EXCRETORY SYSTEMPP 993-998

FUNCTION

• Every cell in the body produces metabolic waste.

• The skin, lungs, and kidneys make up this system.

SKIN• Excretes water, salts, small amounts of

nitrogenous wastes

LUNGS

• Excretes water vapor and CO2

KIDNEYS

• Formation and excretion of urine • Mostly water to keep wastes dissolved and

easier to excrete

EX. kidney stones

FILTRATION

• Blood forced into kidneys to clean out urea, wastes, excess water, and various substances in the blood stream

REABSORPTION

• Some substances return to blood maintain balance

ELIMINATION• Urine passes through the ureters to be

stored in bladder until it is secreted through the urethra

URINE• Normally made of

urea (from broken down proteins), water, and salt

• Very light yellow color

WHAT URINE TELLS US

• Proteins may leak into the urine if the kidney is damaged

• Too dark in color indicates dehydration• Brown color indicates bleeding from the

kidneys• Urine will have a high glucose count if the

individual is diabetic• Low or no glucose indicates hypoglycemia,

which results from too much insulin

Figure 44.19-2

ThirstHypothalamus

ADH

Pituitarygland

Osmoreceptors inhypothalamus trigger

release of ADH.

STIMULUS:Increase in blood

osmolarity (forinstance, after

sweating profusely)

Homeostasis:Blood osmolarity

(300 mOsm/L)

Drinking reducesblood osmolarity

to set point.

H2O reab-sorption helps

prevent furtherosmolarityincrease.

Increasedpermeability

Distaltubule

Collecting duct

HOMEOSTASIS• Urine production is regulated by the

antidiuretic hormone (ADH) • An increase in water in your blood triggers

the release of ADH, causing your kidneys to take up more water to be excreted out