Mammalogy
(Fall 2012 Althoff)
LEC
10A
• Urinary (Excretory)
Systems Overview
• Body Fluid Regulation
LECTURE 25 – Division of Labor - Part III
CH 36-37
Overview of Excretion
External Environment
gut
lungs
kidney
Blood
TISSUES
CELLS
skin
liver
Body Fluid Regulation
• Keys here: ION & H20 concentrations
• Key ions: Na+, Cl-, K+ and HCO3• Body fluids gain mineral ions from
eating foods and drinking fluids
• Excretion is the primary way the body
loses ions
• H20: in via eating foods that contain H20,
and drinking H20…and via metabolism (e.g.
cellular respiration produces H20 =
metabolic water
Differences in Osmolarity
(i.e., solute concentration
• If difference in concentration between
two regions, H2O tends to move from
regions of greater concentrations to
regions of lower concentrations.
• Thus H20 moves to regions of highest
ION CONCENTRATIONS
Fishes & Body Fluid Regulation
FRESHWATER FISH
DOES NOT
DRINK
salt actively taken
up by gills
passive gain of water
across body surface
and through gills
large amounts
of hypotonic urine
contain little salts
Fishes & Body Fluid Regulation
MARINE FISH
passive loss of
water through gills
salt actively excreted
by gills
DRINKS
SEAWATER
small amounts
of
isotonic urine
Contains
some salts
Nitrogenous Waste Products
• NITROGENOUS WASTES = breakdown of
various molecules, including nucleic acids
and amino acids
• AMINO ACIDS NOT used for protein
synthesis are broken down by the body to
generate energy or converted to fats or
carbs that can be stored…
• …this requires amino groups (-NH2) be
removed excreted as ammonia, urea, or
uric acid
Nitrogenous
Wastes
PROTEINS
amino acids
-NH2
ammonia
Need water to excrete
Need energy to produce
urea
uric acid
Nitrogenous waste
• Ammonia
habitat
water
animals
aquatic invertebrates.
bony fishes
amphibian larvae
toxicity
highest
• Urea
land
adult amphibians
mammals
2nd
highest
• Uric acid
land
insects
birds
reptiles
lowest
Maintenance System
(1 of 3…digestive & respiratory other 2)
• URINARY SYSTEM—kidneys, bladder, & tubes
A) rids blood of metabolic wastes
B) helps regulate fluid level & chemical
content of blood
• EXCRETION = rids body of metabolic wastes
(remember cellular metabolism) and breakdown
of substances that enter the body (non-digestive
system).
Major
role in
maintaining
HOMESTASIS
Metabolic wastes OUT
FUNCTIONS of the Urinary System
Regulate water content of blood
Regulate ion concentrations:
Na+, Ca+,
K+, Cl-
Regulate pH of blood
Produce erythropoietin  RBC
production increases
Eliminate cellular waste such as urea,
drugs, etc.
Organs of the
URINARY System
• Kidney (2)
• Ureter (1 per kidney)
• Urinary bladder
• Urethra
ORGANS
• KIDNEYS – where urine is made
• URETERS— muscular tubing carrying urine
from kidney to bladder
• BLADDER— muscular bag that stores urine
until urination (holds ~600 ml)
• URETHRA— carries urine out of body
URETHRA –some important “minute”
• Length:
20 cm long,
4 cm long
• Passes through prostate gland in
don’t have).
(females
--prostate gland contributes fluid to
semen that serves as buffer by raising
pH of semen to >6.5 to overcome
3.5-4.0 pH environment of vagina
• If prostate gland enlarges, it reduces
urethrea’s ability to maintain original
diameter
600 ml capacity,
…..internal
sphincter “relaxed”
at 250 ml
INTERNAL SPHINCTER
EXTERNAL SPHINCTER
KIDNEY is “the”
functional unit
of the urinary
system
Kidney MACROanatomy
• Blood supply
• Cortex
• Medulla
• Renal Pelvis
Kidney- NEPHRON
•
•
•
•
Functional unit of the kidney
1,000,000 per kidney
Actually produces urine
Transerves the renal cortex and renal
medulla
• Very detailed structurally speaking
Kidney
• Nephron
MICROanatomy
Nephron Detail
Afferent arteriole
Efferent arteriole
GLOMERULUS
Glomerular capsule
Proximal convoluted
tubule (PCT)
Loop of the Nephron
Distal convoluted
tubule (DCT)
Collecting duct
4
5
3
2
1
8
3
6
7
GLOMERULAR
FILTRATION
SEM picture
Of a
glomerulus
1
NEPHRON CAPS
2
Site where, if high
blood pressure
or injury,
RBC “escape” an
end up in urine
Proximal convoluted tubule (PCT)
CROSS-SECTIONAL view
Microvilli (many per cell)
URINE
FORMATION
3
GLOMERULAR
FILTRATION
1
TUBULAR
ABSORPTION
TUBULAR
2
SECRETION
4
And….then there
is urine
Keep in mind
nephron
transverses
Cortex
AND
medulla
regions of
the kidney
Glomerular FILTRATION
• Blood is “filtered” (but typically only things
dissolved…not formed elements of blood)
• Filtrate is one-way….balance of blood
moves on through blood vessel
• Blood in urine “happens” here….before it
gets to the bladder…. BAD!!!!
Tubular REABSORPTION
• H20 taken out of urine (was part of blood
that “filtered out” (60-70%)
• NaCl (salts) taken out (think….osmosis
process here) (60-70%)
• Urine becomes more and more
concentrated
Tubular SECRETION
• Drugs secreted from blood  DCT (distal
convulated tubule)
• K+, H+, etc. Secreted from blood  DCT
(active transport!!!)
• NaCl could be reabsorbed here ??? (if low in
concentration)
• H2O still being taken out of urine, becomes more
and more concentrated
1
3
osmosis
active
transport
2
diffusion
4
Processes and materials “moved”
Osmosis
• H2O
Active Transport
• NaCl
• Nutrients
Diffusion
• Urea
• NaCl
•
•
•
•
Drugs
K+
H+
NH3
3
1
2
4
Changes in
concentrations of
H20, salts, etc.
INSIDE
&
OUTSIDE
the tubules
as urine it flows from
renal cortex to
renal medulla and
back up to renal
cortex….
The KING of minimizing H20 loss
from the process of urine formation!
KANGAROO RATS (Dipodomys sp.)
Controlling pH of the blood…..
H+
CAPILLARY
H++NH3 NH4
HCO3-
KIDNEY
TUBULE
NH4 = ammonium
Hormones & the Urinary System
• RENIN – promotes retention of NaCl
• ANH – (atrial natriuretic hormone) suppresses
retention of NaCl
• ADH – (antidiuretic hormone) increases H20
taken out of urine
• DIRURETICS including alcohol, caffeine drinks:
they inhibit ADH, thus not as much
reabsorption of H20
• Aldosterone– secreted by kidneys promotes K+
secretion.
SUMMARY:
Urine Formation
•
•
•
•
•
•
Glomerulus
Proximal con. tubule
Distal con. tubule
Ureter
Bladder
Urethra
H20 retention is…
• Diuretics
• Antidiuretics
decreased
increased