Animals need to absorb
nutrients to obtain energy. The process of breaking down food to
obtain nutrients is called digestion. Animals are adapted to ingest
and digest food in different ways, but many invertebrates and all
vertebrate animals have a specialized digestive system to facilitate
the processes involved.
Structurally simple animals
like sponges, flatworms and hydras have a simple digestive system
with a single opening. Other animals have a complete digestive
system running from the mouth to the anus.
This Lesson looks at the
general structure of an animal digestive system, Well go on to
follow the path of food through the human digestive system,
examining the roles of the different organs involved, and seeing how
fats, carbohydrates and proteins in foods are broken down by enzymes
and other chemicals in the digestive tract.
Well also examine the
control of the digestive system, which involves both nervous and