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Introduction
•  Cellular metabolism produces wastes
Chapter 25
–  CO2
–  Urea
–  Ammonia
•  Kidneys rid the body of most nitrogenous wastes
•  Kidneys regulate the chemical make-up of blood
The Urinary System
General Functions
•  Serves as a blood filter
•  Toxins, metabolic wastes leave the body in
urine
•  H2O, glucose, and amino acids are returned to
blood
Organs of the Urinary System
•  Kidneys (paired)
–  Perform filtering
functions and
manufacture urine
•  Ureters (paired)
–  Transport urine
•  Urinary bladder
(single)
–  Stores urine
•  Urethra (single)
–  Transports urine
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Location of the Kidneys
•  Lie against the dorsal
body wall
•  Beneath the parietal
peritoneum
•  In the superior lumbar
region
–  Protected by the
lower part of the rib
cage
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Anatomy of the Kidney
•  External Anatomy
–  Hilus
–  Renal capsule
–  Renal artery
–  Renal vein
–  Ureter
•  Internal Anatomy
–  Renal cortex
–  Renal medulla
•  Renal pyramids
•  Renal papilla
–  Renal pelvis
–  Calyces
Human Anatomy, 3rd edition
Prentice Hall, © 2001
1
Blood Supply of the Kidney
•  Approximately ¼ of
the total blood supply
passes through the
kidneys each minute
•  Renal artery branches
Nephrons and Urine Formation
•  Nephrons form the
urine product
–  Filtration
–  Reabsorption
–  Secretion
–  Supplies pyramids
and cortex
•  Each kidney contains
about 1 million
nephrons
•  Venous blood leaves
the cortex and medulla
–  Small veins join the
renal vein
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Structure of a Nephron
•  2 main structures
–  Glomerulus
–  Renal tubule
•  Bowman’s
capsule
•  Proximal
convoluted tubule
•  Henle’s Loop
•  Distal convoluted
tubule
Human Anatomy, 3rd edition
Prentice Hall, © 2001
The Glomerulus - Filtration
•  Blood enters
glomerulus
–  Afferent arteriole
•  Glomerulus filters
blood
–  Forms filtrate
•  Blood leaves
glomerulus
•  Collecting duct
–  Receives urine from
nephrons
–  Delivers final urine
Anatomy, 3rd edition
product into calyces Human
Prentice Hall, © 2001
Renal Tubule – Reabsorption & Secretion
•  Reabsorption
–  Efferent arteriole
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Control of Blood Composition
•  Excretion of nitrogen-containing
compounds
–  Substances move
from filtrate into
peritubular
capillaries
•  Active transport
•  Most occurs in
proximal
convoluted tubule
–  Urea
–  Uric acid
•  Water and electrolyte balance
–  Regulated by hormones
•  Secretion
–  Substances move
from peritubular
capillaries into
filtrate
–  Control of blood pH
http://home.earthlink.net/~dayvdanls/nephron.gif
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Summary of Urine Flow
•  Kidneys produce urine
–  Filtration
–  Reabsorption
–  Secretion
•  Ureters
•  Bladder
•  Urethra
www.foxriverwatch.com/kidney_works.jpg
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