AP Biology 2008-2009

Excretory System: removal of metabolic waste

Principal Wastes of ExcretionMetabolic Activity Wastes Produced

Respiration Carbon dioxide and water

Dehydration Synthesis Water

Protein Metabolism (deamination)

Nitrogenous wastes (Ammonia, urea, uric acids)

Other metabolic activities Mineral salts

• These wastes are often toxic to the organism and must be removed

• Excretion: removal of the wastes products of metabolism

Regents Biology

What liquid waste do we make?

Digesting protein makes poison nitrogen waste = ammonia = poison

H

CO2 + H2O

NH2 + H+ = ammonia NH3

H

HN C—OH

|| O

H|

—C—|

Regents Biology

The kind of waste you make depends on where you live Freshwater

Ammonia directly into environment

Land Urea

Urine Land egg layer

uric acid Non-toxic;

crystalline

Nitrogen waste

Regents Biology

Excretion in Plants

Because the wastes of photosynthesis are the reactants of respiration, plants have few wastes to excrete Excess CO2 and H2O

can be released through stomates

Some wastes can be stores in plant cell vaculoues

Regents Biology

Excretion in Simple Organisms Protozoans and Hydra: wastes are

released through the cell membrane directly into the watery environment In paramecia, excess water is pumped

out by a contractile vacuole

Regents Biology

Excretion in Simple Organisms Earthworm: Carbon dioxide is excreted

through moist skin Nephridia: excretory tissue that absorb

water, excess salts, urea and ammonia

Regents Biology

Excretion in Simple Organisms

Grasshopper: Malpighian tubules open into the digestive tract, removing wastes from the blood Nitrogenous wastes

are converted to uric acid

CO2 is released through tracheal tubes and then spiracles

Regents Biology

Human Excretory Organs Lungs: CO2 and diffuses from the blood

into the alveolar space and is then exhaled, along with some water vapor

Liver: large glandular organ that performs many functions, including excretion Disposal of Hemoglobin: old red blood cells

are broken down in the liver, creating bile salts which are eliminated in feces

Disposal of nitrogenous wastes: amino acids are broken down in the liver forming urea, which is filtered out of the body by the kidneys

Regents Biology

Human Excretory Organs

Sweat Glands: small, coiled tubular exocrine glands found in the surface of the skin Sweat contains water, salts and

some nitrogenous wastes Perspiration: formation of

sweat Sweat is very important for

temperature regulation Evaporation of sweat helps to

cool the body

Regents Biology

Human kidney Mammals have a pair of

bean-shaped kidneys supplied with blood by a renal artery and a

renal vein Functional unit is a nephron

Regents Biology

Proximaltubule

Distal tubule

Glomerulus

Collecting duct

Loop of Henle

Aminoacids

Glucose

H2O

H2O

H2O

H2O

H2O

H2O

Na+ Cl-

Mg++ Ca++

Bowman’s capsule

Na+ Cl-

1. blood flows through

capillaries into glomerulus

2. Filtration: water, salts, urea, amino

acids, glucose diffuse out of

blood into Bowman’s Capsule

3. Reabsorption: some water, salts, amino

acids, glucose are reabsorbed through active transport into

capillaries

4. Excretion: fluid formed at end of tubule consists of water, salts, urea, called

urine

Regents Biology

nephronblood osmolarity

ADH

increasedwater

reabsorption

increasethirst

high

Endocrine System Control

pituitary

too many solutes in blood dehydration, high salt diet

release ADH from pituitary gland antidiuretic hormone

increases permeability of collecting duct & reabsorption of water in kidneys

increase water absorption back into blood decrease urination

Regents Biology

Human Excretory Organs

Bladder

Urinary Bladder: urine is brought to the bladder for temporary storage by two ureters.

The bladder eliminates urine through the urethra.

Regents Biology

Malfunctions of the Excretory System Kidney Disease: many diseases affect the kidney

This could be caused by a diet high in protein exceeding the capacity of the kidney

Gout: a form of arthritis in which excess uric acid crystallizes in the joints