Unit 7: Human Body Systems Part 2

 1. What metabolic processes create wastes?  2. What are the waste products that are created during these processes?  3. How are cellular wastes excreted?

 Define excretion:  Process by which metabolic wastes and excess substances are removed by an organism.  Helps organism to maintain homeostasis.

 Remember:  Egestion means the process by which indigestible material is released from the body (feces).  Excretion is the removal of the waste products of cellular metabolism from an organism.

** Remember: Metabolism is the sum of all chemical reactions occurring in a cell.

Metabolic ProcessWastes Produced Dehydration SynthesisWater Aerobic Cellular RespirationCarbon Dioxide and Water Protein MetabolismAmmonia, Urea, Uric Acid

 Organs Involved in Removal of Metabolic Wastes in Humans: 1. lungs 2. skin 3. liver 4. kidneys

Lungs (CO 2, H 2 O vapor) Liver (drugs,etc.) Kidneys

1. Lungs  Waste products of aerobic cellular respiration (CO2 and H2O vapor) are excreted by lungs.  Removed from body through process of exhalation.

2. Skin  Serves many functions, including excretion.  Excretory function = elimination of water, salts, urea through sweat glands (perspiration)  Sweat evaporates from skin and cools body.  Helps to maintain homeostasis by maintaining a constant body temperature.

3. Liver  Excretory functions include: a. Break down of worn out RBC’s b. Detoxification (purifies):  Removes harmful substances (bacteria, certain drugs and hormones)

-Largest organ in body -Weighs about 3 pound -Has about 500 functions

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 C. Formation of urea – Results from break-down of amino acids:  Excess amino acids (those not used in synthesis of proteins for growth and tissue repair) are broken down in liver into nitrogenous wastes.  Amino acids  Ammonia  Urea  Bloodstream then carries urea to kidneys for further processing.

 Includes:  Kidneys, ureters, bladder, and urethra (see diagrams)

4. Kidneys = 2 major functions: filter blood and reabsorb nutrients  1. Control concentration of most materials in body fluids, such as H 2 O.  Important in maintaining homeostasis.  2. Filter out wastes of cellular metabolism. Also filter out urea (nitrogenous waste) out of blood and convert it to urine.

 Nephron = Functional unit of kidney (see diagram)  Job = filtration and reabsorption  Each kidney has about 1.25 million nephrons (increase surface area!)

 Filtration (on diagram):  Occurs in glomerulus (ball of capillaries)  Where H2O, salts, urea, amino acids, glucose are filtered out by diffusion.  Filtrate then moves into Bowman’s capsule.

 Reabsorption (on diagram):  Materials then move into renal tubules of each nephron.  Where H2O returns to bloodstream by osmosis.  Where minerals, amino acids, glucose are reabsorbed by active transport into bloodstream.  Returns important substances to blood (water conservation)

 Flow of Urine:  After reabsorption occurs in the renal tubules, the only fluid remaining in the tubules is urine.  The tubules join to form the ureters (1 for each kidney). Urine travels from tubules into ureters then to urinary bladder.

 Urinary bladder temporarily stores urine.  Urine is excreted from urinary bladder through urethra.

 cology-Excretion cology-Excretion

 Water and Temperature Balance  Body regulates water and temperature balance through the life function of excretion.  During Exercise:  Your body produces less urine in order to conserve water.  Also, your body produces and releases sweat which evaporates from the skin and cools your body.

 1. Kidney Disease  Kidneys are unable to function properly and may result in body’s inability to get rid of waste through urine  Most commonly caused by diabetes (high levels of glucose)

 Dialysis  Artificial machine used to filter blood when your kidneys have failed – keeps your body in balance  Removes waste, salt and extra water to prevent them from building up in the body  Keeps a safe level of certain chemicals in your blood, such as potassium, sodium and bicarbonate  Helps to control blood pressure

 Kidney Transplantation  For patients with kidney failure

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 2. Kidney Stones  Mass of crystals that separate from urine and build up in the kidney.  Travel through urinary tract and pass out of the body in urine.