Digestive and Excretory Systems

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Chapter 39

• Digestive and Excretory Systems

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FOOD PYRAMID
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• Fats, oils, and sweets (top of the pyramid)
• Use sparingly
• Milk, Yogurt, Cheese
• 2-3 servings a day
• Meat, Beans, Eggs, Nuts
• 2-3 servings a day
• Vegetables
• 3-5 servings a day
• Fruits
• 2-4 servings a day
• Grains, bread, cereal
• 6-11 servings a day

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• Regardless of the source, the excess calories you
  eat will be stored as either glycogen or body fat
  and you will gain weight
• Obesity is being more than 20 heavier than your
  ideal body weight and significantly increases the
  risk of diabetes and heart disease.

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• Vitamins are organic substances that occur in
  many foods in small amounts that are necessary
  for normal metabolic functioning and dissolve in
  water or fat.
• Minerals are naturally occurring inorganic
  substances that are used to make certain body
  structures and substances, in normal nerve and
  muscle function, and maintain osmotic balances.
  Minerals are soluble in water.

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Digestion

• The process of breaking down food into molecules
  the body can use is called digestion.

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• The digestive system takes in food, breaks it
  down into molecules that can be absorbed, and
  gets rid of undigested molecules and wastes.
• Food travels more than 8 m (26 ft) through your
  digestive tract.
• Digestion begins as soon as food is ingested
• Saliva moistens and lubricates food and contains
  amylases which are enzymes that begin the
  breakdown of carbohydrates.

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• Digestive tract includes mouth, pharynx,
  esophagus, stomach, small intestine, large
  intestine, and rectum.

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• Liver, pancreas, and gallbladder deliver
  secretions to digestive tract.

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• Food moves past the pharynx, triggers a
  swallowing response which moves the epiglottis
  moving the food into the esophagus instead of the
  trachea.
• Successive rhythmic waves of smooth muscle
  contractions in the esophagus is called
  peristalsis move the food into the stomach.

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• Esophagus is a long tube that connects the mouth
  and stomach and is around 10 inches long.
• The stomach is the saclike organ just below the
  diaphragm that stores food and chemically and
  mechanically break down food.

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• Gastric juice is a combinations of hydrochloric
  acid and pepsin.
• Swallowed food can spend 2 to 6 hours in the
  stomach.
• A coating of mucus protects the lining of the
  stomach from gastric juices.

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• Food passes from the stomach to the small
  intestine which is about 6m long and functions
  mainly in digestion and absorption of nutrients.
• Food remains in the small intestine for 3 to 6
  hours.

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• The first part of the small intestine, called the
  duodenum, receives secretions from the pancreas,
  liver, and gallbladder.
• Lipases from the pancreas digest fat.

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• Lining of small intestine is covered with
  fingerlike projections called villi which
  increase the area available for absorption.

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• Wastes then move into the large intestine.
• Mostly mineral ions and water are absorbed in the
  large intestine.

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• The final segment of the large intestine is the
  rectum from here solid feces are eliminated
  through the anus.
• Undigested material pass through the large
  intestine and are expelled in 12 to 24 hours.

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• Livers role in digestion and metabolism
• Secrets bile which aids in emulsification of
  fats
• Breaks down glycogen when its needed for energy

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Digestive System Disorders

• Jaundice is a condition in which the eyes, skin
  and urine become abnormally yellow as a result of
  increased bile pigments in the blood.
• Anorexia nervosa is an eating disorder in which
  people starve themselves.
• Bulimia is an eating disorder in which people
  engage in frequent binging then purging.

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EXCRETION

• Excretion is the process that rids the body of
  toxic chemicals, excess water, salts, and CO2,
  while maintaining osmotic and pH balances.

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• Organs of excretion
• Lungs rid the body of CO2
• Kidneys rid the body of nitrogen
• wastes, salt, water, and urea.
• Skin rids the body of water and salts

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Kidney

• Each kidney is composed of roughly 1 million
  microscopic blood filtering units called
  nephrons.
• 3 phases occur as blood flows through nephrons
  filtration, reabsorption, and secretion.

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Urine that is excreted from the body is formed
from water, urea, and salts that are left over
after the reabsorption and secretion processes.
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• Ureters are tubes that carry the urine from the
  kidneys to the urinary bladder which stores the
  urine and expands as it fills.
• The urinary bladder can hold about 0.6L of urine.
  
• Urine leaves the bladder and exits the body
  through a tube called the urethra.
• Elimination of urine from the body through the
  urethra is called urination.

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• Kidney dialysis or hemodialysis is a procedure
  for filtering blood by using a machine.
• Kidney Transplant is a more permanent solution to
  kidney failure. Major problem is rejection of the
  organ.