Urinary System
What are the functions of the urinary system?
**Osmoregulation – water and salts
Waste excretion
metabolic wastes (N)
If water is plentiful then NH3
If water is limited then Urea
If water is scarce then Uric acid
Hormone production – blood cell
formation as a result of erythropoeitin secretion.
http://www.elitesavers.com/funny/peeing.jpg
Urinary System
What are the “rules of thumb”
regarding water and salts for
different classes of vertebrates?
Fresh water organisms – excrete
water and conserve salt
Salt water organisms – excrete
salt and conserve water
Terrestrial organisms – modify
salt and water loss appropriately
Urinary System
What is the basic pattern and
what is an archinephros?
Nephron – functional
unit of kidneys
Renal corpuscle:
1) Glomerulus
2) Renal tubules
3) Excretory ducts
Urinary System
What is the basic pattern and
what is an archinephros?
Nephron – functional unit of
kidneys
Renal corpuscle –
Urinary System
What are the 3 basic processes involved with
urine formation?
1) Filtration – glomerulus
2) Reabsorption – renal tubules
3) Secretion – renal tubules
Other processes include:
4) Concentration – renal tubules and
collecting ducts
5) Storage – bladder
6) Micturition – bladder, sphincters & urethra
Urinary System
Where does filtration take place?
Renal corpuscle =
glomerulus &
Bowman’s capsule
Bowman’s capsule =
parietal and visceral
layers
Urinary System
What is involved with producing filtrate?
Filtration Pressure…
Flow depends on pressure
Fluids and solutes move from >
press. to < press.
Why is there a difference in
pressure?
GCP = Glomerular capillary pressure
CP = Capsule pressure
COP = Colloidal osmotic pressure
Urinary System
What is the route of blood flow through the kidney and
how does this fit with REABSORPTION?
Afferent
arteriole to
glomerulus to
Efferent
arteriole to
peritubular
capillaries to
vasa recta,
then back out
Urinary System
What is the role of secretion in urine production?
Moving wastes
into nephron
both passive and
active
Passive (NH3)
Active /
countertransport
(ex. H+, K+,
Penicillin)
Urinary System
How is urine concentrated?
Urinary System
How do kidneys form
embryologically?
Nephrogenic mesoderm –
lateral to mesodermal somites
Where are the kidneys in
Necturus?
Tubules appear at cephalic end
Paired ducts develop and form
caudad until they reach posterior
and form opening
Posterior tubules
Urinary System
What is an archinephros?
Hypothetical “kidney”–
Believed to be the
prototype from a
segmented ancestor
Urinary System
Urinary System
Why would glomeruli be larger
in freshwater fish and aquatic
amphibians… and smaller in
marine fishes and tetrapods
(especially in tetrapods of arid
environments)?
Urinary System
How are kidneys organized?
Urinary System
Where can one find a kidney?
Location:
Small of your back
Size:
fist-sized
Surrounded by
connective tissue
(renal capsule)
Protected by
renal fat pad (perirenal fat)
Urinary System
Gross anatomy!
retroperitoneal
peritoneal
cavity
Urinary System
What is extrarenal salt excretion
and how does it occur?
Gills – actively transport across
lamellar membranes
Salt glands – can empty into
nasal canals or mouth
http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/marine-iguana.jpg
What other anatomy is significant?
Transitional
epithelium
lines the
ureters &
urinary bladder
Stratified
&
Stretchy
Contract =
peristaltic
movements
What other anatomy is significant?
Transitional
epithelium
lines the
ureters &
urinary bladder
Stratified
&
Stretchy
Contract =
peristaltic
movements