The Excretory System
STRUCTURES
Kidneys – filter blood of wastes
Ureter – tube leading to bladder
Urinary bladder – smooth muscle bag that
stores urine
Specifics…
KIDNEY
– Nephrons – filtering unit of kidney.
– Blood enters nephron carrying wastes.
– Blood travels into the capillaries of the
nephron called the glomerulus
– In the nephron, under high pressure, water,
glucose, vitamins, amino acids, protein wastes,
salts, and ions from the blood pass out of the
blood into a part of the nephron called the
Bowman’s capsule.
Glomerulus
Bowman’s
capsule
Nephron
Kidney
Specifics…
– Bowman’s capsule – part of nephron
– As liquid passes into the capsule it passes
through a narrow, U-shaped tubule that
reabsorbs water, glucose, and amino acids.
Water also diffused back into the blood
capillaries.
Formation of urine!
Urine – liquid that remains in the tubule:
composed of excess water, waste
molecules, and excess ions
YOU PRODUCE ABOUT 2L OF URINE
PER DAY!!!
Waste flows out of the kidneys,
through the ureter into the
urinary bladder, and out of the
body through a tube called the
urethra.
Urinary System and
Homeostasis
Major waste products – ammonia and urea
– THESE ARE TOXIC TO THE BODY!
Kidneys control level of sodium in blood
by removing and reabsorbing sodium.
Kidneys regulate pH of blood as well.
Urine Regulation
Hypothalamus - small part of brain that
controls many body processes
– Produces hormone ADH (antidiuretic
hormone) that stimulates reabsorption of water
in a nephron.