Excretory System Chapter 38 Section 3

Excretion The process by which excess substances and waste products are removed from an organism Organisms would die if wastes were not removed Also removes excess heat from an organism to help maintain homeostasis by maintaining a constant temperature

Organs of Excretion Lungs Kidneys Liver Skin

Metabolic Wastes CO2 and H2O from cellular respiration Nitrogen compounds (ammonia, urea, uric acid) produced during the breakdown of amino acids Mineral salts (NaCl, K, sulfate)- are products of other metabolic reactions REMEMBER- Egestion is the elimination of undigested food- NOT metabolic waste!!

Excretion in Protists Wastes diffuse out of the cell into water CO2, mineral salts, ammonia (NH3) are the waste products NH3 is soluble in water Water is also a waste product and the removal of water requires active transport Water collects in the contractile vacuole and is periodically expelled

Diagram of Paramecium Biology 104 - 7A Paramecium Osmoregulation

Excretion in the Hydra Wastes diffuse out of the cells Water is removed through active transport

Excretion in the Earthworm Most cells are not in contact with the environment Requires special organs- Nephridia There are 1 pair of nephridia in each body segment Cellular wastes diffuse into the body fluid which enters the nephridia Cilia moves fluid through a tubule which ends in a bladder

Earthworm (continued) The bladder opens to the environment through a nephridiopore Wastes leave the earthworm as urine- made of water, mineral salts, NH3, and urea (made from NH3 and CO2 and is soluble in water)

Diagram of an Earthworm

Excretion in the Grasshopper Excretory organs are the Malpighian tubules Wastes in the blood enter tubules through diffusion and active transport These wastes then enter the intestine Uric acid is formed- dry nitrogenous waste product which is excreted through the anus and is not soluble in water This conserves water in the grasshopper

Diagram of a Grasshopper

Excretion In Humans- Liver Removes harmful substances (bacteria, drugs, hormones) from blood Changes these substances to less harmful forms (detoxification) These substances are then returned to the blood Cirrhosis- Liver becomes nonfunctional Detoxification can not occur Due to overloading the liver with toxins

Liver (continued) Jaundice- Build-up of metabolic wastes in the bile Occurs when the liver is not functioning Bile is not excreted properly Skin looks yellow due to build-up of hemoglobin products

Liver (continued) Excess amino acids are broken down in the liver form ammonia (very poisonous) to urea (less poisonous) Urea diffuses into the blood and is brought to the kidneys

Urinary System Made up of- Kidneys- produce urine Ureter- tube which takes urine to Urinary bladder- stores urine Urethra- tube through which urine is excreted to the environment

Kidneys 2 of them in the back, just below the diaphragm Remove wastes of cellular metabolism Regulate concentration of water, salts, other substances Can not live without kidneys

Structure of the Kidneys Cortex- outer part Medulla- middle part Pelvis- inner part Blood is filtered through the cortex Medulla is made up of tubes- collecting ducts Collecting ducts carry filtered substances (filtrate) to pelvis

Kidney (continued) Pelvis is a cavity connected to the ureter Urine is formed from the filtrate and drains into the ureter Kidney is made up of many nephrons Nephrons filter wastes from blood One part of the nephron is in the cortex (glomerulus), the rest is in the medulla (loop of Henle)

Kidney (continued) Renal arteries bring blood with the metabolic wastes to the kidney These arteries branch into capillaries which form the glomerulus (part of the nephron) Blood leaves the kidney through the renal vein Wastes are left in the kidney

Diagram of Kidney Diagram of Kidney

Urine Formation 1st stage- wastes AND useful substances are filtered out of the blood (filtration stage) 2nd stage- useful substances are reabsorbed by blood (reabsorption stage) Reabsorption is important in conserving water Increases the concentration of the filtrate

Urine Formation (continued) Glucose, amino acids, Na+, K+ are reabsorbed Kidneys can only reabsorb so much of a substance, if the blood has too much, it will be excreted (glucose in diabetes) After reabsorption, urine remains Urine is made up of water, urea, salts

Urine Formation (continued) Kidney stones- substances which crystallize in the kidney or ureter Dialysis- machine which filters blood when kidneys fail

Lungs Excrete CO2 and H2O

Skin 2 Layers- Epidermis protects the dermis Dermis- Epidermis- outer layer Dermis- inner layer Epidermis protects the dermis Dermis- Elastic connective tissue Contains sebaceous glands, sweat glands, blood vessels, hair follicles

Skin (continued) Protects the body Is waterproof Sweat contains water, small amount of urea, and salts Removes excess heat by evaporation of sweat and opening of blood vessels Shivering and muscle tension produces heat