1. So, how does the nephron take blood and turn it into urine???

4. Blood Flow of Kidney Blood comes in via the Renal Artery
Branches down into afferent arteriole, which feeds the glomerulus with blood

5. Blood Flow of Kidney
Blood passes through the glomerular capillary, where filtration occurs.
Most water & solutes are separated from the blood and pushed into the nephron.
Blood leaves the glomerulus through the efferent arteriole
These are the only capillaries in your body that don’t have gas exchange!

6. Blood Flow of Kidney
Blood continues to peritubular capillaries, where reabsorption, secretion and gas exchange occurs
Blood leaves through branched venules, and eventually renal vein

7. Urine Formation Occurs through three processes… Filtration
Reabsorption
Secretion

8. Filtration
Separation of blood from the glomerular capillaries into the glomerulus.
Substances that leave the capillaries and enter the nephron includes…
Blood plasma
Water
Small Solutes
Erythrocytes and proteins are NOT filter into the nephron.
Blood pressure must be good for filtrate to pass through capillary walls!
Approx. 1 L of blood passes through kidney per minute… of this, about mL is filtered out

9. Reabsorption
Most happens at proximal convoluted tubule, but can happen all along renal tubule!
Water and solutes reenter the blood stream into peritubular capillaries
Mostly done by active transport (exception is water: passive transport)
Includes…
Water
Glucose
Amino Acids
Ions (H+, K+, Na+, Cl-, HCO3-)

10. Reabsorption
Some of these substances will be left in the urine – if the body doesn’t need them to maintain homeostasis
Nitrogen wastes tend NOT to be reabsorbed (or poorly if they are)
Urea: Formed by the liver (protein breakdown)
Uric Acid: Nucleic acids metabolized
Creatinine: Muscle metabolism
Also, excess water is NOT reabsorbed
All are found in high amounts in urine
Approx. 99% of filtrate is reabsorbed (taken back from filtrate to blood)

11. Secretion
Some substances are pushed into the nephron from the peritubular capillaries.
Recall that most substances enter the nephron from the glomerular capillaries within the glomerulus
Includes…
Creatinine
H+, K+ ions
Drugs
Any materials left in the nephron move out the collecting duct, through the renal pelvis, and down the ureter to the bladder

12. http://www. argosymedical

13. So, anything that’s left after filtration, absorption, and secreting by the kidney tubules is then called URINE.

14. Urine
Yellow in color
Color due to urochrome (pigment resulting from destroying hemoglobin); more solutes (less water/solvent) yields deeper color
Has an odor, but becomes more “ammonia” smelling if allowed to stand

15. Urine pH slightly acidic
More dense than distilled water (water + solutes)
Common solutes include H+ & K+ ions, urea, uric acid, creatinine, ammonia, and HCO3-

16. Urine then continues down to URETERS

17. Ureters Ureters travel down toward bladder
Peristalsis aids gravity in urine transport

18. Urine then heads to the BLADDER

19. Bladder Smooth, collapsable sac Stores urine temporarily
Flaps of bladder mucosa cover the ureter openings to prevent backflow of urine

20. Bladder Trigone – three openings of the bladder Two from the ureters
One to the urethra

21. Bladder Wall Three layers of smooth muscle (detrusor muscle)
Also, transitional epithelium – which has the unique characteristic of being able to stretch and slide

22. Bladder
Sphincters
Internal Urethreal: involuntary, keeps urethra closed
External Urethral: lower, formed by skeletal muscle, voluntary

23. http://highered. mcgraw-hill

24. Urine then exits the body through the URETHRA

25. Urethra
Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis
Length
Females – 3–4 cm (1 inch), along wall of vagina
Males – 20 cm (8 inches), through prostate & penis
Function
Females – only carries urine
Males – carries urine and is a passageway for sperm cells

27. Facts to know about Urinary System…
Each kidney has over ONE MILLION nephrons
It takes about four minutes for all of your blood to be filtered through a kidney
A moderately full bladder holds about 500 mL of urine, but it can hold up to 1 liter
In 24 hours, kidneys filter out liters of blood plasma, but only produce about liters of urine

28. Remember some of the functions of kidneys…
1. Excretion of nitrogen-containing wastes (which we discussed last class!)
2. Maintaining water balance
3. Regulate blood pressure
4. Ensuring proper blood pH
We’ve talked about number 1, but we will discuss 2 through 4 today!

29. Maintaining Water Balance
Normal amount of water in the human body
Young adult females – 50%
Young adult males – 60%
Babies – 75%
Old age – 45%
Water is necessary for many body functions and levels must be maintained

30. Maintaining Water Balance
Intracellular Fluid
2/3 of body fluid, found in cells
Extracellular Fluid
1/3 of body fluid, found outside cells
Includes blood plasma, cerebrospinal fluid, tissue fluid, and others
Ions (Electrolytes) are dissolved in much of this fluid

31. Maintaining Water Balance
Changes in electrolyte balance causes water to move in and out of the cells
Alters blood volume and blood pressure
Can impair the activity of cells

32. Maintaining Water Balance
Water intake must equal water output (about 2500 mL / 2.5 L every day)
Sources for water intake
Ingested foods and fluids
Water produced from metabolic processes
Sources for water output
Vaporization out of the lungs
Lost in perspiration
Leaves the body in the feces
Urine production

34. Maintaining Water Balance
How does your body know that it is lacking water?
How does it fix the problem???
And how do your kidneys regulate your blood pressure at the same time?

35. Way #1: ADH Water loss leads to low blood pressure
…which leads to low filtrate production
…which leads to unusual composition of blood
…which causes your hypothalamus to say, “hey, something’s wrong!”
The hypothalamus then sends out a nerve signal to the pituitary gland
…which releases ADH (antidiuretic hormone)
…which stimulates the kidney’s collecting ducts to reabsorb more water
… which causes blood pressure and volume to rise! (more filtrate will be produced!)

36. Way #2: Renin-Angiotensin Mechanism
Water loss leads to low blood pressure
…which will stimulate the release of renin (an enzyme)
…which will speed up the production of angiotensin (a hormone)
…which will cause vasoconstriction (higher blood pressure!)

37. Way #2: Renin-Angiotensin Mechanism
Angiotensin will also stimulate the production of aldosterone
Aldosterone acts on the distal convoluted tubules
…and stimulates them to reabsorb more Na+ and water
…which increases blood pressure and volume!

38. Maintaining Blood pH pH is the measure of the concentration of H+ ions
More H+, more acidic
pH level 0-7: acidic
pH level 7-14: basic
pH level at 7: neutral

39. Maintaining Blood pH
Blood pH must remain between 7.35 and 7.45 to maintain homeostasis
Alkalosis – pH above 7.45
Acidosis – pH below 7.35 (while not “acidic”, it still has more H+ than normal!)

40. Maintaining Blood pH
Many metabolic processes will produce acids to throw off this balance!
Lactic Acid in your muscles
Fatty Acids
Carbonic Acid (formed by CO2 and H2O mixing in your blood!)
Your kidneys help your body to maintain its optimal pH by controlling H+ and HCO3- absorption & secretion

41. Urinary Conditions Kidney Stones Also called Renal Calculi
Solid crystals that are formed from ions in urine
Can be the size of grains of sand up to golf-ball sized
As small as 2-3 mm can block the ureters

42. Urinary Conditions Kidney Stones, con’t
Usually detected by an X-Ray or Ultrasound
Some small stones may pass on their own
Larger stones must either be broken up with Shock Wave Lithotripsy or be removed with surgery

44. FYI: Stones can look different depending on what ions precipitated out!

45. http://www. youtube. com/watch

46. Urinary Conditions Urinary Incontinence (UI)
Involuntary leakage of urine
Different Types…

47. Stress UI
Due to insufficient strength of pelvic floor muscles
In men, is common following removal of the prostate
In women, is common as a result of pregnancy and childbirth
Urge UI
Involuntary loss of urine due to random spasms of the bladder muscles
Can be due to damage of nerves

48. Functional UI
A person knows they need to go, but cannot make it to the bathroom in time, usually due to some issue with thinking, moving, or communicating
Overflow UI
Because of weak bladder muscles or some sort of nervous system condition, the bladder is never completely emptied
This causes the person to “dribble” out urine

49. Urinary Conditions Urinary Tract Infection
Caused by a bacteria that has entered through the urethra and multiplied in the urine
UTI’s are more common in those who are sexually active, and those with anatomical malformations of the urinary tract
Females are more prone than males to UTI’s because the urethra is much shorter and closer to the anus than in males
Usually treated with antibiotics

50. Old Wives’ Tale???
Some say that cranberry juice can lower the rate of UTI’s because certain components of the juice can prevent the adherence of certain pathogens to the epithelium of the urinary bladder

51. Renal Failure Decreased rate of glomerular filtration
Can be caused by injury or by disease (including high blood pressure and diabetes)
Can be detected by elevated fluid and ion levels in the blood
Nitrogen wastes (such as urea) remain in the blood
Can lead to cardiovascular disease
If situation is bad enough, it can lead to the need for dialysis or a kidney transplant

52. Dialysis
Provides an artificial replacement for lost kidney function for people with renal failure
Utilizes the principles of diffusion, where substances in water tend to move from areas of higher concentration to lower concentrations
Blood flows by one side of a semi-permeable membrane, and a special fluid flows by the opposite side
Small solutes (such as ions and nitrogen wastes) are removed, but larger solutes (such as RBC’s and large proteins) remain in the blood

55. Dr. Willem Kolff, a Dutch physician, constructed the first working dialyzer in 1943 during the Nazi occupation of the Netherlands. Due to the scarcity of available resources, Kolff had to improvise and built the initial machine using sausage skins, drink cans, a washing machine, and various other items that were available at the time. Over the following two years, Kolff treated 16 patients that suffering from acute kidney failure using his machine, but the results proved unsuccessful. Then in 1945, a 67 year old woman in uremic coma regained consciousness following 11 hours of haemodialysis with the dialyzer, and lived for another 7 years before passing away of an unrelated condition. This was the first patient to ever be successfully treated with dialysis.

59. Urinalysis
Urinalysis is a diagnostic physical, chemical, and microscopic examination of a urine sample (specimen)
Specimens can be obtained by normal emptying of the bladder (voiding) or by a hospital procedure called catheterization

60. Purposes of Urinalysis
General evaluation of health
Diagnosis of metabolic, systemic, or endocrine disorders
Diagnosis of diseases or disorders of the kidneys or urinary tract
Monitoring of patients with diabetes
Testing for pregnancy
Screening for drug abuse

61. Urinalysis
Dipsticks are thin strips of plastic that change color in the presence of specific substances… can be used to measure…
Specific gravity (density)
Acidity of the urine (pH)
The presence of blood, proteins, or sugars
Substances produced during the breakdown of fatty acids (ketones)