Life on Earth
Audesirk & Audesirk
Prentice-Hall, Inc.


Chapter 23: At a Glance


Nutrition
  • The primary sources of energy are carbohydrates and fats.
  • Lipids include fats, phospholipids, and cholesterol.
  • Carbohydrates, including sugars and starches, are a source of quick energy.
  • Proteins, composed of amino acids, perform a wide range of functions within the body.
  • Minerals are elements and small inorganic molecules required by the body.
  • Vitamins are required in small amounts and play many roles in metabolism.
  • Nutritional guidelines help people obtain a balanced diet.

    The Challenge of Digestion

    Human Digestion
  • The mechanical and chemical breakdown of food begins in the mouth.
  • The esophagus conducts food to the stomach, where digestion continues.
  • Most digestion occurs in the small intestine.
  • Most absorption occurs in the small intestine.
  • Water is absorbed and feces are formed in the large intestine.
  • Digestion is controlled by the nervous system and hormones.

    The Functions of the Urinary System

    The Human Urinary System
  • Urine is formed in the kidneys.
  • Blood is filtered by the glomerulus.
  • The blood filtrate is converted to urine in the nephron.
  • The loop of Henle allows urine to become concentrated.
  • The kidneys are important organs of homeostasis.



  • Designed in cooperation with Andrew Stull and Steven Brunasso.

    Last Update - July 25, 1997

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