In a nutshell...
• The body uses a variety of small molecules (amino acids, fatty acids,
glucose) for its metabolic needs. Food is mechanically and chemically
broken down into these molecules during digestion, after which they can be
taken up by body cells through the separate process of absorption.
• Food travels in a one-way path from mouth to esophagus to stomach to
small intestine to large intestine to anus.
• Organs and structures in the digestive system are specialized for specific
functions in digestion.
• Digestive enzymes are specific hydrolytic enzymes that have a preferred
temperature and pH.
• Proper nutrition is necessary to health
DIGESTION: the mechanical and chemical breaking down of
ingested food into particles, then into molecules small enough to
move through epithelial cells and into the internal environment.
• ABSORPTION: the passage of digested nutrients from the gut lumen
into the blood or lymph, which distributes them through the body.
• ELIMINATION: the expulsion of indigestible residues from the body.
We will look at DIGESTION first.
• During digestion, proteins are broken down into amino acids, carbohydrates into glucose, fat to glycerol
and fatty acids, nucleic acids to nucleotides.
• Digestion is an EXTRACELLULAR process. It occurs within the gut (a tube that runs from mouth to
anus).
• Digestion is achieved through the cooperation of a number of body parts and organ systems, and its
coordination depends on the actions of several key HORMONES. Let’s first look at the parts of the