Download Urinary System

Ch 25: The Urinary System
Section 1: Functions of the Urinary System
Role of the Urinary System
Urinary System
- Plays a crucial role in maintaining homeostasis
- Major challenge:
*Remove wastes without losing too much water or
dissolved nutrients in the process.
Danger!!
- If water levels fluctuate too much, chemical processes
that run the body may shut down.
Role of the Urinary System
Kidneys
- Organs in which the fluid portion of the blood is
collected
- Allow H2O/important nutrients to be reabsorbed into
bloodstream
- Filter out toxic substances & cellular wastes.
- Combine excess vitamins, salts, hormones, water &
excrete them as urine
Functions of the Urinary System
The urinary system helps maintain homeostasis in
several ways:
1) Regulates various ions in the blood (Na, K, Cl-, & Ca)
2) Regulates water content in the blood
3) Maintains proper pH of the blood
4) Retains important nutrients (glucose, proteins, etc)
5) Secretes hormones that stimulate RBC production
6) Eliminates cellular waste products (urea)
Dealing with Amino Acid Metabolism
Amino Acid Metabolism:
- The digestion & processing of proteins
Important things to note about A. A. Metabolism:
- Some amino acids have their amino groups removed & used
by the body.
- All other amino groups are released as ammonia (very toxic)
- Ammonia sent to liver & converted to urea (much less toxic)
- Urea filtered from blood by kidneys & excreted as urine
Ch 25: The Urinary System
Section 2: Structures & Functions of the
Human Urinary System
Anatomy of the Urinary System
Urinary system consists of:
- Kidneys
- Ureters
- Urinary Bladder
- Urethra
Anatomy of the Urinary System
Kidneys
- “Paired” organs located on either side of spinal column
& slightly above the waist
- Shaped like beans (5 in long, 3 in wide, 1 in thick)
- Blood carrying wastes enters kidney thru renal artery
- After being filtered, blood exits kidney thru renal vein
- Urine is created from wastes
Anatomy of the Urinary System
Anatomy of the Urinary System
Ureters
- Long tubes connecting
each kidney to the
bladder
- Carry urine from the
kidney to the bladder
Anatomy of the Urinary System
Urinary Bladder
- Temporarily stores urine from the kidneys
- Smooth, collapsible, muscular bag
- Walls composed of transitional epithelium giving it the
ability to stretch
- When bladder stretches, receptors in the walls trigger
the bladder to contract (reflex action)
- Capable of holding up to 500mL of fluid
- Desire to urinate begins at about 100mL
Anatomy of the Urinary System
Female bladder is much smaller than male
bladder due to space taken up by uterus.
Therefore, females have a legitimate reason
for needing more pit stops on long trips. 
Anatomy of the Urinary System
Urethra
- Thin-walled tube that carries urine from bladder to
outside of body
- Release of urine controlled by two sphincters:
1) Internal urethral sphincter (involuntary)
2) External urethral sphincter (voluntary)
The Nephron & Urine Formation
Nephrons
- Structural & functional units of the kidneys
- 1 million of them located in the outer cortex of kidney
- Tiny filters responsible for forming the urine
The Nephron & Urine Formation
Parts of a Nephron:
1) Glomerulus
- Dense knot of capillaries
where wastes & fluid from
blood is filtered
2) Bowman’s Capsule
- Cuplike structure that
surrounds glomerulus
-Collects water, nutrients, &
wastes
The Nephron & Urine Formation
Parts of a Nephron:
3) Proximal Tubule
- Returns H2O & nutrients
back to bloodstream
4) Loop of Henle
- Helps create accurate
H2O/Salt concentrations
in bloodstream
The Nephron & Urine Formation
Parts of a Nephron:
5) Distal Tubule
- Absorbs any remaining
wastes in bloodstream
6) Collecting Ducts
- Urine is completely
formed at this point
- Continued H2O removal
further concentrating
urine
The Nephron & Urine Formation
Ch 25: The Urinary System
Section 3: Control of the Urinary System
Regulation of Urinary System
Regulation primarily governed by hormones:
1) Antidiuretic hormone (ADH)
- Prevents excessive water loss in urine
- Causes distal tubule to allow more H2O to be
reabsorbed from the urine
2) Aldosterone
- Regulates sodium ion content
Regulation of Urinary System
Kidneys help regulate blood pressure :
1) Renin
- Enzyme released from kidneys when BP drops
- Directly affects angiotensin
2) Angiotensin
- Hormone always found in bloodstream
- When it comes in contact w/ Renin, it causes arterioles
to constrict…raises BP
Regulation of Urinary System
Kidneys help regulate O2 levels:
1) Erythropoietin
- If oxygen levels drop, this is released by kidneys.
- Travels to bone marrow & stimulates RBC growth
- ↑ RBC = ↑ hemoglobin = ↑ O2
**Kidney failure almost always leads to anemia (low RBC
count) due to insufficient erythropoietin production.
Ch 25: The Urinary System
Section 4: Homeostatic Imbalances
Homeostatic Imbalances
The kidney is a relatively rugged organ.
However…
If the kidney fails, death occurs fast!
(Usually within 2 weeks)
The kidneys are vulnerable to attack from several sources:
1) Some painkilling medications can destroy kidney function
2) Infection by bacteria can also be a major problem
3) Most common form of kidney failure is diabetes
Homeostatic Imbalances
Urinary Tract Infections (UTI)
- Infections of urethra caused by bacteria
Bladder Infections
- Infections of bladder caused by bacteria
*Both significantly more likely in women than men…why?
Homeostatic Imbalances
Kidney Stones
- Solid mass composed of tiny crystals
- Formed in kidneys when urine contains too much of a
certain substance…usually calcium or phosphate
- Chronic dehydration plays a major role in formation
- Irregularly shaped, usually w/ very sharp edges
- Usually will pass through ureters & out of body
- Sometimes must be pulverized w/ ultrasound
- Worst case scenario = surgical removal
Homeostatic Imbalances
Treatment of Kidney Disease:
1) Hemodialysis
- Done with dialysis machine (developed in 1945)
- Utilizes principle of diffusion across a semi-permeable
membrane
- Acts as an artificial kidney
Homeostatic Imbalances
Treatment of Kidney Disease:
1) Hemodialysis (Cont.)
- Blood supply is diverted from body, through machine
where filtration takes place, & then returned to body
- Patient must remain on dialysis for 4-6 hrs at a time 3
times per week.
- Only works for about 10 years (at most)…food/drink
intake must be very carefully regulated
Homeostatic Imbalances
Treatment of Kidney Disease:
2) Kidney Transplant
- Only an option when kidney is too damaged for dialysis
- Only one required to sustain life
3) Bioartificial kidney
- Still in clinical phase…but high hopes that this will be a
viable option in the future
4) Science fiction or Real possibility??
- Pharamaceutical companies currently funding research
into genetically engineered pig kidneys that wouldn’t
be rejected by humans
Aging and the Urinary System
As you get older…
- there is a progressive decline in urinary function
- bladder shrinks
- urinary retention becomes more common in males due
to enlarging prostate gland
Interesting Fact
One of the early diagnostic tests for diabetes…
…doctor would take urine sample & taste it!
If sweet tasting, patient almost certainly was a
diabetic…urine contained excess sugars from
blood