Download Excretory System

Excretory System
Excretion – removal of metabolic waste
Urinary system
• made-up of the kidneys,
ureters, bladder, and urethra
• kidneys filter waste from
blood; collected as urine
• flows through ureters to the
bladder
• stored then leaves through
urethra
Kidney Structure
• 3 regions;
• Renal medulla - inner
• Renal cortex – outer part
(contains nephrons)
• Renal pelvis - funnel shaped
structure in the center of the
kidney.
• 2 blood vessels enter and leave each kidney
– renal artery enters
– renal vein exists
Functional Unit of the Kidneys
• nephrons
– approx 1 million per kid
• 3 functions:
– filtration of water and solutes from the blood
– reabsorption of water and molecules back into
the blood
– secretion of waste products from surrounding
capillaries
Filtration
• Blood enters a nephron into the glomerulus
• The glomerulus is encased by the Bowman’s
capsule
– fluid from the blood is filtered
– the filtrate contains water, urea, glucose, salts, amino
acids, and vitamins
• urea - nitrogenous product made by the
liver
• brought to liver as ammonia , converted to
less harmful substance (urea) and enters the
blood stream
Reabsorption
• Material removed from blood at Bowman’s
cap makes it way back into the blood
• happens along nephron’s tubular parts
Secretion
• waste and toxic material secreted from
blood
• purified blood returned to circulatory sys
through renal vein
Nephron
The Kidneys ensure that the composition of our
Blood remains Constant
• Concentration of water in blood
– Drink too much liquid, and the Kidneys will
decrease the rate of reabsorption, excess water
is excreted.
• Level of salt in blood
– Eat Salty Foods and the Kidneys will respond
by returning less salt to the Blood by
reabsorption. Excess is excreted
• water reabsorption is controlled by the
antidiuretic hormone (ADH)
• ADH is released from the pituitary gland in
the brain
Kidney Stones
• excess wastes crystallize