1. 31
The Urinary System

2. Learning Outcomes (cont.)
31.1 Describe the structure, location, and functions of the kidney.
31.2 Explain how nephrons filter blood and form urine.

3. Learning Outcomes (cont.)
31.3 Compare the locations, structures, and functions of the ureters, bladder, and urethra.
31.4 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.

4. Urinary System Organs Introduction Kidneys Ureters Bladder Urethra
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Nephrons are microscopic structures within the kidneys that filter blood, remove waste products, and form urine.
System functions to remove waste products from the blood
Nephrons filter the blood and form the urine

5. The Kidneys Maintain homeostasis Remove metabolic waste products
Secrete hormones
Erythropoietin
Renin
Retroperitoneal at level of lumbar vertebrae
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Homeostasis – a balanced, stable state within the body
Metabolic wastes are combined with water and ions to form urine, which is excreted from the body.
Hormones secreted by the body
Erythropoietin – stimulates the red bone marrow to produce red blood cells
Renin – helps to regulate blood pressure.
The kidneys
Bean-shaped, reddish brown organs covered by tough, fibrous capsules.
Retroperitoneal in position on either side of the vertebral column at about the level of the lumbar vertebrae
Kidneys

6. Learning Outcomes: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.
Back

7. The Kidneys (cont.) Renal sinus Renal pelvis
Concave depression on the kidney's surface
Hilum
Renal pelvis
Expansion of the ureter
Divides into calyces
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Renal sinus – the surface area of the concave depression of the kidney
Hilum – point of entry for artery, vein, and ureter
Renal pelvis – this same area inside the kidney
Kidney

8. The Kidneys (cont.) Renal cortex – outermost layer Renal medulla
Middle portion
Divides into renal pyramids
Renal column – between pyramids
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Renal pyramids – triangular-shaped areas
The renal cortex covers the pyramids and also dips down between the pyramids.
Renal column – the portion of the cortex between pyramids
Kidney

9. Learning Outcomes: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.
Back

10. Nephrons Renal corpuscle Glomerulus ~ capillaries Bowman’s capsule
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Nephrons remove waste products from the blood.
Each kidney contains about 1 million nephrons that are located in the renal medulla
Renal corpuscle
Where blood filtration occurs
Glomerulus – a mass of capillaries
Bowman’s capsule, or glomerular capsule – the capsule that surrounds the glomerulus
Nephron

11. Nephrons Renal tubules – extend from Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Renal tubules
Proximal convoluted tubule – directly attached to the bowman’s capsule and eventually straightens out to become the loop of henle
The loop of henle – curves back toward the renal corpuscle and starts to twist again, becoming the distal convoluted tubule
Distal convoluted tubules – merge with distal convoluted tubules from other nephrons to form collecting ducts.
The ducts collect urine and deliver it to the renal pelvis, which in turn empties urine into the ureters.
Nephron

12. Peritubular Capillaries
Nephrons (cont.)
Glomerulus
Renal artery
Afferent arterioles
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Narrowing of capillaries in glomeruli causes filtration of the blood by forcing blood through the capillary walls.
Peritubular capillaries are wrapped around the renal tubules of the nephron.
Cleansed blood leaves the peritubular capillaries through veins in the kidneys.
Renal vein
Peritubular Capillaries
Efferent arterioles
Nephron

13. Learning Outcomes: 31.1 Describe the structure, location, and functions of the kidney.
Back

14. Correct! Apply Your Knowledge What is the function of the kidney?
ANSWER: Maintain hemostasis by removing metabolic waste products from the blood, secreting erythropoietin to help regulate RBC production, and secreting renin to help regulate the BP.
Learning Outcomes: Describe the structure, location, and functions of the kidney.
Correct!

15. Urine Formation Glomerular Filtration Occurs in renal corpuscles
Fluid part of the blood
Into Bowman’s capsule
Becomes glomerular filtrate
Learning Outcome: Explain how nephrons filter blood and form urine.
Three processes of urine formation
Glomerular filtration
Tubular reabsorption
Tubular secretion
Glomerular filtration – the fluid part of blood is forced from the glomerulus.
The fluid in Bowman’s capsule is called the glomerular filtrate.
Glomerulus

16. Urine Formation (cont.)
Glomerular filtration
Filtration pressure – that needed to force filtrate from the glomerulus into Bowman’s capsule
Rate of filtration
Sympathetic nervous system control
Constriction of afferent arterioles
Learning Outcome: Explain how nephrons filter blood and form urine.
Glomerular filtration depends on
Filtration pressure
Determined by blood pressure
If blood pressure is too low, glomerular filtrate will not form.
If the blood pressure increases, filtration pressure also increases increasing the rate of filtration and the amount of glomerular filtrate.
Rate of filtration
If blood pressure or blood volume drops, the SNS causes the afferent arterioles in the kidneys to constrict decreasing the glomerular filtration pressure so less glomerular filtrate is formed.
When less glomerular filtrate is formed, less urine is ultimately formed. This allows the body to retain fluids that are needed to raise blood pressure and blood volume.
Glomerulus

17. Learning Outcome: 31.2 Explain how nephrons filter blood and form urine.
Previous

18. Tubular Reabsorption Glomerular filtrate  proximal convoluted tubule
Reabsorption of needed substances
Water reabsorption  hormonal regulation
Antidiuretic hormone (ADH)
Aldosterone
 water reabsorption,  urine production
Learning Outcome: Explain how nephrons filter blood and form urine.
The second process in urine formation.
Nutrients, water, and ions pass through the walls of the renal tubule into the peritubular capillaries.
Water reabsorption varies depending on the presence of antidiuretic hormone (ADH) and aldosterone.
The retention of fluid results in an increase in blood pressure and is one of the reasons why diuretics are successful in treating some forms of hypertension.
Tubular Reabsorption

19. Tubular Secretion
Substances move from blood in the peritubular capillaries into the renal tubules
Secreted substances
Drugs
Hydrogen ions
Waste products
Learning Outcome: Explain how nephrons filter blood and form urine.
Third process of urine formation
All of the secreted substances will be excreted in the urine.
Tubular Secretion

20. Tubular Reabsorption Tubular Secretion Previous
Learning Outcome: Explain how nephrons filter blood and form urine.
Previous
Tubular Reabsorption
Tubular Secretion

21. Urine Composition Mostly water Urea and uric acid
Trace amounts of amino acids and various ions
Secretion of waste products helps to maintain the acid-base balance
Learning Outcome: Explain how nephrons filter blood and form urine.
Urea and uric acid are waste products formed by the breakdown of proteins and nucleic acids.
Refer to CONNECT to see an animation about Renal Function.

22. Apply Your Knowledge Nice Job! Match the following:
___ Second process in urine formation
___ Substances move from blood into renal tubules reabsorption
___ Depends on filtration pressure
___ Third process of urine formation
___ First process of urine formation
___ Filtrate flows into the proximal convoluted tubule B
ANSWER:
Glomerular filtration
Tubular Reabsorption
Tubular Secretion C A
Learning Outcome: Explain how nephrons filter blood and form urine. C
Nice Job! A B

23. The Ureters, Urinary Bladder, and Urethra
Long muscular tubes
Carry urine to the bladder using peristalsis
Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
The ureters, bladder and urethra transport and store urine after it is formed in the kidneys.

24. Urinary Bladder Trigone – triangle on internal floor of bladder
Detrusor muscle – smooth muscle of bladder wall
Micturition
Process of urination
Triggered by stretching of the bladder
Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
A distensible organ located in the pelvic cavity.
Its function is to store urine (up to 600 mL on average) until it is eliminated from the body.
Trigone of the bladder – triangle is formed by the openings from the urethra and the ureters.
Detrusor muscle – contracts to push urine from the bladder into the urethra
Bladder

25. Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
Previous

26. Urinary Bladder (cont.)
Micturition
Brain stem and cerebral cortex
Impulses to contract urethra  inhibit micturition impulse until ready to urinate
Spinal cord
Parasympathetic nerves stimulate detrusor muscle
Bladder distends
Stretch receptors
Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
The major events of micturition are
The urinary bladder distends as it fills with urine.
The distension stimulates stretch receptors in the bladder wall, signaling the micturition center in the spinal cord.
Parasympathetic nerves stimulate the detrusor muscle, which begins rhythmic contractions that trigger the sense of the need to urinate.
The brain stem and cerebral cortex send impulses to voluntarily contract the external urethral sphincter and to inhibit the micturition impulse.
Upon the decision to urinate, the external urethral sphincter is relaxed and impulses from the pons and hypothalamus start the micturition reflex.
Contraction of the detrusor muscle occurs and urine is expelled through the urethra.

27. Urethra Moves urine from the bladder to the outside world
Shorter in females – patient education
Urinate when urge occurs
Drink adequate clear fluids
Wipe front to back
Urinate after intercourse
Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
Females are more susceptible than males to urinary tract infections
Shorter urethra
Proximity of urethra to anus and vagina
Urethra

28. Apply Your Knowledge Impressive! ANSWER: True or False:
___ Ureters move urine by peristalsis.
___ The detrusor is formed by the openings of the ureters and urethra.
___ The process of micturition is triggered when the bladder contains about 150 ml urine.
___ The urethra move urine from the kidney to the bladder.
___ The urethra is longer in females.
___ Contraction of the detrusor muscle pushes urine from the bladder. T F
trigone T
Learning Outcome: Compare the locations, structures, and functions of the ureters, bladder, and urethra.
ureters F F
males T

29. Diseases and Disorders of the Urinary System
Disease/Disorder
Description
Acute kidney (renal) failure
Sudden loss of kidney function; may be reversible with treatment
Chronic kidney (renal) failure
Kidneys slowly lose ability to function; not reversible
Cystitis
Urinary bladder infection; more common in females
Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.
Acute kidney (renal) failure
Causes and risk factors of kidney failure include burns, dehydration, low blood pressure, hemorrhaging, allergic reactions, obstruction of the renal artery, various poisons, alcohol abuse, trauma to the kidneys and skeletal muscles, blood disorders, blood transfusion reactions, kidney stones, urinary tract infections, enlarged prostate, childbirth, immune system disorders, and food poisoning involving the bacteria E. coli.
Chronic kidney (renal) failure – the patient may be asymptomatic until the kidneys have lost about 90% of their function.
Cystitis – caused by various types of bacteria and may be caused by the placement of a catheter in the bladder.

30. Diseases and Disorders of the Urinary System
Disease/Disorder
Description
Glomerulonephritis
Inflammation of the glomeruli of the kidney; one cause of chronic renal failure
Incontinence
Inability to control urination
Polycystic kidney disease
Enlargement of kidneys because of the presence of many cysts within them; slow, progressive disease
Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.
Glomerulonephritis – caused by renal diseases, immune disorders, and bacterial infections.
Incontinence
Causes
Various medications, excessive coughing (for example, in smokers), UTIs, nervous system disorders, and bladder cancer.
Prostate problems in men
Weakness of the urinary sphincters from surgery, trauma, or pregnancy
Prevented by avoiding urinary bladder irritants such as coffee, cigarettes, diuretics, and various medications.
Polycystic kidney disease – hereditary via an inherited dominant gene from a parent

31. Diseases and Disorders of the Urinary System
Disease/Disorder
Description
Pyelonephritis
Complicated urinary tract infection; begins with a bladder infection and spreads to both kidneys; can be acute or chronic
Renal calculi
Kidney stones; can become lodged in ducts within kidneys or ureters
Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.
Pyelonephritis – caused by bacteria, a bladder infection, kidney stones, or an obstruction of the urinary system ducts.
Renal calculi – caused by gouty arthritis, defects of the ureters, overly concentrated urine, and urinary tract infections.

32. Apply Your Knowledge GOOD JOB! Matching: ANSWER:
___ Complicated urinary tract infection A. Pyelonephritis
___ Inability to control urination B. Glomerulonephritis
___ Kidney stones C. Incontinence
___ Slow loss of kidney function D. Chronic renal failure
___ Bladder infection E. Renal calculi
___ Inflammation of the glomeruli F. Cystitis
___ Kidney enlargement due to cysts G. Acute renal failure
___ Sudden loss of kidney function H. Polycystic kidney disease
ANSWER:
GOOD JOB! A C E D F
Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system. B H G

33. In Summary
31.1 The retroperitoneal kidneys are composed of the outer renal cortex and inner renal medulla.
Their function is to remove metabolic wastes from the body.

34. In Summary 31.2 A nephron is a single kidney cell.
It is composed of a renal corpuscle composed of the glomerulus and the Bowman’s capsule and the three sections of the renal tubule: the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule.
The nephrons filter blood and form urine through three processes: glomerular filtration, tubular reabsorption, and tubular secretion.

35. In Summary (cont.)
31.3 The ureters are long tubes extending from each renal pelvis that bring urine to the bladder for storage. The urethra is the muscular tube extending from the bladder that allows urine to be expelled from the body.

36. In Summary (cont.)
31.4 There are many common diseases and disorders of the urinary system with varied signs, symptoms, and treatments. Some of these include acute kidney (renal) failure, chronic kidney (renal) failure, cystitis, glomerulonephritis, incontinence, polycystic kidney disease, pyelonephritis, and renal calculi.

37. End of Chapter 31 This too shall pass—just like a kidney stone.
~H. Madson