1. The Urinary System eliminates waste . . .
Some waste products of urine =
Nitrogenous wastes (from protein breakdown)
Extra electrolytes
Certain toxins and drugs

2. . . . to help regulate these very important things:
Water balance
Electrolytes
Acid-base balance in the blood
Blood pressure
DIGESTIVE SYSTEM
RESPIRATORY SYSTEM
CARDIOVASCULAR SYSTEM
URINARY SYSTEM
water, solutes
elimination of excess water, salts, wastes
AND, kidneys also
Manage RBC production (erythropoietin)
Activate vitamin D

3. Organs of the Urinary System
Kidneys – primary functional organs!
Ureters – drain urine to bladder
Urinary bladder – store urine
Urethra – drain urine from body
These are really just fancy plumbing

4. Kidneys are fairly well protected…
Located against dorsal body wall
Protected (somewhat) by lower ribs
Anchored and protected (with fat) by 3 surrounding membranes
Figure 15.1b

5. Kidney Features
Renal hilum – indentation where ureters and blood vessels enter/exit kidney
Adrenal glands on top

6. Regions of the Kidney Renal cortex—outer region
Renal medulla—inside cortex
Medullary pyramids and renal columns
Renal pelvis—inner collecting tube (moves urine to ureters)
Figure 15.2b

7. Participating…
The major functional organs of the urinary system are the ____________ that are surrounded by ____ protective membranes. The primary functions of the urinary system include which of the following?
Maintenance of blood pressure
Maintenance of water and electrolyte balance
Maintenance of acid-base balance
Writing your name in the snow
kidneys 3

8. Kidneys filter blood, i.e. control plasma composition
1/4th of blood supply passes through kidneys per minute!
Renal artery = arterial blood supply (to be filtered)
Renal vein = filtered blood drainage
Filtration occurs across capillaries = glomerulus in between

9. Nephron =. functional unit of kidney, i. e
Nephron = functional unit of kidney, i.e. actual site of urine formation
Main structures of nephrons =
Glomerulus – leaky knot of capillaries
Renal tubule – collects urine, manages urine composition
Glomerulus empties plasma into renal tubule, let’s take a closer look at making urine!

10. Step 1 of urine formation = glomerular filtration
High pressure inside glomerulus forces plasma into glomerular capsule (a.k.a. Bowman’s capsule)
Normally, cells too big to pass, just plasma
Glomerular capsule = beginning of renal tubule
Figure 15.3c

11. Step 2 = tubular reabsorption of valuable nutrients
Immediately after filtration, nutrients move back into blood
Capillaries surrounding renal tubule = peritubular capillaries
H2O, glucose, amino acids, electrolytes re-enter blood
Most reabsorption occurs across Proximal Convoluted Tubule (PCT)

12. Step 3 = tubular secretion
Some waste must be actively transported into tubules
Includes extra H+ (pH control)

13. Participating…
The functional unit of the kidney is known as the __________ . The three steps of urine formation are: 1. ______________, 2. ______________, and 3. ___________.
nephron
filtration
reabsorption
secretion

14. What the?... Let’s review: Urine Formation
Figure 15.4

15. Characteristics of Urine
In 24 hours, 1.0 to 1.8 liters of urine are produced
Solutes (unneeded waste) normally found in urine
Na+, K+, H+
Urea, uric acid, creatinine
Ammonia
Bicarbonate ions
99% of filtrate gets back into blood via reabsorption!!

16. Abnormal Urine Constituents can help diagnose problems…
Table 15.1

17. 2 types of nephrons… Cortical nephrons – found in cortex, most common
Juxtamedullary nephrons – penetrate the medulla via the Loop of Henle
Loop of Henle helps reabsorb H2O

18. Collecting Ducts receive urine from multiple nephrons
Deliver urine into calyces and renal pelvis
Renal pelvis delivers urine to ureters

19. Ureters direct flow to Bladder
Bladder emptied out by urethra
Urethra is short in females, also close to anus = urinary tract infections
This holds up to 1 liter!
Urination (micturition) is controlled by voluntary external sphincter
Figure 15.6

20. In males, urethra also part of reproductive system
Urethra = passage for urine and semen in men
Figure 15.7

21. Participating…
The loop of Henle helps maximize the re-absorption of_______ . The urethra of ________ functions in both urinary and ______________ systems and is longer than the urethra of __________.
water
males
reproductive
females

22. Kidneys help control plasma composition of blood
Remove nitrogenous waste (not reabsorbed)
Maintain water and electrolyte balance
Ensure proper pH

23. Maintaining Water and Electrolyte Balance
Falling systemic blood pressure volume
Reduced filtrate volume or solute content in renal tubules
JG cells of kidneys
(+)
(+) = stimulates
Renin-angiotension system
Neural regulation (sympathetic nervous system effects)
Effects of ADH release
Renin
Release
Leads to
Angiotensin II formed in blood
Systemic arterioles
Vasoconstriction
Peripheral resistance
Adrenal cortex
Aldosterone
Kidney tubules
Na+ reabsorption (and H2O absorption)
Blood volume
Rising blood pressure
Causes
Results in
Secretes
Targets
Releases
Inhibits baroreceptors in blood vessels
Sympathetic nervous system
Hypothalamic osmoreceptors
Posterior pituitary
ADH (antidiuretic hormone)
Collecting ducts of kidneys
H2O reabsorption
KEY:
Osmoreceptors in hypothalmus detect water content of plasma…
…stimulates thirst and release of ADH (antidiuretic hormone) = more H2O saved
Figure 15.11

24. Maintaining Water and Electrolyte Balance
Falling systemic blood pressure volume
Reduced filtrate volume or solute content in renal tubules
JG cells of kidneys
(+)
(+) = stimulates
Renin-angiotension system
Neural regulation (sympathetic nervous system effects)
Effects of ADH release
Renin
Release
Leads to
Angiotensin II formed in blood
Systemic arterioles
Vasoconstriction
Peripheral resistance
Adrenal cortex
Aldosterone
Kidney tubules
Na+ reabsorption (and H2O absorption)
Blood volume
Rising blood pressure
Causes
Results in
Secretes
Targets
Releases
Inhibits baroreceptors in blood vessels
Sympathetic nervous system
Hypothalamic osmoreceptors
Posterior pituitary
ADH (antidiuretic hormone)
Collecting ducts of kidneys
H2O reabsorption
KEY:
Low filtrate volume OR low b.p. = aldosterone release…
…aldosterone  Na+ reabsorption and H2O retention
Major BP control mechanism!
Figure 15.11

25. Kidneys help control plasma composition of the blood
Remove nitrogenous waste (not reabsorbed)
Maintain water and electrolyte balance
Ensure proper pH

26. Buffers = chemicals that prevent drastic changes in pH
Bind to H+ when pH drops
Release H+ when pH rises
Bicarbonate (remember this?) = blood buffer
H2CO HCO3- + H+
HCl + NaHCO3  H2CO3 + NaCl
strong acid weak base weak acid salt
NaOH + H2CO3  NaHCO3 + H2O
strong base weak acid weak base water
Figure 15.12

27. Kidneys help control pH by managing H+ and bicarbonate
pH of urine = 4.5 to 8.0 depending on body’s needs and diet
In general:
High protein diet = acidic urine; Vegetarian = alkaline urine

28. Angiotensin II formed in blood Peripheral resistance
Participating…
Sensations of thirst are generated by the ____________ that also stimulates the release of _________ to stimulate the reabsorption of more _________ by the kidneys. ____________ help prevent great fluctuation on blood pH and are also maintained by the kidneys.
hypothalmus
ADH
water
Buffers
Falling systemic blood pressure volume
Reduced filtrate volume or solute content in renal tubules
JG cells of kidneys
(+)
(+) = stimulates
Renin-angiotension system
Neural regulation (sympathetic nervous system effects)
Effects of ADH release
Renin
Release
Leads to
Angiotensin II formed in blood
Systemic arterioles
Vasoconstriction
Peripheral resistance
Adrenal cortex
Aldosterone
Kidney tubules
Na+ reabsorption (and H2O absorption)
Blood volume
Rising blood pressure
Causes
Results in
Secretes
Targets
Releases
Inhibits baroreceptors in blood vessels
Sympathetic nervous system
Hypothalamic osmoreceptors
Posterior pituitary
ADH (antidiuretic hormone)
Collecting ducts of kidneys
H2O reabsorption
KEY: