Excretory System

Removes cellular wastes from the body

Excretion is: the removal of metabolic

wastes

Main Excretory organs involved are:

kidneys liver lungsskin

Major metabolic wastes: carbon dioxide and water

CO2 and H2O are from cellular respiration certain nitrogen compounds

Breakdown of amino acids from proteins produces nitrogen compounds

Urea Ammonia Uric acid

mineral salts from metabolism Sodium chloride (NaCl) Potassium sulfate (K2SO4)

Detoxificationchanges harmful substances

into inactive or less poisonous substancesThese inactive substances

are returned to blood and are filtered by kidneys.

Liver

liver

Amino acids are broken down.amino group, NH2→ changed to ammonia, NH3 → changed to urea (less poisonous)

Urea diffuses back into bloodstream and is filtered out by the kidneys.

Formation of Urea in Liver:

Urinary SystemKidneys ureter urinary bladder urethra

KidneysTwo main functions:

1. Filters the blood (removes wastes from cellular

metabolism)

2. Reabsorbs water

***If kidneys cannot perform these functions a person will die due to toxins building up.

Kidney Structure3 layers of the kidney Cortex- outer layer blood is filtered to

remove waste and excess substances Medulla- middle layer made up of tubes

called collecting ducts that carry the filtered substances (filtrate) to the innermost layer of the kidney

Pelvis- cavity that collects the filtrate and connects the kidney to the ureter which exits the kidney

Nephrons waste filtering unit of the kidney

found in the cortex and the medulla 1.25 million nephrons in each kidney Contains glomerulus, Bowman’s capsule and a

renal tubule

Filtration in Nephrons1. Blood enters kidney through renal artery,2. Small substances and wastes diffuse from the

glomerulus capillaries into the Bowman’s capsule collecting cup and into the renal tubule of the pelvis,

3. Water and some dissolved substances are reabsorbed into the blood through the capillary

4. Clean blood leaves the kidney through the renal vein

So where does the waste go???Urine- final waste fluid excreted made up of water, urea and various salts 1-1.5 liters of urine are produced every 24

hoursUreter- tube connects kidney to urinary bladder; urine travels from kidney to bladderUrinary Bladder- collects and stores urine for excretionUrethra- during urination urine travels from the bladder to the outside of the body

SkinExcretion- Small amounts of urea and salts in sweat Removal of excess heat

Blood vessels dilate bringing more warm blood to skin surface

Sweat is produced by sweat glands Sweat absorbs body heat and evaporates to water

vapor and body heat leaves the body in the water vapor Body cools as a result of the evaporation

LungsExcretion- Removes CO2 and water from

cellular respiration

Excretion Disorders Renal Failure- kidneys stop filtering the

blood and wastes and fluid build up in the body and death can result Treatment- dialysis- artificial machine filters

and cleans the blood (works because of diffusion)

*Presence of protein, sugar, or other needed substances indicates other conditions such as diabetes or cardiovascular disease