of the UTI depends on its location in The name of the UTI depends on its location in the urinary tract. An infection in the bladder is the urinary tract. An infection in the bladder is called cystitis. If the infection is in one or both of called cystitis. If the infection is in one or both of the kidneys, the infection is called pyelonephritis. the kidneys, the infection is called pyelonephritis. This type of UTI can cause serious damage to the This type of UTI can cause serious damage to the kidneys if it is not adequately treated.kidneys if it is not adequately treated.

Summary of Main PointsSummary of Main Points

• The urinary system is composed of the The urinary system is composed of the kidneys and their nephrons, ureters, urinary kidneys and their nephrons, ureters, urinary bladder and urethrabladder and urethra

• Urine formation is accomplished by:Urine formation is accomplished by: FiltrationFiltration ReabsorptionReabsorption SecretionSecretion

• Maintains:Maintains:– Water-salt balanceWater-salt balance– Acid-base balanceAcid-base balance

• Dialysis can mimic the kidney functionDialysis can mimic the kidney function