The Excretory System
Excretion- removal of waste
produced during body functions
Occurs through:
1.
2.
3.
4.
Intestine- digestive wastes, salts
Skin (sweat glands)- water, electrolytes
Lungs- carbon dioxide, water
Kidneys- toxins, water, N cmpds,
electrolytes
Urinary System Functions
A. maintain water concentration in blood
B. maintain concentration of ions like Na &
K
C. form urine
D. influence rate of secretion of hormones
like ADH
E. alter pH (acid- base balance)
Why bother with all of these?
Basic Anatomy of the Urinary
System
Gross Anatomy- KIDNEY
1. lie in retroperitoneal position
2. Fat cushion holds it in position
3. medial surface with concave hilus
Not that type….
Gross Anatomy- KIDNEY
4. Cortex- outer and lighter
5. Medulla- inner and darker
1. Cortex region of kidney
2. Medulla region of kidney
Gross Anatomy- KIDNEY
6. Most of the medulla is made up of RENAL
PYRAMIDS with a base facing outward and
papilla facing the hilus
Gross Anatomy- KIDNEY
7. Cortical tissue dips into the medulla between
the pyramids, forming RENAL COLUMNS
Gross Anatomy- KIDNEY
8. Each renal papilla juts into a cup-like CALYX
– Urine leaving the renal papilla collects here before
leaving the body
Gross Anatomy- KIDNEY
9. The calyces join to form the renal pelvis. It
narrows as it exits the hilum to become the
ureter.
10. BLOOD VESSELS
Renal artery brings ¼ of all blood to kidney/min.
Branches into
Interlobar arteries- extend toward the cortex
Changes names
Arcuate arteries- base of pyramids
Changes names
Interlobular arteries- afferent arterioles that branch
into the glomerulus where blood is filtered
10. BLOOD VESSELS (continued)
Efferent arterioles
Blood flows into
Peritubular capillaries (vasa recta) 
Interlobular vein  Arcuate vein  Interlobar
vein  renal vein
But, I am not going to test
you on this stuff!
Macroscopic Kidneys
A. Capsule & hilus
B. Renal sinus
1. renal pelvis
2. major calyces
3. minor calyces
C. Renal medulla
1. renal pyramids
a. papilla
2. Renal column
D. Renal cortex
B. Gross Anatomy- URETER
1. 28 cm long
2. Allows urine to travel
from kidney to urinary
bladder
3. 3 layers of tissue:
– Mucous lining
– Smooth muscle middle
– DWF outer layer
C. URINARY BLADDER
1. behind symphysis pubis
2. mostly smooth muscle aka detrusor muscle lined
with transitional epithelium
3. 3 openings: 2 from ureters and one into the
urethra
4. Has valve to prevent backflow into kidney
5. Functions
– urine reservoir
– aided by urethra, expels urine from body
Male Urethra
Female Urethra
Gross Anatomy- URETHRA
1. 3 cm in females; 20 cm in males
2. Male urethra (URINE) passes through
prostate gland where it is joined by 2
ejacuatory ducts (SEMEN) then travels
through penis and ends at the urinary
meatus at the tip of the penis.
3. In females, completely separate from
vagina
4. Micturition- urination
1. Voluntary relaxation of
external sphincter muscle
of bladder
2. Detrusor muscle
contracts
3. Parasympathetic nerve
control
4. Incontinence
Microscopic Structure of the
NEPHRON
• Filtering unit of kidney
• Process blood plasma
• Form urine
• 1.25 million per kidney
• Looks like a funnel with a
long, winding stem
NEPHRON
Components
1. renal corpuscle
2. PCT
3. loop of Henle
4. DCT
5. Collecting tubule & duct
The Nephron
• The nephron is the
functional unit of the
kidney, responsible
for the actual
purification and
filtration of the
blood.
• About one million
nephrons are in the
cortex of each
kidney.
The NEPHRON
RENAL CORPUSCLEin the cortex
1. Bowman’s capsule
• Cup-shaped mouth of
nephron
2. Glomerulus
• capillaries in BC
• Pores (fenestrations)
• Basement membrane
The Glomerulus
Microscopic Structure of the
NEPHRON
PROXIMAL TUBULEin cortex
– Closest to BC
(“proximal”)
– Aka PCT (proximal
convoluted tubule)
– Brush border
(microvilli) face
lumen- increase
surface area
The NEPHRON
LOOP OF HENLE (LOH)
• Renal tubule beyond the PCT
–
–
–
–
Descending limb (thin)
Sharp turn
Ascending limb (thick)
Dips into medulla
cortex
medulla
THE NEPHRON
DISTAL TUBULE
• Aka DCT (distal
convoluted tubule)
• Beyond LOH (“distal”)
• Juxtaglomerular
apparatus
THE NEPHRON
COLLECTING DUCT
– Straight tubule joined by distal tubules of
several nephrons
– Fuse to form papillary ducts which deliver
urine to the calyces
Overview of KIDNEY FUNCTION
1. FILTRATION
– Occurs in glomerulus
– Dependent on
Glomerular Filtration Rate
(GFR)
– Filter water and solutes
from blood into renal
tubule
• Glucose
• Amino acids
• Nitrogen wastes
KIDNEY FUNCTION-Filtration
• FILTRATION
– What’s left in the
blood?
• Blood cells
• Most plasma proteins
– What causes it?
• Pressure gradient
(high to low)
• Related to blood
pressure
Filtration
GFR is directly dependent on blood
pressure.
a. If GFR (BP) is too high, filtrate flows too
fast and substances are NOT reabsorbed
urine flow increases water is lost blood
volume drops  blood pressure drops.
b. If GFR (BP) is too low, filtrate flows too slow
and substancesare retained too much
urine flow decreases  water is preserved 
blood volume increases  blood pressure
increases.
Overview of KIDNEY FUNCTION
2. REABSORPTION
– Occurs in mostly in
PCT and little in LOH,
DCT, CD
– Put good things in the
renal tubule back into
the blood (peritubular
capillaries)
• Water
• Electrolytes
• Nutrients
Overview of KIDNEY FUNCTION
• REABSORPTION
– Healthy kidneys
reabsorb
• Glucose (if not…)
• Amino acids
• Sodium
• Water
Overview of KIDNEY FUNCTION
• REABSORPTION
– Substances that are NOT reabsorbed fully
• Things that lack carriers
• Things that are not lipid soluble
• Things that are too large
• Examples: urea, creatinine, uric acid
Overview of KIDNEY FUNCTION
• REABSORPTION
– ADH causes the
distal and
collecting tubules
to become more
permeable to
water
– This allows
hypertonic urine to
be formed
Overview of KIDNEY FUNCTION
• SECRETION
– PCT mostly
– Reabsorption in reverse
– Movement of small molecules out of the
peritubular blood and into the tubule for
excretion
• Including K, H, urea, ammonia
• Dispose certain drugs
• Helps control blood pH
Review Questions
•
•
•
•
Do you know the names of the structures?
What is GFR? What regulates it?
Why is reabsorption important?
Where is the only place glucose is
reabsorbed?
• Where does ADH act? What does it do?
Making Urine
•
•
•
•
•
•
Choose your water solution (Normal or Dehydrated)
Fill the cup 2/3 of the way with that solution
Add ½ dropper of Urea + vitamins
Add ½ dropper of acid
Check pH with pH paper
If you desire, pimp your urine with 1 dropper of the following:
Condition/ Diabetes
Substance
Glucose
+
Urinary
Tract Infect
Kidney
Failure
-
+
Blood
-
+
+
Protein
-
-
+
Answer the following questions on
a piece of paper and turn it in?
1.
2.
3.
4.
5.
Did you drink the urine?
What type did you make?
How did it taste?
Did it taste like you expected?
If you did not drink it, why not?
(please provide at least three
reasons)
URINE COMPOSITION
• Water- 95%
• Other substances- 5%
– Nitrogen wastes
– Electrolytes
– Toxins
– Pigments
– Hormones
– Abnormal stuff like blood, glucose, casts,
calculi
URINE COMPOSITION
• Characteristics
– Color
– Compounds
– Slight odor
– 4.6-8.0 pH (fresh is acidic)
– 1.001- 1.035 specific gravity
FLUID, ELECTROLYTE, and
ACID-BASE BALANCE
• FLUID
– Water accounts for 50-60% total weight (why less in obese
people?)
• 37% of this is ECF
• 63% of this is ICF
FLUID, ELECTROLYTE, and
ACID-BASE BALANCE
• Mechanisms to maintain
fluid balance
– Volumes of ICP, ECF,
plasma, and total volume
of water relatively
constant
– Adjust output (urine
volume) to intake
– Adjust fluid intake (liquids
we drink, water in food we
eat, water formed by
catabolism)
Anatomy of Micturition & Incontinence
•
•
•
•
Detrusor muscle with an External and Internal sphincter
Normal capacity 300-600cc
First urge to void 150-300cc
CNS control
– Pons - facilitates
– Cerebral cortex - inhibits
• Harmonal effects - estrogen
Bladder Pressure-Volume Relationship:
Or how to hold it
Treatment Options
• Reduce amount and timing of fluid
intake
• Avoid bladder stimulants (caffeine)
• Use diuretics judiciously (not before
bed)
• Reduce physical barriers to toilet (use
bedside commode)
1
Pessaries
Predisposing conditions to UTI
• Female
• Short urethra, proximity to
anus, termination
beneath labia
• Sexual activity
• Pregnancy
– 2-3% have UTI in preg, 2030% with asx bacteriuria
• decreased ureteral
peristalsis, temp. incomp
ofvesicoureteral valves
Urethritis
• 􀂃 Acute dysuria,
frequency
• 􀂃 Often need to suspect
sexually
• transmitted pathogens
esp. if sx more than 2
days, no hematuria, no
suprapubic
• pain, new sexual partner,
cervicitis
Cystitis
• Sx: frequency, dysuria,
urgency, suprapubic pain
• Cloudy, malodorous urine
(nonspec.)
• Leukocyte esterase
positive = pyuria
• Nitrite positive (but not
always)
• WBC (2-5 with sx) and
bacteria on urine
microscopy
Nephrolithiasis: kidney stones
• Supersat. of urine by stone
forming constituents
• Freq. stone types: Calcium
(most common), struvite,
oxalate, uric acid
• Risk factors: metabolic
disturbances, previous UTI,
gout, genetic
• Incidence = 2-3%
• Hematuria (rarely dangerous
by itself)
• Dangerous combo =
obstruction + infection
Addison’s Disease
Addison's disease occurs when the adrenal glands do not
produce enough of the hormone cortisol and, in some cases,
the hormone aldosterone
Cystocele
the wall between a woman’s bladder and her vagina
weakens and allows the bladder to droop into the vagina
• mild—grade 1—when the
bladder droops only a short way
into the vagina.
• severe—grade 2—the bladder
sinks far enough to reach the
opening of the vagina.
• advanced—grade 3—cystocele
occurs when the bladder bulges
out through the opening of the
vagina.
Nocturnal enuresis
•
•
•
•
•
•
Hormonal problems.
Bladder problems.
Genetics.
Sleep problems.
Medical conditions
Psychological problems.