1. Human Anatomy & Physiology
Urinary System
Water control and waste disposal
Human Anatomy & Physiology
Dr. Romano

2. Homeostasis The urinary system maintains homeostasis in several ways:
Removal of urea (nitrogenous waste) from the bloodstream.
Control of water and salt balance in the bloodstream.
Involved in blood pressure regulation.

3. Kidney Functions Maintain Fluid (Water) Balance
Maintain Acid-Base Balance
Maintain Ion (Electrolyte) Balance
Excrete Nitrogenous Wastes
Maintains Blood Pressure
Stimulates Red Blood Cell Production in the Bone Marrow

5. Urinary system anatomy
Main structures of the urinary system:
kidneys
ureters
bladder
urethra

6. Location of the Urinary System
Kidneys = 2 dark red organs with a kidney bean shape lie against the dorsal body wall in the abdominal cavity.
Kidneys lie beneath the lowest (12th) ribs

7. Location of the Urinary System
The ureters leave the kidney at the renal pelvis to enter the bladder in the pelvic area
The urethra brings urine from the bladder to outside the body

8. Anatomy of the Kidney Main structures of the mammalian kidney:
renal cortex
renal medula
nephrons

9. Anatomy of the Nephron Glomerulus Proximal tubule Loop of Henle
Distal tubule

10. Nephrons and Urine Formation
The nephron is the basic unit of structure and function in the kidney
Each kidney has over a million nephrons

11. Parts of a Nephron Each nephron consists of:
Glomerulus = a knot of capillaries
Renal tubule which coils & twists from the glomerulus & ends with the collecting duct

12. Glomerulus
This is the only place in the system where the blood is actually “filtered.”
Blood pressure is used to push plasma through capillary walls and into the Bowman’s capsule.

13. Proximal tubule
Nutrients (salts, vitamins, etc.) are moved out of the tubule through active transport.
Water follows the nutrients by osmosis.

14. Distal tubule
Active transport is used to move more nutrients out of the concentrated urine.
Some ions, drugs, and toxins are actively pumped into the tubule.

15. Loop of Henle
Tissue around the Loop of Henle is salty, from active transport and diffusion of sodium chloride.
The salty conditions allow water to diffuse out of the loop.

16. Proximal & Distal Tubule

17. Collecting Duct
More water leaves the tube by osmosis, since the tube is surrounded by salty tissue.
Some urea leaves by diffusion, and may be cycled through the system.

19. What drives filtration in the glomerulus?
Osmosis
Smooth muscle contractions
Salt gradients
Blood pressure

20. Three Steps in Urine Formation
Filtration
Tubular Reabsorption
Tubular Secretion
(see page 507)

21. How is Urine Formed? Urine forms from three processes:
Filtration- blood plasma without proteins that pass through the glomerulus. Wastes enter the renal tubule
Tubular Reabsorption- useful substances from the filtrate (water, sugar, ions) are returned to the blood
Tubular Secretion- ions, waste, and drugs are removed into the urine

23. Blood Supply to the Kidney

24. Measure of Kidney Function
GFR: Glomerular Filtration Rate

25. What are the wastes? Nitrogenous wastes include:
Urea – made in the liver from protein breakdown
Uric acid – when nucleic acids are metabolized
Creatinine – metabolism of muscle

26. Urine Nitrogen wastes, unnecessary ions, water
Kidney filters 150 liters of blood plasma per day
We make liters of urine a day
Kidneys are very efficient 

27. Ammonia and Urea Ammonia is toxic and highly water soluble.
The liver turns ammonia into urea, which is less toxic and less soluble.

28. Characteristics of Urine
Freshly voided urine is clear/pale to yellow
Pigment is due to body’s destruction of hemoglobin in red blood cells
Urine is sterile
Odor is like ammonia if allowed to stand
Certain substances alter the odor (coffee, asparagus, etc.)

29. Characteristics of Urine
Urine is slightly acid pH (6)
There should NOT be sugar or protein in normal urine
Few wbc and rbc may be found in urine
If many wbc are found, then infection is present

31. What Comes Next?
Urine leaves each kidney through the collecting duct at the renal pelvis to enter the ureters
Each ureter then enters the urinary bladder in the pelvis

32. Female Urinary System

33. Male Urinary System

34. Homeostatic Imbalance
Urethritis
Cystitis
Pyelonephritis
Incontinence
Urinary retention
Kidney stones

35. Erythropoietin The kidney makes the hormone erythropoietin
Erythropoietin travels to the bone marrow and stimulates the production of new blood cells.
How does this maintain homeostasis?

36. Regulating water
Antidiuretic hormone (ADH or vasopressin) is part of a negative feedback system that regulates water in the mammalian body.
ADH increases the permeability of the distal tubule, allowing greater water recovery.
ADH causes the collecting duct to reabsorb more water = less urine.

38. If a person were given a dose of ADH, what would happen?
More water lost through kidneys.
More potassium secreted by nephron.
More water retained in the kidneys.
More sodium secreted by nephron.

39. Caffeine and alcohol are diuretics.
Diuretics cause the kidney to excrete more water.
Alcohol inhibits ADH release, while caffeine interferes with its activity.
Part of the symptoms of a hangover are due to dehydration. What causes the dehydration?
why is a cup of coffee not a good cure for a hangover?

40. The Kidney & Blood Pressure
The kidneys make hormones that affect blood pressure:
ADH – reabsorbs water
Renin-Angiotensin which causes the adrenal gland to make aldosterone  reabsorbs sodium ion (salt)

41. Blood Buffers The kidneys maintain normal pH (7.4 range)
Kidney has a bicarbonate buffer system which “neutralizes” excess acid

42. Renal Failure

43. Dialysis